linux.git/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_backlight.c, branch master Linux kernel source tree drm/amd/display: Fix backlight control for luminance-capable OLED 2026-09-02T20:51:47+00:00 Roman Li Roman.Li@amd.com 2026-08-21T16:19:10+00:00 5a67d2e055897a36acb4e48082986fb4a4eebdd3 [WHY] For some eDP panels VESA aux backlight control is necessary, otherwise they stay black. [HOW] When AUX backlight control is used, select BACKLIGHT_CONTROL_VESA_AUX for panels that advertise panel_luminance_control. Reviewed-by: Hansen Dsouza <hansen.dsouza@amd.com> Signed-off-by: Roman Li <Roman.Li@amd.com> Signed-off-by: Alex Hung <alex.hung@amd.com> Tested-by: Dan Wheeler <daniel.wheeler@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> (cherry picked from commit 42f698bd061d76d5f4c84a195e465cfbeec775e4) 
[WHY]
For some eDP panels VESA aux backlight control is necessary,
otherwise they stay black.

[HOW]
When AUX backlight control is used, select BACKLIGHT_CONTROL_VESA_AUX for
panels that advertise panel_luminance_control.

Reviewed-by: Hansen Dsouza <hansen.dsouza@amd.com>
Signed-off-by: Roman Li <Roman.Li@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 42f698bd061d76d5f4c84a195e465cfbeec775e4)
drm/amd/display: Scale custom brightness curve from full range 2026-08-19T14:03:37+00:00 Akhmed Zhitaev zhitaevakh@gmail.com 2026-08-13T17:09:59+00:00 6fd83a1c2cdea48c396f600795217fbdfb8124f6 Custom brightness curves use an 8-bit input signal. After exporting the full PWM range to userspace, the curve normalizer still divides requests by the physical PWM span. On panels with a nonzero minimum PWM level, this can produce a curve input greater than 255 and send an invalid backlight level to DC. Scale the userspace [0..max] range to the curve's [0..255] range instead. This retains the full advertised range and keeps the reverse readback conversion unchanged. Fixes: 8dbd72cb7900 ("drm/amd/display: Export full brightness range to userspace") Cc: stable@vger.kernel.org Signed-off-by: Akhmed Zhitaev <zhitaevakh@gmail.com> Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org> (Move to amdgpu_dm_backlight.c) Link: https://patch.msgid.link/20260813170959.22073-1-zhitaevakh@gmail.com Signed-off-by: Mario Limonciello <mario.limonciello@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> 
Custom brightness curves use an 8-bit input signal.  After exporting the
full PWM range to userspace, the curve normalizer still divides requests
by the physical PWM span.  On panels with a nonzero minimum PWM level,
this can produce a curve input greater than 255 and send an invalid
backlight level to DC.

Scale the userspace [0..max] range to the curve's [0..255] range
instead.  This retains the full advertised range and keeps the reverse
readback conversion unchanged.

Fixes: 8dbd72cb7900 ("drm/amd/display: Export full brightness range to userspace")
Cc: stable@vger.kernel.org
Signed-off-by: Akhmed Zhitaev <zhitaevakh@gmail.com>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
(Move to amdgpu_dm_backlight.c)
Link: https://patch.msgid.link/20260813170959.22073-1-zhitaevakh@gmail.com
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
drm/amd/display: Replace amdgpu_dm_kunit_helpers.h with dm_helpers.h 2026-07-28T22:32:36+00:00 Bhawanpreet Lakha bhawanpreet.lakha@amd.com 2026-07-07T14:21:50+00:00 4d6eabd9bf7cbc96968726b7197cf5189a9dfe89 Drop the amdgpu_dm_kunit_helpers.h include across the amdgpu_dm source files and use dm_helpers.h instead Assisted-by: Copilot:Claude-Opus-4.8 Reviewed-by: Alex Hung <alex.hung@amd.com> Signed-off-by: Bhawanpreet Lakha <bhawanpreet.lakha@amd.com> Signed-off-by: Wayne Lin <wayne.lin@amd.com> Tested-by: Dan Wheeler <daniel.wheeler@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> 
Drop the amdgpu_dm_kunit_helpers.h include across the amdgpu_dm source
files and use dm_helpers.h instead

