drm/i915/bxt: BLC implementation

Enabling BLC on BXT.
Includes register definition, and new functions for BXT.

In BXT, there are 2 sets of registers for BLC. Until there is clarity
about which set would be effective, set 1 is being used.
This would have to be re-visited if there is any change or when 2 LFPs are
enabled on BXT.

This patch enables brightness change which would be effected by use of
hot-keys or sysfs entry.

TODO:- BLC implementation will have to re-visited when
1. there is clarity about which set of registers has to be used and when.
2. CDCLK frequency is changed

v2: Jani's review comments
	- Modified comment in i915_reg.h
	- Renamed register defintions
	- Removed definition of duty cycle max. Not required now and its not 64-bit.

v3:
  - Rebase on top of VLV/CHV backlight changes, in particuliar
    bxt_set_backlight() now has a different prototype (Damien)
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Vandana Kannan <vandana.kannan@intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Shankar, Uma <uma.shankar@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -3486,6 +3486,18 @@ enum skl_disp_power_wells {
 #define UTIL_PIN_CTL		0x48400
 #define   UTIL_PIN_ENABLE	(1 << 31)
 
+/* BXT backlight register definition. */
+#define BXT_BLC_PWM_CTL1			0xC8250
+#define   BXT_BLC_PWM_ENABLE			(1 << 31)
+#define   BXT_BLC_PWM_POLARITY			(1 << 29)
+#define BXT_BLC_PWM_FREQ1			0xC8254
+#define BXT_BLC_PWM_DUTY1			0xC8258
+
+#define BXT_BLC_PWM_CTL2			0xC8350
+#define BXT_BLC_PWM_FREQ2			0xC8354
+#define BXT_BLC_PWM_DUTY2			0xC8358
+
+
 #define PCH_GTC_CTL		0xe7000
 #define   PCH_GTC_ENABLE	(1 << 31)
 

drivers/gpu/drm/i915/intel_panel.c

@@ -536,6 +536,14 @@ static u32 vlv_get_backlight(struct intel_connector *connector)
 	return _vlv_get_backlight(dev, pipe);
 }
 
+static u32 bxt_get_backlight(struct intel_connector *connector)
+{
+	struct drm_device *dev = connector->base.dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	return I915_READ(BXT_BLC_PWM_DUTY1);
+}
+
 static u32 intel_panel_get_backlight(struct intel_connector *connector)
 {
 	struct drm_device *dev = connector->base.dev;
@@ -616,6 +624,14 @@ static void vlv_set_backlight(struct intel_connector *connector, u32 level)
 	I915_WRITE(VLV_BLC_PWM_CTL(pipe), tmp | level);
 }
 
+static void bxt_set_backlight(struct intel_connector *connector, u32 level)
+{
+	struct drm_device *dev = connector->base.dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	I915_WRITE(BXT_BLC_PWM_DUTY1, level);
+}
+
 static void
 intel_panel_actually_set_backlight(struct intel_connector *connector, u32 level)
 {
@@ -741,6 +757,18 @@ static void vlv_disable_backlight(struct intel_connector *connector)
 	I915_WRITE(VLV_BLC_PWM_CTL2(pipe), tmp & ~BLM_PWM_ENABLE);
 }
 
+static void bxt_disable_backlight(struct intel_connector *connector)
+{
+	struct drm_device *dev = connector->base.dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	u32 tmp;
+
+	intel_panel_actually_set_backlight(connector, 0);
+
+	tmp = I915_READ(BXT_BLC_PWM_CTL1);
+	I915_WRITE(BXT_BLC_PWM_CTL1, tmp & ~BXT_BLC_PWM_ENABLE);
+}
+
 void intel_panel_disable_backlight(struct intel_connector *connector)
 {
 	struct drm_device *dev = connector->base.dev;
@@ -947,6 +975,33 @@ static void vlv_enable_backlight(struct intel_connector *connector)
 	I915_WRITE(VLV_BLC_PWM_CTL2(pipe), ctl2 | BLM_PWM_ENABLE);
 }
 
+static void bxt_enable_backlight(struct intel_connector *connector)
+{
+	struct drm_device *dev = connector->base.dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct intel_panel *panel = &connector->panel;
+	u32 pwm_ctl;
+
+	pwm_ctl = I915_READ(BXT_BLC_PWM_CTL1);
+	if (pwm_ctl & BXT_BLC_PWM_ENABLE) {
+		DRM_DEBUG_KMS("backlight already enabled\n");
+		pwm_ctl &= ~BXT_BLC_PWM_ENABLE;
+		I915_WRITE(BXT_BLC_PWM_CTL1, pwm_ctl);
+	}
+
+	I915_WRITE(BXT_BLC_PWM_FREQ1, panel->backlight.max);
+
+	intel_panel_actually_set_backlight(connector, panel->backlight.level);
+
+	pwm_ctl = 0;
+	if (panel->backlight.active_low_pwm)
+		pwm_ctl |= BXT_BLC_PWM_POLARITY;
+
+	I915_WRITE(BXT_BLC_PWM_CTL1, pwm_ctl);
+	POSTING_READ(BXT_BLC_PWM_CTL1);
+	I915_WRITE(BXT_BLC_PWM_CTL1, pwm_ctl | BXT_BLC_PWM_ENABLE);
+}
+
 void intel_panel_enable_backlight(struct intel_connector *connector)
 {
 	struct drm_device *dev = connector->base.dev;
@@ -1299,6 +1354,30 @@ static int vlv_setup_backlight(struct intel_connector *connector, enum pipe pipe
 	return 0;
 }
 
+static int
+bxt_setup_backlight(struct intel_connector *connector, enum pipe unused)
+{
+	struct drm_device *dev = connector->base.dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct intel_panel *panel = &connector->panel;
+	u32 pwm_ctl, val;
+
+	pwm_ctl = I915_READ(BXT_BLC_PWM_CTL1);
+	panel->backlight.active_low_pwm = pwm_ctl & BXT_BLC_PWM_POLARITY;
+
+	panel->backlight.max = I915_READ(BXT_BLC_PWM_FREQ1);
+	if (!panel->backlight.max)
+		return -ENODEV;
+
+	val = bxt_get_backlight(connector);
+	panel->backlight.level = intel_panel_compute_brightness(connector, val);
+
+	panel->backlight.enabled = (pwm_ctl & BXT_BLC_PWM_ENABLE) &&
+		panel->backlight.level != 0;
+
+	return 0;
+}
+
 int intel_panel_setup_backlight(struct drm_connector *connector, enum pipe pipe)
 {
 	struct drm_device *dev = connector->dev;
@@ -1350,7 +1429,13 @@ void intel_panel_init_backlight_funcs(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
-	if (IS_BROADWELL(dev) || (INTEL_INFO(dev)->gen >= 9)) {
+	if (IS_BROXTON(dev)) {
+		dev_priv->display.setup_backlight = bxt_setup_backlight;
+		dev_priv->display.enable_backlight = bxt_enable_backlight;
+		dev_priv->display.disable_backlight = bxt_disable_backlight;
+		dev_priv->display.set_backlight = bxt_set_backlight;
+		dev_priv->display.get_backlight = bxt_get_backlight;
+	} else if (IS_BROADWELL(dev) || IS_SKYLAKE(dev)) {
 		dev_priv->display.setup_backlight = bdw_setup_backlight;
 		dev_priv->display.enable_backlight = bdw_enable_backlight;
 		dev_priv->display.disable_backlight = pch_disable_backlight;