Bug 109602

Summary: Artifacts present in video since about kernel verion 4.19.2
Product: DRI Reporter: Trevor McGrath <bcsucks>
Component: DRM/IntelAssignee: Intel GFX Bugs mailing list <intel-gfx-bugs>
Status: CLOSED WORKSFORME QA Contact: Intel GFX Bugs mailing list <intel-gfx-bugs>
Severity: minor    
Priority: low CC: intel-gfx-bugs
Version: XOrg git   
Hardware: x86-64 (AMD64)   
OS: Linux (All)   
Whiteboard: Triaged
i915 platform: IVB i915 features:
Description Flags
Picture from display showin one set of black lines on image at FHD resolution. none

Description Trevor McGrath 2019-02-10 00:36:27 UTC
Created attachment 143354 [details]
Picture from display showin one set of black lines on image at FHD resolution.

On gentoo, nothing changed but kernel. After kernel build of kernel version some 3 months ago I notice in HD4000 graphics of ivy bridge strange phenomenon. Black lines every few lines. Looks like some stride value incorrect computed. 

Have attach image with picture showing black lines. FWIW if screenshot taken lines do not appear. I tested with display with external and internal displays and only appears with linux. Running macos problem not appear.
Comment 1 Lakshmi 2019-02-10 19:24:16 UTC
Can you attach dmesg from boot with kernel parameters drm.debug=0x1e log_buf_len=4M? 
Also, I would recommend you to check the behavior with latest drmtip (https://cgit.freedesktop.org/drm-tip).
Comment 2 Trevor McGrath 2019-02-14 21:20:01 UTC
No, I don't think that the logs would be helpful.

I make git bisect and found problem introduced in commit a46a7350b1e85fe78580f6a4c809a876867a9df8
Comment 3 Trevor McGrath 2019-02-14 21:21:25 UTC
Yes, I know that you are going to ask the bleeding obvious. I took the code out and the problem disappeared.
Comment 4 Jani Nikula 2019-02-20 14:13:47 UTC
Please let us be the judge of what we'll find helpful or not.

Please try drm-tip as suggested in comment #1 and attach the full dmesg.

The bisected regressing commit a46a7350b1e8 ("drm/i915: Fix ilk+ watermarks when disabling pipes") is a stable backport to v4.19.3. The original upstream commit is df5e31c204b3 ("drm/i915: Fix ilk+ watermarks when disabling pipes") introduced in v4.20.
Comment 5 Trevor McGrath 2019-03-02 22:34:50 UTC
strange. When I do git log --pretty=oneline v4.19.2..v4.19.3 | head -12 | tail -1
I see this:
a46a7350b1e85fe78580f6a4c809a876867a9df8 drm/i915: Fix ilk+ watermarks when disabling pipes
Comment 6 Lakshmi 2019-03-07 14:56:32 UTC
Trevor, still having issue with latest drmtip?
Comment 7 Lakshmi 2019-04-12 09:08:59 UTC
No feedback for more than a month. I assume the latest drmtip fixed the issue.
Closing this bug as WORKSFORME. 
Please reopen the bug if this issue appears on drmtip.

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