[Intel-gfx] [PATCH i-g-t v4 4/5] kms_vblank: Switch from using crtc0 statically to explicitly setting mode.

[Ville Syrjälä]

On Tue, May 10, 2016 at 08:19:50PM +0300, Ville Syrjälä wrote:
> On Tue, May 10, 2016 at 08:03:47PM +0300, Marius Vlad wrote:
> > Robert Foss improved test/kms_vblank and in the same time extended it on
> > all outputs and all pipes. The following seems to happen on pipe B (on
> > pipe A the test always works):
> > 
> > [46795.932490] [drm:drm_wait_vblank] returning 66 to client
> > [46795.932509] [drm:drm_ioctl] pid=17715, dev=0xe200, auth=1, DRM_IOCTL_WAIT_VBLANK
> > [46795.932512] [drm:drm_queue_vblank_event] event on vblank count 132, current 66, crtc 1

That 132 was already confusing me, so I started to look the full log. I
then noticed the following pattern:
[46795.882483] [drm:drm_queue_vblank_event] event on vblank count 129, current 63, crtc 1
[46795.899180] [drm:drm_queue_vblank_event] event on vblank count 130, current 64, crtc 1
[46795.915843] [drm:drm_queue_vblank_event] event on vblank count 131, current 65, crtc 1
[46795.932512] [drm:drm_queue_vblank_event] event on vblank count 132, current 66, crtc 1

So the target vblank count was incrementing in lockstep with the current
counter value, which then told me these are relative waits instead of
absolute as they should have been. It's a bug in the pipe_id_to_vbl_flag().
I replied to the relevant mail already.

-- 
Ville Syrjälä
Intel OTC