Bug 92018

Summary:

DPMS blanking breaks Intel TearFree

Product:

xorg

Reporter:

Das <dasnegro>

Component:

Driver/intel

Assignee:

Chris Wilson <chris>

Status:

RESOLVED FIXED

QA Contact:

Intel GFX Bugs mailing list <intel-gfx-bugs>

Severity:

normal

Priority:

medium

Version:

unspecified

Hardware:

All

OS:

Linux (All)

Whiteboard:

i915 platform:

i915 features:

Attachments:

Description	Flags
Xorg.0.log	none
Always progess the shadow buffer after redisplay	none
Always flag the shadow buffer after resetting it fr DPMS on	none

Description Das 2015-09-16 07:25:25 UTC

Hey guys

When recovering from DPMS screen blanking, TearFree in my xorg configuration doesn't seem to have any effect anymore. 

xf86-video-intel = 2.99.917+381+g5772556-1 on Haswell refresh
mesa = 10.6.7

How to reproduce

1. Enable TearFree: https://wiki.archlinux.org/index.php/Intel_graphics#Tear-free_video
2. Restart X and enjoy no tearing
3. Run: xset dpms force off
4. Resume from blanking
5. Enjoy your broken TearFree/tearing

Comment 1 Chris Wilson 2015-09-16 12:17:33 UTC

Please attach your Xorg.0.log.

Comment 2 Das 2015-09-17 08:14:43 UTC

Created attachment 118323 [details]
Xorg.0.log

Added the Xorg log. This happens with both UXA and SNA

Comment 3 Das 2015-09-17 08:27:11 UTC

If it helps: If I disable TearFree and enable compton with the glx backend, I get no tearing after unblanking

Also, the tearing seems to be most noticeable in firefox, with smooth scrolling on

Comment 4 Chris Wilson 2015-09-17 12:16:30 UTC

It should be that the only way TearFree fails is when it is disabled by some allocation failure, or a failure whilst flipping. The latter is permanent (since the kernel is upset and we have no reason to expect it to recover) and logged (notable by its absence in the attached!). The former should be transient, and only noted in the debug logs. If you have the patience, recompiling with ./autogen.sh --enable-debug=full and attaching the massive Xorg.0.log following the failure would be very useful.

Comment 5 dimon 2015-10-25 11:35:30 UTC

I'm having the same issue, see xorg.log with debugging enabled.
http://tempsend.com/114F0FC96A

Comment 6 Chris Wilson 2015-10-25 15:45:41 UTC

Created attachment 119186 [details] [review]
Always progess the shadow buffer after redisplay

Thanks, I can see what the problem is, just need to think carefully about the ramifications. The attached should help, but at the very least it is treating the symptom rather than the cause.

Comment 7 Chris Wilson 2015-10-26 11:47:54 UTC

Created attachment 119198 [details] [review]
Always flag the shadow buffer after resetting it fr DPMS on

This should be the real fix!

Comment 8 dimon 2015-10-26 12:28:32 UTC

Thanks Chris, it works.

Comment 9 Chris Wilson 2015-10-26 12:48:35 UTC

And thanks for the bug report and feedback.

commit be3748802398a741208715233d36935378ceff58
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Sun Oct 25 15:41:10 2015 +0000

    sna: Always flag the shadow buffer after resetting it fr DPMS on
    
    When switching the outputs back on, we show the current front buffer and
    so for TearFree we always then need to flag the front buffer as active.
    Failing to do so left us rendering straight onto the scanout, defeating
    the notion of TearFree.
    
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92018
    Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

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