drm/i915: assert_panel_unlocked() in chv_enable_pll()

Supposedly the power sequencer still locks out the DPLL registers on
CHV, so let's issue a warning if it's still locked when enabling the
DPLL.

Also drop the redundant IS_MOBILE() check for VLV when we check the same
thing.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1458052809-23426-6-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/intel_display.c

@@ -1535,8 +1535,7 @@ static void vlv_enable_pll(struct intel_crtc *crtc,
 	assert_pipe_disabled(dev_priv, pipe);
 
 	/* PLL is protected by panel, make sure we can write it */
-	if (IS_MOBILE(dev_priv->dev))
-		assert_panel_unlocked(dev_priv, pipe);
+	assert_panel_unlocked(dev_priv, pipe);
 
 	I915_WRITE(reg, dpll);
 	POSTING_READ(reg);
@@ -1571,6 +1570,9 @@ static void chv_enable_pll(struct intel_crtc *crtc,
 
 	assert_pipe_disabled(dev_priv, pipe);
 
+	/* PLL is protected by panel, make sure we can write it */
+	assert_panel_unlocked(dev_priv, pipe);
+
 	mutex_lock(&dev_priv->sb_lock);
 
 	/* Enable back the 10bit clock to display controller */