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?

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https://bugs.launchpad.net/bugs/921321

Title:
  nouveau: dark screen after suspend/resume

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