linux-kernel - Re: [PATCH v1] drm/tegra: gem: Fix CPU-cache maintenance for BO's allocated using get

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Date:   Wed, 3 Apr 2019 13:47:51 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] drm/tegra: gem: Fix CPU-cache maintenance for BO's
 allocated using get_pages()

07.03.2019 1:55, Dmitry Osipenko пишет:
> The allocated pages need to be invalidated in CPU caches. On ARM32 the
> DMA_BIDIRECTIONAL flag only ensures that data is written-back to DRAM and
> the data stays in CPU cache lines. While the DMA_FROM_DEVICE flag ensures
> that the corresponding CPU cache lines are getting invalidated and nothing
> more, that's exactly what is needed for a newly allocated pages.
> 
> This fixes randomly failing rendercheck tests on Tegra30 using the
> Opentegra driver for tests that use small-sized pixmaps (10x10 and less,
> i.e. 1-2 memory pages) because apparently CPU reads out stale data from
> caches and/or that data is getting evicted to DRAM at the time of HW job
> execution.
> 
> Cc: stable <stable@...r.kernel.org>
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>

Thierry, please don't forget about this patch.