[Dell Precision 7520] kernel 5.15.0-41 update results in dim screen (5.13.0-52 OK)

[Mike Kordosky]

A recent update to 5.15.0-41 results in my laptop screen (Dell Precision 7520) being unable to come up to full brightness. I have verified that I can revert to 5.13.0-52 and the problem is not there. I looked at /sys/class/backlight/nv_backlight/max_brightness which lists 1023 in the newer kernel and 100 in the older one. I have verified that changing the brightness manually does change /sys/class/backlight/nv_backlight/brightness, all the way up to 1023, but it's just not enough... the screen is still very dim. The other screen (standalone monitor through docking station) on a two-headed display is fine. I tried to write 100 into max_brightness but of course, the "file" is read-only.

[Mike Kordosky (mike-kordosky)]

Verified that the behavior is the same when the laptop is used stand-alone, unconnected to a docking station.

[Aaron Rainbolt (arraybolt3)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. Please execute the following command only once, as it will automatically gather debugging information, in a terminal:
apport-collect 1981727

When reporting bugs in the future please use apport by using 'ubuntu-bug' and the name of the package affected. You can learn more about this functionality at https://wiki.ubuntu.com/ReportingBugs.

[Mike Kordosky (mike-kordosky)]

Perhaps this comment from the changes log is relevant:

amd/display: set backlight only if required

[Mike Kordosky (mike-kordosky)]

For whatever reason I don't have crashdb.conf ...

kordosky@miketop5:~$ apport-collect 1981727
Traceback (most recent call last):
  File "/usr/share/apport/apport-gtk", line 596, in <module>
    app = GTKUserInterface()
  File "/usr/share/apport/apport-gtk", line 56, in __init__
    apport.ui.UserInterface.__init__(self)
  File "/usr/lib/python3/dist-packages/apport/ui.py", line 206, in __init__
    self.crashdb = apport.crashdb.get_crashdb(None)
  File "/usr/lib/python3/dist-packages/apport/crashdb.py", line 822, in get_crashdb
    with open(conf) as f:
FileNotFoundError: [Errno 2] No such file or directory: '/etc/apport/crashdb.conf'