linux.git/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c, branch master

drm/i915/backlight: Remove DP_EDP_BACKLIGHT_AUX_ENABLE_CAP check for DPCD backlight

2026-07-20T10:30:37Z

Turns out some panels allow only AUX based backlight by just setting the DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP and not setting the DP_EDP_BACKLIGHT_AUX_ENABLE_CAP. If we make DP_EDP_BACKLIGHT_AUX_ENABLE_CAP a necessity for AUX based DPCD backlight these panels loose the ability to manipulate backlight via AUX, especially ones with no PWM controller. Remove this check from function so that panels who do not advertise DP_EDP_BACKLIGHT_AUX_ENABLE_CAP but advertise DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP are able to manipulate backlight again. Fixes: ed8be780bdbc ("drm/i915/backlight: Fix VESA backlight possible check condition") Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/work_items/16507 Signed-off-by: Suraj Kandpal Reviewed-by: Michał Grzelak Link: https://patch.msgid.link/20260716030959.436430-1-suraj.kandpal@intel.com (cherry picked from commit 7d594b24c915afb4b0c5fb8875403253daef5b24) Signed-off-by: Rodrigo Vivi

Revert "drm/i915/backlight: Remove try_vesa_interface"

2026-06-05T10:07:24Z

This reverts commit 40d2f5820951dee818d05c14677277048bd85f9f. Removing the try_vesa_interface gate caused a backlight regression on panels whose VBT correctly reports INTEL_BACKLIGHT_DISPLAY_DDI and whose PWM path is the actual backlight control, but whose DPCD optimistically advertises DP_EDP_BACKLIGHT_AUX_ENABLE_CAP / _BRIGHTNESS_AUX_SET_CAP. After the commit such panels silently bind to the VESA AUX backlight funcs; AUX writes complete but the panel ignores them, leaving brightness stuck (no-op backlight). Observed on at least KBL and TGL eDP setups. Signed-off-by: Suraj Kandpal Reviewed-by: Ankit Nautiyal Link: https://patch.msgid.link/20260517024709.1016121-1-suraj.kandpal@intel.com (cherry picked from commit f30fddb4402313aa5301a74d721638d343395269) Signed-off-by: Tvrtko Ursulin

drm/i915/backlight: Fix VESA backlight possible check condition

2026-04-14T07:04:44Z

VESA backlight enable is possible when BACKLIGHT_AUX_ENABLE_CAPABLE is true via AUX command or when BACKLIGHT_PIN_ENABLE_CAPABLE is true via eDP connector pin. Similarly, backlight brightness adjustment can be done via AUX-based control or PWM pin-based control. It means there can be three configurations: 1) Full AUX-based: Enable and adjustment both via AUX. We currently support this (apart from the AUX luminance-based backlight control). 2) Hybrid: Enable via the BL_ENABLE pin, adjustment via either AUX or PWM. 3) Fully PWM pin-based: Enable via the BL_ENABLE pin, adjustment via PWM. Since that only 1 is supported as of now we need to make sure we do not try to manipulate backlight when BACKLIGHT_AUX_ENABLE_CAPABLE is not set. Also fix return value when condition is not fulfilled. Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/work_items/15907 Fixes: 0fb03890d182 ("drm/i915/backlight: Check if VESA backlight is possible") Signed-off-by: Suraj Kandpal Tested-by: Ville Syrjälä Reviewed-by: Ankit Nautiyal Link: https://patch.msgid.link/20260407030710.1440046-1-suraj.kandpal@intel.com (cherry picked from commit 102d44b3a8fad96e94e9ccd0579986c14a1f2f75) Signed-off-by: Tvrtko Ursulin

drm/i915/backlight: Check if VESA backlight is possible

2026-03-18T02:30:30Z

Check if BACKLIGHT_BRIGHTNESS_AUX_SET_CAPABLE bit is set then EDP_PWMGEN_BIT_COUNT_CAP_MIN and EDP_PWMGEN_BIT_COUNT_CAP_MAX follow the eDP 1.4b Section 10.3. Which states min should be >= 1 and max should be >= min. Some legacy panels do not follow this properly. They set the BACKLIGHT_BRIGHTNESS_AUX_SET_CAPABLE bit while not correctly populating the min and max fields leading to a 0 max value. Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/7514 Fixes: 40d2f5820951 ("drm/i915/backlight: Remove try_vesa_interface") Signed-off-by: Suraj Kandpal Reviewed-by: Pranay Samala Link: https://patch.msgid.link/20260316031850.81794-1-suraj.kandpal@intel.com

drm/i915/backlight: Provide clear description on how backlight level is controlled

2026-03-03T03:00:17Z

Currently it takes us multiple log prints to arrive at the conclusion on how we are actually controlling backlight level. Make the logging concise. Signed-off-by: Suraj Kandpal Reviewed-by: Arun R Murthy Link: https://patch.msgid.link/20260302040613.3324049-8-suraj.kandpal@intel.com

drm/i915/backlight: Update debug log during backlight setup

2026-03-03T02:58:54Z

With luminance_set which represents PANEL_LUMINANCE_OVERRIDE, we have another variable to decide if we use PWM or DPCD. Make drm_dbg_kms log represent that. Signed-off-by: Suraj Kandpal Reviewed-by: Arun R Murthy Link: https://patch.msgid.link/20260302040613.3324049-7-suraj.kandpal@intel.com

drm/i915/backlight: Short circuit intel_dp_aux_supports_hdr_backlight

2026-03-03T02:58:54Z

intel_dp_aux_supports_hdr_backlight() prints debug message for intel HDR backlight version. This is fine when dealing with eDP 1.4b and lower. When we are talking about eDP 1.5 it causes confusion in logs since we need to use VESA AUX backlight functions but this print causes confusion as to which path code take. Short circuit this function with a eDP version check. Make sure this is only called if eDP <= 1.4b Signed-off-by: Suraj Kandpal Reviewed-by: Arun R Murthy Link: https://patch.msgid.link/20260302040613.3324049-6-suraj.kandpal@intel.com

drm/i915/backlight: Check luminance_set when disabling PWM via AUX VESA backlight

2026-03-03T02:58:54Z

When deciding what if PWM funcs need to be disabled take into account luminance_set too. We do this since it is also used to decide if we are enabling PWM backlight funcs or not. Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/15671 Signed-off-by: Suraj Kandpal Reviewed-by: Arun R Murthy Link: https://patch.msgid.link/20260302040613.3324049-5-suraj.kandpal@intel.com

drm/i915/backlight: Take luminance_set into account for VESA backlight

2026-03-03T02:58:54Z

When deciding what functions to enable to help control backlight we used to only check aux_enable. Now with PANEL_LUMINANCE_OVERRIDE in picture we need to take care that we do not enable PWM function if luminance_set is set. Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/15671 Signed-off-by: Suraj Kandpal Reviewed-by: Arun R Murthy Link: https://patch.msgid.link/20260302040613.3324049-4-suraj.kandpal@intel.com

drm/i915/backlight: Use intel_panel variable instead of intel_connector

2026-03-03T02:58:54Z

Use the intel_panel variable since it has already been declared and looks cleaner. Signed-off-by: Suraj Kandpal Reviewed-by: Arun R Murthy Link: https://patch.msgid.link/20260302040613.3324049-3-suraj.kandpal@intel.com