drm/i915: Don't get hw state from DVO chip unless DVO is enabled

Certain DVO chips (ns2501 for example) don't like to be accessed unless
the PLL is running. Simply skip the DVO get_hw_state if the DVO port
is disabled.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_dvo.c

@@ -112,7 +112,15 @@ static struct intel_dvo *intel_attached_dvo(struct drm_connector *connector)
 
 static bool intel_dvo_connector_get_hw_state(struct intel_connector *connector)
 {
+	struct drm_device *dev = connector->base.dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_dvo *intel_dvo = intel_attached_dvo(&connector->base);
+	u32 tmp;
+
+	tmp = I915_READ(intel_dvo->dev.dvo_reg);
+
+	if (!(tmp & DVO_ENABLE))
+		return false;
 
 	return intel_dvo->dev.dev_ops->get_hw_state(&intel_dvo->dev);
 }