drm/i915/ehl: Don't program PHY_MISC on EHL PHY C

Although EHL added a third combo PHY, no PHY_MISC register was added for
PHY C.  The bspec indicates that there's no need to program the "DE to
IO Comp Pwr Down" setting for this PHY that we usually need to set in
PHY_MISC.

v2:
 - Add IS_ELKHARTLAKE() guards since future platforms that have a PHY C
   are likely to reinstate the PHY_MISC register.  (Jose)
 - Use goto's to skip PHY_MISC programming & minimize code deltas. (Jose)

Bspec: 33148
Cc: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190626000352.31926-4-matthew.d.roper@intel.com
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>

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

@@ -183,9 +183,13 @@ static void cnl_combo_phys_uninit(struct drm_i915_private *dev_priv)
 static bool icl_combo_phy_enabled(struct drm_i915_private *dev_priv,
 				  enum port port)
 {
-	return !(I915_READ(ICL_PHY_MISC(port)) &
-		 ICL_PHY_MISC_DE_IO_COMP_PWR_DOWN) &&
-		(I915_READ(ICL_PORT_COMP_DW0(port)) & COMP_INIT);
+	/* The PHY C added by EHL has no PHY_MISC register */
+	if (IS_ELKHARTLAKE(dev_priv) && port == PORT_C)
+		return I915_READ(ICL_PORT_COMP_DW0(port)) & COMP_INIT;
+	else
+		return !(I915_READ(ICL_PHY_MISC(port)) &
+			 ICL_PHY_MISC_DE_IO_COMP_PWR_DOWN) &&
+			(I915_READ(ICL_PORT_COMP_DW0(port)) & COMP_INIT);
 }
 
 static bool icl_combo_phy_verify_state(struct drm_i915_private *dev_priv,
@@ -299,6 +303,14 @@ static void icl_combo_phys_init(struct drm_i915_private *dev_priv)
 			continue;
 		}
 
+		/*
+		 * Although EHL adds a combo PHY C, there's no PHY_MISC
+		 * register for it and no need to program the
+		 * DE_IO_COMP_PWR_DOWN setting on PHY C.
+		 */
+		if (IS_ELKHARTLAKE(dev_priv) && port == PORT_C)
+			goto skip_phy_misc;
+
 		/*
 		 * EHL's combo PHY A can be hooked up to either an external
 		 * display (via DDI-D) or an internal display (via DDI-A or
@@ -313,6 +325,7 @@ static void icl_combo_phys_init(struct drm_i915_private *dev_priv)
 		val &= ~ICL_PHY_MISC_DE_IO_COMP_PWR_DOWN;
 		I915_WRITE(ICL_PHY_MISC(port), val);
 
+skip_phy_misc:
 		cnl_set_procmon_ref_values(dev_priv, port);
 
 		if (port == PORT_A) {
@@ -343,10 +356,19 @@ static void icl_combo_phys_uninit(struct drm_i915_private *dev_priv)
 			DRM_WARN("Port %c combo PHY HW state changed unexpectedly\n",
 				 port_name(port));
 
+		/*
+		 * Although EHL adds a combo PHY C, there's no PHY_MISC
+		 * register for it and no need to program the
+		 * DE_IO_COMP_PWR_DOWN setting on PHY C.
+		 */
+		if (IS_ELKHARTLAKE(dev_priv) && port == PORT_C)
+			goto skip_phy_misc;
+
 		val = I915_READ(ICL_PHY_MISC(port));
 		val |= ICL_PHY_MISC_DE_IO_COMP_PWR_DOWN;
 		I915_WRITE(ICL_PHY_MISC(port), val);
 
+skip_phy_misc:
 		val = I915_READ(ICL_PORT_COMP_DW0(port));
 		val &= ~COMP_INIT;
 		I915_WRITE(ICL_PORT_COMP_DW0(port), val);