drm/i915/bxt: Force reprogramming a PHY with invalid HW state

It's possible that BIOS enables PHY0, but it programmes only the first
channel on it. Since we program the PHYs only during driver loading this
is an incorrect configuration from the driver's point of view, since we
may use both channels eventually. Detect this scenario and force
reprogramming the PHY in this case.

The actual scenario for me was that the lane optimization for the second
channel in PHY0 was not setup by BIOS and so a state verification
warning was triggered. Everything else was setup properly.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461174366-16758-4-git-send-email-imre.deak@intel.com

drivers/gpu/drm/i915/intel_ddi.c

@@ -1775,23 +1775,32 @@ static void broxton_phy_wait_grc_done(struct drm_i915_private *dev_priv,
 		DRM_ERROR("timeout waiting for PHY%d GRC\n", phy);
 }
 
+static bool broxton_phy_verify_state(struct drm_i915_private *dev_priv,
+				     enum dpio_phy phy);
+
 static void broxton_phy_init(struct drm_i915_private *dev_priv,
 			     enum dpio_phy phy)
 {
 	enum port port;
 	u32 ports, val;
 
 	if (broxton_phy_is_enabled(dev_priv, phy)) {
-		DRM_DEBUG_DRIVER("DDI PHY %d already enabled, "
-				 "won't reprogram it\n", phy);
 		/* Still read out the GRC value for state verification */
 		if (phy == DPIO_PHY0)
 			dev_priv->bxt_phy_grc = broxton_get_grc(dev_priv, phy);
 
-		return;
-	}
+		if (broxton_phy_verify_state(dev_priv, phy)) {
+			DRM_DEBUG_DRIVER("DDI PHY %d already enabled, "
+					 "won't reprogram it\n", phy);
 
-	DRM_DEBUG_DRIVER("DDI PHY %d not enabled, enabling it\n", phy);
+			return;
+		}
+
+		DRM_DEBUG_DRIVER("DDI PHY %d enabled with invalid state, "
+				 "force reprogramming it\n", phy);
+	} else {
+		DRM_DEBUG_DRIVER("DDI PHY %d not enabled, enabling it\n", phy);
+	}
 
 	val = I915_READ(BXT_P_CR_GT_DISP_PWRON);
 	val |= GT_DISPLAY_POWER_ON(phy);