drm/i915/dp: Write panel override luminance values

Write panel override luminance values which helps the TCON decide
if tone mapping needs to be enabled or not.

Signed-off-by: Suraj Kandpal <[e-mail]>
Reviewed-by: Sebastian Wick <[e-mail]>
Signed-off-by: Uma Shankar <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c

···
 	return aux ? "DPCD" : "PWM";
 }
 
+static void
+intel_dp_aux_write_panel_luminance_override(struct intel_connector *connector)
+{
+	struct drm_i915_private *i915 = to_i915(connector->base.dev);
+	struct intel_panel *panel = &connector->panel;
+	struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
+	int ret;
+	u8 buf[4] = {};
+
+	buf[0] = panel->backlight.min & 0xFF;
+	buf[1] = (panel->backlight.min & 0xFF00) >> 8;
+	buf[2] = panel->backlight.max & 0xFF;
+	buf[3] = (panel->backlight.max & 0xFF00) >> 8;
+
+	ret = drm_dp_dpcd_write(&intel_dp->aux,
+				INTEL_EDP_HDR_PANEL_LUMINANCE_OVERRIDE,
+				buf, sizeof(buf));
+	if (ret < 0)
+		drm_dbg_kms(&i915->drm,
+			    "Panel Luminance DPCD reg write failed, err:-%d\n",
+			    ret);
+}
+
 static int
 intel_dp_aux_hdr_setup_backlight(struct intel_connector *connector, enum pipe pipe)
 {
···
 		panel->backlight.max = 512;
 		panel->backlight.min = 0;
 	}
+
+	intel_dp_aux_write_panel_luminance_override(connector);
 
 	drm_dbg_kms(&i915->drm, "[CONNECTOR:%d:%s] Using AUX HDR interface for backlight control (range %d..%d)\n",
 		    connector->base.base.id, connector->base.name,