Read DP_EDP_BACKLIGHT_MODE_SET_REGISTER during VESA AUX backlight
capability checks and reject panels using
DP_EDP_BACKLIGHT_CONTROL_MODE_PRODUCT.
i915 supports VESA AUX backlight only in
DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD. Reject panels that expose AUX
backlight capability bits when their active backlight control mode is
DP_EDP_BACKLIGHT_CONTROL_MODE_PRODUCT.
Fixes: 40d2f5820951 ("drm/i915/backlight: Remove try_vesa_interface")
Signed-off-by: Suraj Kandpal <[email protected]>
---
drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
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 a8d56ebf06a2..fadc4b2faa4c 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
@@ -613,7 +613,7 @@ static bool
check_if_vesa_backlight_possible(struct intel_dp *intel_dp)
{
int ret;
- u8 bit_min, bit_max;
+ u8 bit_min, bit_max, mode_reg;
/*
* Since we only support Fully AUX Based VESA Backlight interface make
sure
@@ -623,6 +623,15 @@ check_if_vesa_backlight_possible(struct intel_dp *intel_dp)
intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP))
return false;
+ ret = drm_dp_dpcd_read_byte(&intel_dp->aux,
DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
+ &mode_reg);
+ if (ret < 0)
+ return false;
+
+ if ((mode_reg & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) ==
+ DP_EDP_BACKLIGHT_CONTROL_MODE_PRODUCT)
+ return false;
+
ret = drm_dp_dpcd_read_byte(&intel_dp->aux,
DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, &bit_min);
if (ret < 0)
return false;
--
2.34.1
