Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

[karo-tx-linux.git] / drivers / net / ethernet / chelsio / cxgb4vf / sge.c

/*
 * This file is part of the Chelsio T4 PCI-E SR-IOV Virtual Function Ethernet
 * driver for Linux.
 *
 * Copyright (c) 2009-2010 Chelsio Communications, Inc. All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/if_vlan.h>
#include <linux/ip.h>
#include <net/ipv6.h>
#include <net/tcp.h>
#include <linux/dma-mapping.h>
#include <linux/prefetch.h>

#include "t4vf_common.h"
#include "t4vf_defs.h"

#include "../cxgb4/t4_regs.h"
#include "../cxgb4/t4fw_api.h"
#include "../cxgb4/t4_msg.h"

/*
 * Constants ...
 */
enum {
        /*
         * Egress Queue sizes, producer and consumer indices are all in units
         * of Egress Context Units bytes.  Note that as far as the hardware is
         * concerned, the free list is an Egress Queue (the host produces free
         * buffers which the hardware consumes) and free list entries are
         * 64-bit PCI DMA addresses.
         */
        EQ_UNIT = SGE_EQ_IDXSIZE,
        FL_PER_EQ_UNIT = EQ_UNIT / sizeof(__be64),
        TXD_PER_EQ_UNIT = EQ_UNIT / sizeof(__be64),

        /*
         * Max number of TX descriptors we clean up at a time.  Should be
         * modest as freeing skbs isn't cheap and it happens while holding
         * locks.  We just need to free packets faster than they arrive, we
         * eventually catch up and keep the amortized cost reasonable.
         */
        MAX_TX_RECLAIM = 16,

        /*
         * Max number of Rx buffers we replenish at a time.  Again keep this
         * modest, allocating buffers isn't cheap either.
         */
        MAX_RX_REFILL = 16,

        /*
         * Period of the Rx queue check timer.  This timer is infrequent as it
         * has something to do only when the system experiences severe memory
         * shortage.
         */
        RX_QCHECK_PERIOD = (HZ / 2),

        /*
         * Period of the TX queue check timer and the maximum number of TX
         * descriptors to be reclaimed by the TX timer.
         */
        TX_QCHECK_PERIOD = (HZ / 2),
        MAX_TIMER_TX_RECLAIM = 100,

        /*
         * Suspend an Ethernet TX queue with fewer available descriptors than
         * this.  We always want to have room for a maximum sized packet:
         * inline immediate data + MAX_SKB_FRAGS. This is the same as
         * calc_tx_flits() for a TSO packet with nr_frags == MAX_SKB_FRAGS
         * (see that function and its helpers for a description of the
         * calculation).
         */
        ETHTXQ_MAX_FRAGS = MAX_SKB_FRAGS + 1,
        ETHTXQ_MAX_SGL_LEN = ((3 * (ETHTXQ_MAX_FRAGS-1))/2 +
                                   ((ETHTXQ_MAX_FRAGS-1) & 1) +
                                   2),
        ETHTXQ_MAX_HDR = (sizeof(struct fw_eth_tx_pkt_vm_wr) +
                          sizeof(struct cpl_tx_pkt_lso_core) +
                          sizeof(struct cpl_tx_pkt_core)) / sizeof(__be64),
        ETHTXQ_MAX_FLITS = ETHTXQ_MAX_SGL_LEN + ETHTXQ_MAX_HDR,

        ETHTXQ_STOP_THRES = 1 + DIV_ROUND_UP(ETHTXQ_MAX_FLITS, TXD_PER_EQ_UNIT),

        /*
         * Max TX descriptor space we allow for an Ethernet packet to be
         * inlined into a WR.  This is limited by the maximum value which
         * we can specify for immediate data in the firmware Ethernet TX
         * Work Request.
         */
        MAX_IMM_TX_PKT_LEN = FW_WR_IMMDLEN_MASK,

        /*
         * Max size of a WR sent through a control TX queue.
         */
        MAX_CTRL_WR_LEN = 256,

        /*
         * Maximum amount of data which we'll ever need to inline into a
         * TX ring: max(MAX_IMM_TX_PKT_LEN, MAX_CTRL_WR_LEN).
         */
        MAX_IMM_TX_LEN = (MAX_IMM_TX_PKT_LEN > MAX_CTRL_WR_LEN
                          ? MAX_IMM_TX_PKT_LEN
                          : MAX_CTRL_WR_LEN),

        /*
         * For incoming packets less than RX_COPY_THRES, we copy the data into
         * an skb rather than referencing the data.  We allocate enough
         * in-line room in skb's to accommodate pulling in RX_PULL_LEN bytes
         * of the data (header).
         */
        RX_COPY_THRES = 256,
        RX_PULL_LEN = 128,

        /*
         * Main body length for sk_buffs used for RX Ethernet packets with
         * fragments.  Should be >= RX_PULL_LEN but possibly bigger to give
         * pskb_may_pull() some room.
         */
        RX_SKB_LEN = 512,
};

/*
 * Software state per TX descriptor.
 */
struct tx_sw_desc {
        struct sk_buff *skb;            /* socket buffer of TX data source */
        struct ulptx_sgl *sgl;          /* scatter/gather list in TX Queue */
};

/*
 * Software state per RX Free List descriptor.  We keep track of the allocated
 * FL page, its size, and its PCI DMA address (if the page is mapped).  The FL
 * page size and its PCI DMA mapped state are stored in the low bits of the
 * PCI DMA address as per below.
 */
struct rx_sw_desc {
        struct page *page;              /* Free List page buffer */
        dma_addr_t dma_addr;            /* PCI DMA address (if mapped) */
                                        /*   and flags (see below) */
};

/*
 * The low bits of rx_sw_desc.dma_addr have special meaning.  Note that the
 * SGE also uses the low 4 bits to determine the size of the buffer.  It uses
 * those bits to index into the SGE_FL_BUFFER_SIZE[index] register array.
 * Since we only use SGE_FL_BUFFER_SIZE0 and SGE_FL_BUFFER_SIZE1, these low 4
 * bits can only contain a 0 or a 1 to indicate which size buffer we're giving
 * to the SGE.  Thus, our software state of "is the buffer mapped for DMA" is
 * maintained in an inverse sense so the hardware never sees that bit high.
 */
enum {
        RX_LARGE_BUF    = 1 << 0,       /* buffer is SGE_FL_BUFFER_SIZE[1] */
        RX_UNMAPPED_BUF = 1 << 1,       /* buffer is not mapped */
};

/**
 *      get_buf_addr - return DMA buffer address of software descriptor
 *      @sdesc: pointer to the software buffer descriptor
 *
 *      Return the DMA buffer address of a software descriptor (stripping out
 *      our low-order flag bits).
 */
static inline dma_addr_t get_buf_addr(const struct rx_sw_desc *sdesc)
{
        return sdesc->dma_addr & ~(dma_addr_t)(RX_LARGE_BUF | RX_UNMAPPED_BUF);
}

/**
 *      is_buf_mapped - is buffer mapped for DMA?
 *      @sdesc: pointer to the software buffer descriptor
 *
 *      Determine whether the buffer associated with a software descriptor in
 *      mapped for DMA or not.
 */
static inline bool is_buf_mapped(const struct rx_sw_desc *sdesc)
{
        return !(sdesc->dma_addr & RX_UNMAPPED_BUF);
}

/**
 *      need_skb_unmap - does the platform need unmapping of sk_buffs?
 *
 *      Returns true if the platform needs sk_buff unmapping.  The compiler
 *      optimizes away unnecessary code if this returns true.
 */
static inline int need_skb_unmap(void)
{
#ifdef CONFIG_NEED_DMA_MAP_STATE
        return 1;
#else
        return 0;
#endif
}

/**
 *      txq_avail - return the number of available slots in a TX queue
 *      @tq: the TX queue
 *
 *      Returns the number of available descriptors in a TX queue.
 */
static inline unsigned int txq_avail(const struct sge_txq *tq)
{
        return tq->size - 1 - tq->in_use;
}

/**
 *      fl_cap - return the capacity of a Free List
 *      @fl: the Free List
 *
 *      Returns the capacity of a Free List.  The capacity is less than the
 *      size because an Egress Queue Index Unit worth of descriptors needs to
 *      be left unpopulated, otherwise the Producer and Consumer indices PIDX
 *      and CIDX will match and the hardware will think the FL is empty.
 */
static inline unsigned int fl_cap(const struct sge_fl *fl)
{
        return fl->size - FL_PER_EQ_UNIT;
}

/**
 *      fl_starving - return whether a Free List is starving.
 *      @adapter: pointer to the adapter
 *      @fl: the Free List
 *
 *      Tests specified Free List to see whether the number of buffers
 *      available to the hardware has falled below our "starvation"
 *      threshold.
 */
static inline bool fl_starving(const struct adapter *adapter,
                               const struct sge_fl *fl)
{
        const struct sge *s = &adapter->sge;

        return fl->avail - fl->pend_cred <= s->fl_starve_thres;
}

/**
 *      map_skb -  map an skb for DMA to the device
 *      @dev: the egress net device
 *      @skb: the packet to map
 *      @addr: a pointer to the base of the DMA mapping array
 *
 *      Map an skb for DMA to the device and return an array of DMA addresses.
 */
static int map_skb(struct device *dev, const struct sk_buff *skb,
                   dma_addr_t *addr)
{
        const skb_frag_t *fp, *end;
        const struct skb_shared_info *si;

        *addr = dma_map_single(dev, skb->data, skb_headlen(skb), DMA_TO_DEVICE);
        if (dma_mapping_error(dev, *addr))
                goto out_err;

        si = skb_shinfo(skb);
        end = &si->frags[si->nr_frags];
        for (fp = si->frags; fp < end; fp++) {
                *++addr = skb_frag_dma_map(dev, fp, 0, skb_frag_size(fp),
                                           DMA_TO_DEVICE);
                if (dma_mapping_error(dev, *addr))
                        goto unwind;
        }
        return 0;

unwind:
        while (fp-- > si->frags)
                dma_unmap_page(dev, *--addr, skb_frag_size(fp), DMA_TO_DEVICE);
        dma_unmap_single(dev, addr[-1], skb_headlen(skb), DMA_TO_DEVICE);

out_err:
        return -ENOMEM;
}

static void unmap_sgl(struct device *dev, const struct sk_buff *skb,
                      const struct ulptx_sgl *sgl, const struct sge_txq *tq)
{
        const struct ulptx_sge_pair *p;
        unsigned int nfrags = skb_shinfo(skb)->nr_frags;

        if (likely(skb_headlen(skb)))
                dma_unmap_single(dev, be64_to_cpu(sgl->addr0),
                                 be32_to_cpu(sgl->len0), DMA_TO_DEVICE);
        else {
                dma_unmap_page(dev, be64_to_cpu(sgl->addr0),
                               be32_to_cpu(sgl->len0), DMA_TO_DEVICE);
                nfrags--;
        }

        /*
         * the complexity below is because of the possibility of a wrap-around
         * in the middle of an SGL
         */
        for (p = sgl->sge; nfrags >= 2; nfrags -= 2) {
                if (likely((u8 *)(p + 1) <= (u8 *)tq->stat)) {
unmap:
                        dma_unmap_page(dev, be64_to_cpu(p->addr[0]),
                                       be32_to_cpu(p->len[0]), DMA_TO_DEVICE);
                        dma_unmap_page(dev, be64_to_cpu(p->addr[1]),
                                       be32_to_cpu(p->len[1]), DMA_TO_DEVICE);
                        p++;
                } else if ((u8 *)p == (u8 *)tq->stat) {
                        p = (const struct ulptx_sge_pair *)tq->desc;
                        goto unmap;
                } else if ((u8 *)p + 8 == (u8 *)tq->stat) {
                        const __be64 *addr = (const __be64 *)tq->desc;