Assisted-by: Copilot:Claude-Opus-4.8
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Bhawanpreet Lakha <bhawanpreet.lakha@amd.com>
Signed-off-by: Wayne Lin <wayne.lin@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
drm/amd/display: Force PWM backlight on Lenovo Legion 5 15ARH05 2026-07-15T13:15:43+00:00 Alessandro Rinaldi ale@alerinaldi.it 2026-06-26T14:36:00+00:00 81b39f43e7e53589491e2eef6bad5389626b4b9c 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> 
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>
drm/amd/display: Test panel power savings sysfs 2026-07-15T13:15:39+00:00 Alex Hung alex.hung@amd.com 2026-06-30T00:43:57+00:00 db546ee97153c95ea719da015cf002f970175605 [WHAT] Add KUnit coverage using a DRM-managed connector fixture. Tests cover show() mapping immediate-disable to 0 and reporting an active ABM level, and store() handling the disable mapping, the forbidden update, invalid text, and out-of-range input. show() writes through a page-backed buffer because sysfs_emit() requires one. Assisted-by: Copilot:Claude-Opus-4.8 Reviewed-by: Bhawanpreet Lakha <bhawanpreet.lakha@amd.com> Signed-off-by: Alex Hung <alex.hung@amd.com> Signed-off-by: George Zhang <george.zhang@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> 
[WHAT]
Add KUnit coverage using a DRM-managed connector fixture.

Tests cover show() mapping immediate-disable to 0 and reporting an active
ABM level, and store() handling the disable mapping, the forbidden update,
invalid text, and out-of-range input. show() writes through a page-backed
buffer because sysfs_emit() requires one.

Assisted-by: Copilot:Claude-Opus-4.8
Reviewed-by: Bhawanpreet Lakha <bhawanpreet.lakha@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: George Zhang <george.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
drm/amd/display: Test backlight device registration 2026-07-15T13:15:39+00:00 Alex Hung alex.hung@amd.com 2026-06-30T00:40:26+00:00 0198bf2a7c707bf1a73cda80df7200f7317520f5 [WHAT] Add KUnit test to amdgpu_dm_register_backlight_device() and cover its bl_idx == -1 early return, which must leave the backlight device slot untouched. Assisted-by: Copilot:Claude-Opus-4.8 Reviewed-by: Bhawanpreet Lakha <bhawanpreet.lakha@amd.com> Signed-off-by: Alex Hung <alex.hung@amd.com> Signed-off-by: George Zhang <george.zhang@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> 
[WHAT]
Add KUnit test to amdgpu_dm_register_backlight_device() and
cover its bl_idx == -1 early return, which must leave the
backlight device slot untouched.

Assisted-by: Copilot:Claude-Opus-4.8
Reviewed-by: Bhawanpreet Lakha <bhawanpreet.lakha@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: George Zhang <george.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
drm/amd/display: Test backlight level readback path 2026-07-15T13:15:39+00:00 Alex Hung alex.hung@amd.com 2026-06-30T00:39:36+00:00 c50a4305dfc2e91681c3991af3006ccbb2ec0eb7 [WHAT] Add KUnit coverage for the backlight level read path. A faked link_service vtable returns canned PWM and AUX brightness values, letting the tests verify both the successful readback and the DC_ERROR/AUX-failure fallbacks to the cached brightness, plus the get_brightness() device-index wrapper. Assisted-by: Copilot:Claude-Opus-4.8 Reviewed-by: Bhawanpreet Lakha <bhawanpreet.lakha@amd.com> Signed-off-by: Alex Hung <alex.hung@amd.com> Signed-off-by: George Zhang <george.zhang@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> 
[WHAT]
Add KUnit coverage for the backlight level read path.

A faked link_service vtable returns canned PWM and AUX brightness values,
letting the tests verify both the successful readback and the
DC_ERROR/AUX-failure fallbacks to the cached brightness, plus the
get_brightness() device-index wrapper.

