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.
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).
No, I don't think that the logs would be helpful.
I make git bisect and found problem introduced in commit a46a7350b1e85fe78580f6a4c809a876867a9df8
Yes, I know that you are going to ask the bleeding obvious. I took the code out and the problem disappeared.
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.