eDP is supposed to use VESA interface when using revision 1.5 and above,
use Intel interface for backlight control otherwise. Add check to
use correct interface.

Signed-off-by: Suraj Kandpal <suraj.kand...@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 8 +++++++-
 1 file changed, 7 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 c846ef4acf5b..09e82f24d030 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
@@ -604,6 +604,7 @@ static const struct intel_panel_bl_funcs 
intel_dp_vesa_bl_funcs = {
 int intel_dp_aux_init_backlight_funcs(struct intel_connector *connector)
 {
        struct intel_display *display = to_intel_display(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;
@@ -640,6 +641,10 @@ int intel_dp_aux_init_backlight_funcs(struct 
intel_connector *connector)
                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
@@ -653,7 +658,8 @@ int intel_dp_aux_init_backlight_funcs(struct 
intel_connector *connector)
         * 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.
         */
-       if (try_intel_interface && 
intel_dp_aux_supports_hdr_backlight(connector)) {
+       if (try_intel_interface && 
intel_dp_aux_supports_hdr_backlight(connector) &&
+           intel_dp->edp_dpcd[0] <= DP_EDP_14b) {
                drm_dbg_kms(dev, "[CONNECTOR:%d:%s] Using Intel proprietary eDP 
backlight controls\n",
                            connector->base.base.id, connector->base.name);
                panel->backlight.funcs = &intel_dp_hdr_bl_funcs;
-- 
2.34.1

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