Bug#964839: bbswitch-dkms: Fails to re-enable graphics after suspend with kernel 5.7

[Felix Dörre]

Package: bbswitch-dkms
Version: 0.8-9
Severity: important

Dear Maintainer,

After upgrading to kernel 5.7, bbswitch fails to re-enable the graphics card deterministically after resuming from standby.
Rebooting the system solves the problem until the next standby. Booting with the still installed kernel 5.6 does not show any problems.

The relevant errors from dmesg (when booting with a 5.7 kernel, verifying that bbswitch works, entering standby, resuming from standby, verifying that bbswitch does not work):
[   34.472822] nvidia-modeset: Unloading
[   34.489477] nvidia-nvlink: Unregistered the Nvlink Core, major device number 243
[   34.583390] bbswitch: disabling discrete graphics
[   34.600540] pci 0000:01:00.0: refused to change power state from D0 to D3hot
[   40.298879] PM: suspend entry (deep)
....
[   45.751278] PM: suspend exit
....
[   48.589904] bbswitch: enabling discrete graphics
[   48.589911] pci 0000:01:00.0: can't change power state from D3cold to D0 (config space inaccessible)
[   48.589915] pci 0000:01:00.0: can't change power state from D3cold to D0 (config space inaccessible)

I can provide a full dmesg log if this is needed. I am also not sure, if this is a kernel bug or a bbswitch bug. With kernel 5.6 bbswitch works flawlessly.

-- System Information:
Debian Release: bullseye/sid
  APT prefers unstable-debug
  APT policy: (500, 'unstable-debug'), (500, 'unstable'), (500, 'stable'), (1, 'experimental-debug'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 5.6.0-1-amd64 (SMP w/8 CPU cores)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=C.UTF-8, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE=C.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages bbswitch-dkms depends on:
ii  dkms  2.8.2-2

bbswitch-dkms recommends no packages.

Versions of packages bbswitch-dkms suggests:
ii  bumblebee  3.2.1-23

-- no debconf information