Assisted-by: Copilot:Claude-Opus-4.8
Reviewed-by: Bhawanpreet Lakha <bhawanpreet.lakha@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: George Zhang <george.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
drm/amd/display: Test backlight level programming path 2026-07-15T13:15:39+00:00 Alex Hung alex.hung@amd.com 2026-06-30T00:37:52+00:00 ee486cb800915b2fc7ecfd108982198045860060 [WHAT] Add KUnit coverage for the backlight level write path in amdgpu_dm_backlight.c. Tests cover stream lookup hit/miss, the connector-off and no-stream early returns, and the AUX/PWM/idle-reallow programming branches. The DC programming calls stay safe by injecting a NULL power module and keeping idle optimizations a no-op via disable_idle_power_optimizations. Assisted-by: Copilot:Claude-Opus-4.8 Reviewed-by: Bhawanpreet Lakha <bhawanpreet.lakha@amd.com> Signed-off-by: Alex Hung <alex.hung@amd.com> Signed-off-by: George Zhang <george.zhang@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> 
[WHAT]
Add KUnit coverage for the backlight level write path in
amdgpu_dm_backlight.c.

Tests cover stream lookup hit/miss, the connector-off and no-stream early
returns, and the AUX/PWM/idle-reallow programming branches. The DC
programming calls stay safe by injecting a NULL power module and keeping
idle optimizations a no-op via disable_idle_power_optimizations.

Assisted-by: Copilot:Claude-Opus-4.8
Reviewed-by: Bhawanpreet Lakha <bhawanpreet.lakha@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: George Zhang <george.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
drm/amd/display: Fix backlight max_brightness to match exported range 2026-07-15T13:15:39+00:00 Mario Limonciello mario.limonciello@amd.com 2026-06-29T20:27:00+00:00 bd9e2b5b0473c75abc0f4134dfe79ecbfb16610d [Why] FWTS autobrightness fails on eDP panels because actual_brightness can read higher than the advertised max_brightness (e.g. 63576 vs 62451). The conversion helpers expose the firmware PWM range to userspace as [0..max]. But max_brightness is advertised as (max - min), which is smaller. So reading the level can return a value above max_brightness. This regressed in commit 4b61b8a39051 ("drm/amd/display: Add debugging message for brightness caps"), which changed max_brightness to (max - min) and undid commit 8dbd72cb7900 ("drm/amd/display: Export full brightness range to userspace"). [How] Advertise max_brightness as max, and scale the initial AC/DC brightness against max too. Update the KUnit expectations to match. Fixes: 4b61b8a39051 ("drm/amd/display: Add debugging message for brightness caps") Reviewed-by: Alex Hung <alex.hung@amd.com> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com> Signed-off-by: George Zhang <george.zhang@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> 
[Why]
FWTS autobrightness fails on eDP panels because actual_brightness can
read higher than the advertised max_brightness (e.g. 63576 vs 62451).

The conversion helpers expose the firmware PWM range to userspace as
[0..max].  But max_brightness is advertised as (max - min), which is
smaller.  So reading the level can return a value above max_brightness.

This regressed in commit 4b61b8a39051 ("drm/amd/display: Add debugging
message for brightness caps"), which changed max_brightness to
(max - min) and undid commit 8dbd72cb7900 ("drm/amd/display: Export full
brightness range to userspace").

[How]
Advertise max_brightness as max, and scale the initial AC/DC brightness
against max too.  Update the KUnit expectations to match.

Fixes: 4b61b8a39051 ("drm/amd/display: Add debugging message for brightness caps")
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: George Zhang <george.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
drm/amd/display: Enable CACP on Linux 2026-07-14T23:12:34+00:00 Chenyu Chen chen-yu.chen@amd.com 2026-03-05T12:11:50+00:00 7b0cc308521696107828b0c6c72c5793fa279cbd [Why] Enable OLED panels to save more power on the Linux platform by enabling CACP support on Linux. [How] Update abm_feature_support() to return ABM_CACP_SUPPORT for OLED panels. Enable ABM property for all eDP panels including OLED to support CACP via set_abm_level. Reviewed-by: Sun peng (Leo) Li <sunpeng.li@amd.com> Signed-off-by: Chenyu Chen <chen-yu.chen@amd.com> Signed-off-by: George Zhang <george.zhang@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> 
[Why]
Enable OLED panels to save more power on the Linux platform by
enabling CACP support on Linux.

[How]
Update abm_feature_support() to return ABM_CACP_SUPPORT for OLED
panels. Enable ABM property for all eDP panels including OLED to
support CACP via set_abm_level.

Reviewed-by: Sun peng (Leo) Li <sunpeng.li@amd.com>
Signed-off-by: Chenyu Chen <chen-yu.chen@amd.com>
Signed-off-by: George Zhang <george.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>