                        dma_unmap_page(dev, be64_to_cpu(addr[0]),
                                       be32_to_cpu(p->len[0]), DMA_TO_DEVICE);
                        dma_unmap_page(dev, be64_to_cpu(addr[1]),
                                       be32_to_cpu(p->len[1]), DMA_TO_DEVICE);
                        p = (const struct ulptx_sge_pair *)&addr[2];
                } else {
                        const __be64 *addr = (const __be64 *)tq->desc;

                        dma_unmap_page(dev, be64_to_cpu(p->addr[0]),
                                       be32_to_cpu(p->len[0]), DMA_TO_DEVICE);
                        dma_unmap_page(dev, be64_to_cpu(addr[0]),
                                       be32_to_cpu(p->len[1]), DMA_TO_DEVICE);
                        p = (const struct ulptx_sge_pair *)&addr[1];
                }
        }
        if (nfrags) {
                __be64 addr;

                if ((u8 *)p == (u8 *)tq->stat)
                        p = (const struct ulptx_sge_pair *)tq->desc;
                addr = ((u8 *)p + 16 <= (u8 *)tq->stat
                        ? p->addr[0]
                        : *(const __be64 *)tq->desc);
                dma_unmap_page(dev, be64_to_cpu(addr), be32_to_cpu(p->len[0]),
                               DMA_TO_DEVICE);
        }
}

/**
 *      free_tx_desc - reclaims TX descriptors and their buffers
 *      @adapter: the adapter
 *      @tq: the TX queue to reclaim descriptors from
 *      @n: the number of descriptors to reclaim
 *      @unmap: whether the buffers should be unmapped for DMA
 *
 *      Reclaims TX descriptors from an SGE TX queue and frees the associated
 *      TX buffers.  Called with the TX queue lock held.
 */
static void free_tx_desc(struct adapter *adapter, struct sge_txq *tq,
                         unsigned int n, bool unmap)
{
        struct tx_sw_desc *sdesc;
        unsigned int cidx = tq->cidx;
        struct device *dev = adapter->pdev_dev;

        const int need_unmap = need_skb_unmap() && unmap;

        sdesc = &tq->sdesc[cidx];
        while (n--) {
                /*
                 * If we kept a reference to the original TX skb, we need to
                 * unmap it from PCI DMA space (if required) and free it.
                 */
                if (sdesc->skb) {
                        if (need_unmap)
                                unmap_sgl(dev, sdesc->skb, sdesc->sgl, tq);
                        dev_consume_skb_any(sdesc->skb);
                        sdesc->skb = NULL;
                }

                sdesc++;
                if (++cidx == tq->size) {
                        cidx = 0;
                        sdesc = tq->sdesc;
                }
        }
        tq->cidx = cidx;
}

/*
 * Return the number of reclaimable descriptors in a TX queue.
 */
static inline int reclaimable(const struct sge_txq *tq)
{
        int hw_cidx = be16_to_cpu(tq->stat->cidx);
        int reclaimable = hw_cidx - tq->cidx;
        if (reclaimable < 0)
                reclaimable += tq->size;
        return reclaimable;
}

/**
 *      reclaim_completed_tx - reclaims completed TX descriptors
 *      @adapter: the adapter
 *      @tq: the TX queue to reclaim completed descriptors from
 *      @unmap: whether the buffers should be unmapped for DMA
 *
 *      Reclaims TX descriptors that the SGE has indicated it has processed,
 *      and frees the associated buffers if possible.  Called with the TX
 *      queue locked.
 */
static inline void reclaim_completed_tx(struct adapter *adapter,
                                        struct sge_txq *tq,
                                        bool unmap)
{
        int avail = reclaimable(tq);

        if (avail) {
                /*
                 * Limit the amount of clean up work we do at a time to keep
                 * the TX lock hold time O(1).
                 */
                if (avail > MAX_TX_RECLAIM)
                        avail = MAX_TX_RECLAIM;

                free_tx_desc(adapter, tq, avail, unmap);
                tq->in_use -= avail;
        }
}

/**
 *      get_buf_size - return the size of an RX Free List buffer.
 *      @adapter: pointer to the associated adapter
 *      @sdesc: pointer to the software buffer descriptor
 */
static inline int get_buf_size(const struct adapter *adapter,
                               const struct rx_sw_desc *sdesc)
{
        const struct sge *s = &adapter->sge;

        return (s->fl_pg_order > 0 && (sdesc->dma_addr & RX_LARGE_BUF)
                ? (PAGE_SIZE << s->fl_pg_order) : PAGE_SIZE);
}

/**
 *      free_rx_bufs - free RX buffers on an SGE Free List
 *      @adapter: the adapter
 *      @fl: the SGE Free List to free buffers from
 *      @n: how many buffers to free
 *
 *      Release the next @n buffers on an SGE Free List RX queue.   The
 *      buffers must be made inaccessible to hardware before calling this
 *      function.
 */
static void free_rx_bufs(struct adapter *adapter, struct sge_fl *fl, int n)
{
        while (n--) {
                struct rx_sw_desc *sdesc = &fl->sdesc[fl->cidx];

                if (is_buf_mapped(sdesc))
                        dma_unmap_page(adapter->pdev_dev, get_buf_addr(sdesc),
                                       get_buf_size(adapter, sdesc),
                                       PCI_DMA_FROMDEVICE);
                put_page(sdesc->page);
                sdesc->page = NULL;
                if (++fl->cidx == fl->size)
                        fl->cidx = 0;
                fl->avail--;
        }
}

/**
 *      unmap_rx_buf - unmap the current RX buffer on an SGE Free List
 *      @adapter: the adapter
 *      @fl: the SGE Free List
 *
 *      Unmap the current buffer on an SGE Free List RX queue.   The
 *      buffer must be made inaccessible to HW before calling this function.
 *
 *      This is similar to @free_rx_bufs above but does not free the buffer.
 *      Do note that the FL still loses any further access to the buffer.
 *      This is used predominantly to "transfer ownership" of an FL buffer
 *      to another entity (typically an skb's fragment list).
 */
static void unmap_rx_buf(struct adapter *adapter, struct sge_fl *fl)
{
        struct rx_sw_desc *sdesc = &fl->sdesc[fl->cidx];

        if (is_buf_mapped(sdesc))
                dma_unmap_page(adapter->pdev_dev, get_buf_addr(sdesc),
                               get_buf_size(adapter, sdesc),
                               PCI_DMA_FROMDEVICE);
        sdesc->page = NULL;
        if (++fl->cidx == fl->size)
                fl->cidx = 0;
        fl->avail--;
}

/**
 *      ring_fl_db - righ doorbell on free list
 *      @adapter: the adapter
 *      @fl: the Free List whose doorbell should be rung ...
 *
 *      Tell the Scatter Gather Engine that there are new free list entries
 *      available.
 */
static inline void ring_fl_db(struct adapter *adapter, struct sge_fl *fl)
{
        u32 val;

        /*
         * The SGE keeps track of its Producer and Consumer Indices in terms
         * of Egress Queue Units so we can only tell it about integral numbers
         * of multiples of Free List Entries per Egress Queue Units ...
         */
        if (fl->pend_cred >= FL_PER_EQ_UNIT) {
                val = PIDX(fl->pend_cred / FL_PER_EQ_UNIT);
                if (!is_t4(adapter->params.chip))
                        val |= DBTYPE(1);
                wmb();
                t4_write_reg(adapter, T4VF_SGE_BASE_ADDR + SGE_VF_KDOORBELL,
                             DBPRIO(1) |
                             QID(fl->cntxt_id) | val);
                fl->pend_cred %= FL_PER_EQ_UNIT;
        }
}

/**
 *      set_rx_sw_desc - initialize software RX buffer descriptor
 *      @sdesc: pointer to the softwore RX buffer descriptor
 *      @page: pointer to the page data structure backing the RX buffer
 *      @dma_addr: PCI DMA address (possibly with low-bit flags)
 */
static inline void set_rx_sw_desc(struct rx_sw_desc *sdesc, struct page *page,
                                  dma_addr_t dma_addr)
{
        sdesc->page = page;
        sdesc->dma_addr = dma_addr;
}

/*
 * Support for poisoning RX buffers ...
 */
#define POISON_BUF_VAL -1

static inline void poison_buf(struct page *page, size_t sz)
{
#if POISON_BUF_VAL >= 0
        memset(page_address(page), POISON_BUF_VAL, sz);
#endif
}

/**
 *      refill_fl - refill an SGE RX buffer ring
 *      @adapter: the adapter
 *      @fl: the Free List ring to refill
 *      @n: the number of new buffers to allocate
 *      @gfp: the gfp flags for the allocations
 *
 *      (Re)populate an SGE free-buffer queue with up to @n new packet buffers,
 *      allocated with the supplied gfp flags.  The caller must assure that
 *      @n does not exceed the queue's capacity -- i.e. (cidx == pidx) _IN
 *      EGRESS QUEUE UNITS_ indicates an empty Free List!  Returns the number
 *      of buffers allocated.  If afterwards the queue is found critically low,
 *      mark it as starving in the bitmap of starving FLs.
 */
static unsigned int refill_fl(struct adapter *adapter, struct sge_fl *fl,
                              int n, gfp_t gfp)
{
        struct sge *s = &adapter->sge;
        struct page *page;
        dma_addr_t dma_addr;
        unsigned int cred = fl->avail;
        __be64 *d = &fl->desc[fl->pidx];
        struct rx_sw_desc *sdesc = &fl->sdesc[fl->pidx];

        /*
         * Sanity: ensure that the result of adding n Free List buffers
         * won't result in wrapping the SGE's Producer Index around to
         * it's Consumer Index thereby indicating an empty Free List ...
         */
        BUG_ON(fl->avail + n > fl->size - FL_PER_EQ_UNIT);

        /*
         * If we support large pages, prefer large buffers and fail over to
         * small pages if we can't allocate large pages to satisfy the refill.
         * If we don't support large pages, drop directly into the small page
         * allocation code.
         */
        if (s->fl_pg_order == 0)
                goto alloc_small_pages;

        while (n) {
                page = alloc_pages(gfp | __GFP_COMP | __GFP_NOWARN,
                                   s->fl_pg_order);
                if (unlikely(!page)) {
                        /*
                         * We've failed inour attempt to allocate a "large
                         * page".  Fail over to the "small page" allocation
                         * below.
                         */
                        fl->large_alloc_failed++;
                        break;
                }
                poison_buf(page, PAGE_SIZE << s->fl_pg_order);

                dma_addr = dma_map_page(adapter->pdev_dev, page, 0,
                                        PAGE_SIZE << s->fl_pg_order,
                                        PCI_DMA_FROMDEVICE);
                if (unlikely(dma_mapping_error(adapter->pdev_dev, dma_addr))) {
                        /*
                         * We've run out of DMA mapping space.  Free up the
                         * buffer and return with what we've managed to put
                         * into the free list.  We don't want to fail over to
                         * the small page allocation below in this case
                         * because DMA mapping resources are typically
                         * critical resources once they become scarse.
                         */
                        __free_pages(page, s->fl_pg_order);
                        goto out;
                }
                dma_addr |= RX_LARGE_BUF;
                *d++ = cpu_to_be64(dma_addr);

                set_rx_sw_desc(sdesc, page, dma_addr);
                sdesc++;

                fl->avail++;
                if (++fl->pidx == fl->size) {
                        fl->pidx = 0;
                        sdesc = fl->sdesc;
                        d = fl->desc;
                }
                n--;
        }

alloc_small_pages:
        while (n--) {
                page = __skb_alloc_page(gfp | __GFP_NOWARN, NULL);
                if (unlikely(!page)) {
                        fl->alloc_failed++;
                        break;
                }
                poison_buf(page, PAGE_SIZE);

                dma_addr = dma_map_page(adapter->pdev_dev, page, 0, PAGE_SIZE,
                                       PCI_DMA_FROMDEVICE);
                if (unlikely(dma_mapping_error(adapter->pdev_dev, dma_addr))) {
                        put_page(page);
                        break;
                }
                *d++ = cpu_to_be64(dma_addr);

                set_rx_sw_desc(sdesc, page, dma_addr);
                sdesc++;

                fl->avail++;
                if (++fl->pidx == fl->size) {
                        fl->pidx = 0;
                        sdesc = fl->sdesc;
                        d = fl->desc;
                }
        }

out:
        /*
         * Update our accounting state to incorporate the new Free List
         * buffers, tell the hardware about them and return the number of
         * buffers which we were able to allocate.
         */
        cred = fl->avail - cred;
        fl->pend_cred += cred;
        ring_fl_db(adapter, fl);

        if (unlikely(fl_starving(adapter, fl))) {
                smp_wmb();
                set_bit(fl->cntxt_id, adapter->sge.starving_fl);
        }

        return cred;
}

/*
 * Refill a Free List to its capacity or the Maximum Refill Increment,
 * whichever is smaller ...
 */
static inline void __refill_fl(struct adapter *adapter, struct sge_fl *fl)
{
        refill_fl(adapter, fl,
                  min((unsigned int)MAX_RX_REFILL, fl_cap(fl) - fl->avail),
                  GFP_ATOMIC);
}

