Bug#1010365: linux: failure to boot on Raspberry Pi Compute Module 4 (black screen)

[Cyril Brulebois <cyril@debamax.com>]

Source: linux
Version: 5.17.3-1
Severity: important
X-Debbugs-Cc: raspi-firmware@packages.debian.org

Hi,

In the process of testing patches for the Raspberry Pi Compute Modules
(CM3 and CM4), for bullseye[1][2] and bookworm[2], I discovered that
bookworm images don't boot on the CM4.

 1. https://bugs.debian.org/1010317
 2. https://bugs.debian.org/996937

The usual start-up rainbow is displayed, the screen turns to black and
nothing happens. My first stop was trying to downgrade the bootloader
(shipped by the raspi-firmware package) to the bullseye's version, but
that didn't help.

Then I moved to starting from a bullseye image (which boots), upgrading
the raspi-firmware package, that still boots.

Then I deployed 5.16.18-1 (from snapshot.debian.org), that still boots.

Then I deployed 5.17.3-1, and it broke booting.

I'll try and pinpoint when it broke using the various intermediary
versions:

 - 5.17~rc3-1~exp1
 - 5.17~rc4-1~exp1
 - 5.17~rc5-1~exp1
 - 5.17~rc6-1~exp1
 - 5.17~rc7-1~exp1
 - 5.17~rc8-1~exp1
 - 5.17.1-1~exp1

and then try to figure out what broke exactly. Contrary to my earlier
efforts to introduce support for that hardware a few months ago, I
haven't been following upstream changes recently, so I'll need to catch
up.


Cheers,
-- 
Cyril Brulebois -- Debian Consultant @ DEBAMAX -- https://debamax.com/