garbled screen with RPI4 on 5.10-rc2

[Lucas Nussbaum]

On 03/11/20 at 15:33 +0100, Stefan Schake wrote:
> Your kernel command line from the initial post seems to already have a
> 
> video=HDMI-A-1:1920x1080M at 60
> 
> setting, and this will override any HDMI detection.

Ah, right!

Adding:
disable_fw_kms_setup=1
to config.txt fixes this (this is documented in https://www.raspberrypi.org/documentation/configuration/cmdline-txt.md)

Thanks!

Now I'm confused: with the state of 5.10-rc2, should I get hardware
acceleration in X? Mesa still uses llvmpipe here. (but maybe something
else is too old in Debian 10)

- Lucas