drm/i915: Do vlv cmnlane toggle w/a in more cases

In case the cmnlane power well is down but cmnreset isn't asserted we
would currently skip the off+on toggle for the power well. That could
leave cmnreset deasserted while cmnlane is powered down which might
lead to problems with the PHY.

To avoid such issues skip the cmnlane toggle only if both cmnlane and
disp2d wells are up and cmnreset is already deasserted. In all other
cases power down the cmnlane well which will also make sure cmnreset
gets asserted correctly while cmnlane is powered down.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_runtime_pm.c

@@ -1137,12 +1137,9 @@ static void vlv_cmnlane_wa(struct drm_i915_private *dev_priv)
 	struct i915_power_well *disp2d =
 		lookup_power_well(dev_priv, PUNIT_POWER_WELL_DISP2D);
 
-	/* nothing to do if common lane is already off */
-	if (!cmn->ops->is_enabled(dev_priv, cmn))
-		return;
-
 	/* If the display might be already active skip this */
-	if (disp2d->ops->is_enabled(dev_priv, disp2d) &&
+	if (cmn->ops->is_enabled(dev_priv, cmn) &&
+	    disp2d->ops->is_enabled(dev_priv, disp2d) &&
 	    I915_READ(DPIO_CTL) & DPIO_CMNRST)
 		return;