drm/i915: add eDP checking functions for the display code

The display code needs to distinguish between CPU and PCH attached eDP
panels, so add some helpers to handle that.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/intel_dp.c

@@ -95,6 +95,25 @@ static struct intel_dp *intel_attached_dp(struct drm_connector *connector)
 			    struct intel_dp, base);
 }
 
+/**
+ * intel_encoder_is_pch_edp - is the given encoder a PCH attached eDP?
+ * @encoder: DRM encoder
+ *
+ * Return true if @encoder corresponds to a PCH attached eDP panel.  Needed
+ * by intel_display.c.
+ */
+bool intel_encoder_is_pch_edp(struct drm_encoder *encoder)
+{
+	struct intel_dp *intel_dp;
+
+	if (!encoder)
+		return false;
+
+	intel_dp = enc_to_intel_dp(encoder);
+
+	return is_pch_edp(intel_dp);
+}
+
 static void intel_dp_start_link_train(struct intel_dp *intel_dp);
 static void intel_dp_complete_link_train(struct intel_dp *intel_dp);
 static void intel_dp_link_down(struct intel_dp *intel_dp);

drivers/gpu/drm/i915/intel_drv.h

@@ -212,6 +212,7 @@ intel_dp_set_m_n(struct drm_crtc *crtc, struct drm_display_mode *mode,
 extern bool intel_pch_has_edp(struct drm_crtc *crtc);
 extern bool intel_dpd_is_edp(struct drm_device *dev);
 extern void intel_edp_link_config (struct intel_encoder *, int *, int *);
+extern bool intel_encoder_is_pch_edp(struct drm_encoder *encoder);
 
 /* intel_panel.c */
 extern void intel_fixed_panel_mode(struct drm_display_mode *fixed_mode,