drm/i915: Sanitize PHY state during display core uninit

To work around a DMC/Punit issue on ICL where the driver's
ICL_PORT_COMP_DW8/IREFGEN PHY setting is lost when entering/exiting DC6
state, make sure to reinit the PHY whenever disabling DC states.
Similarly the driver's PHY/DBUF/CDCLK settings should have been preserved
across DC5/6 transitions, so check this on all platforms.

This gets rid of the following WARN during suspend:
Combo PHY A HW state changed unexpectedly
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190816095523.15800-1-imre.deak@intel.com

drivers/gpu/drm/i915/display/intel_display_power.c

@@ -963,8 +963,7 @@ static void gen9_assert_dbuf_enabled(struct drm_i915_private *dev_priv)
 	     "Unexpected DBuf power power state (0x%08x)\n", tmp);
 }
 
-static void gen9_dc_off_power_well_enable(struct drm_i915_private *dev_priv,
-					  struct i915_power_well *power_well)
+static void gen9_disable_dc_states(struct drm_i915_private *dev_priv)
 {
 	struct intel_cdclk_state cdclk_state = {};
 
@@ -988,6 +987,12 @@ static void gen9_dc_off_power_well_enable(struct drm_i915_private *dev_priv,
 		intel_combo_phy_init(dev_priv);
 }
 
+static void gen9_dc_off_power_well_enable(struct drm_i915_private *dev_priv,
+					  struct i915_power_well *power_well)
+{
+	gen9_disable_dc_states(dev_priv);
+}
+
 static void gen9_dc_off_power_well_disable(struct drm_i915_private *dev_priv,
 					   struct i915_power_well *power_well)
 {
@@ -4510,7 +4515,7 @@ static void skl_display_core_uninit(struct drm_i915_private *dev_priv)
 	struct i915_power_domains *power_domains = &dev_priv->power_domains;
 	struct i915_power_well *well;
 
-	gen9_set_dc_state(dev_priv, DC_STATE_DISABLE);
+	gen9_disable_dc_states(dev_priv);
 
 	gen9_dbuf_disable(dev_priv);
 
@@ -4571,7 +4576,7 @@ static void bxt_display_core_uninit(struct drm_i915_private *dev_priv)
 	struct i915_power_domains *power_domains = &dev_priv->power_domains;
 	struct i915_power_well *well;
 
-	gen9_set_dc_state(dev_priv, DC_STATE_DISABLE);
+	gen9_disable_dc_states(dev_priv);
 
 	gen9_dbuf_disable(dev_priv);
 
@@ -4631,7 +4636,7 @@ static void cnl_display_core_uninit(struct drm_i915_private *dev_priv)
 	struct i915_power_domains *power_domains = &dev_priv->power_domains;
 	struct i915_power_well *well;
 
-	gen9_set_dc_state(dev_priv, DC_STATE_DISABLE);
+	gen9_disable_dc_states(dev_priv);
 
 	/* 1. Disable all display engine functions -> aready done */
 
@@ -4698,7 +4703,7 @@ static void icl_display_core_uninit(struct drm_i915_private *dev_priv)
 	struct i915_power_domains *power_domains = &dev_priv->power_domains;
 	struct i915_power_well *well;
 
-	gen9_set_dc_state(dev_priv, DC_STATE_DISABLE);
+	gen9_disable_dc_states(dev_priv);
 
 	/* 1. Disable all display engine functions -> aready done */