From f599288d55e5816c2cf468880e3120ed0b34080e Mon Sep 17 00:00:00 2001 From: Fabio Estevam Date: Mon, 25 Aug 2014 13:34:17 -0300 Subject: [PATCH] net: fec_mxc: Poll FEC_TBD_READY after polling TDAR When testing the FEC driver on a mx6solox we noticed that the TDAR bit gets always cleared prior then the READY bit is cleared in the last BD, which causes FEC packets reception to always fail. As explained by Ye Li: "The TDAR bit is cleared when the descriptors are all out from TX ring, but on mx6solox we noticed that the READY bit is still not cleared right after TDAR. These are two distinct signals, and in IC simulation, we found that TDAR always gets cleared prior than the READY bit of last BD becomes cleared. In mx6solox, we use a later version of FEC IP. It looks like that this intrinsic behaviour of TDAR bit has changed in this newer FEC version." Fix this by polling the READY bit of BD after the TDAR polling, which covers the mx6solox case and does not harm the other SoCs. No performance drop has been noticed with this patch applied when testing TFTP transfers on several boards of different i.mx SoCs. Signed-off-by: Fabio Estevam Acked-by: Marek Vasut --- drivers/net/fec_mxc.c | 30 +++++++++++++++++++++++++++--- 1 file changed, 27 insertions(+), 3 deletions(-) diff --git a/drivers/net/fec_mxc.c b/drivers/net/fec_mxc.c index d310016516..549d648613 100644 --- a/drivers/net/fec_mxc.c +++ b/drivers/net/fec_mxc.c @@ -719,13 +719,37 @@ static int fec_send(struct eth_device *dev, void *packet, int length) break; } - if (!timeout) + if (!timeout) { ret = -EINVAL; + goto out; + } - invalidate_dcache_range(addr, addr + size); - if (readw(&fec->tbd_base[fec->tbd_index].status) & FEC_TBD_READY) + /* + * The TDAR bit is cleared when the descriptors are all out from TX + * but on mx6solox we noticed that the READY bit is still not cleared + * right after TDAR. + * These are two distinct signals, and in IC simulation, we found that + * TDAR always gets cleared prior than the READY bit of last BD becomes + * cleared. + * In mx6solox, we use a later version of FEC IP. It looks like that + * this intrinsic behaviour of TDAR bit has changed in this newer FEC + * version. + * + * Fix this by polling the READY bit of BD after the TDAR polling, + * which covers the mx6solox case and does not harm the other SoCs. + */ + timeout = FEC_XFER_TIMEOUT; + while (--timeout) { + invalidate_dcache_range(addr, addr + size); + if (!(readw(&fec->tbd_base[fec->tbd_index].status) & + FEC_TBD_READY)) + break; + } + + if (!timeout) ret = -EINVAL; +out: debug("fec_send: status 0x%x index %d ret %i\n", readw(&fec->tbd_base[fec->tbd_index].status), fec->tbd_index, ret); -- 2.39.2