Bug 72750

Summary: [BYT]Flicker screen shows on VGA output while testing testdisplay -f 38.25,800,832,912,1024,600,603,607,624
Product: DRI Reporter: Guo Jinxian <jinxianx.guo>
Component: DRM/IntelAssignee: Jesse Barnes <jbarnes>
Status: CLOSED FIXED QA Contact: Intel GFX Bugs mailing list <intel-gfx-bugs>
Severity: normal    
Priority: medium CC: intel-gfx-bugs, lucas
Version: XOrg git   
Hardware: Other   
OS: All   
Whiteboard:
i915 platform: i915 features:
Attachments:
Description Flags
dmesg none

Description Guo Jinxian 2013-12-16 09:40:15 UTC 
Environment:
--------------------------
Kernel: drm-intel-testing
commit 95d42e7d341861132ffec806328dd7fc85516995
Merge: cf8f3ba 2a0a016
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Fri Dec 13 17:57:43 2013 +0100

    Merge remote-tracking branch 'origin/topic/core-stuff' into drm-intel-nightly

Bug detailed description:
-----------------------------
Flicker screen while testing testdisplay -f 38.25,800,832,912,1024,600,603,607,624
It occurs on 1 machine(total test on 3 machines).It's first time to run display test on this machine, and we didn't find good point.

Steps:
---------------------------
./testdisplay -f 38.25,800,832,912,1024,600,603,607,624
Comment 1 Guo Jinxian 2013-12-16 09:46:06 UTC 
The testing runs on 2 pipe mode(eDP+VGA) and the flicker screen shows on VGA screen. If only pluged VGA, flicker screen will doesn't shown.
Comment 2 Daniel Vetter 2013-12-16 10:00:03 UTC 
Can you please attach a debug dmesg here?

Also a short video of the flickering might help.
Comment 3 Guo Jinxian 2013-12-17 00:51:52 UTC 
Created attachment 90849 [details]
dmesg
Comment 4 Guo Jinxian 2013-12-17 01:21:43 UTC 
(In reply to comment #2)
> Can you please attach a debug dmesg here?
> 
> Also a short video of the flickering might help.

Please check the dmesg in attachment. 

About video, It's bigger than the attachment limit, I upload it on youtube, here is the link: http://youtu.be/NXzOA9Ye208
Comment 5 Daniel Vetter 2014-01-08 17:31:27 UTC 
Is the 800x600 mode the only one that flickers like this?

I presume it works well on other machines, but with the same monitor (just to rule out an issue with the screen)?

Video looks like pipe underruns or some other clock instability.
Comment 6 Guo Jinxian 2014-01-09 01:08:04 UTC 
(In reply to comment #5)
> Is the 800x600 mode the only one that flickers like this?
> 
> I presume it works well on other machines, but with the same monitor (just
> to rule out an issue with the screen)?
> 
> Video looks like pipe underruns or some other clock instability.

Yes, Only 800x600 mode has this issue, it works well on 1024x768 mode.

We doesn't find this issue on other machines(HSW BDW)

This issue occurs on HDMI output too, plese refer to https://bugs.freedesktop.org/show_bug.cgi?id=72751
Comment 7 Daniel Vetter 2014-01-10 08:06:27 UTC 
Hm, sounds like the PLL is a bit unstable at that dotclock. Jesse, can you try to escalate to hw guys?
Comment 8 Guo Jinxian 2014-03-28 02:07:56 UTC 
I checked on latest -nightly(e5ad48d0d4f08e5db537901a2d7b2f0750ddd88c), This bug  unable to reproduce.
Comment 9 Elizabeth 2017-10-06 14:41:21 UTC 
Closing old verified.

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