[Bug 99491] New: Tearing with DRI3 in OpenGL applications

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=99491

            Bug ID: 99491
           Summary: Tearing with DRI3 in OpenGL applications
           Product: xorg
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Driver/Radeon
          Assignee: xorg-driver-ati at lists.x.org
          Reporter: andreaskem at web.de
        QA Contact: xorg-team at lists.x.org

Created attachment 129091
  --> https://bugs.freedesktop.org/attachment.cgi?id=129091&action=edit
dmesg output

Hello graphics team,

I am on an almost up-to-date (kernel at 4.9.4 ATM) Arch Linux system with the
[testing] repository enabled. My hardware is the old integrated GPU in an AMD
E2-2000 mobile CPU (Wrestler [Radeon HD 7340]) using the Radeon r600 driver.

A few weeks ago before Christmas, I noticed that a stable tear appeared in
movie players and games using OpenGL on X11. This was most likely caused by a
package update but I did not investigate further. In hindsight, the reason was
most likely the package update from xf86-video-ati 7.8.0-2 ->
7.8.99.r13.g404c6475 that I performed on 2016-12-16 (There appeared an Arch bug
report implicating this version [1]. The package is currently at
7.8.99.r16.gea30d856 but the problem still exists. As far as I can see, nobody
else reported this upstream, yet.).

I have a 1366x768 display and the tear seems to appear be at a height of ~100
pixels from the top. Also, it seems to start at 0x0 (from top left) with a
short diagonal to about 100x100 and then reaches horizontally all the way to
the right. This tear does not appear under Wayland, for me. It also seems to
disappear as soon as DRI3 is disabled by setting the xorg.conf option or by
setting LIBGL_DRI3_DISABLE=1 before starting, e.g. the video player or the game
(video player: mpv --vo=opengl --hwdec=vdpau, game: Stardew Valley). As far as
I remember, I had DRI3 explicitly enabled in my xorg.conf without any problems
before this package update.

I tried capturing the issue with my cell phone camera but was unsuccessful.

Reading the mailing list, I noticed a few recent bug reports due to DRI3 but I
did not find one complaining about tearing. Similar reports appear to be quite
a bit older. I might have missed something, though or somebody else
participating in [1] might have reported it in the meantime.

The versions of the packages that might be relevant are:

xf86-video-ati 7.8.99.r16.gea30d856
linux 4.9.4
xorg-server 1.19.1
mesa 13.0.3
llvm 3.9.1

The Xorg.0.log, glxinfo output and kernel log should be attached.

Thank you for your work on the graphics stack.

---
[1] https://bugs.archlinux.org/task/52620

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