[PATCH RFC v3 8/8] drm/mediatek: Use dp_connector helpers to expose link training state
Kory Maincent
kory.maincent at bootlin.com
Mon Oct 12 08:11:03 PDT 2026
Adopt the DRM core DisplayPort helpers by setting DRM_BRIDGE_OP_DP and
populating the bridge dp_link_caps at probe time. Report the sink
capabilities on hotplug, reset them on disconnect, and report the link
parameters once link training succeeds.
Signed-off-by: Kory Maincent <kory.maincent at bootlin.com>
---
Not tested. I believed I had a board with this device, but it actually uses
an anx7625 bridge. I'm unable to test it; it would be appreciated if
someone else could, so the change isn't dropped.
Changes in v3:
- Sync and report sink capabilities from the HPD thread for DisplayPort,
or in atomic_enable for eDP. Reset them on unplug, or atomic disable
and only report link parameters after successful training.
- Add connection_mutex lock for DisplayPort in the IRQ thread.
Changes in v2:
- Remove voltage swing and pre emphasis properties.
---
drivers/gpu/drm/mediatek/mtk_dp.c | 79 +++++++++++++++++++++++++++++++++++++--
1 file changed, 75 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index f656b85b84212..2e2596eaa342e 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -1812,6 +1812,35 @@ 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;
+ bool dsc = false;
+
+ 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, dsc);
+}
+
+static void mtk_dp_report_link_train(struct mtk_dp *mtk_dp)
+{
+ struct drm_modeset_lock *lock;
+ int ret;
+
+ if (!mtk_dp->conn)
+ return;
+
+ lock = &mtk_dp->conn->dev->mode_config.connection_mutex;
+ ret = drm_modeset_lock_single_interruptible(lock);
+ if (ret)
+ return;
+
+ _mtk_dp_report_link_train(mtk_dp);
+
+ drm_modeset_unlock(lock);
+}
+
static int mtk_dp_training(struct mtk_dp *mtk_dp)
{
int ret;
@@ -2015,6 +2044,8 @@ static irqreturn_t mtk_dp_hpd_event_thread(int hpd, void *dev)
ret = mtk_dp_training(mtk_dp);
if (ret)
drm_err(mtk_dp->drm_dev, "Training failed, %d\n", ret);
+ else
+ mtk_dp_report_link_train(mtk_dp);
mtk_dp->enabled = true;
}
@@ -2145,9 +2176,12 @@ mtk_dp_bdg_detect(struct drm_bridge *bridge, struct drm_connector *connector)
struct mtk_dp *mtk_dp = mtk_dp_from_bridge(bridge);
enum drm_connector_status ret = connector_status_disconnected;
bool enabled = mtk_dp->enabled;
+ int err;
- if (!mtk_dp->train_info.cable_plugged_in)
+ if (!mtk_dp->train_info.cable_plugged_in) {
+ drm_dp_sink_reset_caps(connector);
return ret;
+ }
if (!enabled)
mtk_dp_aux_panel_poweron(mtk_dp, true);
@@ -2160,9 +2194,18 @@ mtk_dp_bdg_detect(struct drm_bridge *bridge, struct drm_connector *connector)
* whether we connect to a sink device.
*/
- if (drm_dp_read_sink_count(&mtk_dp->aux) > 0)
+ if (drm_dp_read_sink_count(&mtk_dp->aux) > 0) {
ret = connector_status_connected;
+ err = drm_dp_sink_sync_caps(connector, &mtk_dp->aux, NULL);
+ if (err)
+ drm_dbg_kms(mtk_dp->aux.drm_dev,
+ "%s: error sink caps synchronisation (%d)\n",
+ mtk_dp->aux.name, err);
+ } else {
+ drm_dp_sink_reset_caps(connector);
+ }
+
if (!enabled)
mtk_dp_aux_panel_poweron(mtk_dp, false);
@@ -2390,12 +2433,20 @@ static void mtk_dp_bridge_atomic_enable(struct drm_bridge *bridge,
if (mtk_dp->data->bridge_type == DRM_MODE_CONNECTOR_eDP) {
mtk_dp_aux_panel_poweron(mtk_dp, true);
+ ret = drm_dp_sink_sync_caps(mtk_dp->conn, &mtk_dp->aux, NULL);
+ if (ret)
+ drm_dbg_kms(mtk_dp->aux.drm_dev,
+ "%s: error sink caps synchronisation (%d)\n",
+ mtk_dp->aux.name, ret);
+
/* Training */
ret = mtk_dp_training(mtk_dp);
if (ret) {
drm_err(mtk_dp->drm_dev, "Training failed, %d\n", ret);
goto power_off_aux;
}
+
+ _mtk_dp_report_link_train(mtk_dp);
}
ret = mtk_dp_video_config(mtk_dp);
@@ -2435,6 +2486,7 @@ static void mtk_dp_bridge_atomic_disable(struct drm_bridge *bridge,
if (mtk_dp->data->bridge_type == DRM_MODE_CONNECTOR_eDP) {
mtk_dp->enabled = false;
mtk_dp_aux_panel_poweron(mtk_dp, false);
+ drm_dp_sink_reset_caps(mtk_dp->conn);
}
mtk_dp_update_plugged_status(mtk_dp);
@@ -2740,11 +2792,14 @@ static int mtk_dp_edp_link_panel(struct drm_dp_aux *mtk_aux)
return 0;
}
+static int mtk_dp_rates[] = {162000, 270000, 540000, 810000};
+
static int mtk_dp_probe(struct platform_device *pdev)
{
+ struct drm_connector_dp_link_caps *source_caps;
struct mtk_dp *mtk_dp;
struct device *dev = &pdev->dev;
- int ret;
+ int ret, i, max_rate;
mtk_dp = devm_drm_bridge_alloc(dev, struct mtk_dp, bridge,
&mtk_dp_bridge_funcs);
@@ -2758,6 +2813,20 @@ static int mtk_dp_probe(struct platform_device *pdev)
if (ret)
return dev_err_probe(dev, ret, "Failed to parse dt\n");
+ source_caps = devm_kzalloc(dev, sizeof(*source_caps), GFP_KERNEL);
+ if (!source_caps)
+ return -ENOMEM;
+
+ source_caps->nlanes = mtk_dp->max_lanes;
+ source_caps->link_rates = mtk_dp_rates;
+
+ max_rate = drm_dp_bw_code_to_link_rate(mtk_dp->max_linkrate);
+ for (i = 0; i < ARRAY_SIZE(mtk_dp_rates); i++)
+ if (mtk_dp_rates[i] > max_rate)
+ break;
+
+ source_caps->nlink_rates = i;
+
/*
* Request the interrupt and install service routine only if we are
* on full DisplayPort.
@@ -2809,6 +2878,8 @@ 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 = source_caps;
+ mtk_dp->bridge.ops = DRM_BRIDGE_OP_DP;
if (mtk_dp->bridge.type == DRM_MODE_CONNECTOR_eDP) {
/*
@@ -2849,7 +2920,7 @@ static int mtk_dp_probe(struct platform_device *pdev)
}
}
} else {
- mtk_dp->bridge.ops = DRM_BRIDGE_OP_DETECT |
+ mtk_dp->bridge.ops |= DRM_BRIDGE_OP_DETECT |
DRM_BRIDGE_OP_EDID | DRM_BRIDGE_OP_HPD;
ret = devm_drm_bridge_add(dev, &mtk_dp->bridge);
if (ret)
--
2.43.0
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