Glitch in newer drm-next/drm-radeon-testing

[Marius Gröger]

Alex Deucher schrieb:
> 2010/6/4 Marius Gröger <marius.groeger at googlemail.com>:
>> Hi All,
>>
>> Michel Dänzer schrieb:
>>> On Mit, 2010-06-02 at 08:07 +0200, Marius Gröger wrote:
>>>> Hello All,
>>>>
>>>> I'm trying the top-of-trunk drm-2.6 trees (both drm-next and
>>>> drm-radeon-testing) with my Radeon HD 3200 GPU over HDMI. The primary
>>>> application is mythtv which uses DRM syncing for the frame
>>>> syncronisation. Now, with the exact same userland software I noticed the
>>>> introduction of sync gliches in the May-timeframe. The
>>>> drm-radeon-testing on May 9 was still ok, but both drm-next and
>>>> drm-radeon-testing at the end of May showed that glitch: every couple of
>>>> seconds there's a very visual hickup, especially in scroll texts.
>>>>
>>>> Apologies for such an unspecific description, and for what almost seems
>>>> like a support request for MythTV. I wouldn't post here if I were not
>>>> 100% sure it must be related with the recent drm changes.
>>> Note that the DRM APIs are intended for use by userspace components of
>>> graphics drivers / API libraries, not applications directly. MythTV
>>> shouldn't use the DRM directly for synchronization but rather use GLX
>>> synchronization APIs.
>> What about that new dri2 vsync stuff which was mentioned related to [Bug
>> 28383]? Could the changes done for that in any way alter the timing? BTW
>> I measured the glitches I'm experiencing and the appear to be to happen
>> in intervals of 10 seconds. Again, all I'm changing is the kernel, and
>> even the kernel config is the same. I'd be most grateful for any
>> clues/hints/tips I could follow to resolve this regression.
>>
>>> If you have dynamic PM enabled, does disabling that help?
>> I checked again and there's method=profile and profile=default. Afaict
>> this is not using dynpm, right?
>>
> 
> Correct.

Ok so with dynpm more or less ruled out, what could have such a visible
impact on the latencies? For instance, are we now more dependent (or
less) on some kind of interrupt or deferred processing than 6 weeks ago?

Btw, I have HDMI audio pretty much ruled out as well.

Thanks
Marius