/**
 *      alloc_ring - allocate resources for an SGE descriptor ring
 *      @dev: the PCI device's core device
 *      @nelem: the number of descriptors
 *      @hwsize: the size of each hardware descriptor
 *      @swsize: the size of each software descriptor
 *      @busaddrp: the physical PCI bus address of the allocated ring
 *      @swringp: return address pointer for software ring
 *      @stat_size: extra space in hardware ring for status information
 *
 *      Allocates resources for an SGE descriptor ring, such as TX queues,
 *      free buffer lists, response queues, etc.  Each SGE ring requires
 *      space for its hardware descriptors plus, optionally, space for software
 *      state associated with each hardware entry (the metadata).  The function
 *      returns three values: the virtual address for the hardware ring (the
 *      return value of the function), the PCI bus address of the hardware
 *      ring (in *busaddrp), and the address of the software ring (in swringp).
 *      Both the hardware and software rings are returned zeroed out.
 */
static void *alloc_ring(struct device *dev, size_t nelem, size_t hwsize,
                        size_t swsize, dma_addr_t *busaddrp, void *swringp,
                        size_t stat_size)
{
        /*
         * Allocate the hardware ring and PCI DMA bus address space for said.
         */
        size_t hwlen = nelem * hwsize + stat_size;
        void *hwring = dma_alloc_coherent(dev, hwlen, busaddrp, GFP_KERNEL);

        if (!hwring)
                return NULL;

        /*
         * If the caller wants a software ring, allocate it and return a
         * pointer to it in *swringp.
         */
        BUG_ON((swsize != 0) != (swringp != NULL));
        if (swsize) {
                void *swring = kcalloc(nelem, swsize, GFP_KERNEL);

                if (!swring) {
                        dma_free_coherent(dev, hwlen, hwring, *busaddrp);
                        return NULL;
                }
                *(void **)swringp = swring;
        }

        /*
         * Zero out the hardware ring and return its address as our function
         * value.
         */
        memset(hwring, 0, hwlen);
        return hwring;
}

/**
 *      sgl_len - calculates the size of an SGL of the given capacity
 *      @n: the number of SGL entries
 *
 *      Calculates the number of flits (8-byte units) needed for a Direct
 *      Scatter/Gather List that can hold the given number of entries.
 */
static inline unsigned int sgl_len(unsigned int n)
{
        /*
         * A Direct Scatter Gather List uses 32-bit lengths and 64-bit PCI DMA
         * addresses.  The DSGL Work Request starts off with a 32-bit DSGL
         * ULPTX header, then Length0, then Address0, then, for 1 <= i <= N,
         * repeated sequences of { Length[i], Length[i+1], Address[i],
         * Address[i+1] } (this ensures that all addresses are on 64-bit
         * boundaries).  If N is even, then Length[N+1] should be set to 0 and
         * Address[N+1] is omitted.
         *
         * The following calculation incorporates all of the above.  It's
         * somewhat hard to follow but, briefly: the "+2" accounts for the
         * first two flits which include the DSGL header, Length0 and
         * Address0; the "(3*(n-1))/2" covers the main body of list entries (3
         * flits for every pair of the remaining N) +1 if (n-1) is odd; and
         * finally the "+((n-1)&1)" adds the one remaining flit needed if
         * (n-1) is odd ...
         */
        n--;
        return (3 * n) / 2 + (n & 1) + 2;
}

/**
 *      flits_to_desc - returns the num of TX descriptors for the given flits
 *      @flits: the number of flits
 *
 *      Returns the number of TX descriptors needed for the supplied number
 *      of flits.
 */
static inline unsigned int flits_to_desc(unsigned int flits)
{
        BUG_ON(flits > SGE_MAX_WR_LEN / sizeof(__be64));
        return DIV_ROUND_UP(flits, TXD_PER_EQ_UNIT);
}

/**
 *      is_eth_imm - can an Ethernet packet be sent as immediate data?
 *      @skb: the packet
 *
 *      Returns whether an Ethernet packet is small enough to fit completely as
 *      immediate data.
 */
static inline int is_eth_imm(const struct sk_buff *skb)
{
        /*
         * The VF Driver uses the FW_ETH_TX_PKT_VM_WR firmware Work Request
         * which does not accommodate immediate data.  We could dike out all
         * of the support code for immediate data but that would tie our hands
         * too much if we ever want to enhace the firmware.  It would also
         * create more differences between the PF and VF Drivers.
         */
        return false;
}

/**
 *      calc_tx_flits - calculate the number of flits for a packet TX WR
 *      @skb: the packet
 *
 *      Returns the number of flits needed for a TX Work Request for the
 *      given Ethernet packet, including the needed WR and CPL headers.
 */
static inline unsigned int calc_tx_flits(const struct sk_buff *skb)
{
        unsigned int flits;

        /*
         * If the skb is small enough, we can pump it out as a work request
         * with only immediate data.  In that case we just have to have the
         * TX Packet header plus the skb data in the Work Request.
         */
        if (is_eth_imm(skb))
                return DIV_ROUND_UP(skb->len + sizeof(struct cpl_tx_pkt),
                                    sizeof(__be64));

        /*
         * Otherwise, we're going to have to construct a Scatter gather list
         * of the skb body and fragments.  We also include the flits necessary
         * for the TX Packet Work Request and CPL.  We always have a firmware
         * Write Header (incorporated as part of the cpl_tx_pkt_lso and
         * cpl_tx_pkt structures), followed by either a TX Packet Write CPL
         * message or, if we're doing a Large Send Offload, an LSO CPL message
         * with an embeded TX Packet Write CPL message.
         */
        flits = sgl_len(skb_shinfo(skb)->nr_frags + 1);
        if (skb_shinfo(skb)->gso_size)
                flits += (sizeof(struct fw_eth_tx_pkt_vm_wr) +
                          sizeof(struct cpl_tx_pkt_lso_core) +
                          sizeof(struct cpl_tx_pkt_core)) / sizeof(__be64);
        else
                flits += (sizeof(struct fw_eth_tx_pkt_vm_wr) +
                          sizeof(struct cpl_tx_pkt_core)) / sizeof(__be64);
        return flits;
}

/**
 *      write_sgl - populate a Scatter/Gather List for a packet
 *      @skb: the packet
 *      @tq: the TX queue we are writing into
 *      @sgl: starting location for writing the SGL
 *      @end: points right after the end of the SGL
 *      @start: start offset into skb main-body data to include in the SGL
 *      @addr: the list of DMA bus addresses for the SGL elements
 *
 *      Generates a Scatter/Gather List for the buffers that make up a packet.
 *      The caller must provide adequate space for the SGL that will be written.
 *      The SGL includes all of the packet's page fragments and the data in its
 *      main body except for the first @start bytes.  @pos must be 16-byte
 *      aligned and within a TX descriptor with available space.  @end points
 *      write after the end of the SGL but does not account for any potential
 *      wrap around, i.e., @end > @tq->stat.
 */
static void write_sgl(const struct sk_buff *skb, struct sge_txq *tq,
                      struct ulptx_sgl *sgl, u64 *end, unsigned int start,
                      const dma_addr_t *addr)
{
        unsigned int i, len;
        struct ulptx_sge_pair *to;
        const struct skb_shared_info *si = skb_shinfo(skb);
        unsigned int nfrags = si->nr_frags;
        struct ulptx_sge_pair buf[MAX_SKB_FRAGS / 2 + 1];

        len = skb_headlen(skb) - start;
        if (likely(len)) {
                sgl->len0 = htonl(len);
                sgl->addr0 = cpu_to_be64(addr[0] + start);
                nfrags++;
        } else {
                sgl->len0 = htonl(skb_frag_size(&si->frags[0]));
                sgl->addr0 = cpu_to_be64(addr[1]);
        }

        sgl->cmd_nsge = htonl(ULPTX_CMD(ULP_TX_SC_DSGL) |
                              ULPTX_NSGE(nfrags));
        if (likely(--nfrags == 0))
                return;
        /*
         * Most of the complexity below deals with the possibility we hit the
         * end of the queue in the middle of writing the SGL.  For this case
         * only we create the SGL in a temporary buffer and then copy it.
         */
        to = (u8 *)end > (u8 *)tq->stat ? buf : sgl->sge;

        for (i = (nfrags != si->nr_frags); nfrags >= 2; nfrags -= 2, to++) {
                to->len[0] = cpu_to_be32(skb_frag_size(&si->frags[i]));
                to->len[1] = cpu_to_be32(skb_frag_size(&si->frags[++i]));
                to->addr[0] = cpu_to_be64(addr[i]);
                to->addr[1] = cpu_to_be64(addr[++i]);
        }
        if (nfrags) {
                to->len[0] = cpu_to_be32(skb_frag_size(&si->frags[i]));
                to->len[1] = cpu_to_be32(0);
                to->addr[0] = cpu_to_be64(addr[i + 1]);
        }
        if (unlikely((u8 *)end > (u8 *)tq->stat)) {
                unsigned int part0 = (u8 *)tq->stat - (u8 *)sgl->sge, part1;

                if (likely(part0))
                        memcpy(sgl->sge, buf, part0);
                part1 = (u8 *)end - (u8 *)tq->stat;
                memcpy(tq->desc, (u8 *)buf + part0, part1);
                end = (void *)tq->desc + part1;
        }
        if ((uintptr_t)end & 8)           /* 0-pad to multiple of 16 */
                *end = 0;
}

/**
 *      check_ring_tx_db - check and potentially ring a TX queue's doorbell
 *      @adapter: the adapter
 *      @tq: the TX queue
 *      @n: number of new descriptors to give to HW
 *
 *      Ring the doorbel for a TX queue.
 */
static inline void ring_tx_db(struct adapter *adapter, struct sge_txq *tq,
                              int n)
{
        /*
         * Warn if we write doorbells with the wrong priority and write
         * descriptors before telling HW.
         */
        WARN_ON((QID(tq->cntxt_id) | PIDX(n)) & DBPRIO(1));
        wmb();
        t4_write_reg(adapter, T4VF_SGE_BASE_ADDR + SGE_VF_KDOORBELL,
                     QID(tq->cntxt_id) | PIDX(n));
}

