diff options
| author | Suraj Kandpal <suraj.kandpal@intel.com> | 2026-03-16 06:18:51 +0300 |
|---|---|---|
| committer | Suraj Kandpal <suraj.kandpal@intel.com> | 2026-03-18 05:30:30 +0300 |
| commit | 0fb03890d18205ec0909fc47049eceae8ba36457 (patch) | |
| tree | 663a78f550e4b0ee08953de4044635baced9235c | |
| parent | 3ccc8a922906703cd0efdf1bdd6186f18f7e23ec (diff) | |
| download | linux-0fb03890d18205ec0909fc47049eceae8ba36457.tar.xz | |
drm/i915/backlight: Check if VESA backlight is possible
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 <suraj.kandpal@intel.com>
Reviewed-by: Pranay Samala <pranay.samala@intel.com>
Link: https://patch.msgid.link/20260316031850.81794-1-suraj.kandpal@intel.com
| -rw-r--r-- | drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 32 |
1 files changed, 31 insertions, 1 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 a7b186d0e3c4..d0c76632a946 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c @@ -610,6 +610,34 @@ static int intel_dp_aux_vesa_setup_backlight(struct intel_connector *connector, } static bool +check_if_vesa_backlight_possible(struct intel_dp *intel_dp) +{ + int ret; + u8 bit_min, bit_max; + + if (!(intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP)) + return true; + + ret = drm_dp_dpcd_read_byte(&intel_dp->aux, DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, &bit_min); + if (ret < 0) + return false; + + bit_min &= DP_EDP_PWMGEN_BIT_COUNT_MASK; + if (bit_min < 1) + return false; + + ret = drm_dp_dpcd_read_byte(&intel_dp->aux, DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX, &bit_max); + if (ret < 0) + return false; + + bit_max &= DP_EDP_PWMGEN_BIT_COUNT_MASK; + if (bit_max < bit_min) + return false; + + return true; +} + +static bool intel_dp_aux_supports_vesa_backlight(struct intel_connector *connector) { struct intel_display *display = to_intel_display(connector); @@ -625,12 +653,14 @@ intel_dp_aux_supports_vesa_backlight(struct intel_connector *connector) return true; } - if (drm_edp_backlight_supported(intel_dp->edp_dpcd)) { + if (drm_edp_backlight_supported(intel_dp->edp_dpcd) && + check_if_vesa_backlight_possible(intel_dp)) { drm_dbg_kms(display->drm, "[CONNECTOR:%d:%s] AUX Backlight Control Supported!\n", connector->base.base.id, connector->base.name); return true; } + return false; } |