drm/i915/ibx, cpt: Don't attempt to register eDP if LVDS was detected

Atm on IBX/CPT we attempt to detect if eDP is present even if LVDS was
already detected and an encoder for it was registered. This involves
trying to read out the eDP DPCD, which in turn needs the same power
sequencer that LVDS uses. Poking at the VDD line at an unexpected time
may or may not interfere with the LVDS panel, but it's probably safer to
prevent this. Registering both an LVDS and an eDP connector would also
present a similar problem accessing the shared PPS at any point later in
an unexpected way.

We also need this to be able fix PPS initialization before its first use
in the next patch. For that we want to be sure that PPS is not in use
by LVDS.

v2:
- Split out the PPS init fix to a separate patch. (Chris)
- Add comment about eDP init depending on LVDS init. (Chris)
- Make the use of the intel_encoder ptr less error prone.
v3:
- Use IBX/CPT reference instead of the incorrect ILK, add a WARN about
  this. (Ville)
v4:
- Use a helper to get the lvds encoder instead of opencoding the same.
  (Ville)

CC: Ville Syrjälä <ville.syrjala@linux.intel.com>
CC: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> (v2)
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> (v3)
Link: http://patchwork.freedesktop.org/patch/msgid/1466499109-20240-2-git-send-email-imre.deak@intel.com

drivers/gpu/drm/i915/intel_display.c

@@ -14708,6 +14708,11 @@ static void intel_setup_outputs(struct drm_device *dev)
 	struct intel_encoder *encoder;
 	bool dpd_is_edp = false;
 
+	/*
+	 * intel_edp_init_connector() depends on this completing first, to
+	 * prevent the registeration of both eDP and LVDS and the incorrect
+	 * sharing of the PPS.
+	 */
 	intel_lvds_init(dev);
 
 	if (intel_crt_present(dev))

drivers/gpu/drm/i915/intel_dp.c

@@ -5313,6 +5313,19 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
 	if (!is_edp(intel_dp))
 		return true;
 
+	/*
+	 * On IBX/CPT we may get here with LVDS already registered. Since the
+	 * driver uses the only internal power sequencer available for both
+	 * eDP and LVDS bail out early in this case to prevent interfering
+	 * with an already powered-on LVDS power sequencer.
+	 */
+	if (intel_get_lvds_encoder(dev)) {
+		WARN_ON(!(HAS_PCH_IBX(dev_priv) || HAS_PCH_CPT(dev_priv)));
+		DRM_INFO("LVDS was detected, not registering eDP\n");
+
+		return false;
+	}
+
 	pps_lock(intel_dp);
 	intel_edp_panel_vdd_sanitize(intel_dp);
 	pps_unlock(intel_dp);

drivers/gpu/drm/i915/intel_drv.h

@@ -1460,6 +1460,7 @@ void intel_dp_dual_mode_set_tmds_output(struct intel_hdmi *hdmi, bool enable);
 
 /* intel_lvds.c */
 void intel_lvds_init(struct drm_device *dev);
+struct intel_encoder *intel_get_lvds_encoder(struct drm_device *dev);
 bool intel_is_dual_link_lvds(struct drm_device *dev);
 
 

drivers/gpu/drm/i915/intel_lvds.c

@@ -809,20 +809,22 @@ static const struct dmi_system_id intel_dual_link_lvds[] = {
 	{ }	/* terminating entry */
 };
 
+struct intel_encoder *intel_get_lvds_encoder(struct drm_device *dev)
+{
+	struct intel_encoder *intel_encoder;
+
+	for_each_intel_encoder(dev, intel_encoder)
+		if (intel_encoder->type == INTEL_OUTPUT_LVDS)
+			return intel_encoder;
+
+	return NULL;
+}
+
 bool intel_is_dual_link_lvds(struct drm_device *dev)
 {
-	struct intel_encoder *encoder;
-	struct intel_lvds_encoder *lvds_encoder;
+	struct intel_encoder *encoder = intel_get_lvds_encoder(dev);
 
-	for_each_intel_encoder(dev, encoder) {
-		if (encoder->type == INTEL_OUTPUT_LVDS) {
-			lvds_encoder = to_lvds_encoder(&encoder->base);
-
-			return lvds_encoder->is_dual_link;
-		}
-	}
-
-	return false;
+	return encoder && to_lvds_encoder(&encoder->base)->is_dual_link;
 }
 
 static bool compute_is_dual_link_lvds(struct intel_lvds_encoder *lvds_encoder)