drm/i915: don't save/restore backlight hist ctl registers

This is not used within the driver, and merely saving/restoring these
registers isn't going to do any good anyway. In fact, it's possible it's
actively harmful. Any code enabling the feature should handle this
completely in the regular platform specific enable/disable backlight
functions.
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -799,7 +799,6 @@ struct i915_suspend_saved_registers {
 	u32 saveBLC_HIST_CTL;
 	u32 saveBLC_PWM_CTL;
 	u32 saveBLC_PWM_CTL2;
-	u32 saveBLC_HIST_CTL_B;
 	u32 saveBLC_CPU_PWM_CTL;
 	u32 saveBLC_CPU_PWM_CTL2;
 	u32 saveFPB0;

drivers/gpu/drm/i915/i915_suspend.c

@@ -207,14 +207,8 @@ static void i915_save_display(struct drm_device *dev)
 		dev_priv->regfile.savePP_CONTROL = I915_READ(PCH_PP_CONTROL);
 		if (HAS_PCH_IBX(dev) || HAS_PCH_CPT(dev))
 			dev_priv->regfile.saveLVDS = I915_READ(PCH_LVDS);
-	} else if (IS_VALLEYVIEW(dev)) {
-		dev_priv->regfile.saveBLC_HIST_CTL =
-			I915_READ(VLV_BLC_HIST_CTL(PIPE_A));
-		dev_priv->regfile.saveBLC_HIST_CTL_B =
-			I915_READ(VLV_BLC_HIST_CTL(PIPE_B));
-	} else {
+	} else if (!IS_VALLEYVIEW(dev)) {
 		dev_priv->regfile.savePP_CONTROL = I915_READ(PP_CONTROL);
-		dev_priv->regfile.saveBLC_HIST_CTL = I915_READ(BLC_HIST_CTL);
 		if (IS_MOBILE(dev) && !IS_I830(dev))
 			dev_priv->regfile.saveLVDS = I915_READ(LVDS);
 	}
@@ -262,13 +256,7 @@ static void i915_restore_display(struct drm_device *dev)
 		I915_WRITE(PCH_PP_OFF_DELAYS, dev_priv->regfile.savePP_OFF_DELAYS);
 		I915_WRITE(PCH_PP_DIVISOR, dev_priv->regfile.savePP_DIVISOR);
 		I915_WRITE(PCH_PP_CONTROL, dev_priv->regfile.savePP_CONTROL);
-	} else if (IS_VALLEYVIEW(dev)) {
-		I915_WRITE(VLV_BLC_HIST_CTL(PIPE_A),
-			   dev_priv->regfile.saveBLC_HIST_CTL);
-		I915_WRITE(VLV_BLC_HIST_CTL(PIPE_B),
-			   dev_priv->regfile.saveBLC_HIST_CTL);
-	} else {
-		I915_WRITE(BLC_HIST_CTL, dev_priv->regfile.saveBLC_HIST_CTL);
+	} else if (!IS_VALLEYVIEW(dev)) {
 		I915_WRITE(PP_ON_DELAYS, dev_priv->regfile.savePP_ON_DELAYS);
 		I915_WRITE(PP_OFF_DELAYS, dev_priv->regfile.savePP_OFF_DELAYS);
 		I915_WRITE(PP_DIVISOR, dev_priv->regfile.savePP_DIVISOR);

drivers/gpu/drm/i915/i915_ums.c

@@ -290,6 +290,7 @@ void i915_save_display_reg(struct drm_device *dev)
 		dev_priv->regfile.saveBLC_PWM_CTL = I915_READ(BLC_PWM_CTL);
 		if (INTEL_INFO(dev)->gen >= 4)
 			dev_priv->regfile.saveBLC_PWM_CTL2 = I915_READ(BLC_PWM_CTL2);
+		dev_priv->regfile.saveBLC_HIST_CTL = I915_READ(BLC_HIST_CTL);
 	}
 
 	return;
@@ -319,6 +320,7 @@ void i915_restore_display_reg(struct drm_device *dev)
 		if (INTEL_INFO(dev)->gen >= 4)
 			I915_WRITE(BLC_PWM_CTL2, dev_priv->regfile.saveBLC_PWM_CTL2);
 		I915_WRITE(BLC_PWM_CTL, dev_priv->regfile.saveBLC_PWM_CTL);
+		I915_WRITE(BLC_HIST_CTL, dev_priv->regfile.saveBLC_HIST_CTL);
 	}
 
 	/* Panel fitter */