From mboxrd@z Thu Jan 1 00:00:00 1970 From: Troy Kisky Subject: Re: [PATCH net-next V2 7/8] net: fec: don't transfer ownership until descriptor write is complete Date: Wed, 24 Feb 2016 13:39:14 -0700 Message-ID: <56CE14F2.8010005@boundarydevices.com> References: <1454709170-19527-1-git-send-email-troy.kisky@boundarydevices.com> <1454709170-19527-8-git-send-email-troy.kisky@boundarydevices.com> <56B5DE6C.9080407@cogentembedded.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: fabio.estevam@freescale.com, l.stach@pengutronix.de, andrew@lunn.ch, tremyfr@gmail.com, linux@arm.linux.org.uk, linux-arm-kernel@lists.infradead.org, laci@boundarydevices.com, shawnguo@kernel.org, johannes@sipsolutions.net, arnd@arndb.de To: Sergei Shtylyov , netdev@vger.kernel.org, davem@davemloft.net, B38611@freescale.com Return-path: Received: from mail-pa0-f49.google.com ([209.85.220.49]:35052 "EHLO mail-pa0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758161AbcBXUjP (ORCPT ); Wed, 24 Feb 2016 15:39:15 -0500 Received: by mail-pa0-f49.google.com with SMTP id ho8so19235959pac.2 for ; Wed, 24 Feb 2016 12:39:15 -0800 (PST) In-Reply-To: <56B5DE6C.9080407@cogentembedded.com> Sender: netdev-owner@vger.kernel.org List-ID: On 2/6/2016 4:52 AM, Sergei Shtylyov wrote: > Hello. > > On 2/6/2016 12:52 AM, Troy Kisky wrote: > >> If you don't own it, you shouldn't write to it. >> >> Signed-off-by: Troy Kisky >> --- >> drivers/net/ethernet/freescale/fec_main.c | 14 +++++++++++++- >> 1 file changed, 13 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c >> index ca2708d..97ca72a 100644 >> --- a/drivers/net/ethernet/freescale/fec_main.c >> +++ b/drivers/net/ethernet/freescale/fec_main.c >> @@ -390,6 +390,10 @@ fec_enet_txq_submit_frag_skb(struct fec_enet_priv_tx_q *txq, >> >> bdp->cbd_bufaddr = cpu_to_fec32(addr); >> bdp->cbd_datlen = cpu_to_fec16(frag_len); >> + /* Make sure the updates to rest of the descriptor are >> + * performed before transferring ownership. >> + */ >> + wmb(); >> bdp->cbd_sc = cpu_to_fec16(status); >> } >> >> @@ -499,6 +503,10 @@ static int fec_enet_txq_submit_skb(struct fec_enet_priv_tx_q *txq, >> >> bdp->cbd_datlen = cpu_to_fec16(buflen); >> bdp->cbd_bufaddr = cpu_to_fec32(addr); >> + /* Make sure the updates to rest of the descriptor are performed before >> + * transferring ownership. >> + */ >> + wmb(); >> >> /* Send it on its way. Tell FEC it's ready, interrupt when done, >> * it's the last BD of the frame, and to put the CRC on the end. > [...] >> @@ -1484,6 +1491,11 @@ rx_processing_done: >> ebdp->cbd_prot = 0; >> ebdp->cbd_bdu = 0; >> } >> + /* Make sure the updates to rest of the descriptor are >> + * performed before transferring ownership. >> + */ >> + wmb(); >> + bdp->cbd_sc = cpu_to_fec16(status); > > I think you can use "ligter" dma_wmb() in this case. > Thanks for the review, I added a patch to the end of the series to address this. Troy