/sys/class/backlight/nv_backlight doesn't work on Dell Precision 7530 GP107GLM [Quadro P1000 Mobile]

Submitted by Kai-Heng Feng

Assigned to Nouveau Project

Link to original bug (#110407)

Description

This laptop has an BIOS option "Switchable Graphics". When the options is selected, it behaves like a normal Optimus laptop. In this case, brightness sysfs works since it's driven by Intel graphics.

When the options is deselected, the Intel graphics device disappears, Nvidia is the only graphics device. The issue happens in this case.

Changing /sys/class/backlight/nv_backlight/brightness, the brightness level remains the same - almost no backlight.

Using proprietary driver, brightness gets changed correctly by /sys/class/backlight/nvidia_0/brightness.

No trace while using MMIOTRACE, under proprietary driver.