Bug 217328

Summary:	Open Firmware framebuffer cannot find of-display
Product:	Drivers	Reporter:	Cyril Brulebois (cyril)
Component:	Console/Framebuffers	Assignee:	James Simmons (jsimmons)
Status:	NEW ---
Severity:	normal	CC:	carnil
Priority:	P1
Hardware:	All
OS:	Linux
URL:	https://bugs.debian.org/1033058
Kernel Version:	v6.2-rc8	Subsystem:
Regression:	Yes	Bisected commit-id:	241d2fb56a18473af5f2ff0d512992a996eb64dd

Description Cyril Brulebois 2023-04-12 09:02:45 UTC

Hi,

Initially spotted in Debian as a regression of the Debian Installer on ppc64el, which is currently following the stable linux-6.1.y branch: v6.1.12 regresses, and the installer gets stuck on a black screen instead of opening the usual interface.

Frédéric Bonnard checked that reverting 241d2fb56a18473af5f2ff0d512992a996eb64dd (first shipped in v6.2-rc8) makes the regression go away. For completeness, the regression shows up in the linux-6.1.y branch via the a7f0ec26cd67e7ad6e56753694fddb67a9730f27 cherry-pick (first shipped in v6.1.12).

Since the existing code in drivers/video/fbdev/offb.c only cares about "of-display", I've tested switching it to caring about "of-display.0" instead (without looping/trying possible other device nodes), and the resulting Debian Installer builds starts happily again.

I'll submit the patch in a moment, I wanted to have a reference in bugzilla first.

I've noticed that drivers/gpu/drm/tiny/ofdrm.c (first shipped in v6.2-rc1) is very likely to have the exact same problem, but I don't think I can easily confirm this. I might submit a patch for it anyway.

Comment 1 Cyril Brulebois 2023-04-12 10:01:46 UTC

The cover letter and the two patches: https://lore.kernel.org/all/20230412095509.2196162-1-cyril@debamax.com/T/#t