MLK-10194 Revert "MA-6031 tty: serial: imx: reduce the transmit and receive latency"

The patch "MA-6031 tty: serial: imx: reduce the transmit and receive latency"
cannot pass stress test, so revert it now.

Signed-off-by: Fugang Duan <B38611@freescale.com>

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 97eab99a8f466dfc131d4090fa7fd0b2fa85a357..d557f1efb405f0c2d3dcf218e99ee7d47a39d062 100644 (file)
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -244,6 +244,8 @@ struct imx_port {
        struct imx_dma_rxbuf    rx_buf;
        unsigned int            tx_bytes;
        unsigned int            dma_tx_nents;
+       struct delayed_work     tsk_dma_tx;
+       struct work_struct      tsk_dma_rx;
        wait_queue_head_t       dma_wait;
        unsigned int            saved_reg[11];
 #define DMA_TX_IS_WORKING 1
@@ -505,8 +507,6 @@ static inline void imx_transmit_buffer(struct imx_port *sport)
                imx_stop_tx(&sport->port);
 }
 
-static void imx_dma_tx(struct imx_port *sport);
-
 static void dma_tx_callback(void *data)
 {
        struct imx_port *sport = data;
@@ -522,6 +522,7 @@ static void dma_tx_callback(void *data)
        spin_lock_irqsave(&sport->port.lock, flags);
        xmit->tail = (xmit->tail + sport->tx_bytes) & (UART_XMIT_SIZE - 1);
        sport->port.icount.tx += sport->tx_bytes;
+       spin_unlock_irqrestore(&sport->port.lock, flags);
 
        dev_dbg(sport->port.dev, "we finish the TX DMA.\n");
 
@@ -529,29 +530,31 @@ static void dma_tx_callback(void *data)
        smp_mb__after_clear_bit();
        uart_write_wakeup(&sport->port);
 
+       schedule_delayed_work(&sport->tsk_dma_tx, msecs_to_jiffies(1));
+
        if (waitqueue_active(&sport->dma_wait)) {
                wake_up(&sport->dma_wait);
                dev_dbg(sport->port.dev, "exit in %s.\n", __func__);
                return;
        }
-
-       if (!uart_circ_empty(xmit) && !uart_tx_stopped(&sport->port))
-               imx_dma_tx(sport);
-       spin_unlock_irqrestore(&sport->port.lock, flags);
 }
 
-static void imx_dma_tx(struct imx_port *sport)
+static void dma_tx_work(struct work_struct *w)
 {
+       struct delayed_work *delay_work = to_delayed_work(w);
+       struct imx_port *sport = container_of(delay_work, struct imx_port, tsk_dma_tx);
        struct circ_buf *xmit = &sport->port.state->xmit;
        struct scatterlist *sgl = sport->tx_sgl;
        struct dma_async_tx_descriptor *desc;
        struct dma_chan *chan = sport->dma_chan_tx;
        struct device *dev = sport->port.dev;
+       unsigned long flags;
        int ret;
 
        if (test_and_set_bit(DMA_TX_IS_WORKING, &sport->flags))
                return;
 
+       spin_lock_irqsave(&sport->port.lock, flags);
        sport->tx_bytes = uart_circ_chars_pending(xmit);
 
        if (sport->tx_bytes > 0) {
@@ -565,6 +568,7 @@ static void imx_dma_tx(struct imx_port *sport)
                        sport->dma_tx_nents = 1;
                        sg_init_one(sgl, xmit->buf + xmit->tail, sport->tx_bytes);
                }
+               spin_unlock_irqrestore(&sport->port.lock, flags);
 
                ret = dma_map_sg(dev, sgl, sport->dma_tx_nents, DMA_TO_DEVICE);
                if (ret == 0) {
@@ -588,6 +592,7 @@ static void imx_dma_tx(struct imx_port *sport)
                dma_async_issue_pending(chan);
                return;
        }
+       spin_unlock_irqrestore(&sport->port.lock, flags);
 err_out:
        clear_bit(DMA_TX_IS_WORKING, &sport->flags);
        smp_mb__after_clear_bit();
@@ -635,7 +640,7 @@ static void imx_start_tx(struct uart_port *port)
        }
 
        if (sport->dma_is_enabled) {
-               imx_dma_tx(sport);
+               schedule_delayed_work(&sport->tsk_dma_tx, 0);
                return;
        }
 
@@ -909,8 +914,9 @@ static void dma_rx_push_data(struct imx_port *sport, struct tty_struct *tty,
        }
 }
 
-static void dma_rx_work(struct imx_port *sport)
+static void dma_rx_work(struct work_struct *w)
 {
+       struct imx_port *sport = container_of(w, struct imx_port, tsk_dma_rx);
        struct tty_struct *tty = sport->port.state->port.tty;
        unsigned int cur_idx = sport->rx_buf.cur_idx;
 
@@ -971,7 +977,7 @@ static void dma_rx_callback(void *data)
                dev_err(sport->port.dev, "overwrite!\n");
 
        if (count)
-               dma_rx_work(sport);
+               schedule_work(&sport->tsk_dma_rx);
 }
 
 static int start_rx_dma(struct imx_port *sport)
@@ -1210,6 +1216,11 @@ static int imx_startup(struct uart_port *port)
                && !sport->dma_is_inited)
                imx_uart_dma_init(sport);
 
+       if (sport->dma_is_inited) {
+               INIT_DELAYED_WORK(&sport->tsk_dma_tx, dma_tx_work);
+               INIT_WORK(&sport->tsk_dma_rx, dma_rx_work);
+       }
+
        spin_lock_irqsave(&sport->port.lock, flags);
        /*
         * Finally, clear and enable interrupts