Linux passes PWM eDP brightness through two owners. The display manager maps the request into the firmware range and applies the ATIF custom curve. The power module then derives a percentage from that hardware value and applies the same curve and range again. A non-zero firmware minimum consequently prevents zero from reaching the panel minimum. The split also leaves the custom-curve disable policy and final PWM mask attached to the wrong owner.
Patch 1 keeps pre-power-module custom-curve output in the userspace domain, which also fixes affected stable kernels. Patch 2 covers that conversion with a non-zero firmware minimum. Patch 3 passes zero-anchored millipercent into the power module and moves the panel policy, curve, range, trace units, and final effective-PWM mask to that owner. Patch 4 covers ordinary PWM, forced PWM, AMD-AUX fallback, true AUX, multiple panels, endpoints, interior values, clamping, and invalid ranges. The complete series passed all 85 AMD backlight UML KUnit cases on the current base and after clean application to Linux 7.3-rc1. It was built into one kernel, booted on two Strix Halo systems, and produced the same AMDGPU module on both. An instrumented physical panel test observed: request 0 -> 0 millipercent -> PWM 3084 -> success request 65535 -> 100000 millipercent -> PWM 65535 -> success The panel visibly reached minimum and maximum brightness, then returned to its starting level. No fatal kernel event followed. The true AUX path was covered by KUnit but was not available for a physical test. The existing LUT-unaware hardware readback inverse is unchanged. Andrei Rusu de Castro (4): drm/amd/display: keep custom brightness curve in userspace domain drm/amd/display: test custom brightness with non-zero minimum drm/amd/display: pass userspace brightness to power module drm/amd/display: test power module brightness input domain .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 6 +- .../display/amdgpu_dm/amdgpu_dm_backlight.c | 59 ++- .../display/amdgpu_dm/amdgpu_dm_backlight.h | 5 +- .../amd/display/amdgpu_dm/amdgpu_dm_trace.h | 3 +- .../tests/amdgpu_dm_backlight_test.c | 447 +++++++++++++++++- .../drm/amd/display/modules/inc/mod_power.h | 1 + .../gpu/drm/amd/display/modules/power/power.c | 2 + .../drm/amd/display/modules/power/power_abm.c | 6 +- .../amd/display/modules/power/power_helpers.h | 1 + 9 files changed, 494 insertions(+), 36 deletions(-)
