[PATCH v2 10/10] drm/bridge: analogix_dp: Handle HPD notification from downstream bridge

[Damon Ding]

When the display pipeline includes a display-connector bridge with
hpd-gpios configured, the connector's hotplug status is managed by the
display-connector bridge through its GPIO, not by the Analogix DP
controller's native HPD. In this configuration, the DP controller's
internal HPD polling in analogix_dp_detect_hpd() does not reflect the
actual connection state.

Implement the .hpd_notify bridge callback to receive connection status
updates from downstream bridges. Cache the connection status in a
connection_notified flag, and use it to short-circuit
analogix_dp_detect_hpd() when a downstream bridge has already confirmed
the connection.

Signed-off-by: Damon Ding <damon.ding@xxxxxxxxxxxxxx>
---
 .../gpu/drm/bridge/analogix/analogix_dp_core.c   | 16 ++++++++++++++++
 .../gpu/drm/bridge/analogix/analogix_dp_core.h   |  1 +
 2 files changed, 17 insertions(+)

diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
index a5a50b9ab8a7..f0476a60ece3 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
@@ -68,6 +68,13 @@ static int analogix_dp_detect_hpd(struct analogix_dp_device *dp)
 {
 	int timeout_loop = 0;
 
+	/*
+	 * Trust connection status from downstream bridge (e.g.,
+	 * display-connector with hpd-gpios).
+	 */
+	if (dp->plat_data->next_bridge && dp->connection_notified)
+		return 0;
+
 	while (timeout_loop < DP_TIMEOUT_LOOP_COUNT) {
 		if (analogix_dp_get_plug_in_status(dp) == 0)
 			return 0;
@@ -1247,6 +1254,14 @@ static void analogix_dp_bridge_atomic_post_disable(struct drm_bridge *bridge,
 		DRM_ERROR("Failed to enable psr (%d)\n", ret);
 }
 
+static void analogix_dp_bridge_notify(struct drm_bridge *bridge, struct drm_connector *connector,
+				      enum drm_connector_status status)
+{
+	struct analogix_dp_device *dp = to_dp(bridge);
+
+	dp->connection_notified = (status == connector_status_connected);
+}
+
 static const struct drm_bridge_funcs analogix_dp_bridge_funcs = {
 	.atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
 	.atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
@@ -1259,6 +1274,7 @@ static const struct drm_bridge_funcs analogix_dp_bridge_funcs = {
 	.attach = analogix_dp_bridge_attach,
 	.edid_read = analogix_dp_bridge_edid_read,
 	.detect = analogix_dp_bridge_detect,
+	.hpd_notify = analogix_dp_bridge_notify,
 };
 
 static int analogix_dp_dt_parse_pdata(struct analogix_dp_device *dp)
diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h
index bcb5674801a2..cd8a5d52f973 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h
@@ -169,6 +169,7 @@ struct analogix_dp_device {
 	bool			fast_train_enable;
 	bool			psr_supported;
 	bool			last_bridge_is_panel;
+	bool			connection_notified;
 
 	u8 dpcd[DP_RECEIVER_CAP_SIZE];
 
-- 
2.34.1