Regression 2.6.27 -> 2.6.28

[Alex Deucher]

On Sat, Jan 31, 2009 at 8:26 AM, Michel Dänzer <michel at daenzer.net> wrote:
> On Fri, 2009-01-30 at 20:52 +0100, Jörg-Volker Peetz wrote:
>>
>> But with radeon_crtc_modeset_ioctl() calls in legacy_crtc_dpms() in
>> xf86-video-ati/src/legacy_crtc.c disabled like this:
>>
>> $ diff legacy_crtc.c legacy_crtc.c.orig
>> 671,672c671,672
>> <     /*    if (mode == DPMSModeOff)
>> <           radeon_crtc_modeset_ioctl(crtc, FALSE); */
>> ---
>> >     if (mode == DPMSModeOff)
>> >     radeon_crtc_modeset_ioctl(crtc, FALSE);
>> 710c710
>> <       /* radeon_crtc_modeset_ioctl(crtc, TRUE); */
>> ---
>> >     radeon_crtc_modeset_ioctl(crtc, TRUE);
>>
>> the wakeups stayed below 5/s after xset dpms force off.
>
> Okay. Unfortunately, we can't just remove these calls, or 3D
> applications with sync-to-vblank enabled may hang after a mode switch.
> We need to know the exact conditions under which the CRTC frame counter
> registers reset to zero, then we can move these calls where they are
> really necessary.

The crtc frame counters are reset when the crtc is disabled or when
the the frame count reset registers are written to.

Alex