exa broke xaa pixmap cache?

Roland Scheidegger rscheidegger_lists at hispeed.ch
Fri Sep 23 03:11:52 PDT 2005

Roland Scheidegger wrote:
> I've some issues when using good old xaa with the current radeon driver. 
> After starting a 3d app, the background image gets broken. This only 
> seems to happen when there isn't a lot of video memory available (I only 
> noticed it because I've reduced the amount of pixmap cache the X server 
> reserves but it happens with the "standard" code as well, if I reduce 
> the memory of my card to 32MB instead of 64MB, which will cause it to 
> allocate less than the default 5*framebuffer size). It's actually not 
> 100% broken, the background image on the desktop gets moved up by about 
> 30%, the upper 70% otherwise correct but the bottom 30% (e.g. the part 
> which normally would be at the top) shows obvious tiling artifacts.
> Not sure though if it was actually the exa patch causing this (it worked 
> previously with a 2 week old build).

This was caused because in RadeonDRITransitionTo3d the block setting the 
surface registers and enabling pageflip was moved up to the start of the 
function. It seems this won't work because xaa still uses the memory 
later freed in that function as pixmap cache, thus setting the tiling 
there is wrong and enabling pageflip will overwrite some of the area as 
it will copy the front buffer into what it thinks is back buffer but is 
still pixmap cache. Not completely sure why it causes permanent pixmap 
damage, does XAA copy back pixmap cache from video memory to another 


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