exa broke xaa pixmap cache?

[Benjamin Herrenschmidt]

> 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 
> location?

Yes; I think it does. We need to put back those calls at the end of the
function in the XAA case.

Ben.