Comment # 7 on bug 1193599 from Takashi Iwai

(In reply to Patrik Jakobsson from comment #2)
> Possible upstream bug report:
> https://gitlab.freedesktop.org/drm/intel/-/issues/4458
(In reply to Patrik Jakobsson from comment #3)
> One person claims a similar problem disappeared between v5.14.6 and v5.15.7.

As far as I checked, both of the above are about Thinkpad P15 Gen 1, and it's
also with Cometlake-H.  So this could be a problem with that chip.

> Possible fixes are:
> 9af4bf2171c1 drm/i915/dp: return proper DPRX link training result
> c8dead5751b8 drm/i915/dp: Use max params for panels < eDP 1.4
> 
> Both were backported to the 15.4 kernel in mid/late September.

Right, those should have been already covered.