https://bugs.freedesktop.org/show_bug.cgi?id=105152
Bug ID: 105152
Summary: Display artifacts related to DCC on radeonsi
Product: Mesa
Version: git
Hardware: x86-64 (AMD64)
OS: Linux (All)
Status: NEW
Severity: normal
Priority: medium
Component: Drivers/Gallium/radeonsi
Assignee: dri-devel@lists.freedesktop.org
Reporter: mario.klei...@tuebingen.mpg.de
QA Contact: dri-devel@lists.freedesktop.org
Created attachment 137424
--> https://bugs.freedesktop.org/attachment.cgi?id=137424=edit
apitrace exposing the problem in realtime replay
This i observe on radeonsi with a Volcanic Islands R9 380 TONGA with one
specific demo in my toolkit.
What the demo does is it renders between 1 and 5 textured quads on top of each
other, each quad with the same texture, but different texture coordinates and
"zoom". It uses alpha-blending with GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA to
blend the layers together. All in an endless animation that creates an
interesting "infinite zoom" effect.
Attached an apitrace of a few seconds of execution of the animation loop.
If the demo doesn't draw about more than 3 such quads per animation frame on
top of each other, the animation looks correct. With 5 quads i get some weird
dynamic noise in some parts of the displayed content, as if parts of the pixels
would somehow overflow and wrap around.
If one steps through the apitrace, looking up state at swapbuffers, each
rendered frame looks correct, but if one replays the trace in real-time, the
visual artifacts show up, so it doesn't seem to be a rendering problem, but
some kind of interaction with DCC?
If i set R600_DEBUG=nodccfb then all artifacts disappear.
Running on older Evergreen hw under r600 instead of radeonsi doesn't cause
these artifacts.
The problem was already present in some earlier Mesa version (17.2 as shipping
in Ubuntu 17.10), and is present in master.
Another way to reproduce is running the demo on a Debian/Ubuntu system via:
1. apt install octave-psychtoolbox-3
2. octave --eval ShepardZoomDemo
Source code of the demo under:
https://github.com/Psychtoolbox-3/Psychtoolbox-3/blob/master/Psychtoolbox/PsychDemos/OpenGL4MatlabDemos/ShepardZoomDemo.m
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