drm/i915: fix intel_prepare_ddi

At the moment intel_prepare_ddi buffer will iterate through both MST and
CRT encoders, which is incorrect. Neither of these encoder types have an
embedding intel_digital_port object, so for these encoder types we will
use random data when dereferencing the corresponding
intel_digital_port->port field.

Introduced in
commit b403745c84592b26a0713e6944c2b109f6df5c82
Author: Damien Lespiau <damien.lespiau@intel.com>
Date:   Mon Aug 4 22:01:33 2014 +0100

    drm/i915: Iterate through the initialized DDIs to prepare their buffers

v2:
- fix getting at the port for MST encoders too
- make sure that intel_prepare_ddi_buffers() gets called for port E too
  (Paulo)

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90067
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/i915_drv.h

@@ -251,11 +251,6 @@ enum hpd_pin {
 			    &dev->mode_config.connector_list,	\
 			    base.head)
 
-#define for_each_digital_port(dev, digital_port)		\
-	list_for_each_entry(digital_port,			\
-			    &dev->mode_config.encoder_list,	\
-			    base.base.head)
-
 #define for_each_encoder_on_crtc(dev, __crtc, intel_encoder) \
 	list_for_each_entry((intel_encoder), &(dev)->mode_config.encoder_list, base.head) \
 		if ((intel_encoder)->base.crtc == (__crtc))

drivers/gpu/drm/i915/intel_ddi.c

@@ -256,12 +256,11 @@ intel_dig_port_supports_hdmi(const struct intel_digital_port *intel_dig_port)
  * in either FDI or DP modes only, as HDMI connections will work with both
  * of those
  */
-static void intel_prepare_ddi_buffers(struct drm_device *dev,
-				      struct intel_digital_port *intel_dig_port)
+static void intel_prepare_ddi_buffers(struct drm_device *dev, enum port port,
+				      bool supports_hdmi)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	u32 reg;
-	int port = intel_dig_port->port;
 	int i, n_hdmi_entries, n_dp_entries, n_edp_entries, hdmi_default_entry,
 	    size;
 	int hdmi_level = dev_priv->vbt.ddi_port_info[port].hdmi_level_shift;
@@ -272,7 +271,7 @@ static void intel_prepare_ddi_buffers(struct drm_device *dev,
 	const struct ddi_buf_trans *ddi_translations;
 
 	if (IS_BROXTON(dev)) {
-		if (!intel_dig_port_supports_hdmi(intel_dig_port))
+		if (!supports_hdmi)
 			return;
 
 		/* Vswing programming for HDMI */
@@ -360,7 +359,7 @@ static void intel_prepare_ddi_buffers(struct drm_device *dev,
 		reg += 4;
 	}
 
-	if (!intel_dig_port_supports_hdmi(intel_dig_port))
+	if (!supports_hdmi)
 		return;
 
 	/* Choose a good default if VBT is badly populated */
@@ -380,18 +379,27 @@ static void intel_prepare_ddi_buffers(struct drm_device *dev,
  */
 void intel_prepare_ddi(struct drm_device *dev)
 {
-	struct intel_digital_port *intel_dig_port;
+	struct intel_encoder *intel_encoder;
 	bool visited[I915_MAX_PORTS] = { 0, };
 
 	if (!HAS_DDI(dev))
 		return;
 
-	for_each_digital_port(dev, intel_dig_port) {
-		if (visited[intel_dig_port->port])
+	for_each_intel_encoder(dev, intel_encoder) {
+		struct intel_digital_port *intel_dig_port;
+		enum port port;
+		bool supports_hdmi;
+
+		ddi_get_encoder_port(intel_encoder, &intel_dig_port, &port);
+
+		if (visited[port])
 			continue;
 
-		intel_prepare_ddi_buffers(dev, intel_dig_port);
-		visited[intel_dig_port->port] = true;
+		supports_hdmi = intel_dig_port &&
+				intel_dig_port_supports_hdmi(intel_dig_port);
+
+		intel_prepare_ddi_buffers(dev, port, supports_hdmi);
+		visited[port] = true;
 	}
 }