From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sergei Shtylyov Date: Sun, 04 Aug 2013 14:10:39 +0000 Subject: Re: [PATCH v2] tmio_mmc_dma: fix PIO fallback on SDHI Message-Id: <51FE60DF.400@cogentembedded.com> List-Id: References: <201308030233.29446.sergei.shtylyov@cogentembedded.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Guennadi Liakhovetski Cc: linux-mmc@vger.kernel.org, ian@mnementh.co.uk, cjb@laptop.org, linux-sh@vger.kernel.org, max.filippov@cogentembedded.com Hello. On 04-08-2013 2:36, Guennadi Liakhovetski wrote: >> I'm testing SH-Mobile SDHI driver in DMA mode with a new DMA controller using >> 'bonnie++' and getting DMA error after which the tmio_mmc_dma.c code falls back >> to PIO but all commands time out after that. It turned out that the fallback >> code calls tmio_mmc_enable_dma() with RX/TX channels already freed and pointers >> to them cleared, so that the function bails out early instead of clearing the >> DMA bit in the CTL_DMA_ENABLE register. The regression was introduced by commit >> 162f43e31c5a376ec16336e5d0ac973373d54c89 (mmc: tmio: fix a deadlock). >> Moving tmio_mmc_enable_dma() calls to the top of the PIO fallback code in >> tmio_mmc_start_dma_{rx|tx}() helps. >> Signed-off-by: Sergei Shtylyov >> Cc: stable@vger.kernel.org # 3.1+ > Acked-by: Guennadi Liakhovetski > Not sure though how far back in stable this really has to go. We don't > have any real-life problem reports with older kernels, do we? If we did, that error would have been fixed earlier, wouldn't it? > I think > approach to which patches should get into stable changed recently. Haven't heard about that (or seen any change in the policy). The issue with this bug is its catastrophic consequencies: you can hardly ^C or ^Z out of 'bonnie++' when it happens (in fact, you cannot ^C at all). IIRC you can't even kill it from another shell. > Thanks > Guennadi WBR, Sergei