drm/i915: use pch backlight override on hsw too

Currently the difference between backlight control on HSW vs. BDW/SKL is
that on HSW we modify the duty cycle on the CPU register, and have the
hardware pass the changes on to the PCH registers. We still drive the
PCH PWM on both. While HSW and BDW use the same LPT PCH, BDW does not
pass these messages on to the PCH. Therefore on BDW we need to enable
the PCH override bit, and program the PCH directly. (On SPT PCH, this
mode is the default.) We could as well do this on HSW too, and in fact
I've been told this is what a certain other operating system does. So
use PCH backlight override on HSW too.

This simplifies some follow-up code, but it does have the danger of
breaking backlight on HSW machines. It should work, but mysterious are
the ways of backlight.

While at it, name the related backlight hooks according to the PCH
rather than the CPU for clarity.

Cc: Clint Taylor <clinton.a.taylor@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Clint Taylor <Clinton.A.Taylor@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_panel.c

@@ -484,7 +484,7 @@ static u32 intel_panel_compute_brightness(struct intel_connector *connector,
 	return val;
 }
 
-static u32 bdw_get_backlight(struct intel_connector *connector)
+static u32 lpt_get_backlight(struct intel_connector *connector)
 {
 	struct drm_device *dev = connector->base.dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -576,7 +576,7 @@ static u32 intel_panel_get_backlight(struct intel_connector *connector)
 	return val;
 }
 
-static void bdw_set_backlight(struct intel_connector *connector, u32 level)
+static void lpt_set_backlight(struct intel_connector *connector, u32 level)
 {
 	struct drm_device *dev = connector->base.dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -729,6 +729,18 @@ void intel_panel_set_backlight_acpi(struct intel_connector *connector,
 	mutex_unlock(&dev_priv->backlight_lock);
 }
 
+static void lpt_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(BLC_PWM_PCH_CTL1);
+	I915_WRITE(BLC_PWM_PCH_CTL1, tmp & ~BLM_PCH_PWM_ENABLE);
+}
+
 static void pch_disable_backlight(struct intel_connector *connector)
 {
 	struct drm_device *dev = connector->base.dev;
@@ -829,7 +841,7 @@ void intel_panel_disable_backlight(struct intel_connector *connector)
 	mutex_unlock(&dev_priv->backlight_lock);
 }
 
-static void bdw_enable_backlight(struct intel_connector *connector)
+static void lpt_enable_backlight(struct intel_connector *connector)
 {
 	struct drm_device *dev = connector->base.dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -1243,7 +1255,7 @@ static u32 get_backlight_min_vbt(struct intel_connector *connector)
 	return scale(min, 0, 255, 0, panel->backlight.max);
 }
 
-static int bdw_setup_backlight(struct intel_connector *connector, enum pipe unused)
+static int lpt_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;
@@ -1260,7 +1272,7 @@ static int bdw_setup_backlight(struct intel_connector *connector, enum pipe unus
 
 	panel->backlight.min = get_backlight_min_vbt(connector);
 
-	val = bdw_get_backlight(connector);
+	val = lpt_get_backlight(connector);
 	panel->backlight.level = intel_panel_compute_brightness(connector, val);
 
 	panel->backlight.enabled = (pch_ctl1 & BLM_PCH_PWM_ENABLE) &&
@@ -1519,12 +1531,12 @@ void intel_panel_init_backlight_funcs(struct drm_device *dev)
 		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;
-		dev_priv->display.set_backlight = bdw_set_backlight;
-		dev_priv->display.get_backlight = bdw_get_backlight;
+	} else if (HAS_PCH_LPT(dev) || HAS_PCH_SPT(dev)) {
+		dev_priv->display.setup_backlight = lpt_setup_backlight;
+		dev_priv->display.enable_backlight = lpt_enable_backlight;
+		dev_priv->display.disable_backlight = lpt_disable_backlight;
+		dev_priv->display.set_backlight = lpt_set_backlight;
+		dev_priv->display.get_backlight = lpt_get_backlight;
 	} else if (HAS_PCH_SPLIT(dev)) {
 		dev_priv->display.setup_backlight = pch_setup_backlight;
 		dev_priv->display.enable_backlight = pch_enable_backlight;