Bug 92874

Summary: FBC on HD4600 causes screen flickering on certain screen content
Product: DRI Reporter: Petr Kulhavy <brain>
Component: DRM/IntelAssignee: Intel GFX Bugs mailing list <intel-gfx-bugs>
Status: CLOSED INVALID QA Contact: Intel GFX Bugs mailing list <intel-gfx-bugs>
Severity: normal    
Priority: medium CC: brain, intel-gfx-bugs, przanoni
Version: unspecified   
Hardware: x86-64 (AMD64)   
OS: All   
Whiteboard:
i915 platform: HSW i915 features: display/FBC
Attachments:
Description Flags
Video record of the issue none

Description Petr Kulhavy 2015-11-09 21:03:46 UTC 
Machine: Asus "Zenbook" UX501
CPU: i7 4720HQ
GPU: Intel HD4600
Kernel 4.3.2
OS: Kubuntu 15.10

After enabling FBC with kernel option "i915.enable_fbc=1" the screen flickers with specific video content. Typically Firefox browser with some page. As an example the "https://01.org/linuxgraphics/community/kernel" at the default zoom level.

Please note that my notebook has 4k display. I have seen the issue only on the built-in panel, not on an external screen.

The flickering typically looks like the picture is switching between correct look and the same picture shifted down. The Y offset varies depending on the content. So does the flickering frequency. In the above example the offset is about half of the screen height.

If the content changes, e.g. change the zoom level in Firefox (on the above example it's sufficient to scroll down to the text so the picture disappears), the flickering changes or disappears.
Comment 1 Petr Kulhavy 2015-11-09 21:16:46 UTC 
Created attachment 119524 [details]
Video record of the issue
Comment 2 Paulo Zanoni 2016-01-29 21:16:23 UTC 
Hi

Does this problem still happen if you use the most recent drm-intel-nightly branch from http://cgit.freedesktop.org/drm-intel ?

Thanks,
Paulo
Comment 3 Paulo Zanoni 2016-10-28 11:39:38 UTC 
Closing bug due to no response from the bug reporter in 10 months, plus the fact that we fixed a huge pile of FBC bugs after this bug was reported.

If you think the bug is still present, feel free to reopen it, but please test it against a newer Kernel with drm.debug=0xe and provide the dmesg output.

Thanks,
Paulo

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