linux-kernel - Re: [PATCH 3/3] drm: omapdrm: Do no allocate non-scanout GEMs through DMM/TILER

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Date:   Thu, 17 Feb 2022 14:46:00 +0200
From:   Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To:     Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>, tomba@...nel.org,
        airlied@...ux.ie, daniel@...ll.ch
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-omap@...r.kernel.org, merlijn@...zup.org, tony@...mide.com
Subject: Re: [PATCH 3/3] drm: omapdrm: Do no allocate non-scanout GEMs through
 DMM/TILER

Hi,

On 19/01/2022 12:23, Ivaylo Dimitrov wrote:
> On devices with DMM, all allocations are done through either DMM or TILER.
> DMM/TILER being a limited resource means that such allocations will start
> to fail before actual free memory is exhausted. What is even worse is that
> with time DMM/TILER space gets fragmented to the point that even if we have
> enough free DMM/TILER space and free memory, allocation fails because there
> is no big enough free block in DMM/TILER space.
> 
> Such failures can be easily observed with OMAP xorg DDX, for example -
> starting few GUI applications (so buffers for their windows are allocated)
> and then rotating landscape<->portrait while closing and opening new
> windows soon results in allocation failures.
> 
> Fix that by mapping buffers through DMM/TILER only when really needed,
> like, for scanout buffers.

Doesn't this break users that get a buffer from omapdrm and expect it to 
be contiguous?

  Tomi