Linux 3.x: Flickering when logging into GNOME Shell or Unity

[Alex Deucher]

On Wed, Oct 17, 2012 at 11:26 AM, Paul Menzel
<paulepanter at users.sourceforge.net> wrote:
> Dear Linux folks,
>
>
>
> Am Mittwoch, den 17.10.2012, 16:49 +0200 schrieb Paul Menzel:
>
>> setting up an ASUS M2A-VM after some months with
>>
>>         [    3.178337] [drm] initializing kernel modesetting (RS690 0x1002:0x791E 0x1043:0x826D).
>>
>> logging in into GNOME Shell (GNOME 3) or for testing with Ubuntu 12.04
>> and Unity, the image flickers for a second and then works normally.
>>
>> Turning on debugging
>>
>>         /sys/module/drm/parameters$ echo "0x06" | sudo tee debug
>>         sudo: unable to resolve host granit
>>         0x06
>>
>> before logging in, the following is logged. Looking at the source code,
>> I do not see that this is supposed to be a problem. But maybe you can
>> figure out more.
>>
>>         [  454.896408] [drm:drm_mode_addfb], [FB:41]
>>         [  454.896427] [drm:radeon_crtc_page_flip], flip-ioctl() cur_fbo = ffff880072438400, cur_bbo = ffff880037072400
>
> trying Linux 3.5
>
>         $ dpkg -l linux-image-3.5* | grep ii | tr -s ' ' | cut -d ' ' -f 2-4
>         linux-image-3.5-trunk-amd64 3.5.5-1~experimental.1 amd64
>
> the flickering is still there.

I don't see anything wrong in the log.  Does the flicker occur at
regular intervals or just at start up?  I suspect the flicker may be
due to your desktop environment probing for monitors at startup which
causes a flicker if nothing is attached to the analog ports (VGA,
s-video) as that results in a load detection operation to probe for
old monitors without EDIDs or analog TVs.

Alex