linux-kernel - Re: [PATCH] drm/vc4: Allow using more than 256MB of CMA memory.

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Message-ID: <87shldglhn.fsf@eliezer.anholt.net>
Date:   Wed, 12 Apr 2017 18:11:16 -0700
From:   Eric Anholt <eric@...olt.net>
To:     dri-devel@...ts.freedesktop.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/vc4: Allow using more than 256MB of CMA memory.

Eric Anholt <eric@...olt.net> writes:

> Until now, we've had to limit Raspberry Pi to 256MB of CMA memory to
> keep from triggering the hardware addressing bug between of the tile
> binner of the tile alloc memory (where the top 4 bits come from the
> tile state data array's address).
>
> To work around that and allow more memory to be reserved for graphics,
> allocate a single BO to store tile state data arrays and tile
> alloc/overflow memory while the GPU is active, and make sure that that
> one BO doesn't happen to cross a 256MB boundary.  With that in place,
> we can allocate textures and shaders anywhere in system memory (still
> contiguous, of course).

Ping for reviewers on this one -- it's a pretty big usability win.

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