Hi Marek,
On Fri, Aug 22, 2014 at 7:26 AM, Marek Vasut marex@denx.de wrote:
Thanks for clarification. Fabio, can you please document this with a big comment in the code ?
Yes, I can do that in v6.
Does the below version look good?
From 782be534aa37ba3da2f8d0ed607b26b2dd71c7d7 Mon Sep 17 00:00:00 2001
From: Fabio Estevam fabio.estevam@freescale.com Date: Fri, 22 Aug 2014 17:59:44 -0300 Subject: [PATCH v6 2/2] 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 fabio.estevam@freescale.com --- Changes since v5: - Put explanation why we need to poll READY bit after TDAR into the code
drivers/net/fec_mxc.c | 29 ++++++++++++++++++++++++++--- 1 file changed, 26 insertions(+), 3 deletions(-)
diff --git a/drivers/net/fec_mxc.c b/drivers/net/fec_mxc.c index 6afc827..bdd8108 100644 --- a/drivers/net/fec_mxc.c +++ b/drivers/net/fec_mxc.c @@ -719,13 +719,36 @@ 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);