superrob1500
/
mirror-linux
mirror of https://github.com/torvalds/linux
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Revert "drm/i915/backlight: Remove try_vesa_interface" 

This reverts commit 40d2f58209.

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 <suraj.kandpal@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Link: https://patch.msgid.link/20260517024709.1016121-1-suraj.kandpal@intel.com
(cherry picked from commit f30fddb4402313aa5301a74d721638d343395269)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
master
Suraj Kandpal 2026-05-17 08:17:09 +05:30 committed by Tvrtko Ursulin
parent 26eb7c0a7a
commit 2914709c91
1 changed files with 12 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
View File

@ -691,10 +691,9 @@ int intel_dp_aux_init_backlight_funcs(struct intel_connector *connector)
struct intel_dp *intel_dp = intel_attached_dp(connector);
struct drm_device *dev = connector->base.dev;
struct intel_panel *panel = &connector->panel;
bool try_intel_interface = false;
bool try_intel_interface = false, try_vesa_interface = false;
/*
* Check the VBT and user's module parameters to figure out which
/* Check the VBT and user's module parameters to figure out which
* interfaces to probe
*/
switch (display->params.enable_dpcd_backlight) {
@ -703,6 +702,7 @@ int intel_dp_aux_init_backlight_funcs(struct intel_connector *connector)
case INTEL_DP_AUX_BACKLIGHT_AUTO:
switch (panel->vbt.backlight.type) {
case INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE:
try_vesa_interface = true;
break;
case INTEL_BACKLIGHT_DISPLAY_DDI:
try_intel_interface = true;
@ -715,12 +715,20 @@ int intel_dp_aux_init_backlight_funcs(struct intel_connector *connector)
if (panel->vbt.backlight.type != INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE)
try_intel_interface = true;
try_vesa_interface = true;
break;
case INTEL_DP_AUX_BACKLIGHT_FORCE_VESA:
try_vesa_interface = true;
break;
case INTEL_DP_AUX_BACKLIGHT_FORCE_INTEL:
try_intel_interface = true;
break;
}
/* For eDP 1.5 and above we are supposed to use VESA interface for brightness control */
if (intel_dp->edp_dpcd[0] >= DP_EDP_15)
try_vesa_interface = true;
/*
* Since Intel has their own backlight control interface, the majority of machines out there
* using DPCD backlight controls with Intel GPUs will be using this interface as opposed to
@ -733,9 +741,6 @@ int intel_dp_aux_init_backlight_funcs(struct intel_connector *connector)
* panel with Intel's OUI - which is also required for us to be able to detect Intel's
* backlight interface at all. This means that the only sensible way for us to detect both
* interfaces is to probe for Intel's first, and VESA's second.
*
* Also there is a chance some VBTs may advertise false Intel backlight support even if the
* TCON DPCD says otherwise. This means we keep VESA interface as fallback in that case.
*/
if (try_intel_interface && intel_dp->edp_dpcd[0] <= DP_EDP_14b &&
intel_dp_aux_supports_hdr_backlight(connector)) {
@ -745,7 +750,7 @@ int intel_dp_aux_init_backlight_funcs(struct intel_connector *connector)
return 0;
}
if (intel_dp_aux_supports_vesa_backlight(connector)) {
if (try_vesa_interface && intel_dp_aux_supports_vesa_backlight(connector)) {
drm_dbg_kms(dev, "[CONNECTOR:%d:%s] Using VESA eDP backlight controls\n",
connector->base.base.id, connector->base.name);
panel->backlight.funcs = &intel_dp_vesa_bl_funcs;