drm/i915: unify remaining register save/restore code a bit

Use the same conditions, group by features, add comments.
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_suspend.c

@@ -203,21 +203,19 @@ static void i915_save_display(struct drm_device *dev)
 		i915_save_display_reg(dev);
 
 	/* LVDS state */
-	if (HAS_PCH_SPLIT(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.savePP_CONTROL = I915_READ(PP_CONTROL);
-		if (IS_MOBILE(dev) && !IS_I830(dev))
+	else if (INTEL_INFO(dev)->gen <= 4 && IS_MOBILE(dev) && !IS_I830(dev))
 		dev_priv->regfile.saveLVDS = I915_READ(LVDS);
-	}
 
+	/* Panel power sequencer */
 	if (HAS_PCH_SPLIT(dev)) {
+		dev_priv->regfile.savePP_CONTROL = I915_READ(PCH_PP_CONTROL);
 		dev_priv->regfile.savePP_ON_DELAYS = I915_READ(PCH_PP_ON_DELAYS);
 		dev_priv->regfile.savePP_OFF_DELAYS = I915_READ(PCH_PP_OFF_DELAYS);
 		dev_priv->regfile.savePP_DIVISOR = I915_READ(PCH_PP_DIVISOR);
 	} else if (!IS_VALLEYVIEW(dev)) {
+		dev_priv->regfile.savePP_CONTROL = I915_READ(PP_CONTROL);
 		dev_priv->regfile.savePP_ON_DELAYS = I915_READ(PP_ON_DELAYS);
 		dev_priv->regfile.savePP_OFF_DELAYS = I915_READ(PP_OFF_DELAYS);
 		dev_priv->regfile.savePP_DIVISOR = I915_READ(PP_DIVISOR);
@@ -246,11 +244,13 @@ static void i915_restore_display(struct drm_device *dev)
 	if (drm_core_check_feature(dev, DRIVER_MODESET))
 		mask = ~LVDS_PORT_EN;
 
+	/* LVDS state */
 	if (HAS_PCH_IBX(dev) || HAS_PCH_CPT(dev))
 		I915_WRITE(PCH_LVDS, dev_priv->regfile.saveLVDS & mask);
 	else if (INTEL_INFO(dev)->gen <= 4 && IS_MOBILE(dev) && !IS_I830(dev))
 		I915_WRITE(LVDS, dev_priv->regfile.saveLVDS & mask);
 
+	/* Panel power sequencer */
 	if (HAS_PCH_SPLIT(dev)) {
 		I915_WRITE(PCH_PP_ON_DELAYS, dev_priv->regfile.savePP_ON_DELAYS);
 		I915_WRITE(PCH_PP_OFF_DELAYS, dev_priv->regfile.savePP_OFF_DELAYS);