----------------------------------------------------------------------
Message: 1
Date: Tue, 1 Jun 2010 12:25:42 -0700 (PDT)
From: bugzilla-dae...@freedesktop.org
Subject: [Bug 28341] Flickering screen in Neverball on
drm-radeon-testing
To: dri-devel@lists.freedesktop.org
Message-ID: <20100601192542.ace5b130...@annarchy.freedesktop.org>
Content-Type: text/plain; charset="UTF-8"
https://bugs.freedesktop.org/show_bug.cgi?id=28341
--- Comment #3 from Magnus Jensen <mag...@jensenligan.se>
2010-06-01 12:25:42 PDT ---
Sorry. ignore my last attachment. These errors continue to spawn
and i don't
think they are related to neverball. i'm going to recompile mesa
and ddx, and
post another dmesg soon.
Just waiting for a kernel compile to finish.
I saw a similar flickering with latest Xorg stack (mesa master,
xserver, ddx etc. master) and the 2.6.34 tree from radeon testing
with my own toolkit on a R600 gpu. This setup uses the new dri sync &
swap bits and changes how glXSwapbuffers works.
My best hunch would be that submission of new rendering commands by
the direct rendering client to the gpu doesn't block after a
glXSwapbuffers() call until the bufferswap completed, i.e., some
synchronization is missing there.
This shows flickering, but load and timing dependent...
.... glXXX rendering commands to draw image.
glXSwapBuffers();
glBegin(GL_POINTS);
glVertex2i(10,10);
glEnd();
glFinish();
Take a swap completion timestamp here.
glClear();
...more rendering commands
-> I use this glVertex2i, .... glFinish() sequence to wait for swap
completion and get a timestamp. This works on any os/gpu combo ever
tested, but doesn't seem to work reliably anymore with the new radeon
sync & swap bits in place. Display flickers, presumably because the
glClear() executes almost immediately after the glXSwapBuffers is
scheduled, and before the bufferswap has actually taken place ->
Clear the backbuffer before swapping.
This however:
.... glXXX rendering commands to draw image.
glXSwapBuffers();
glXWaitForSbcOML(...);
glClear();
...
does work, because the new glXWaitForSbcOML() blocks the client until
swap completion, so glClear() can only get submitted to the gpu after
the swap completed.
[Except that glXWaitForSbcOML itself currently has a bug, for which
i'll send a patch for xorg master/1.8.1 soon].
Didn't do detailed testing, but maybe this points into the right
direction?
best,
-mario
*********************************************************************
Mario Kleiner
Max Planck Institute for Biological Cybernetics
Spemannstr. 38
72076 Tuebingen
Germany
e-mail: mario.klei...@tuebingen.mpg.de
office: +49 (0)7071/601-1623
fax: +49 (0)7071/601-616
www: http://www.kyb.tuebingen.mpg.de/~kleinerm
*********************************************************************
"For a successful technology, reality must take precedence
over public relations, for Nature cannot be fooled."
(Richard Feynman)
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