Am 23.06.2014 21:46, schrieb Dieter Nützel:
Am 23.06.2014 11:34, schrieb Michel Dänzer:
On 18.06.2014 18:14, Christian König wrote:
Am 18.06.2014 07:53, schrieb Michel Dänzer:
Looking into these issues has got me thinking about the use of the
page
flip interrupt: If the page flip interrupt arrives before the
corresponding
vertical blank interrupt, the DRM vblank counter will be lower than
expected by 1 in drm_send_vblank_event(). I suspect this is the
cause of
(WW) RADEON(0): radeon_dri2_flip_event_handler: Pageflip
completion
event has impossible msc [x-1] < target_msc [x]
messages in the X log file which have been popping up in bug reports
lately.
This also results in 0s being returned to the client for the MSC and
timestamp of the swap completion, which could cause all kinds of bad
behaviour.
First of all thanks for looking into it. Are you getting this on 3.16
or
3.15?
I haven't actually run into this myself yet. I thought I'd seen it in
several bug reports, but right now I can only find
https://bugs.freedesktop.org/show_bug.cgi?id=80029#c17 , which seems
to
include the page flipping changes from 3.16.
With 3.16-rc2 I get it now on my RV730 AGP as in the above bug report.
But only the lines in Xorg.0.log.
NO signs of any damage/error in use.
Since 3.15 and 3.16 (rc2 only) my system is rock solid.
I've tried 3.15-rc7 + Christian's pflip rework (did some little
handwork), too.
It was solid but I saw the reported flip/black distortion in the below
part during Kwin 4.13 cube screen effect (rotation). Your fix for
3.16-rc1 fixed that.
Before 3.15/3.16-rcX I got some hangs from time to time during system
boot.
Nothing in the logs but SSD RAID1 rebuild. Maybe it was MD related an
NOT r600/DRM.
3.16-rcX (3.15-rc7+pflip patches) seems to be more responsive that
3.15, for me.
First and latest attchments from bug #80141
https://bugs.freedesktop.org/attachment.cgi?id=101605
show same.
Where should I add/send my Xorg.0.log?
Cheers,
Dieter
Addendum:
I can reliable generate such lines in Xorg.0.log with KWin cube desktop
effect.
Rotate screens with mouse wheel or screen switcher => new entry in
Xorg.0.log. If it happens I notice ('see') flip delay.
[ 9893.183] (WW) RADEON(0): radeon_dri2_flip_event_handler: Pageflip
completion event has impossible msc 594382 < target_msc 594383
[ 10859.753] (WW) RADEON(0): radeon_dri2_flip_event_handler: Pageflip
completion event has impossible msc 652497 < target_msc 652498
[ 10915.719] (WW) RADEON(0): radeon_dri2_flip_event_handler: Pageflip
completion event has impossible msc 655863 < target_msc 655864
[ 10916.817] (WW) RADEON(0): radeon_dri2_flip_event_handler: Pageflip
completion event has impossible msc 655929 < target_msc 655930
[ 10925.843] (WW) RADEON(0): radeon_dri2_flip_event_handler: Pageflip
completion event has impossible msc 656472 < target_msc 656473
[ 10926.774] (WW) RADEON(0): radeon_dri2_flip_event_handler: Pageflip
completion event has impossible msc 656528 < target_msc 656529
[ 10965.519] (WW) RADEON(0): radeon_dri2_flip_event_handler: Pageflip
completion event has impossible msc 658859 < target_msc 658860
[ 11081.878] (WW) RADEON(0): radeon_dri2_flip_event_handler: Pageflip
completion event has impossible msc 665846 < target_msc 665847
I don't think that the pflip irq is thrown earlier than the vblank,
but
on 3.16 it might actually be that we program the flip so fast into
the
hardware that we do it one frame earlier than planned.
So userspace is notified of the previous vertical blank period and
calls
the page flip ioctl in response, which then manages to program the
scanout address update into the hardware before the scanout address
update is latched during the previous vertical blank period?
To avoid that scenario, one possibility might be to check if we're in
vertical blank before calling radeon_page_flip(), and if so sleep for
1ms or so before trying again? That might unnecessarily delay flips on
other CRTCs though...
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