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Date: Thu, 9 Nov 2017 09:27:38 +0200 From: Adrian Hunter <adrian.hunter@...el.com> To: Linus Walleij <linus.walleij@...aro.org> Cc: Ulf Hansson <ulf.hansson@...aro.org>, linux-mmc <linux-mmc@...r.kernel.org>, linux-block <linux-block@...r.kernel.org>, linux-kernel <linux-kernel@...r.kernel.org>, Bough Chen <haibo.chen@....com>, Alex Lemberg <alex.lemberg@...disk.com>, Mateusz Nowak <mateusz.nowak@...el.com>, Yuliy Izrailov <Yuliy.Izrailov@...disk.com>, Jaehoon Chung <jh80.chung@...sung.com>, Dong Aisheng <dongas86@...il.com>, Das Asutosh <asutoshd@...eaurora.org>, Zhangfei Gao <zhangfei.gao@...il.com>, Sahitya Tummala <stummala@...eaurora.org>, Harjani Ritesh <riteshh@...eaurora.org>, Venu Byravarasu <vbyravarasu@...dia.com>, Shawn Lin <shawn.lin@...k-chips.com>, Christoph Hellwig <hch@....de> Subject: Re: [PATCH V13 07/10] mmc: block: blk-mq: Add support for direct completion On 08/11/17 11:28, Linus Walleij wrote: > On Fri, Nov 3, 2017 at 2:20 PM, Adrian Hunter <adrian.hunter@...el.com> wrote: > >> For blk-mq, add support for completing requests directly in the ->done >> callback. That means that error handling and urgent background operations >> must be handled by recovery_work in that case. >> >> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com> > > I tried enabling this on my MMC host (mmci) but I got weird > DMA error messages when I did. > > I guess this has not been tested on a non-DMA-coherent > system? I don't see what DMA-coherence has to do with anything. Possibilities: - DMA unmapping doesn't work in an atomic context - requests' DMA operations have to be synchronized with each other > I think I might be seeing this because the .pre and .post > callbacks need to be strictly sequenced, and this is > maybe not taken into account here? I looked at mmci but that did not seem to be the case. > Isn't there as risk > that the .post callback of the next request is called before > the .post callback of the previous request has returned > for example? Of course, the requests are treated as independent. If the separate DMA operations require synchronization, that is for the host driver to fix.
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