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bad177fa75
The Lenovo Legion 5 15ARH05 (Renoir) ships a BOE 0x08DF eDP panel that advertises AUX/DPCD backlight control, so amdgpu's automatic detection (amdgpu_backlight == -1) selects AUX. On this panel the AUX backlight path has no effect: brightness writes are accepted but the panel level never changes, the display is stuck at a fixed brightness and max_brightness is reported as a bogus 511000. As a result neither the desktop brightness slider nor the brightness hotkeys do anything. Forcing PWM backlight (amdgpu.backlight=0) restores working control: max_brightness becomes 65535 and the level tracks writes. This has long been applied by users as a manual kernel-parameter workaround. Extend the generic panel backlight quirk with a force_pwm flag, add an entry for the Legion 5 15ARH05 / BOE 0x08DF panel, and have amdgpu disable AUX backlight (use PWM) when the quirk matches and the user lets the driver auto-select the backlight type. Signed-off-by: Alessandro Rinaldi <ale@alerinaldi.it> Tested-by: Alessandro Rinaldi <ale@alerinaldi.it> Reviewed-by: George Zhang <george.zhang@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> (cherry picked from commit 81b39f43e7e53589491e2eef6bad5389626b4b9c) Cc: stable@vger.kernel.org