thinkpad x1 carbon display flickering after update to 5.12. good on 5.11.x (i915)

[Oleksandr Natalenko]

Hello.

On Fri, May 14, 2021 at 10:24:26AM +0200, Thomas Stein wrote:
> After upgrading to linux 5.12 the display on my X1 Carbon Gen 2 starts to
> flicker. Well actually it seems to turn off and on again and again. Here a
> link to a video a person posted who has the same issue as me obviousely. https://linuxove.com/thinkpad-x1-carbon-gen-3-display-flickering-on-linux-kernel-5-12/
> 
> This happens without having Xorg running too. So it can't be related to
> Xorg. The kernel boots and after a few seconds, the kernel messages scoll
> through, the flickering starts. Nothing special in dmesg.
> 
> dmesg:
> 
> himbeere at rather ~ $ dmesg | grep i915
> [    0.713595] i915 0000:00:02.0: vgaarb: deactivate vga console
> [    0.720280] i915 0000:00:02.0: vgaarb: changed VGA decodes:
> olddecodes=io+mem,decodes=io+mem:owns=io+mem
> [    0.741494] i915 0000:00:02.0: [drm] Panel advertises DPCD backlight
> support, but VBT disagrees. If your backlight controls don't work try
> booting with i915.enable_dpcd_backlight=1. If your machine needs this,
> please file a _new_ bug report on drm/i915, see
> https://gitlab.freedesktop.org/drm/intel/-/wikis/How-to-file-i915-bugs for
> details.
> [    1.864837] [drm] Initialized i915 1.6.0 20201103 for 0000:00:02.0 on
> minor 0
> [    1.875907] fbcon: i915drmfb (fb0) is primary device
> [    3.158255] i915 0000:00:02.0: [drm] fb0: i915drmfb frame buffer device
> himbeere at rather ~ $
> 
> Downgrading to 5.11 solves the issue for me. Any ideas?

Does [1] fix your issue?

[1] https://cgit.freedesktop.org/drm-tip/patch/?id=acca7762eb71bc05a8f28d29320d193150051f79

-- 
  Oleksandr Natalenko (post-factum)