usb: typec: tcpm: Wait for vbus discharge to VSAFE0V before toggling

index be0b6469dd3d..0ed71725980f 100644
@@ -62,6 +62,8 @@
 	S(SNK_TRANSITION_SINK_VBUS),		\
 	S(SNK_READY),				\
 						\
+	S(VBUS_DISCHARGE),			\
+						\
 	S(ACC_UNATTACHED),			\
 	S(DEBUG_ACC_ATTACHED),			\
 	S(AUDIO_ACC_ATTACHED),			\

@@ -438,6 +440,9 @@ struct tcpm_port {
 	enum tcpm_ams next_ams;
 	bool in_ams;
 
+	/* Auto vbus discharge state */
+	bool auto_vbus_discharge_enabled;
+
 #ifdef CONFIG_DEBUG_FS
 	struct dentry *dentry;
 	struct mutex logbuffer_lock;	/* log buffer access lock */

@@ -3413,6 +3418,8 @@ static int tcpm_src_attach(struct tcpm_port *port)
 	if (port->tcpc->enable_auto_vbus_discharge) {
 		ret = port->tcpc->enable_auto_vbus_discharge(port->tcpc, true);
 		tcpm_log_force(port, "enable vbus discharge ret:%d", ret);
+		if (!ret)
+			port->auto_vbus_discharge_enabled = true;
 	}
 
 	ret = tcpm_set_roles(port, true, TYPEC_SOURCE, tcpm_data_role_for_source(port));

@@ -3495,6 +3502,8 @@ static void tcpm_reset_port(struct tcpm_port *port)
 	if (port->tcpc->enable_auto_vbus_discharge) {
 		ret = port->tcpc->enable_auto_vbus_discharge(port->tcpc, false);
 		tcpm_log_force(port, "Disable vbus discharge ret:%d", ret);
+		if (!ret)
+			port->auto_vbus_discharge_enabled = false;
 	}
 	port->in_ams = false;
 	port->ams = NONE_AMS;

@@ -3568,6 +3577,8 @@ static int tcpm_snk_attach(struct tcpm_port *port)
 		tcpm_set_auto_vbus_discharge_threshold(port, TYPEC_PWR_MODE_USB, false, VSAFE5V);
 		ret = port->tcpc->enable_auto_vbus_discharge(port->tcpc, true);
 		tcpm_log_force(port, "enable vbus discharge ret:%d", ret);
+		if (!ret)
+			port->auto_vbus_discharge_enabled = true;
 	}
 
 	ret = tcpm_set_roles(port, true, TYPEC_SINK, tcpm_data_role_for_sink(port));

@@ -3684,6 +3695,12 @@ static void run_state_machine(struct tcpm_port *port)
 	switch (port->state) {
 	case TOGGLING:
 		break;
+	case VBUS_DISCHARGE:
+		if (port->port_type == TYPEC_PORT_SRC)
+			tcpm_set_state(port, SRC_UNATTACHED, PD_T_SAFE_0V);
+		else
+			tcpm_set_state(port, SNK_UNATTACHED, PD_T_SAFE_0V);
+		break;
 	/* SRC states */
 	case SRC_UNATTACHED:
 		if (!port->non_pd_role_swap)

@@ -4669,7 +4686,9 @@ static void _tcpm_cc_change(struct tcpm_port *port, enum typec_cc_status cc1,
 	case SRC_READY:
 		if (tcpm_port_is_disconnected(port) ||
 		    !tcpm_port_is_source(port)) {
-			if (port->port_type == TYPEC_PORT_SRC)
+			if (port->auto_vbus_discharge_enabled && !port->vbus_vsafe0v)
+				tcpm_set_state(port, VBUS_DISCHARGE, 0);
+			else if (port->port_type == TYPEC_PORT_SRC)
 				tcpm_set_state(port, SRC_UNATTACHED, 0);
 			else
 				tcpm_set_state(port, SNK_UNATTACHED, 0);

@@ -4703,7 +4722,18 @@ static void _tcpm_cc_change(struct tcpm_port *port, enum typec_cc_status cc1,
 			tcpm_set_state(port, SNK_DEBOUNCED, 0);
 		break;
 	case SNK_READY:
-		if (tcpm_port_is_disconnected(port))
+		/*
+		 * When set_auto_vbus_discharge_threshold is enabled, CC pins go
+		 * away before vbus decays to disconnect threshold. Allow
+		 * disconnect to be driven by vbus disconnect when auto vbus
+		 * discharge is enabled.
+		 *
+		 * EXIT condition is based primarily on vbus disconnect and CC is secondary.
+		 * "A port that has entered into USB PD communications with the Source and
+		 * has seen the CC voltage exceed vRd-USB may monitor the CC pin to detect
+		 * cable disconnect in addition to monitoring VBUS.
+		 */
+		if (!port->auto_vbus_discharge_enabled && tcpm_port_is_disconnected(port))
 			tcpm_set_state(port, unattached_state(port), 0);
 		else if (!port->pd_capable &&
 			 (cc1 != old_cc1 || cc2 != old_cc2))

@@ -4803,9 +4833,16 @@ static void _tcpm_cc_change(struct tcpm_port *port, enum typec_cc_status cc1,
 		 */
 		break;
 
+	case VBUS_DISCHARGE:
+		/* Do nothing. Waiting for vsafe0v signal */
+		break;
 	default:
-		if (tcpm_port_is_disconnected(port))
-			tcpm_set_state(port, unattached_state(port), 0);
+		if (tcpm_port_is_disconnected(port)) {
+			if (port->auto_vbus_discharge_enabled && !port->vbus_vsafe0v)
+				tcpm_set_state(port, VBUS_DISCHARGE, 0);
+			else
+				tcpm_set_state(port, unattached_state(port), 0);
+		}
 		break;
 	}
 }

@@ -4988,9 +5025,12 @@ static void _tcpm_pd_vbus_off(struct tcpm_port *port)
 		break;
 
 	default:
-		if (port->pwr_role == TYPEC_SINK &&
-		    port->attached)
-			tcpm_set_state(port, SNK_UNATTACHED, 0);
+		if (port->pwr_role == TYPEC_SINK && port->attached) {
+			if (port->auto_vbus_discharge_enabled && !port->vbus_vsafe0v)
+				tcpm_set_state(port, VBUS_DISCHARGE, 0);
+			else
+				tcpm_set_state(port, SNK_UNATTACHED, 0);
+		}
 		break;
 	}
 }

@@ -5012,6 +5052,12 @@ static void _tcpm_pd_vbus_vsafe0v(struct tcpm_port *port)
 			tcpm_set_state(port, tcpm_try_snk(port) ? SNK_TRY : SRC_ATTACHED,
 				       PD_T_CC_DEBOUNCE);
 		break;
+	case VBUS_DISCHARGE:
+		if (port->port_type == TYPEC_PORT_SRC)
+			tcpm_set_state(port, SRC_UNATTACHED, 0);
+		else
+			tcpm_set_state(port, SNK_UNATTACHED, 0);
+		break;
 	default:
 		break;
 	}