#1003160 DisplayPort External Monitor no longer recognised after update to kernel 5.15

Package:
xserver-xorg-video-nouveau
Source:
xserver-xorg-video-nouveau
Description:
X.Org X server -- Nouveau display driver
Submitter:
Batwam
Date:
2022-01-09 04:33:03 UTC
Severity:
normal
#1003160#5
Date:
2022-01-05 12:43:37 UTC
From:
To:
Dear Maintainer,

   * Since Debian upgrade from Bullseye/Stable with kernel 5.10 to
Bookworm/Testing with 5.15 kernel, the external monitor connected with
DisplayPort on macbook 5.1 (late 2009) is no longer recognised and only
laptop screen is usable.
   * I checked xrandr and the screen is not listed (not even listed as
"Disconnected"). Note that I am using x11 (not Wayland). Note that I am
unable to test with the nvidia drivers as the legacy-340 drivers are no
longer available.
   * Restarted with 5.10 kernel and the screen is recognised again
   * Note that I am not sure if this is a nouveau issue or other
package (e.g. kernel) as it doesn't look like the port is recognised at
all.

See additional info attached as generated by reportbug
#1003160#10
Date:
2022-01-09 04:27:56 UTC
From:
To:
as an update to the report above, I since noticed that this issue also
occurs if I try to boot from the 5.10.0-10 kernel instead of the
original 5.10.0-09