debcrafters-packages team mailing list archive

[Mario Limonciello <2110585@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

At shutdown time systemd will record the most recently used brightness
value and then attempt to restore it the next boot.

In order to do this; it currently will read the 'actual_brightness'
value and use that to save.

This normally works fine; but GPU drivers don't always show the same
value in 'brightness' and 'actual_brightness' meaning that the wrong
value may be restored the next boot.

This problem is very prominently found on AMD APUs starting with kernel
6.15 due to a new feature called "custom brightness curves".  Custom
brightness curves are brightness values programmed by an OEM in the
firmware to make the panel behave optimally.  The 'actual_brightness' of
some 'brightness' values will be lower.

For example if the brightness a user requested was 150, the
actual_brightness might be 130. So the next boot the brightness will be
"set" to 130, but the actual brightness might be 115. If the user
reboots again it will be set to 115 for the next boot but the actual
brightness might be 100. That is this gets worse and worse each reboot
cycle until the system eventually boots up at minimum brightness.

This has been fixed in upstream systemd in this commit:
https://github.com/systemd/systemd/commit/9a224c307b36610e3675390eb2620e74d0f4efb0

This should be backported to any Ubuntu release that adopts kernel 6.15
or later.  That means that this should be fixed in Questing, followed by
backported to Noble because Noble will get OEM and HWE kernels that are
newer.

** Affects: systemd (Ubuntu)
     Importance: Undecided
         Status: New

** Affects: systemd (Ubuntu Noble)
     Importance: Undecided
         Status: New

** Affects: systemd (Ubuntu Questing)
     Importance: Undecided
         Status: New


** Tags: originate-from-2106669

** Also affects: systemd (Ubuntu Questing)
   Importance: Undecided
       Status: New

** Also affects: systemd (Ubuntu Noble)
   Importance: Undecided
       Status: New

** Tags added: originate-from-2106669

-- 
You received this bug notification because you are a member of
Debcrafters packages, which is subscribed to systemd in Ubuntu.
https://bugs.launchpad.net/bugs/2110585

Title:
  Stop using 'actual_brightness' in systemd

Status in systemd package in Ubuntu:
  New
Status in systemd source package in Noble:
  New
Status in systemd source package in Questing:
  New

Bug description:
  At shutdown time systemd will record the most recently used brightness
  value and then attempt to restore it the next boot.

  In order to do this; it currently will read the 'actual_brightness'
  value and use that to save.

  This normally works fine; but GPU drivers don't always show the same
  value in 'brightness' and 'actual_brightness' meaning that the wrong
  value may be restored the next boot.

  This problem is very prominently found on AMD APUs starting with
  kernel 6.15 due to a new feature called "custom brightness curves".
  Custom brightness curves are brightness values programmed by an OEM in
  the firmware to make the panel behave optimally.  The
  'actual_brightness' of some 'brightness' values will be lower.

  For example if the brightness a user requested was 150, the
  actual_brightness might be 130. So the next boot the brightness will
  be "set" to 130, but the actual brightness might be 115. If the user
  reboots again it will be set to 115 for the next boot but the actual
  brightness might be 100. That is this gets worse and worse each reboot
  cycle until the system eventually boots up at minimum brightness.

  This has been fixed in upstream systemd in this commit:
  https://github.com/systemd/systemd/commit/9a224c307b36610e3675390eb2620e74d0f4efb0

  This should be backported to any Ubuntu release that adopts kernel
  6.15 or later.  That means that this should be fixed in Questing,
  followed by backported to Noble because Noble will get OEM and HWE
  kernels that are newer.

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/2110585/+subscriptions