Same issue on Lenovo ThinkPat P76. Brightness control was working before.
$ uname -r 5.4.0-59-generic
$ lspci |grep -i vga 01:00.0 VGA compatible controller: NVIDIA Corporation TU104GLM [Quadro RTX 5000 Mobile / Max-Q] (rev a1)
$ sudo lshw -c video *-display description: VGA compatible controller product: TU104GLM [Quadro RTX 5000 Mobile / Max-Q] vendor: NVIDIA Corporation physical id: 0 bus info: pci@0000:01:00.0 version: a1 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress vga_controller bus_master cap_list rom configuration: driver=nvidia latency=0 resources: irq:197 memory:ed000000-edffffff memory:c0000000-cfffffff memory:d0000000-d1ffffff ioport:2000(size=128) memory:ee080000-ee0fffff
Downgrade to 450 works for me too.
Same issue on Lenovo ThinkPat P76. Brightness control was working before.
$ uname -r
5.4.0-59-generic
$ lspci |grep -i vga
01:00.0 VGA compatible controller: NVIDIA Corporation TU104GLM [Quadro RTX 5000 Mobile / Max-Q] (rev a1)
$ sudo lshw -c video
capabilities: pm msi pciexpress vga_controller bus_master cap_list rom
configuration: driver=nvidia latency=0 ed000000- edffffff memory: c0000000- cfffffff memory: d0000000- d1ffffff ioport: 2000(size= 128) memory: ee080000- ee0fffff
*-display
description: VGA compatible controller
product: TU104GLM [Quadro RTX 5000 Mobile / Max-Q]
vendor: NVIDIA Corporation
physical id: 0
bus info: pci@0000:01:00.0
version: a1
width: 64 bits
clock: 33MHz
resources: irq:197 memory:
Downgrade to 450 works for me too.