/**
 *      inline_tx_skb - inline a packet's data into TX descriptors
 *      @skb: the packet
 *      @tq: the TX queue where the packet will be inlined
 *      @pos: starting position in the TX queue to inline the packet
 *
 *      Inline a packet's contents directly into TX descriptors, starting at
 *      the given position within the TX DMA ring.
 *      Most of the complexity of this operation is dealing with wrap arounds
 *      in the middle of the packet we want to inline.
 */
static void inline_tx_skb(const struct sk_buff *skb, const struct sge_txq *tq,
                          void *pos)
{
        u64 *p;
        int left = (void *)tq->stat - pos;

        if (likely(skb->len <= left)) {
                if (likely(!skb->data_len))
                        skb_copy_from_linear_data(skb, pos, skb->len);
                else
                        skb_copy_bits(skb, 0, pos, skb->len);
                pos += skb->len;
        } else {
                skb_copy_bits(skb, 0, pos, left);
                skb_copy_bits(skb, left, tq->desc, skb->len - left);
                pos = (void *)tq->desc + (skb->len - left);
        }

        /* 0-pad to multiple of 16 */
        p = PTR_ALIGN(pos, 8);
        if ((uintptr_t)p & 8)
                *p = 0;
}

/*
 * Figure out what HW csum a packet wants and return the appropriate control
 * bits.
 */
static u64 hwcsum(const struct sk_buff *skb)
{
        int csum_type;
        const struct iphdr *iph = ip_hdr(skb);

        if (iph->version == 4) {
                if (iph->protocol == IPPROTO_TCP)
                        csum_type = TX_CSUM_TCPIP;
                else if (iph->protocol == IPPROTO_UDP)
                        csum_type = TX_CSUM_UDPIP;
                else {
nocsum:
                        /*
                         * unknown protocol, disable HW csum
                         * and hope a bad packet is detected
                         */
                        return TXPKT_L4CSUM_DIS;
                }
        } else {
                /*
                 * this doesn't work with extension headers
                 */
                const struct ipv6hdr *ip6h = (const struct ipv6hdr *)iph;

                if (ip6h->nexthdr == IPPROTO_TCP)
                        csum_type = TX_CSUM_TCPIP6;
                else if (ip6h->nexthdr == IPPROTO_UDP)
                        csum_type = TX_CSUM_UDPIP6;
                else
                        goto nocsum;
        }

        if (likely(csum_type >= TX_CSUM_TCPIP))
                return TXPKT_CSUM_TYPE(csum_type) |
                        TXPKT_IPHDR_LEN(skb_network_header_len(skb)) |
                        TXPKT_ETHHDR_LEN(skb_network_offset(skb) - ETH_HLEN);
        else {
                int start = skb_transport_offset(skb);

                return TXPKT_CSUM_TYPE(csum_type) |
                        TXPKT_CSUM_START(start) |
                        TXPKT_CSUM_LOC(start + skb->csum_offset);
        }
}

/*
 * Stop an Ethernet TX queue and record that state change.
 */
static void txq_stop(struct sge_eth_txq *txq)
{
        netif_tx_stop_queue(txq->txq);
        txq->q.stops++;
}

/*
 * Advance our software state for a TX queue by adding n in use descriptors.
 */
static inline void txq_advance(struct sge_txq *tq, unsigned int n)
{
        tq->in_use += n;
        tq->pidx += n;
        if (tq->pidx >= tq->size)
                tq->pidx -= tq->size;
}

/**
 *      t4vf_eth_xmit - add a packet to an Ethernet TX queue
 *      @skb: the packet
 *      @dev: the egress net device
 *
 *      Add a packet to an SGE Ethernet TX queue.  Runs with softirqs disabled.
 */
int t4vf_eth_xmit(struct sk_buff *skb, struct net_device *dev)
{
        u32 wr_mid;
        u64 cntrl, *end;
        int qidx, credits;
        unsigned int flits, ndesc;
        struct adapter *adapter;
        struct sge_eth_txq *txq;
        const struct port_info *pi;
        struct fw_eth_tx_pkt_vm_wr *wr;
        struct cpl_tx_pkt_core *cpl;
        const struct skb_shared_info *ssi;
        dma_addr_t addr[MAX_SKB_FRAGS + 1];
        const size_t fw_hdr_copy_len = (sizeof(wr->ethmacdst) +
                                        sizeof(wr->ethmacsrc) +
                                        sizeof(wr->ethtype) +
                                        sizeof(wr->vlantci));

        /*
         * The chip minimum packet length is 10 octets but the firmware
         * command that we are using requires that we copy the Ethernet header
         * (including the VLAN tag) into the header so we reject anything
         * smaller than that ...
         */
        if (unlikely(skb->len < fw_hdr_copy_len))
                goto out_free;

        /*
         * Figure out which TX Queue we're going to use.
         */
        pi = netdev_priv(dev);
        adapter = pi->adapter;
        qidx = skb_get_queue_mapping(skb);
        BUG_ON(qidx >= pi->nqsets);
        txq = &adapter->sge.ethtxq[pi->first_qset + qidx];

        /*
         * Take this opportunity to reclaim any TX Descriptors whose DMA
         * transfers have completed.
         */
        reclaim_completed_tx(adapter, &txq->q, true);

        /*
         * Calculate the number of flits and TX Descriptors we're going to
         * need along with how many TX Descriptors will be left over after
         * we inject our Work Request.
         */
        flits = calc_tx_flits(skb);
        ndesc = flits_to_desc(flits);
        credits = txq_avail(&txq->q) - ndesc;

        if (unlikely(credits < 0)) {
                /*
                 * Not enough room for this packet's Work Request.  Stop the
                 * TX Queue and return a "busy" condition.  The queue will get
                 * started later on when the firmware informs us that space
                 * has opened up.
                 */
                txq_stop(txq);
                dev_err(adapter->pdev_dev,
                        "%s: TX ring %u full while queue awake!\n",
                        dev->name, qidx);
                return NETDEV_TX_BUSY;
        }

        if (!is_eth_imm(skb) &&
            unlikely(map_skb(adapter->pdev_dev, skb, addr) < 0)) {
                /*
                 * We need to map the skb into PCI DMA space (because it can't
                 * be in-lined directly into the Work Request) and the mapping
                 * operation failed.  Record the error and drop the packet.
                 */
                txq->mapping_err++;
                goto out_free;
        }

        wr_mid = FW_WR_LEN16(DIV_ROUND_UP(flits, 2));
        if (unlikely(credits < ETHTXQ_STOP_THRES)) {
                /*
                 * After we're done injecting the Work Request for this
                 * packet, we'll be below our "stop threshold" so stop the TX
                 * Queue now and schedule a request for an SGE Egress Queue
                 * Update message.  The queue will get started later on when
                 * the firmware processes this Work Request and sends us an
                 * Egress Queue Status Update message indicating that space
                 * has opened up.
                 */
                txq_stop(txq);
                wr_mid |= FW_WR_EQUEQ | FW_WR_EQUIQ;
        }

        /*
         * Start filling in our Work Request.  Note that we do _not_ handle
         * the WR Header wrapping around the TX Descriptor Ring.  If our
         * maximum header size ever exceeds one TX Descriptor, we'll need to
         * do something else here.
         */
        BUG_ON(DIV_ROUND_UP(ETHTXQ_MAX_HDR, TXD_PER_EQ_UNIT) > 1);
        wr = (void *)&txq->q.desc[txq->q.pidx];
        wr->equiq_to_len16 = cpu_to_be32(wr_mid);
        wr->r3[0] = cpu_to_be64(0);
        wr->r3[1] = cpu_to_be64(0);
        skb_copy_from_linear_data(skb, (void *)wr->ethmacdst, fw_hdr_copy_len);
        end = (u64 *)wr + flits;

        /*
         * If this is a Large Send Offload packet we'll put in an LSO CPL
         * message with an encapsulated TX Packet CPL message.  Otherwise we
         * just use a TX Packet CPL message.
         */
        ssi = skb_shinfo(skb);
        if (ssi->gso_size) {
                struct cpl_tx_pkt_lso_core *lso = (void *)(wr + 1);
                bool v6 = (ssi->gso_type & SKB_GSO_TCPV6) != 0;
                int l3hdr_len = skb_network_header_len(skb);
                int eth_xtra_len = skb_network_offset(skb) - ETH_HLEN;

                wr->op_immdlen =
                        cpu_to_be32(FW_WR_OP(FW_ETH_TX_PKT_VM_WR) |
                                    FW_WR_IMMDLEN(sizeof(*lso) +
                                                  sizeof(*cpl)));
                /*
                 * Fill in the LSO CPL message.
                 */
                lso->lso_ctrl =
                        cpu_to_be32(LSO_OPCODE(CPL_TX_PKT_LSO) |
                                    LSO_FIRST_SLICE |
                                    LSO_LAST_SLICE |
                                    LSO_IPV6(v6) |
                                    LSO_ETHHDR_LEN(eth_xtra_len/4) |
                                    LSO_IPHDR_LEN(l3hdr_len/4) |
                                    LSO_TCPHDR_LEN(tcp_hdr(skb)->doff));
                lso->ipid_ofst = cpu_to_be16(0);
                lso->mss = cpu_to_be16(ssi->gso_size);
                lso->seqno_offset = cpu_to_be32(0);
                if (is_t4(adapter->params.chip))
                        lso->len = cpu_to_be32(skb->len);
                else
                        lso->len = cpu_to_be32(LSO_T5_XFER_SIZE(skb->len));

                /*
                 * Set up TX Packet CPL pointer, control word and perform
                 * accounting.
                 */
                cpl = (void *)(lso + 1);
                cntrl = (TXPKT_CSUM_TYPE(v6 ? TX_CSUM_TCPIP6 : TX_CSUM_TCPIP) |
                         TXPKT_IPHDR_LEN(l3hdr_len) |
                         TXPKT_ETHHDR_LEN(eth_xtra_len));
                txq->tso++;
                txq->tx_cso += ssi->gso_segs;
        } else {
                int len;

                len = is_eth_imm(skb) ? skb->len + sizeof(*cpl) : sizeof(*cpl);
                wr->op_immdlen =
                        cpu_to_be32(FW_WR_OP(FW_ETH_TX_PKT_VM_WR) |
                                    FW_WR_IMMDLEN(len));

                /*
                 * Set up TX Packet CPL pointer, control word and perform
                 * accounting.
                 */
                cpl = (void *)(wr + 1);
                if (skb->ip_summed == CHECKSUM_PARTIAL) {
                        cntrl = hwcsum(skb) | TXPKT_IPCSUM_DIS;
                        txq->tx_cso++;
                } else
                        cntrl = TXPKT_L4CSUM_DIS | TXPKT_IPCSUM_DIS;
        }

        /*
         * If there's a VLAN tag present, add that to the list of things to
         * do in this Work Request.
         */
        if (vlan_tx_tag_present(skb)) {
                txq->vlan_ins++;
                cntrl |= TXPKT_VLAN_VLD | TXPKT_VLAN(vlan_tx_tag_get(skb));
        }

        /*
         * Fill in the TX Packet CPL message header.
         */
        cpl->ctrl0 = cpu_to_be32(TXPKT_OPCODE(CPL_TX_PKT_XT) |
                                 TXPKT_INTF(pi->port_id) |
                                 TXPKT_PF(0));
        cpl->pack = cpu_to_be16(0);
        cpl->len = cpu_to_be16(skb->len);
        cpl->ctrl1 = cpu_to_be64(cntrl);

#ifdef T4_TRACE
        T4_TRACE5(adapter->tb[txq->q.cntxt_id & 7],
                  "eth_xmit: ndesc %u, credits %u, pidx %u, len %u, frags %u",
                  ndesc, credits, txq->q.pidx, skb->len, ssi->nr_frags);
#endif

