drm/i915: Parsing LFP brightness control from VBT

LFP brighness control from the VBT block 43 indicates which
controller is used for brightness.
LFP1 brightness control method:
Bit 7-4 = This field controller number of the brightnes controller.
0 = Controller 0
1 = Controller 1
2 = Controller 2
3 = Controller 3
Others = Reserved
Bits 3-0 = This field specifies the brightness control pin to be used on the
platform.
0 = PMIC pin is used for brightness control
1 = LPSS PWM is used for brightness control
2 = Display DDI is used for brightness control
3 = CABC method to control brightness
Others = Reserved

Adding the above fields in dev_priv->vbt and corresponding changes in
parse_backlight()

v2: Jani's review comments addressed
	- Move PWM definitions to intel_bios.h
	- Moving vbt_version to intel_vbt_data
	- Rename brightness to bl_ctrl_data
	- Logging just control_pin instead of string
	- Avoid adding vbt_version in dev_priv
	- Since only DDI option is available as of now, let control pin DDI
	affect dev_priv->vbt.backlight.present

v3: Jani's review comments addressed
	- Drop control_pin
	- Use bdb->version
	- set controller to 0 instead of using control pin define
	- check controller bounds
	- remove superfluous changes in intel_parse_bios

Signed-off-by: Deepak M <m.deepak@intel.com>
Signed-off-by: Vandana Kannan <vandana.kannan@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -1367,6 +1367,7 @@ struct intel_vbt_data {
 		bool present;
 		bool active_low_pwm;
 		u8 min_brightness;	/* min_brightness/255 of max */
+		u8 controller;		/* brightness controller number */
 	} backlight;
 
 	/* MIPI DSI */

drivers/gpu/drm/i915/intel_bios.c

@@ -314,6 +314,7 @@ parse_lfp_backlight(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
 {
 	const struct bdb_lfp_backlight_data *backlight_data;
 	const struct bdb_lfp_backlight_data_entry *entry;
+	const struct bdb_lfp_backlight_control_data *bl_ctrl_data;
 
 	backlight_data = find_section(bdb, BDB_LVDS_BACKLIGHT);
 	if (!backlight_data)
@@ -326,6 +327,7 @@ parse_lfp_backlight(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
 	}
 
 	entry = &backlight_data->data[panel_type];
+	bl_ctrl_data = &backlight_data->blc_ctl[panel_type];
 
 	dev_priv->vbt.backlight.present = entry->type == BDB_BACKLIGHT_TYPE_PWM;
 	if (!dev_priv->vbt.backlight.present) {
@@ -337,12 +339,30 @@ parse_lfp_backlight(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
 	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;
+
+	dev_priv->vbt.backlight.controller = 0;
+	if (bdb->version >= 191) {
+		dev_priv->vbt.backlight.present =
+				bl_ctrl_data->pin == BLC_CONTROL_PIN_DDI;
+		if (!dev_priv->vbt.backlight.present) {
+			DRM_DEBUG_KMS("BL control pin is not DDI (pin %u)\n",
+					bl_ctrl_data->pin);
+			return;
+		}
+		if (bl_ctrl_data->controller == 1)
+			dev_priv->vbt.backlight.controller =
+				bl_ctrl_data->controller;
+	}
+
 	DRM_DEBUG_KMS("VBT backlight PWM modulation frequency %u Hz, "
 		      "active %s, min brightness %u, level %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]);
+
+	DRM_DEBUG_KMS("VBT BL controller %u\n",
+		dev_priv->vbt.backlight.controller);
 }
 
 /* Try to find sdvo panel data */

drivers/gpu/drm/i915/intel_bios.h

@@ -402,10 +402,21 @@ struct bdb_lfp_backlight_data_entry {
 	u8 obsolete3;
 } __packed;
 
+#define BLC_CONTROL_PIN_PMIC		0
+#define BLC_CONTROL_PIN_LPSS_PWM	1
+#define BLC_CONTROL_PIN_DDI		2
+#define BLC_CONTROL_PIN_CABC		3
+
+struct bdb_lfp_backlight_control_data {
+	u8 controller:4;
+	u8 pin:4;
+} __packed;
+
 struct bdb_lfp_backlight_data {
 	u8 entry_size;
 	struct bdb_lfp_backlight_data_entry data[16];
 	u8 level[16];
+	struct bdb_lfp_backlight_control_data blc_ctl[16];
 } __packed;
 
 struct aimdb_header {