Comment 130 for bug 755791

I patched 3.0.4. It's a must-have, but not simple.

It partially fixes. "black box glxgears" nor "irq count freeze" never happen. "pageflip" on-or-off doesn't matter. Xorg.0.log isn't affected. dmesg is the same with unpatched 3.0.4, except MSI:
------------------------------------------------------------------------
@@ -8,12 +8,10 @@
 radeon 0000:01:05.0: GTT: 512M 0x0000000060000000 - 0x000000007FFFFFFF
 [drm] Supports vblank timestamp caching Rev 1 (10.10.2010).
 [drm] Driver supports precise vblank timestamp query.
+radeon 0000:01:05.0: irq 42 for MSI/MSI-X
+radeon 0000:01:05.0: radeon: using MSI.
 [drm] radeon: irq initialized.
 [drm] Detected VRAM RAM=128M, BAR=128M
 [drm] RAM width 128bits DDR
------------------------------------------------------------------------

Glxgears fps is always only 60 (which is 240 with good kms), regardless of "pageflip" or "vblank_mode=0".

But that's not all; The first time I booted the patched kenel, right after udev loaded the module, (I was on VT1) it seemed ok - the screen went high resolution, the previous screen contents were correctly shown, and the cursor continued blinking - but it halted there. Keypresses are echoed to the screen, but Ctrl+Alt+Del didn't work.

It happened only once, and after that, all 5 boots were successful.

It also seems to have a nice side effect; when kms is enabled in the bad kernel, I often experinced a problem in s2ram, but with your patch s2ram has succeeded in some 10 trials in row. So I think we're in the right direction.
(The problem was that for most times suspend doesn't complete, or takes too long, after the screen turns black.)

Since I don't need opengl, I'm quite satisfied with this patch. =P