        /*
         * Fill in the body of the TX Packet CPL message with either in-lined
         * data or a Scatter/Gather List.
         */
        if (is_eth_imm(skb)) {
                /*
                 * In-line the packet's data and free the skb since we don't
                 * need it any longer.
                 */
                inline_tx_skb(skb, &txq->q, cpl + 1);
                dev_consume_skb_any(skb);
        } else {
                /*
                 * Write the skb's Scatter/Gather list into the TX Packet CPL
                 * message and retain a pointer to the skb so we can free it
                 * later when its DMA completes.  (We store the skb pointer
                 * in the Software Descriptor corresponding to the last TX
                 * Descriptor used by the Work Request.)
                 *
                 * The retained skb will be freed when the corresponding TX
                 * Descriptors are reclaimed after their DMAs complete.
                 * However, this could take quite a while since, in general,
                 * the hardware is set up to be lazy about sending DMA
                 * completion notifications to us and we mostly perform TX
                 * reclaims in the transmit routine.
                 *
                 * This is good for performamce but means that we rely on new
                 * TX packets arriving to run the destructors of completed
                 * packets, which open up space in their sockets' send queues.
                 * Sometimes we do not get such new packets causing TX to
                 * stall.  A single UDP transmitter is a good example of this
                 * situation.  We have a clean up timer that periodically
                 * reclaims completed packets but it doesn't run often enough
                 * (nor do we want it to) to prevent lengthy stalls.  A
                 * solution to this problem is to run the destructor early,
                 * after the packet is queued but before it's DMAd.  A con is
                 * that we lie to socket memory accounting, but the amount of
                 * extra memory is reasonable (limited by the number of TX
                 * descriptors), the packets do actually get freed quickly by
                 * new packets almost always, and for protocols like TCP that
                 * wait for acks to really free up the data the extra memory
                 * is even less.  On the positive side we run the destructors
                 * on the sending CPU rather than on a potentially different
                 * completing CPU, usually a good thing.
                 *
                 * Run the destructor before telling the DMA engine about the
                 * packet to make sure it doesn't complete and get freed
                 * prematurely.
                 */
                struct ulptx_sgl *sgl = (struct ulptx_sgl *)(cpl + 1);
                struct sge_txq *tq = &txq->q;
                int last_desc;

                /*
                 * If the Work Request header was an exact multiple of our TX
                 * Descriptor length, then it's possible that the starting SGL
                 * pointer lines up exactly with the end of our TX Descriptor
                 * ring.  If that's the case, wrap around to the beginning
                 * here ...
                 */
                if (unlikely((void *)sgl == (void *)tq->stat)) {
                        sgl = (void *)tq->desc;
                        end = ((void *)tq->desc + ((void *)end - (void *)tq->stat));
                }

                write_sgl(skb, tq, sgl, end, 0, addr);
                skb_orphan(skb);

                last_desc = tq->pidx + ndesc - 1;
                if (last_desc >= tq->size)
                        last_desc -= tq->size;
                tq->sdesc[last_desc].skb = skb;
                tq->sdesc[last_desc].sgl = sgl;
        }

        /*
         * Advance our internal TX Queue state, tell the hardware about
         * the new TX descriptors and return success.
         */
        txq_advance(&txq->q, ndesc);
        dev->trans_start = jiffies;
        ring_tx_db(adapter, &txq->q, ndesc);
        return NETDEV_TX_OK;

out_free:
        /*
         * An error of some sort happened.  Free the TX skb and tell the
         * OS that we've "dealt" with the packet ...
         */
        dev_kfree_skb_any(skb);
        return NETDEV_TX_OK;
}

/**
 *      copy_frags - copy fragments from gather list into skb_shared_info
 *      @skb: destination skb
 *      @gl: source internal packet gather list
 *      @offset: packet start offset in first page
 *
 *      Copy an internal packet gather list into a Linux skb_shared_info
 *      structure.
 */
static inline void copy_frags(struct sk_buff *skb,
                              const struct pkt_gl *gl,
                              unsigned int offset)
{
        int i;

        /* usually there's just one frag */
        __skb_fill_page_desc(skb, 0, gl->frags[0].page,
                             gl->frags[0].offset + offset,
                             gl->frags[0].size - offset);
        skb_shinfo(skb)->nr_frags = gl->nfrags;
        for (i = 1; i < gl->nfrags; i++)
                __skb_fill_page_desc(skb, i, gl->frags[i].page,
                                     gl->frags[i].offset,
                                     gl->frags[i].size);

        /* get a reference to the last page, we don't own it */
        get_page(gl->frags[gl->nfrags - 1].page);
}

/**
 *      t4vf_pktgl_to_skb - build an sk_buff from a packet gather list
 *      @gl: the gather list
 *      @skb_len: size of sk_buff main body if it carries fragments
 *      @pull_len: amount of data to move to the sk_buff's main body
 *
 *      Builds an sk_buff from the given packet gather list.  Returns the
 *      sk_buff or %NULL if sk_buff allocation failed.
 */
static struct sk_buff *t4vf_pktgl_to_skb(const struct pkt_gl *gl,
                                         unsigned int skb_len,
                                         unsigned int pull_len)
{
        struct sk_buff *skb;

        /*
         * If the ingress packet is small enough, allocate an skb large enough
         * for all of the data and copy it inline.  Otherwise, allocate an skb
         * with enough room to pull in the header and reference the rest of
         * the data via the skb fragment list.
         *
         * Below we rely on RX_COPY_THRES being less than the smallest Rx
         * buff!  size, which is expected since buffers are at least
         * PAGE_SIZEd.  In this case packets up to RX_COPY_THRES have only one
         * fragment.
         */
        if (gl->tot_len <= RX_COPY_THRES) {
                /* small packets have only one fragment */
                skb = alloc_skb(gl->tot_len, GFP_ATOMIC);
                if (unlikely(!skb))
                        goto out;
                __skb_put(skb, gl->tot_len);
                skb_copy_to_linear_data(skb, gl->va, gl->tot_len);
        } else {
                skb = alloc_skb(skb_len, GFP_ATOMIC);
                if (unlikely(!skb))
                        goto out;
                __skb_put(skb, pull_len);
                skb_copy_to_linear_data(skb, gl->va, pull_len);

                copy_frags(skb, gl, pull_len);
                skb->len = gl->tot_len;
                skb->data_len = skb->len - pull_len;
                skb->truesize += skb->data_len;
        }

out:
        return skb;
}

/**
 *      t4vf_pktgl_free - free a packet gather list
 *      @gl: the gather list
 *
 *      Releases the pages of a packet gather list.  We do not own the last
 *      page on the list and do not free it.
 */
static void t4vf_pktgl_free(const struct pkt_gl *gl)
{
        int frag;

        frag = gl->nfrags - 1;
        while (frag--)
                put_page(gl->frags[frag].page);
}

/**
 *      do_gro - perform Generic Receive Offload ingress packet processing
 *      @rxq: ingress RX Ethernet Queue
 *      @gl: gather list for ingress packet
 *      @pkt: CPL header for last packet fragment
 *
 *      Perform Generic Receive Offload (GRO) ingress packet processing.
 *      We use the standard Linux GRO interfaces for this.
 */
static void do_gro(struct sge_eth_rxq *rxq, const struct pkt_gl *gl,
                   const struct cpl_rx_pkt *pkt)
{
        struct adapter *adapter = rxq->rspq.adapter;
        struct sge *s = &adapter->sge;
        int ret;
        struct sk_buff *skb;

        skb = napi_get_frags(&rxq->rspq.napi);
        if (unlikely(!skb)) {
                t4vf_pktgl_free(gl);
                rxq->stats.rx_drops++;
                return;
        }

        copy_frags(skb, gl, s->pktshift);
        skb->len = gl->tot_len - s->pktshift;
        skb->data_len = skb->len;
        skb->truesize += skb->data_len;
        skb->ip_summed = CHECKSUM_UNNECESSARY;
        skb_record_rx_queue(skb, rxq->rspq.idx);

        if (pkt->vlan_ex) {
                __vlan_hwaccel_put_tag(skb, cpu_to_be16(ETH_P_8021Q),
                                        be16_to_cpu(pkt->vlan));
                rxq->stats.vlan_ex++;
        }
        ret = napi_gro_frags(&rxq->rspq.napi);

        if (ret == GRO_HELD)
                rxq->stats.lro_pkts++;
        else if (ret == GRO_MERGED || ret == GRO_MERGED_FREE)
                rxq->stats.lro_merged++;
        rxq->stats.pkts++;
        rxq->stats.rx_cso++;
}

/**
 *      t4vf_ethrx_handler - process an ingress ethernet packet
 *      @rspq: the response queue that received the packet
 *      @rsp: the response queue descriptor holding the RX_PKT message
 *      @gl: the gather list of packet fragments
 *
 *      Process an ingress ethernet packet and deliver it to the stack.
 */
int t4vf_ethrx_handler(struct sge_rspq *rspq, const __be64 *rsp,
                       const struct pkt_gl *gl)
{
        struct sk_buff *skb;
        const struct cpl_rx_pkt *pkt = (void *)rsp;
        bool csum_ok = pkt->csum_calc && !pkt->err_vec &&
                       (rspq->netdev->features & NETIF_F_RXCSUM);
        struct sge_eth_rxq *rxq = container_of(rspq, struct sge_eth_rxq, rspq);
        struct adapter *adapter = rspq->adapter;
        struct sge *s = &adapter->sge;

        /*
         * If this is a good TCP packet and we have Generic Receive Offload
         * enabled, handle the packet in the GRO path.
         */
        if ((pkt->l2info & cpu_to_be32(RXF_TCP)) &&
            (rspq->netdev->features & NETIF_F_GRO) && csum_ok &&
            !pkt->ip_frag) {
                do_gro(rxq, gl, pkt);
                return 0;
        }

        /*
         * Convert the Packet Gather List into an skb.
         */
        skb = t4vf_pktgl_to_skb(gl, RX_SKB_LEN, RX_PULL_LEN);
        if (unlikely(!skb)) {
                t4vf_pktgl_free(gl);
                rxq->stats.rx_drops++;
                return 0;
        }
        __skb_pull(skb, s->pktshift);
        skb->protocol = eth_type_trans(skb, rspq->netdev);
        skb_record_rx_queue(skb, rspq->idx);
        rxq->stats.pkts++;

        if (csum_ok && !pkt->err_vec &&
            (be32_to_cpu(pkt->l2info) & (RXF_UDP|RXF_TCP))) {
                if (!pkt->ip_frag)
                        skb->ip_summed = CHECKSUM_UNNECESSARY;
                else {
                        __sum16 c = (__force __sum16)pkt->csum;
                        skb->csum = csum_unfold(c);
                        skb->ip_summed = CHECKSUM_COMPLETE;
                }
                rxq->stats.rx_cso++;
        } else
                skb_checksum_none_assert(skb);

        if (pkt->vlan_ex) {
                rxq->stats.vlan_ex++;
                __vlan_hwaccel_put_tag(skb, htons(ETH_P_8021Q), be16_to_cpu(pkt->vlan));
        }

        netif_receive_skb(skb);

        return 0;
}

/**
 *      is_new_response - check if a response is newly written
 *      @rc: the response control descriptor
 *      @rspq: the response queue
 *
 *      Returns true if a response descriptor contains a yet unprocessed
 *      response.
 */
static inline bool is_new_response(const struct rsp_ctrl *rc,
                                   const struct sge_rspq *rspq)
{
        return RSPD_GEN(rc->type_gen) == rspq->gen;
}

