linux-kernel - Re: [Intel-gfx] [PATCH v3 1/3] drm/gem: don't force writecombine mmap'ing

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Message-ID: <87o91th8gy.fsf@anholt.net>
Date:   Tue, 16 Jul 2019 16:21:01 -0700
From:   Eric Anholt <eric@...olt.net>
To:     Rob Clark <robdclark@...il.com>, dri-devel@...ts.freedesktop.org
Cc:     Rob Clark <robdclark@...omium.org>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        linux-kernel@...r.kernel.org, David Airlie <airlied@...ux.ie>
Subject: Re: [Intel-gfx] [PATCH v3 1/3] drm/gem: don't force writecombine mmap'ing

Rob Clark <robdclark@...il.com> writes:

> From: Rob Clark <robdclark@...omium.org>
>
> The driver should be in control of this.
>
> Signed-off-by: Rob Clark <robdclark@...omium.org>
> ---
> It is possible that this was masking bugs (ie. not setting appropriate
> pgprot) in drivers.  I don't have a particularly good idea for tracking
> those down (since I don't have the hw for most drivers).  Unless someone
> has a better idea, maybe land this and let driver maintainers fix any
> potential fallout in their drivers?
>
> This is necessary for the last patch to fix VGEM brokenness on arm.

This will break at least v3d and panfrost, and it looks like cirrus as
well, since you're now promoting the mapping to cached by default and
drm_gem_shmem_helper now produces cached mappings.  That's all I could
find that would break, but don't trust me on that.


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