On 2/24/2026 8:43 AM, Suraj Kandpal wrote:
Remove try_vesa_interface. This is because we now make VESA Interface
as a fallback mechanism for Panels which needs VESA DPCD AUX backlight
mechanism to work but have a broken VBT indicating otherwise.
I think lets start with the problem:
- some panels need VESA DPCD Aux backlight but VBT says otherwise
- we try with Intel backlight interface first, then check for
try_vesa_interface flag before trying VESA backlight interface
-this causes blankout on such panels as try_vesa_interface is not set
and VESA backlight is not tried.
- remove try_vesa_interface flag and lets attempt VESA backlight
interface as a fallback mechansim.
While at in sneak in a small comment cleanup too.
Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/15679
Signed-off-by: Suraj Kandpal <[email protected]>
---
.../drm/i915/display/intel_dp_aux_backlight.c | 19 +++++++------------
1 file changed, 7 insertions(+), 12 deletions(-)
diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
index eb05ef4bd9f6..a8e9872566cd 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
@@ -644,9 +644,10 @@ 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, try_vesa_interface = false;
+ bool try_intel_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) {
@@ -655,7 +656,6 @@ 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;
@@ -668,20 +668,12 @@ 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
@@ -694,6 +686,9 @@ 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 VBT's may advertise false Intel
backlight support even if the
s/VBT's/VBTs
+ * tcon's DPCD says otherwise. This mean we keep VESA interface as
fallback in that case.
s/tcon/TCON
With above nitpicks sorted, this is:
Reviewed-by: Ankit Nautiyal <[email protected]>
*/
if (try_intel_interface && intel_dp_aux_supports_hdr_backlight(connector)
&&
intel_dp->edp_dpcd[0] <= DP_EDP_14b) {
@@ -703,7 +698,7 @@ int intel_dp_aux_init_backlight_funcs(struct
intel_connector *connector)
return 0;
}
- if (try_vesa_interface && intel_dp_aux_supports_vesa_backlight(connector)) {
+ if (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;
