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

[Marius Gröger]

Am 04.06.2010 17:17, schrieb Alex Deucher:
> 2010/6/4 Marius Gröger<marius.groeger at googlemail.com>:
>> 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.
[...]
> Any chance you can bisect the problematic commit?

I did a second attempt at bisecting and now I'm confident it is this 
commit which broke my real-time performance in mythtv:

commit eb1f8e4f3be898df808e2dfc131099f5831d491d
Author: Dave Airlie <airlied at redhat.com>
Date:   Fri May 7 06:42:51 2010 +0000

     drm/fbdev: rework output polling to be back in the core. (v4)

Having found the commit is the good news. The bad news is that this 
commit is rather large, so again I'd be depended on the experts around 
here to isolate what's going on.

Dave, would you mind giving a hand as well as the author of this commit?

Thanks
Marius