[RV350] Blank screen on DVI output after mode switch or DPMS shutdown

[Achim Gratz]

[This is https://bugzilla.novell.com/show_bug.cgi?id=628039 - posted
here on advice of Greg Kroah-Hartman]

The full history can be checked via the above link, here's my latest
findings:

Linux 3.0.3-42-pae #1 SMP Thu Aug 25 02:17:07 UTC 2011 (026eef6) i686 athlon
i386 GNU/Linux

It has gotten better with the newer kernels/drivers, but all
manifestations of the problem persist:

1) blank screen on DVI output after power-save or mode-switching
 a) mostly with the monitor still indicating a signal
 b) sometimes with the monitor saying "no signal, going to sleep"
 c) very seldomly switching between a) and b) at roughly 20 second intervals

2) sporadic 1..2s of screen going blank in the middle of things

My current workaround is to set a very short (3min) DPMS power-off
limit, since the DPMS related problems I was experiencing in the
beginning seem to be resolved.  If I let that limit expire and then
re-activate the monitor it will most of the time work again.  If I'm in
more of a hurry, I connect/disconect VGA and that will usually resolve
it, too (if not I can work for a while on VGA).

I think that the DVI transmitter PLL is not locking correctly in all
these instances (the problem seems to be slightly modulated with
temperature) and that the original ATI driver either does a better job
of a) checking the lock and resetting the PLL if necessary or b) using a
more stable PLL switching sequence.


While browsing the bugs for the radeon driver I found another way to
reproduce this: If I force DPMS off, sleep ten seconds and then force it
back on, the display will often stay blank.  Waiting more seconds in the
sequence gets it back to working order much more often.



Regards,
Achim.
-- 
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

SD adaptation for Waldorf Blofeld V1.15B11:
http://Synth.Stromeko.net/Downloads.html#WaldorfSDada