linux-kernel - [PATCH 0/3] drm: omapdrm: Fix excessive GEM buffers DMM/CMA usage

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Date:   Wed, 19 Jan 2022 12:23:08 +0200
From:   Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>
To:     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,
        Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>
Subject: [PATCH 0/3] drm: omapdrm: Fix excessive GEM buffers DMM/CMA usage

This patch series fixes excessive DMM or CMA usage of GEM buffers leading to
various runtime allocation failures. The series enables daily usage of devices
without exausting limited resources like CMA or DMM space if GPU rendering is
needed.

The first patch doesn't bring any functional changes, it just moves some
TILER/DMM related code to a separate function, to simplify the review of the
next two patches.

The second patch allows off-CPU rendering to non-scanout buffers. Without that
patch, it is basically impossible to use the driver allocated GEM buffers on
OMAP3 for anything else but a basic CPU rendered examples as if we want GPU
rendering, we must allocate buffers as scanout buffers, which are CMA allocated.
CMA soon gets fragmented and we start seeing allocation failures. Such failres
in Xorg cannot be handeled gracefully, so the system is basically unusable.

Third patch fixes similar issue on OMAP4/5, where DMM/TILER spaces get
fragmented with time, leading to allocation failures.

Series were tested on Motolola Droid4 and Nokia N900, with OMAP DDX and
PVR EXA from https://github.com/maemo-leste/xf86-video-omap

Ivaylo Dimitrov (3):
  drm: omapdrm: simplify omap_gem_pin
  drm: omapdrm: Support exporting of non-contiguous GEM BOs
  drm: omapdrm: Do no allocate non-scanout GEMs through DMM/TILER

 drivers/gpu/drm/omapdrm/omap_gem.c        | 198 +++++++++++++++++-------------
 drivers/gpu/drm/omapdrm/omap_gem.h        |   3 +-
 drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c |   5 +-
 3 files changed, 116 insertions(+), 90 deletions(-)

-- 
1.9.1