drm/i915: Use luminance range calculated during edid parsing

Instead of using fixed 0 - 512 range use luminance range calculated
as a part of edid parsing. As a backup fall back to static 0 - 512.

v3: Clean-ups suggested by Jani Nikula
v2: Use values calculated during edid parsing

Cc: Lyude Paul <lyude@redhat.com>
Cc: Mika Kahola <mika.kahola@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220719095700.14923-4-jouni.hogander@intel.com

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

@@ -278,6 +278,8 @@ intel_dp_aux_hdr_setup_backlight(struct intel_connector *connector, enum pipe pi
 {
 	struct drm_i915_private *i915 = to_i915(connector->base.dev);
 	struct intel_panel *panel = &connector->panel;
+	struct drm_luminance_range_info *luminance_range =
+		&connector->base.display_info.luminance_range;
 	int ret;
 
 	if (panel->backlight.edp.intel.sdr_uses_aux) {
@@ -293,8 +295,17 @@ intel_dp_aux_hdr_setup_backlight(struct intel_connector *connector, enum pipe pi
 		}
 	}
 
-	panel->backlight.max = 512;
-	panel->backlight.min = 0;
+	if (luminance_range->max_luminance) {
+		panel->backlight.max = luminance_range->max_luminance;
+		panel->backlight.min = luminance_range->min_luminance;
+	} else {
+		panel->backlight.max = 512;
+		panel->backlight.min = 0;
+	}
+
+	drm_dbg_kms(&i915->drm, "Using backlight range %d..%d\n", panel->backlight.min,
+		    panel->backlight.max);
+
 	panel->backlight.level = intel_dp_aux_hdr_get_backlight(connector, pipe);
 	panel->backlight.enabled = panel->backlight.level != 0;