/**
 *      restore_rx_bufs - put back a packet's RX buffers
 *      @gl: the packet gather list
 *      @fl: the SGE Free List
 *      @nfrags: how many fragments in @si
 *
 *      Called when we find out that the current packet, @si, can't be
 *      processed right away for some reason.  This is a very rare event and
 *      there's no effort to make this suspension/resumption process
 *      particularly efficient.
 *
 *      We implement the suspension by putting all of the RX buffers associated
 *      with the current packet back on the original Free List.  The buffers
 *      have already been unmapped and are left unmapped, we mark them as
 *      unmapped in order to prevent further unmapping attempts.  (Effectively
 *      this function undoes the series of @unmap_rx_buf calls which were done
 *      to create the current packet's gather list.)  This leaves us ready to
 *      restart processing of the packet the next time we start processing the
 *      RX Queue ...
 */
static void restore_rx_bufs(const struct pkt_gl *gl, struct sge_fl *fl,
                            int frags)
{
        struct rx_sw_desc *sdesc;

        while (frags--) {
                if (fl->cidx == 0)
                        fl->cidx = fl->size - 1;
                else
                        fl->cidx--;
                sdesc = &fl->sdesc[fl->cidx];
                sdesc->page = gl->frags[frags].page;
                sdesc->dma_addr |= RX_UNMAPPED_BUF;
                fl->avail++;
        }
}

/**
 *      rspq_next - advance to the next entry in a response queue
 *      @rspq: the queue
 *
 *      Updates the state of a response queue to advance it to the next entry.
 */
static inline void rspq_next(struct sge_rspq *rspq)
{
        rspq->cur_desc = (void *)rspq->cur_desc + rspq->iqe_len;
        if (unlikely(++rspq->cidx == rspq->size)) {
                rspq->cidx = 0;
                rspq->gen ^= 1;
                rspq->cur_desc = rspq->desc;
        }
}

/**
 *      process_responses - process responses from an SGE response queue
 *      @rspq: the ingress response queue to process
 *      @budget: how many responses can be processed in this round
 *
 *      Process responses from a Scatter Gather Engine response queue up to
 *      the supplied budget.  Responses include received packets as well as
 *      control messages from firmware or hardware.
 *
 *      Additionally choose the interrupt holdoff time for the next interrupt
 *      on this queue.  If the system is under memory shortage use a fairly
 *      long delay to help recovery.
 */
static int process_responses(struct sge_rspq *rspq, int budget)
{
        struct sge_eth_rxq *rxq = container_of(rspq, struct sge_eth_rxq, rspq);
        struct adapter *adapter = rspq->adapter;
        struct sge *s = &adapter->sge;
        int budget_left = budget;

        while (likely(budget_left)) {
                int ret, rsp_type;
                const struct rsp_ctrl *rc;

                rc = (void *)rspq->cur_desc + (rspq->iqe_len - sizeof(*rc));
                if (!is_new_response(rc, rspq))
                        break;

                /*
                 * Figure out what kind of response we've received from the
                 * SGE.
                 */
                rmb();
                rsp_type = RSPD_TYPE(rc->type_gen);
                if (likely(rsp_type == RSP_TYPE_FLBUF)) {
                        struct page_frag *fp;
                        struct pkt_gl gl;
                        const struct rx_sw_desc *sdesc;
                        u32 bufsz, frag;
                        u32 len = be32_to_cpu(rc->pldbuflen_qid);

                        /*
                         * If we get a "new buffer" message from the SGE we
                         * need to move on to the next Free List buffer.
                         */
                        if (len & RSPD_NEWBUF) {
                                /*
                                 * We get one "new buffer" message when we
                                 * first start up a queue so we need to ignore
                                 * it when our offset into the buffer is 0.
                                 */
                                if (likely(rspq->offset > 0)) {
                                        free_rx_bufs(rspq->adapter, &rxq->fl,
                                                     1);
                                        rspq->offset = 0;
                                }
                                len = RSPD_LEN(len);
                        }
                        gl.tot_len = len;

                        /*
                         * Gather packet fragments.
                         */
                        for (frag = 0, fp = gl.frags; /**/; frag++, fp++) {
                                BUG_ON(frag >= MAX_SKB_FRAGS);
                                BUG_ON(rxq->fl.avail == 0);
                                sdesc = &rxq->fl.sdesc[rxq->fl.cidx];
                                bufsz = get_buf_size(adapter, sdesc);
                                fp->page = sdesc->page;
                                fp->offset = rspq->offset;
                                fp->size = min(bufsz, len);
                                len -= fp->size;
                                if (!len)
                                        break;
                                unmap_rx_buf(rspq->adapter, &rxq->fl);
                        }
                        gl.nfrags = frag+1;

                        /*
                         * Last buffer remains mapped so explicitly make it
                         * coherent for CPU access and start preloading first
                         * cache line ...
                         */
                        dma_sync_single_for_cpu(rspq->adapter->pdev_dev,
                                                get_buf_addr(sdesc),
                                                fp->size, DMA_FROM_DEVICE);
                        gl.va = (page_address(gl.frags[0].page) +
                                 gl.frags[0].offset);
                        prefetch(gl.va);

                        /*
                         * Hand the new ingress packet to the handler for
                         * this Response Queue.
                         */
                        ret = rspq->handler(rspq, rspq->cur_desc, &gl);
                        if (likely(ret == 0))
                                rspq->offset += ALIGN(fp->size, s->fl_align);
                        else
                                restore_rx_bufs(&gl, &rxq->fl, frag);
                } else if (likely(rsp_type == RSP_TYPE_CPL)) {
                        ret = rspq->handler(rspq, rspq->cur_desc, NULL);
                } else {
                        WARN_ON(rsp_type > RSP_TYPE_CPL);
                        ret = 0;
                }

                if (unlikely(ret)) {
                        /*
                         * Couldn't process descriptor, back off for recovery.
                         * We use the SGE's last timer which has the longest
                         * interrupt coalescing value ...
                         */
                        const int NOMEM_TIMER_IDX = SGE_NTIMERS-1;
                        rspq->next_intr_params =
                                QINTR_TIMER_IDX(NOMEM_TIMER_IDX);
                        break;
                }

                rspq_next(rspq);
                budget_left--;
        }

        /*
         * If this is a Response Queue with an associated Free List and
         * at least two Egress Queue units available in the Free List
         * for new buffer pointers, refill the Free List.
         */
        if (rspq->offset >= 0 &&
            rxq->fl.size - rxq->fl.avail >= 2*FL_PER_EQ_UNIT)
                __refill_fl(rspq->adapter, &rxq->fl);
        return budget - budget_left;
}

/**
 *      napi_rx_handler - the NAPI handler for RX processing
 *      @napi: the napi instance
 *      @budget: how many packets we can process in this round
 *
 *      Handler for new data events when using NAPI.  This does not need any
 *      locking or protection from interrupts as data interrupts are off at
 *      this point and other adapter interrupts do not interfere (the latter
 *      in not a concern at all with MSI-X as non-data interrupts then have
 *      a separate handler).
 */
static int napi_rx_handler(struct napi_struct *napi, int budget)
{
        unsigned int intr_params;
        struct sge_rspq *rspq = container_of(napi, struct sge_rspq, napi);
        int work_done = process_responses(rspq, budget);

        if (likely(work_done < budget)) {
                napi_complete(napi);
                intr_params = rspq->next_intr_params;
                rspq->next_intr_params = rspq->intr_params;
        } else
                intr_params = QINTR_TIMER_IDX(SGE_TIMER_UPD_CIDX);

        if (unlikely(work_done == 0))
                rspq->unhandled_irqs++;

        t4_write_reg(rspq->adapter,
                     T4VF_SGE_BASE_ADDR + SGE_VF_GTS,
                     CIDXINC(work_done) |
                     INGRESSQID((u32)rspq->cntxt_id) |
                     SEINTARM(intr_params));
        return work_done;
}

/*
 * The MSI-X interrupt handler for an SGE response queue for the NAPI case
 * (i.e., response queue serviced by NAPI polling).
 */
irqreturn_t t4vf_sge_intr_msix(int irq, void *cookie)
{
        struct sge_rspq *rspq = cookie;

        napi_schedule(&rspq->napi);
        return IRQ_HANDLED;
}

/*
 * Process the indirect interrupt entries in the interrupt queue and kick off
 * NAPI for each queue that has generated an entry.
 */
static unsigned int process_intrq(struct adapter *adapter)
{
        struct sge *s = &adapter->sge;
        struct sge_rspq *intrq = &s->intrq;
        unsigned int work_done;

        spin_lock(&adapter->sge.intrq_lock);
        for (work_done = 0; ; work_done++) {
                const struct rsp_ctrl *rc;
                unsigned int qid, iq_idx;
                struct sge_rspq *rspq;

                /*
                 * Grab the next response from the interrupt queue and bail
                 * out if it's not a new response.
                 */
                rc = (void *)intrq->cur_desc + (intrq->iqe_len - sizeof(*rc));
                if (!is_new_response(rc, intrq))
                        break;

                /*
                 * If the response isn't a forwarded interrupt message issue a
                 * error and go on to the next response message.  This should
                 * never happen ...
                 */
                rmb();
                if (unlikely(RSPD_TYPE(rc->type_gen) != RSP_TYPE_INTR)) {
                        dev_err(adapter->pdev_dev,
                                "Unexpected INTRQ response type %d\n",
                                RSPD_TYPE(rc->type_gen));
                        continue;
                }

                /*
                 * Extract the Queue ID from the interrupt message and perform
                 * sanity checking to make sure it really refers to one of our
                 * Ingress Queues which is active and matches the queue's ID.
                 * None of these error conditions should ever happen so we may
                 * want to either make them fatal and/or conditionalized under
                 * DEBUG.
                 */
                qid = RSPD_QID(be32_to_cpu(rc->pldbuflen_qid));
                iq_idx = IQ_IDX(s, qid);
                if (unlikely(iq_idx >= MAX_INGQ)) {
                        dev_err(adapter->pdev_dev,
                                "Ingress QID %d out of range\n", qid);
                        continue;
                }
                rspq = s->ingr_map[iq_idx];
                if (unlikely(rspq == NULL)) {
                        dev_err(adapter->pdev_dev,
                                "Ingress QID %d RSPQ=NULL\n", qid);
                        continue;
                }
                if (unlikely(rspq->abs_id != qid)) {
                        dev_err(adapter->pdev_dev,
                                "Ingress QID %d refers to RSPQ %d\n",
                                qid, rspq->abs_id);
                        continue;
                }

                /*
                 * Schedule NAPI processing on the indicated Response Queue
                 * and move on to the next entry in the Forwarded Interrupt
                 * Queue.
                 */
                napi_schedule(&rspq->napi);
                rspq_next(intrq);
        }

        t4_write_reg(adapter, T4VF_SGE_BASE_ADDR + SGE_VF_GTS,
                     CIDXINC(work_done) |
                     INGRESSQID(intrq->cntxt_id) |
                     SEINTARM(intrq->intr_params));

        spin_unlock(&adapter->sge.intrq_lock);

        return work_done;
}

/*
 * The MSI interrupt handler handles data events from SGE response queues as
 * well as error and other async events as they all use the same MSI vector.
 */
static irqreturn_t t4vf_intr_msi(int irq, void *cookie)
{
        struct adapter *adapter = cookie;

        process_intrq(adapter);
        return IRQ_HANDLED;
}

/**
 *      t4vf_intr_handler - select the top-level interrupt handler
 *      @adapter: the adapter
 *
 *      Selects the top-level interrupt handler based on the type of interrupts
 *      (MSI-X or MSI).
 */
irq_handler_t t4vf_intr_handler(struct adapter *adapter)
{
        BUG_ON((adapter->flags & (USING_MSIX|USING_MSI)) == 0);
        if (adapter->flags & USING_MSIX)
                return t4vf_sge_intr_msix;
        else
                return t4vf_intr_msi;
}

