[PATCH RFC v2 4/4] drm/mediatek: Use dp_connector helpers to report link training state

[Kory Maincent <kory.maincent@bootlin.com>]

Set DRM_BRIDGE_OP_DP and populate dp_link_train_caps with the supported
link rates, lane counts, voltage swing and pre-emphasis levels so the
bridge connector uses drmm_connector_dp_init() and exposes the link
training state properties to userspace.

Store per-lane voltage swing and pre-emphasis values in
mtk_dp_train_info and report the negotiated link parameters via
drm_connector_dp_set_link_train_properties() on training completion.
Clear them via drm_connector_dp_reset_link_train_properties() when a
disconnect is detected in the HPD event thread.

Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
---

This patch has still not been tested. I am in the process of finding the
hardware for that.

Changes in v2:
- Remove voltage swing and pre emphasis properties.
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index eefbc7e0f9c8d..c1e7086104116 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -1789,6 +1789,8 @@ static int mtk_dp_parse_capabilities(struct mtk_dp *mtk_dp)
 		}
 	}
 
+	drm_dp_sink_set_link_caps(mtk_dp->conn, &mtk_dp->aux);
+
 	return 0;
 }
 
@@ -1812,6 +1814,17 @@ static void mtk_dp_train_change_mode(struct mtk_dp *mtk_dp)
 	mtk_dp_reset_swing_pre_emphasis(mtk_dp);
 }
 
+static void mtk_dp_report_link_train(struct mtk_dp *mtk_dp)
+{
+	u32 rate, nlanes;
+
+	rate = drm_dp_bw_code_to_link_rate(mtk_dp->train_info.link_rate);
+	nlanes = mtk_dp->train_info.lane_count;
+
+	drm_dp_set_cur_link_params(mtk_dp->conn, rate, nlanes, false);
+	drm_dp_set_max_link_params(mtk_dp->conn, rate, nlanes);
+}
+
 static int mtk_dp_training(struct mtk_dp *mtk_dp)
 {
 	int ret;
@@ -1892,6 +1905,7 @@ static int mtk_dp_training(struct mtk_dp *mtk_dp)
 	mtk_dp_training_set_scramble(mtk_dp, true);
 	mtk_dp_set_enhanced_frame_mode(mtk_dp);
 
+	mtk_dp_report_link_train(mtk_dp);
 	return 0;
 }
 
@@ -2004,6 +2018,7 @@ static irqreturn_t mtk_dp_hpd_event_thread(int hpd, void *dev)
 			mtk_dp->need_debounce = false;
 			mod_timer(&mtk_dp->debounce_timer,
 				  jiffies + msecs_to_jiffies(100) - 1);
+			drm_dp_sink_reset_link_caps(mtk_dp->conn);
 		} else {
 			mtk_dp_aux_panel_poweron(mtk_dp, true);
 
@@ -2742,6 +2757,12 @@ static int mtk_dp_edp_link_panel(struct drm_dp_aux *mtk_aux)
 
 static int mtk_dp_probe(struct platform_device *pdev)
 {
+	static const u32 dp_rates[] = {162000, 270000, 540000, 810000};
+	static const struct drm_connector_dp_link_caps dp_link_caps = {
+		.nlanes = 4,
+		.nlink_rates = ARRAY_SIZE(dp_rates),
+		.link_rates = dp_rates,
+	};
 	struct mtk_dp *mtk_dp;
 	struct device *dev = &pdev->dev;
 	int ret;
@@ -2809,6 +2830,8 @@ static int mtk_dp_probe(struct platform_device *pdev)
 
 	mtk_dp->bridge.of_node = dev->of_node;
 	mtk_dp->bridge.type = mtk_dp->data->bridge_type;
+	mtk_dp->bridge.dp_link_caps = &dp_link_caps;
+	mtk_dp->bridge.ops = DRM_BRIDGE_OP_DP;
 
 	if (mtk_dp->bridge.type == DRM_MODE_CONNECTOR_eDP) {
 		/*

-- 
2.43.0