linux-kernel - Re: [PATCH v3] dmaengine: tegra-apb: Support per-burst residue granularity

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Date:   Tue, 2 Jul 2019 12:25:17 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Laxman Dewangan <ldewangan@...dia.com>,
        Vinod Koul <vkoul@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Ben Dooks <ben.dooks@...ethink.co.uk>
Cc:     dmaengine@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] dmaengine: tegra-apb: Support per-burst residue
 granularity

27.06.2019 22:47, Dmitry Osipenko пишет:
> Tegra's APB DMA engine updates words counter after each transferred burst
> of data, hence it can report transfer's residual with more fidelity which
> may be required in cases like audio playback. In particular this fixes
> audio stuttering during playback in a chromium web browser. The patch is
> based on the original work that was made by Ben Dooks and a patch from
> downstream kernel. It was tested on Tegra20 and Tegra30 devices.
> 
> Link: https://lore.kernel.org/lkml/20190424162348.23692-1-ben.dooks@codethink.co.uk/
> Link: https://nv-tegra.nvidia.com/gitweb/?p=linux-4.4.git;a=commit;h=c7bba40c6846fbf3eaad35c4472dcc7d8bbc02e5
> Inspired-by: Ben Dooks <ben.dooks@...ethink.co.uk>
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
> 
> Changelog:
> 
> v3:  Added workaround for a hardware design shortcoming that results
>      in a words counter wraparound before end-of-transfer bit is set
>      in a cyclic mode.
> 
> v2:  Addressed review comments made by Jon Hunter to v1. We won't try
>      to get words count if dma_desc is on free list as it will result
>      in a NULL dereference because this case wasn't handled properly.
> 
>      The residual value is now updated properly, avoiding potential
>      integer overflow by adding the "bytes" to the "bytes_transferred"
>      instead of the subtraction.

Is there still any chance to get this into 5.3? Will be very nice! Jon / Vinod ?