/**
 *      sge_rx_timer_cb - perform periodic maintenance of SGE RX queues
 *      @data: the adapter
 *
 *      Runs periodically from a timer to perform maintenance of SGE RX queues.
 *
 *      a) Replenishes RX queues that have run out due to memory shortage.
 *      Normally new RX buffers are added when existing ones are consumed but
 *      when out of memory a queue can become empty.  We schedule NAPI to do
 *      the actual refill.
 */
static void sge_rx_timer_cb(unsigned long data)
{
        struct adapter *adapter = (struct adapter *)data;
        struct sge *s = &adapter->sge;
        unsigned int i;

        /*
         * Scan the "Starving Free Lists" flag array looking for any Free
         * Lists in need of more free buffers.  If we find one and it's not
         * being actively polled, then bump its "starving" counter and attempt
         * to refill it.  If we're successful in adding enough buffers to push
         * the Free List over the starving threshold, then we can clear its
         * "starving" status.
         */
        for (i = 0; i < ARRAY_SIZE(s->starving_fl); i++) {
                unsigned long m;

                for (m = s->starving_fl[i]; m; m &= m - 1) {
                        unsigned int id = __ffs(m) + i * BITS_PER_LONG;
                        struct sge_fl *fl = s->egr_map[id];

                        clear_bit(id, s->starving_fl);
                        smp_mb__after_atomic();

                        /*
                         * Since we are accessing fl without a lock there's a
                         * small probability of a false positive where we
                         * schedule napi but the FL is no longer starving.
                         * No biggie.
                         */
                        if (fl_starving(adapter, fl)) {
                                struct sge_eth_rxq *rxq;

                                rxq = container_of(fl, struct sge_eth_rxq, fl);
                                if (napi_reschedule(&rxq->rspq.napi))
                                        fl->starving++;
                                else
                                        set_bit(id, s->starving_fl);
                        }
                }
        }

        /*
         * Reschedule the next scan for starving Free Lists ...
         */
        mod_timer(&s->rx_timer, jiffies + RX_QCHECK_PERIOD);
}

/**
 *      sge_tx_timer_cb - perform periodic maintenance of SGE Tx queues
 *      @data: the adapter
 *
 *      Runs periodically from a timer to perform maintenance of SGE TX queues.
 *
 *      b) Reclaims completed Tx packets for the Ethernet queues.  Normally
 *      packets are cleaned up by new Tx packets, this timer cleans up packets
 *      when no new packets are being submitted.  This is essential for pktgen,
 *      at least.
 */
static void sge_tx_timer_cb(unsigned long data)
{
        struct adapter *adapter = (struct adapter *)data;
        struct sge *s = &adapter->sge;
        unsigned int i, budget;

        budget = MAX_TIMER_TX_RECLAIM;
        i = s->ethtxq_rover;
        do {
                struct sge_eth_txq *txq = &s->ethtxq[i];

                if (reclaimable(&txq->q) && __netif_tx_trylock(txq->txq)) {
                        int avail = reclaimable(&txq->q);

                        if (avail > budget)
                                avail = budget;

                        free_tx_desc(adapter, &txq->q, avail, true);
                        txq->q.in_use -= avail;
                        __netif_tx_unlock(txq->txq);

                        budget -= avail;
                        if (!budget)
                                break;
                }

                i++;
                if (i >= s->ethqsets)
                        i = 0;
        } while (i != s->ethtxq_rover);
        s->ethtxq_rover = i;

        /*
         * If we found too many reclaimable packets schedule a timer in the
         * near future to continue where we left off.  Otherwise the next timer
         * will be at its normal interval.
         */
        mod_timer(&s->tx_timer, jiffies + (budget ? TX_QCHECK_PERIOD : 2));
}

/**
 *      t4vf_sge_alloc_rxq - allocate an SGE RX Queue
 *      @adapter: the adapter
 *      @rspq: pointer to to the new rxq's Response Queue to be filled in
 *      @iqasynch: if 0, a normal rspq; if 1, an asynchronous event queue
 *      @dev: the network device associated with the new rspq
 *      @intr_dest: MSI-X vector index (overriden in MSI mode)
 *      @fl: pointer to the new rxq's Free List to be filled in
 *      @hnd: the interrupt handler to invoke for the rspq
 */
int t4vf_sge_alloc_rxq(struct adapter *adapter, struct sge_rspq *rspq,
                       bool iqasynch, struct net_device *dev,
                       int intr_dest,
                       struct sge_fl *fl, rspq_handler_t hnd)
{
        struct sge *s = &adapter->sge;
        struct port_info *pi = netdev_priv(dev);
        struct fw_iq_cmd cmd, rpl;
        int ret, iqandst, flsz = 0;

        /*
         * If we're using MSI interrupts and we're not initializing the
         * Forwarded Interrupt Queue itself, then set up this queue for
         * indirect interrupts to the Forwarded Interrupt Queue.  Obviously
         * the Forwarded Interrupt Queue must be set up before any other
         * ingress queue ...
         */
        if ((adapter->flags & USING_MSI) && rspq != &adapter->sge.intrq) {
                iqandst = SGE_INTRDST_IQ;
                intr_dest = adapter->sge.intrq.abs_id;
        } else
                iqandst = SGE_INTRDST_PCI;

        /*
         * Allocate the hardware ring for the Response Queue.  The size needs
         * to be a multiple of 16 which includes the mandatory status entry
         * (regardless of whether the Status Page capabilities are enabled or
         * not).
         */
        rspq->size = roundup(rspq->size, 16);
        rspq->desc = alloc_ring(adapter->pdev_dev, rspq->size, rspq->iqe_len,
                                0, &rspq->phys_addr, NULL, 0);
        if (!rspq->desc)
                return -ENOMEM;

        /*
         * Fill in the Ingress Queue Command.  Note: Ideally this code would
         * be in t4vf_hw.c but there are so many parameters and dependencies
         * on our Linux SGE state that we would end up having to pass tons of
         * parameters.  We'll have to think about how this might be migrated
         * into OS-independent common code ...
         */
        memset(&cmd, 0, sizeof(cmd));
        cmd.op_to_vfn = cpu_to_be32(FW_CMD_OP(FW_IQ_CMD) |
                                    FW_CMD_REQUEST |
                                    FW_CMD_WRITE |
                                    FW_CMD_EXEC);
        cmd.alloc_to_len16 = cpu_to_be32(FW_IQ_CMD_ALLOC |
                                         FW_IQ_CMD_IQSTART(1) |
                                         FW_LEN16(cmd));
        cmd.type_to_iqandstindex =
                cpu_to_be32(FW_IQ_CMD_TYPE(FW_IQ_TYPE_FL_INT_CAP) |
                            FW_IQ_CMD_IQASYNCH(iqasynch) |
                            FW_IQ_CMD_VIID(pi->viid) |
                            FW_IQ_CMD_IQANDST(iqandst) |
                            FW_IQ_CMD_IQANUS(1) |
                            FW_IQ_CMD_IQANUD(SGE_UPDATEDEL_INTR) |
                            FW_IQ_CMD_IQANDSTINDEX(intr_dest));
        cmd.iqdroprss_to_iqesize =
                cpu_to_be16(FW_IQ_CMD_IQPCIECH(pi->port_id) |
                            FW_IQ_CMD_IQGTSMODE |
                            FW_IQ_CMD_IQINTCNTTHRESH(rspq->pktcnt_idx) |
                            FW_IQ_CMD_IQESIZE(ilog2(rspq->iqe_len) - 4));
        cmd.iqsize = cpu_to_be16(rspq->size);
        cmd.iqaddr = cpu_to_be64(rspq->phys_addr);

        if (fl) {
                /*
                 * Allocate the ring for the hardware free list (with space
                 * for its status page) along with the associated software
                 * descriptor ring.  The free list size needs to be a multiple
                 * of the Egress Queue Unit.
                 */
                fl->size = roundup(fl->size, FL_PER_EQ_UNIT);
                fl->desc = alloc_ring(adapter->pdev_dev, fl->size,
                                      sizeof(__be64), sizeof(struct rx_sw_desc),
                                      &fl->addr, &fl->sdesc, s->stat_len);
                if (!fl->desc) {
                        ret = -ENOMEM;
                        goto err;
                }

                /*
                 * Calculate the size of the hardware free list ring plus
                 * Status Page (which the SGE will place after the end of the
                 * free list ring) in Egress Queue Units.
                 */
                flsz = (fl->size / FL_PER_EQ_UNIT +
                        s->stat_len / EQ_UNIT);

                /*
                 * Fill in all the relevant firmware Ingress Queue Command
                 * fields for the free list.
                 */
                cmd.iqns_to_fl0congen =
                        cpu_to_be32(
                                FW_IQ_CMD_FL0HOSTFCMODE(SGE_HOSTFCMODE_NONE) |
                                FW_IQ_CMD_FL0PACKEN(1) |
                                FW_IQ_CMD_FL0PADEN(1));
                cmd.fl0dcaen_to_fl0cidxfthresh =
                        cpu_to_be16(
                                FW_IQ_CMD_FL0FBMIN(SGE_FETCHBURSTMIN_64B) |
                                FW_IQ_CMD_FL0FBMAX(SGE_FETCHBURSTMAX_512B));
                cmd.fl0size = cpu_to_be16(flsz);
                cmd.fl0addr = cpu_to_be64(fl->addr);
        }

        /*
         * Issue the firmware Ingress Queue Command and extract the results if
         * it completes successfully.
         */
        ret = t4vf_wr_mbox(adapter, &cmd, sizeof(cmd), &rpl);
        if (ret)
                goto err;

        netif_napi_add(dev, &rspq->napi, napi_rx_handler, 64);
        rspq->cur_desc = rspq->desc;
        rspq->cidx = 0;
        rspq->gen = 1;
        rspq->next_intr_params = rspq->intr_params;
        rspq->cntxt_id = be16_to_cpu(rpl.iqid);
        rspq->abs_id = be16_to_cpu(rpl.physiqid);
        rspq->size--;                   /* subtract status entry */
        rspq->adapter = adapter;
        rspq->netdev = dev;
        rspq->handler = hnd;

        /* set offset to -1 to distinguish ingress queues without FL */
        rspq->offset = fl ? 0 : -1;

        if (fl) {
                fl->cntxt_id = be16_to_cpu(rpl.fl0id);
                fl->avail = 0;
                fl->pend_cred = 0;
                fl->pidx = 0;
                fl->cidx = 0;
                fl->alloc_failed = 0;
                fl->large_alloc_failed = 0;
                fl->starving = 0;
                refill_fl(adapter, fl, fl_cap(fl), GFP_KERNEL);
        }

        return 0;

err:
        /*
         * An error occurred.  Clean up our partial allocation state and
         * return the error.
         */
        if (rspq->desc) {
                dma_free_coherent(adapter->pdev_dev, rspq->size * rspq->iqe_len,
                                  rspq->desc, rspq->phys_addr);
                rspq->desc = NULL;
        }
        if (fl && fl->desc) {
                kfree(fl->sdesc);
                fl->sdesc = NULL;
                dma_free_coherent(adapter->pdev_dev, flsz * EQ_UNIT,
                                  fl->desc, fl->addr);
                fl->desc = NULL;
        }
        return ret;
}

/**
 *      t4vf_sge_alloc_eth_txq - allocate an SGE Ethernet TX Queue
 *      @adapter: the adapter
 *      @txq: pointer to the new txq to be filled in
 *      @devq: the network TX queue associated with the new txq
 *      @iqid: the relative ingress queue ID to which events relating to
 *              the new txq should be directed
 */
int t4vf_sge_alloc_eth_txq(struct adapter *adapter, struct sge_eth_txq *txq,
                           struct net_device *dev, struct netdev_queue *devq,
                           unsigned int iqid)
{
        struct sge *s = &adapter->sge;
        int ret, nentries;
        struct fw_eq_eth_cmd cmd, rpl;
        struct port_info *pi = netdev_priv(dev);

