drm/i915: Parse panel backlight controller from VBT

Currently the backlight controller is taken as 0. It needs to derive
value from the VBT. Adding the necessary changes.

v2 by Jani:
 - drop obsolete comments, drop redundant initialization (Bob)
 - merge debug logging into one

Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Vidya Srinivas <vidya.srinivas@intel.com>
Reviewed-by: Bob Paauwe <bob.j.paauwe@intel.com>
Tested-by: Bob Paauwe <bob.j.paauwe@intel.com>
Tested-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1481189178-426-1-git-send-email-jani.nikula@intel.com

drivers/gpu/drm/i915/i915_drv.h

@@ -1716,6 +1716,7 @@ struct intel_vbt_data {
 		bool present;
 		bool active_low_pwm;
 		u8 min_brightness;	/* min_brightness/255 of max */
+		u8 controller;		/* brightness controller number */
 		enum intel_backlight_type type;
 	} backlight;
 

drivers/gpu/drm/i915/intel_bios.c

@@ -330,17 +330,19 @@ parse_lfp_backlight(struct drm_i915_private *dev_priv,
 
 		method = &backlight_data->backlight_control[panel_type];
 		dev_priv->vbt.backlight.type = method->type;
+		dev_priv->vbt.backlight.controller = method->controller;
 	}
 
 	dev_priv->vbt.backlight.pwm_freq_hz = entry->pwm_freq_hz;
 	dev_priv->vbt.backlight.active_low_pwm = entry->active_low_pwm;
 	dev_priv->vbt.backlight.min_brightness = entry->min_brightness;
 	DRM_DEBUG_KMS("VBT backlight PWM modulation frequency %u Hz, "
-		      "active %s, min brightness %u, level %u\n",
+		      "active %s, min brightness %u, level %u, controller %u\n",
 		      dev_priv->vbt.backlight.pwm_freq_hz,
 		      dev_priv->vbt.backlight.active_low_pwm ? "low" : "high",
 		      dev_priv->vbt.backlight.min_brightness,
-		      backlight_data->level[panel_type]);
+		      backlight_data->level[panel_type],
+		      dev_priv->vbt.backlight.controller);
 }
 
 /* Try to find sdvo panel data */

drivers/gpu/drm/i915/intel_panel.c

@@ -1039,10 +1039,7 @@ static void bxt_enable_backlight(struct intel_connector *connector)
 	enum pipe pipe = intel_get_pipe_from_connector(connector);
 	u32 pwm_ctl, val;
 
-	/* To use 2nd set of backlight registers, utility pin has to be
-	 * enabled with PWM mode.
-	 * The field should only be changed when the utility pin is disabled
-	 */
+	/* Controller 1 uses the utility pin. */
 	if (panel->backlight.controller == 1) {
 		val = I915_READ(UTIL_PIN_CTL);
 		if (val & UTIL_PIN_ENABLE) {
@@ -1608,19 +1605,11 @@ bxt_setup_backlight(struct intel_connector *connector, enum pipe unused)
 	struct intel_panel *panel = &connector->panel;
 	u32 pwm_ctl, val;
 
-	/*
-	 * For BXT hard coding the Backlight controller to 0.
-	 * TODO : Read the controller value from VBT and generalize
-	 */
-	panel->backlight.controller = 0;
+	panel->backlight.controller = dev_priv->vbt.backlight.controller;
 
 	pwm_ctl = I915_READ(BXT_BLC_PWM_CTL(panel->backlight.controller));
 
-	/* Keeping the check if controller 1 is to be programmed.
-	 * This will come into affect once the VBT parsing
-	 * is fixed for controller selection, and controller 1 is used
-	 * for a prticular display configuration.
-	 */
+	/* Controller 1 uses the utility pin. */
 	if (panel->backlight.controller == 1) {
 		val = I915_READ(UTIL_PIN_CTL);
 		panel->backlight.util_pin_active_low =