From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net v3] ravb: do not use zero-length alignment DMA descriptor Date: Mon, 16 Jan 2017 11:53:50 -0500 (EST) Message-ID: <20170116.115350.943642905478824707.davem@davemloft.net> References: <1484563521-12009-1-git-send-email-horms+renesas@verge.net.au> <96396803-caac-13cd-3e17-f9d10fc608ad@cogentembedded.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: horms+renesas@verge.net.au, magnus.damm@gmail.com, netdev@vger.kernel.org, linux-renesas-soc@vger.kernel.org, masaru.nagai.vx@renesas.com To: sergei.shtylyov@cogentembedded.com Return-path: In-Reply-To: <96396803-caac-13cd-3e17-f9d10fc608ad@cogentembedded.com> Sender: linux-renesas-soc-owner@vger.kernel.org List-Id: netdev.vger.kernel.org From: Sergei Shtylyov Date: Mon, 16 Jan 2017 16:01:49 +0300 > On 01/16/2017 01:45 PM, Simon Horman wrote: > >> From: Masaru Nagai >> >> Due to alignment requirements of the hardware transmissions are split >> into >> two DMA descriptors, a small padding descriptor of 0 - 3 bytes in >> length >> followed by a descriptor for rest of the packet. >> >> In the case of IP packets the first descriptor will never be zero due >> to >> the way that the stack aligns buffers for IP packets. However, for >> non-IP >> packets it may be zero. >> >> In that case it has been reported that timeouts occur, presumably >> because >> transmission stops at the first zero-length DMA descriptor and thus >> the >> packet is not transmitted. However, in my environment a BUG is >> triggered as >> follows: > [...] > >> Fixes: 2f45d1902acf ("ravb: minimize TX data copying") >> Signed-off-by: Masaru Nagai > Signed-off-by: Simon Horman > > Acked-by: Sergei Shtylyov Applied and queued up for -stable, thanks.