        /*
         * Calculate the size of the hardware TX Queue (including the Status
         * Page on the end of the TX Queue) in units of TX Descriptors.
         */
        nentries = txq->q.size + s->stat_len / sizeof(struct tx_desc);

        /*
         * Allocate the hardware ring for the TX ring (with space for its
         * status page) along with the associated software descriptor ring.
         */
        txq->q.desc = alloc_ring(adapter->pdev_dev, txq->q.size,
                                 sizeof(struct tx_desc),
                                 sizeof(struct tx_sw_desc),
                                 &txq->q.phys_addr, &txq->q.sdesc, s->stat_len);
        if (!txq->q.desc)
                return -ENOMEM;

        /*
         * Fill in the Egress Queue Command.  Note: As with the direct use of
         * the firmware Ingress Queue COmmand above in our RXQ allocation
         * routine, ideally, this code would be in t4vf_hw.c.  Again, we'll
         * have to see if there's some reasonable way to parameterize it
         * into the common code ...
         */
        memset(&cmd, 0, sizeof(cmd));
        cmd.op_to_vfn = cpu_to_be32(FW_CMD_OP(FW_EQ_ETH_CMD) |
                                    FW_CMD_REQUEST |
                                    FW_CMD_WRITE |
                                    FW_CMD_EXEC);
        cmd.alloc_to_len16 = cpu_to_be32(FW_EQ_ETH_CMD_ALLOC |
                                         FW_EQ_ETH_CMD_EQSTART |
                                         FW_LEN16(cmd));
        cmd.viid_pkd = cpu_to_be32(FW_EQ_ETH_CMD_AUTOEQUEQE |
                                   FW_EQ_ETH_CMD_VIID(pi->viid));
        cmd.fetchszm_to_iqid =
                cpu_to_be32(FW_EQ_ETH_CMD_HOSTFCMODE(SGE_HOSTFCMODE_STPG) |
                            FW_EQ_ETH_CMD_PCIECHN(pi->port_id) |
                            FW_EQ_ETH_CMD_IQID(iqid));
        cmd.dcaen_to_eqsize =
                cpu_to_be32(FW_EQ_ETH_CMD_FBMIN(SGE_FETCHBURSTMIN_64B) |
                            FW_EQ_ETH_CMD_FBMAX(SGE_FETCHBURSTMAX_512B) |
                            FW_EQ_ETH_CMD_CIDXFTHRESH(SGE_CIDXFLUSHTHRESH_32) |
                            FW_EQ_ETH_CMD_EQSIZE(nentries));
        cmd.eqaddr = cpu_to_be64(txq->q.phys_addr);

        /*
         * Issue the firmware Egress Queue Command and extract the results if
         * it completes successfully.
         */
        ret = t4vf_wr_mbox(adapter, &cmd, sizeof(cmd), &rpl);
        if (ret) {
                /*
                 * The girmware Ingress Queue Command failed for some reason.
                 * Free up our partial allocation state and return the error.
                 */
                kfree(txq->q.sdesc);
                txq->q.sdesc = NULL;
                dma_free_coherent(adapter->pdev_dev,
                                  nentries * sizeof(struct tx_desc),
                                  txq->q.desc, txq->q.phys_addr);
                txq->q.desc = NULL;
                return ret;
        }

        txq->q.in_use = 0;
        txq->q.cidx = 0;
        txq->q.pidx = 0;
        txq->q.stat = (void *)&txq->q.desc[txq->q.size];
        txq->q.cntxt_id = FW_EQ_ETH_CMD_EQID_GET(be32_to_cpu(rpl.eqid_pkd));
        txq->q.abs_id =
                FW_EQ_ETH_CMD_PHYSEQID_GET(be32_to_cpu(rpl.physeqid_pkd));
        txq->txq = devq;
        txq->tso = 0;
        txq->tx_cso = 0;
        txq->vlan_ins = 0;
        txq->q.stops = 0;
        txq->q.restarts = 0;
        txq->mapping_err = 0;
        return 0;
}

/*
 * Free the DMA map resources associated with a TX queue.
 */
static void free_txq(struct adapter *adapter, struct sge_txq *tq)
{
        struct sge *s = &adapter->sge;

        dma_free_coherent(adapter->pdev_dev,
                          tq->size * sizeof(*tq->desc) + s->stat_len,
                          tq->desc, tq->phys_addr);
        tq->cntxt_id = 0;
        tq->sdesc = NULL;
        tq->desc = NULL;
}

/*
 * Free the resources associated with a response queue (possibly including a
 * free list).
 */
static void free_rspq_fl(struct adapter *adapter, struct sge_rspq *rspq,
                         struct sge_fl *fl)
{
        struct sge *s = &adapter->sge;
        unsigned int flid = fl ? fl->cntxt_id : 0xffff;

        t4vf_iq_free(adapter, FW_IQ_TYPE_FL_INT_CAP,
                     rspq->cntxt_id, flid, 0xffff);
        dma_free_coherent(adapter->pdev_dev, (rspq->size + 1) * rspq->iqe_len,
                          rspq->desc, rspq->phys_addr);
        netif_napi_del(&rspq->napi);
        rspq->netdev = NULL;
        rspq->cntxt_id = 0;
        rspq->abs_id = 0;
        rspq->desc = NULL;

        if (fl) {
                free_rx_bufs(adapter, fl, fl->avail);
                dma_free_coherent(adapter->pdev_dev,
                                  fl->size * sizeof(*fl->desc) + s->stat_len,
                                  fl->desc, fl->addr);
                kfree(fl->sdesc);
                fl->sdesc = NULL;
                fl->cntxt_id = 0;
                fl->desc = NULL;
        }
}

/**
 *      t4vf_free_sge_resources - free SGE resources
 *      @adapter: the adapter
 *
 *      Frees resources used by the SGE queue sets.
 */
void t4vf_free_sge_resources(struct adapter *adapter)
{
        struct sge *s = &adapter->sge;
        struct sge_eth_rxq *rxq = s->ethrxq;
        struct sge_eth_txq *txq = s->ethtxq;
        struct sge_rspq *evtq = &s->fw_evtq;
        struct sge_rspq *intrq = &s->intrq;
        int qs;

        for (qs = 0; qs < adapter->sge.ethqsets; qs++, rxq++, txq++) {
                if (rxq->rspq.desc)
                        free_rspq_fl(adapter, &rxq->rspq, &rxq->fl);
                if (txq->q.desc) {
                        t4vf_eth_eq_free(adapter, txq->q.cntxt_id);
                        free_tx_desc(adapter, &txq->q, txq->q.in_use, true);
                        kfree(txq->q.sdesc);
                        free_txq(adapter, &txq->q);
                }
        }
        if (evtq->desc)
                free_rspq_fl(adapter, evtq, NULL);
        if (intrq->desc)
                free_rspq_fl(adapter, intrq, NULL);
}

/**
 *      t4vf_sge_start - enable SGE operation
 *      @adapter: the adapter
 *
 *      Start tasklets and timers associated with the DMA engine.
 */
void t4vf_sge_start(struct adapter *adapter)
{
        adapter->sge.ethtxq_rover = 0;
        mod_timer(&adapter->sge.rx_timer, jiffies + RX_QCHECK_PERIOD);
        mod_timer(&adapter->sge.tx_timer, jiffies + TX_QCHECK_PERIOD);
}

/**
 *      t4vf_sge_stop - disable SGE operation
 *      @adapter: the adapter
 *
 *      Stop tasklets and timers associated with the DMA engine.  Note that
 *      this is effective only if measures have been taken to disable any HW
 *      events that may restart them.
 */
void t4vf_sge_stop(struct adapter *adapter)
{
        struct sge *s = &adapter->sge;

        if (s->rx_timer.function)
                del_timer_sync(&s->rx_timer);
        if (s->tx_timer.function)
                del_timer_sync(&s->tx_timer);
}

/**
 *      t4vf_sge_init - initialize SGE
 *      @adapter: the adapter
 *
 *      Performs SGE initialization needed every time after a chip reset.
 *      We do not initialize any of the queue sets here, instead the driver
 *      top-level must request those individually.  We also do not enable DMA
 *      here, that should be done after the queues have been set up.
 */
int t4vf_sge_init(struct adapter *adapter)
{
        struct sge_params *sge_params = &adapter->params.sge;
        u32 fl0 = sge_params->sge_fl_buffer_size[0];
        u32 fl1 = sge_params->sge_fl_buffer_size[1];
        struct sge *s = &adapter->sge;
        unsigned int ingpadboundary, ingpackboundary;

        /*
         * Start by vetting the basic SGE parameters which have been set up by
         * the Physical Function Driver.  Ideally we should be able to deal
         * with _any_ configuration.  Practice is different ...
         */
        if (fl0 != PAGE_SIZE || (fl1 != 0 && fl1 <= fl0)) {
                dev_err(adapter->pdev_dev, "bad SGE FL buffer sizes [%d, %d]\n",
                        fl0, fl1);
                return -EINVAL;
        }
        if ((sge_params->sge_control & RXPKTCPLMODE_MASK) == 0) {
                dev_err(adapter->pdev_dev, "bad SGE CPL MODE\n");
                return -EINVAL;
        }

        /*
         * Now translate the adapter parameters into our internal forms.
         */
        if (fl1)
                s->fl_pg_order = ilog2(fl1) - PAGE_SHIFT;
        s->stat_len = ((sge_params->sge_control & EGRSTATUSPAGESIZE_MASK)
                        ? 128 : 64);
        s->pktshift = PKTSHIFT_GET(sge_params->sge_control);

        /* T4 uses a single control field to specify both the PCIe Padding and
         * Packing Boundary.  T5 introduced the ability to specify these
         * separately.  The actual Ingress Packet Data alignment boundary
         * within Packed Buffer Mode is the maximum of these two
         * specifications.  (Note that it makes no real practical sense to
         * have the Pading Boudary be larger than the Packing Boundary but you
         * could set the chip up that way and, in fact, legacy T4 code would
         * end doing this because it would initialize the Padding Boundary and
         * leave the Packing Boundary initialized to 0 (16 bytes).)
         */
        ingpadboundary = 1 << (INGPADBOUNDARY_GET(sge_params->sge_control) +
                               X_INGPADBOUNDARY_SHIFT);
        if (is_t4(adapter->params.chip)) {
                s->fl_align = ingpadboundary;
        } else {
                /* T5 has a different interpretation of one of the PCIe Packing
                 * Boundary values.
                 */
                ingpackboundary = INGPACKBOUNDARY_G(sge_params->sge_control2);
                if (ingpackboundary == INGPACKBOUNDARY_16B_X)
                        ingpackboundary = 16;
                else
                        ingpackboundary = 1 << (ingpackboundary +
                                                INGPACKBOUNDARY_SHIFT_X);

                s->fl_align = max(ingpadboundary, ingpackboundary);
        }

        /* A FL with <= fl_starve_thres buffers is starving and a periodic
         * timer will attempt to refill it.  This needs to be larger than the
         * SGE's Egress Congestion Threshold.  If it isn't, then we can get
         * stuck waiting for new packets while the SGE is waiting for us to
         * give it more Free List entries.  (Note that the SGE's Egress
         * Congestion Threshold is in units of 2 Free List pointers.)
         */
        s->fl_starve_thres
                = EGRTHRESHOLD_GET(sge_params->sge_congestion_control)*2 + 1;

        /*
         * Set up tasklet timers.
         */
        setup_timer(&s->rx_timer, sge_rx_timer_cb, (unsigned long)adapter);
        setup_timer(&s->tx_timer, sge_tx_timer_cb, (unsigned long)adapter);

        /*
         * Initialize Forwarded Interrupt Queue lock.
         */
        spin_lock_init(&s->intrq_lock);

        return 0;
}