[PATCH] Radeon Xpress 200M freeze fix

[Matthias Hopf]

ATI Radeon XPRESS 200M freezes on VT switch (often even during initial
Xserver start).  It turned out to be a regression, which was introduced
with git commit 7d9f643ae3d07 for fixing xorg bug 21321.

It seems that on this chip you cannot reliably disable crtcs. I tried to
work around that with usleep()s, but I didn't succeed fully. Patch 2+3
are different attempts, both fix the issue somewhat, but after 5-60 VT
switches (depending on phase of the moon or whatever) the system freezes
again. Note that the freeze happens not at register access time, but
sometime later, sometimes a second later. Increasing the sleep time
doesn't help much.

The attached Patch 1 disables crtc switch-off for the affected chips -
it seems on these chips there is not much potential for power saving
anyway, at least my measurements (when they were successful with one of
my other patches) were pretty inconclusive.

I'd like to see Patch 1 applied. Patches 2 and 3 are just for reference.
If there is a different potential fix, I can reproduce the issue here
and would be able to test patches.

Matthias

-- 
Matthias Hopf <mhopf at suse.de>      __        __   __
Maxfeldstr. 5 / 90409 Nuernberg   (_   | |  (_   |__          mat at mshopf.de
Phone +49-911-74053-715           __)  |_|  __)  |__  R & D   www.mshopf.de
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