drm/tegra: dp: Add DisplayPort link training helper

Add a helper that will perform link training as described in the
DisplayPort specification.
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/dp.h

@@ -12,6 +12,7 @@
 struct drm_display_info;
 struct drm_display_mode;
 struct drm_dp_aux;
+struct drm_dp_link;
 
 /**
  * struct drm_dp_link_caps - DP link capabilities
@@ -56,6 +57,55 @@ struct drm_dp_link_caps {
 void drm_dp_link_caps_copy(struct drm_dp_link_caps *dest,
 			   const struct drm_dp_link_caps *src);
 
+/**
+ * struct drm_dp_link_ops - DP link operations
+ */
+struct drm_dp_link_ops {
+	/**
+	 * @apply_training:
+	 */
+	int (*apply_training)(struct drm_dp_link *link);
+
+	/**
+	 * @configure:
+	 */
+	int (*configure)(struct drm_dp_link *link);
+};
+
+#define DP_TRAIN_VOLTAGE_SWING_LEVEL(x) ((x) << 0)
+#define DP_TRAIN_PRE_EMPHASIS_LEVEL(x) ((x) << 3)
+#define DP_LANE_POST_CURSOR(i, x) (((x) & 0x3) << (((i) & 1) << 2))
+
+/**
+ * struct drm_dp_link_train_set - link training settings
+ * @voltage_swing: per-lane voltage swing
+ * @pre_emphasis: per-lane pre-emphasis
+ * @post_cursor: per-lane post-cursor
+ */
+struct drm_dp_link_train_set {
+	unsigned int voltage_swing[4];
+	unsigned int pre_emphasis[4];
+	unsigned int post_cursor[4];
+};
+
+/**
+ * struct drm_dp_link_train - link training state information
+ * @request: currently requested settings
+ * @adjust: adjustments requested by sink
+ * @pattern: currently requested training pattern
+ * @clock_recovered: flag to track if clock recovery has completed
+ * @channel_equalized: flag to track if channel equalization has completed
+ */
+struct drm_dp_link_train {
+	struct drm_dp_link_train_set request;
+	struct drm_dp_link_train_set adjust;
+
+	unsigned int pattern;
+
+	bool clock_recovered;
+	bool channel_equalized;
+};
+
 /**
  * struct drm_dp_link - DP link capabilities and configuration
  * @revision: DP specification revision supported on the link
@@ -92,6 +142,21 @@ struct drm_dp_link {
 
 	unsigned long rates[DP_MAX_SUPPORTED_RATES];
 	unsigned int num_rates;
+
+	/**
+	 * @ops: DP link operations
+	 */
+	const struct drm_dp_link_ops *ops;
+
+	/**
+	 * @aux: DP AUX channel
+	 */
+	struct drm_dp_aux *aux;
+
+	/**
+	 * @train: DP link training state
+	 */
+	struct drm_dp_link_train train;
 };
 
 int drm_dp_link_add_rate(struct drm_dp_link *link, unsigned long rate);
@@ -106,4 +171,7 @@ int drm_dp_link_choose(struct drm_dp_link *link,
 		       const struct drm_display_mode *mode,
 		       const struct drm_display_info *info);
 
+void drm_dp_link_train_init(struct drm_dp_link_train *train);
+int drm_dp_link_train(struct drm_dp_link *link);
+
 #endif