[PATCH RFC 12/12] 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.
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 34 +++++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index c52cc7c2e2006..119718c1374c5 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -10,6 +10,7 @@
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_bridge.h>
 #include <drm/drm_crtc.h>
+#include <drm/drm_dp_connector.h>
 #include <drm/drm_edid.h>
 #include <drm/drm_of.h>
 #include <drm/drm_panel.h>
@@ -72,6 +73,8 @@ struct mtk_dp_train_info {
 	/* link_rate is in multiple of 0.27Gbps */
 	int link_rate;
 	int lane_count;
+	u8 vswing[4];
+	u8 preemphasis[4];
 	unsigned int channel_eq_pattern;
 };
 
@@ -1561,6 +1564,9 @@ static void mtk_dp_train_update_swing_pre(struct mtk_dp *mtk_dp, int lanes,
 		mtk_dp_set_swing_pre_emphasis(mtk_dp, lane, swing, preemphasis);
 		drm_dp_dpcd_writeb(&mtk_dp->aux, DP_TRAINING_LANE0_SET + lane,
 				   val);
+
+		mtk_dp->train_info.vswing[lane] = swing;
+		mtk_dp->train_info.preemphasis[lane] = preemphasis;
 	}
 }
 
@@ -1812,6 +1818,21 @@ static void mtk_dp_train_change_mode(struct mtk_dp *mtk_dp)
 	mtk_dp_reset_swing_pre_emphasis(mtk_dp);
 }
 
+static int mtk_dp_report_link_train(struct mtk_dp *mtk_dp)
+{
+	struct drm_connector_dp_link_train dp_link_train;
+
+	dp_link_train.rate = drm_dp_bw_code_to_link_rate(mtk_dp->train_info.link_rate);
+	dp_link_train.nlanes = mtk_dp->train_info.lane_count;
+
+	for (int i = 0; i < mtk_dp->train_info.lane_count; i++) {
+		dp_link_train.v_swing[i] = 1 << mtk_dp->train_info.vswing[i];
+		dp_link_train.pre_emph[i] = 1 << mtk_dp->train_info.preemphasis[i];
+	}
+
+	return drm_connector_dp_set_link_train_properties(mtk_dp->conn, &dp_link_train);
+}
+
 static int mtk_dp_training(struct mtk_dp *mtk_dp)
 {
 	int ret;
@@ -1892,7 +1913,7 @@ 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);
 
-	return 0;
+	return mtk_dp_report_link_train(mtk_dp);
 }
 
 static void mtk_dp_video_enable(struct mtk_dp *mtk_dp, bool enable)
@@ -2004,6 +2025,7 @@ 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_connector_dp_reset_link_train_properties(mtk_dp->conn);
 		} else {
 			mtk_dp_aux_panel_poweron(mtk_dp, true);
 
@@ -2742,6 +2764,14 @@ 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_train_caps dp_link_train_caps = {
+		.nlanes = DRM_DP_1LANE | DRM_DP_2LANE | DRM_DP_4LANE,
+		.nrates = ARRAY_SIZE(dp_rates),
+		.rates = dp_rates,
+		.v_swings = DRM_DP_VOLTAGE_SWING_LEVEL_MASK,
+		.pre_emphs = DRM_DP_PRE_EMPH_LEVEL_MASK,
+	};
 	struct mtk_dp *mtk_dp;
 	struct device *dev = &pdev->dev;
 	int ret;
@@ -2809,6 +2839,8 @@ 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_train_caps = &dp_link_train_caps;
+	mtk_dp->bridge.ops = DRM_BRIDGE_OP_DP;
 
 	if (mtk_dp->bridge.type == DRM_MODE_CONNECTOR_eDP) {
 		/*

-- 
2.43.0