black screen with mouse cursor under kernel 5.7.14 with i915 driver on Cherrytrail & Baytrail CPUs

[René J.V. Bertin]

Hi,

Not a KDE issue in itself (I think) but one that certainly does affect Plasma; I'm posting it here to see if someone has seen this too and found a fix.

After installing a home-built 5.7.14 kernel I'm getting an all-black screen with just the mouse cursor visible on my Cherrytrail (N3150) and Baytrail (some Atom CPU in a Chuwi hybrid PC) PCs.  The SDDM greeter screen is fine (as long as I don't invoke the DE switcher) and the VTYs work fine too. Hitting Shift-Alt-F12 gives me a somewhat wonky view on the Konsole kpart (but not any window decoration or panel).

This happens with an old KUbuntu 14.04 but also on a fresh Devuan Beowulf install. The latter sits on a removable drive; if I boot an HP laptop with a somewhat recent i3 the desktop appears just fine.

It looks thus as if there's a regression in the OpenGL and/or direct rendering parts of the i915 driver for lower-end Celeron and Atom CPUs. Googling turned up all kinds of black screen issues (evidently...) but only 1 with the same symptoms but in an older 5.x kernel series (and no solution other than installing an older kernel IIRC).

Does all this ring a bell? Can anyone confirm that Plasma works OK with the latest 5.6 kernel (stock or else with the Con Kolivas patch)?

Thanks,
R.