drm/i915/dpcd_bl: Cache some backlight capabilities in intel_panel.backlight

Since we're about to be moving this code into shared DRM helpers, we might
as well start to cache certain backlight capabilities that can be
determined from the EDP DPCD, and are likely to be relevant to the majority
of drivers using said helpers. The main purpose of this is just to prevent
every driver from having to check everything against the eDP DPCD using DP
macros, which makes the code slightly easier to read (especially since the
names of some of the eDP capabilities don't exactly match up with what we
actually need to use them for, like DP_EDP_BACKLIGHT_BRIGHTNESS_BYTE_COUNT
for instance).
Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210514181504.565252-5-lyude@redhat.com

drivers/gpu/drm/i915/display/intel_display_types.h

@@ -312,6 +312,8 @@ struct intel_panel {
 			struct {
 				u8 pwmgen_bit_count;
 				u8 pwm_freq_pre_divider;
+				bool lsb_reg_used;
+				bool aux_enable;
 			} vesa;
 			struct {
 				bool sdr_uses_aux;

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

@@ -270,13 +270,14 @@ intel_dp_aux_hdr_setup_backlight(struct intel_connector *connector, enum pipe pi
 }
 
 /* VESA backlight callbacks */
-static void set_vesa_backlight_enable(struct intel_dp *intel_dp, bool enable)
+static void set_vesa_backlight_enable(struct intel_connector *connector, bool enable)
 {
+	struct intel_dp *intel_dp = intel_attached_dp(connector);
 	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
 	u8 reg_val = 0;
 
 	/* Early return when display use other mechanism to enable backlight. */
-	if (!(intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP))
+	if (!connector->panel.backlight.edp.vesa.aux_enable)
 		return;
 
 	if (drm_dp_dpcd_readb(&intel_dp->aux, DP_EDP_DISPLAY_CONTROL_REGISTER, &reg_val) != 1) {
@@ -339,9 +340,11 @@ static u32 intel_dp_aux_vesa_get_backlight(struct intel_connector *connector, en
 			    DP_EDP_BACKLIGHT_BRIGHTNESS_MSB);
 		return 0;
 	}
-	level = read_val[0];
-	if (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_BYTE_COUNT)
+
+	if (connector->panel.backlight.edp.vesa.lsb_reg_used)
 		level = (read_val[0] << 8 | read_val[1]);
+	else
+		level = read_val[0];
 
 	return level;
 }
@@ -359,13 +362,14 @@ intel_dp_aux_vesa_set_backlight(const struct drm_connector_state *conn_state,
 	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
 	u8 vals[2] = { 0x0 };
 
-	vals[0] = level;
-
 	/* Write the MSB and/or LSB */
-	if (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_BYTE_COUNT) {
+	if (connector->panel.backlight.edp.vesa.lsb_reg_used) {
 		vals[0] = (level & 0xFF00) >> 8;
 		vals[1] = (level & 0xFF);
+	} else {
+		vals[0] = level;
 	}
+
 	if (drm_dp_dpcd_write(&intel_dp->aux, DP_EDP_BACKLIGHT_BRIGHTNESS_MSB, vals,
 			      sizeof(vals)) != sizeof(vals)) {
 		drm_dbg_kms(&i915->drm,
@@ -419,14 +423,13 @@ intel_dp_aux_vesa_enable_backlight(const struct intel_crtc_state *crtc_state,
 	}
 
 	intel_dp_aux_vesa_set_backlight(conn_state, level);
-	set_vesa_backlight_enable(intel_dp, true);
+	set_vesa_backlight_enable(connector, true);
 }
 
 static void intel_dp_aux_vesa_disable_backlight(const struct drm_connector_state *old_conn_state,
 						u32 level)
 {
-	set_vesa_backlight_enable(enc_to_intel_dp(to_intel_encoder(old_conn_state->best_encoder)),
-				  false);
+	set_vesa_backlight_enable(to_intel_connector(old_conn_state->connector), false);
 }
 
 /*
@@ -524,8 +527,14 @@ static u32 intel_dp_aux_vesa_calc_max_backlight(struct intel_connector *connecto
 static int intel_dp_aux_vesa_setup_backlight(struct intel_connector *connector,
 					     enum pipe pipe)
 {
+	struct intel_dp *intel_dp = intel_attached_dp(connector);
 	struct intel_panel *panel = &connector->panel;
 
+	if (intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP)
+		panel->backlight.edp.vesa.aux_enable = true;
+	if (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_BYTE_COUNT)
+		panel->backlight.edp.vesa.lsb_reg_used = true;
+
 	panel->backlight.max = intel_dp_aux_vesa_calc_max_backlight(connector);
 	if (!panel->backlight.max)
 		return -ENODEV;