Ubuntu
xserver-xorg-video-nouveau package

  1. Bug #921321
  2. Comment #57

Comment 57 for bug 921321

Revision history for this message
In , R-spliet (r-spliet) wrote :

Created attachment 85012
drm/nv50: Fix backlight not working when PWM_DIV is uninitialised (v2)

V2 fixes the reach of this patch.
From what I can tell the PWM_DIV is simply a divider for the initial PWM clock or something, it does not affect the scope of the duty cycle. I therefore assume 0x5e is always a good value to set. Traces from NV50:NVA0 would help verify whether NVIDIA always sets this value or not.
This patch requires acpi_backlight=vendor to be set because it tests for the presence of a backlight by testing drm->backlight. An alternative to this test would be checking for the GPIO to be present and routed to SOR, but I wouldn't be surprised if there is at least one device that expects our driver to route it manually. How should we go about this?