[Bug 43191] Radeons needs 2D (MACRO) color tiling for optimal performance

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=43191

--- Comment #21 from Simon Farnsworth <simon.farnsworth at onelan.co.uk> 2011-12-01 09:50:56 PST ---
Created attachment 54028
  --> https://bugs.freedesktop.org/attachment.cgi?id=54028
Program to demonstrate misrendering issue

Thanks to Jerome's hint, I took some time to try and spot misrendering, as I'm
struggling to see other problems. The attached program shows that I'm getting
bascially correct rendering, but each time I draw to the backbuffer, something
else gets partly overwritten - the front buffer if I haven't attempted a
modeset  after running something that uses OpenGL, something unidentified
otherwise.

At 2560x1440, the rendering to the back buffer partially overwrites the front
buffer - I see a block at the bottom right (approximately - judged by tape
measure - 1280 pixels wide by 45 high) being overwritten.

At 1920x1200, the block at the bottom right is around 400 pixels wide, 45 high.

At 1280x800, the block is still around 45 high, but is now around 640 pixels
wide.

If I modeset via xrandr after running a test, the next run renders perfectly.
If I repeat without modesetting, I'm fine. When a run has rendered perfectly, 

I should also note that I don't see issues with plymouth, or when rendering via
X11, implying that my remaining problem with tiled scanout is getting Mesa to
work properly.

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