usb: typec: tcpm: Send DISCOVER_IDENTITY from dedicated work

In current design, DISCOVER_IDENTITY is queued to VDM state machine
immediately in Ready states and never retries if it fails in the AMS.
Move the process to a delayed work so that when it fails for some
reasons (e.g. Sink Tx No Go), it can be retried by queueing the work
again. Also fix a problem that the vdm_state is not set to a proper
state if it is blocked by Collision Avoidance mechanism.

Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Kyle Tso <kyletso@google.com>
Link: https://lore.kernel.org/r/20210507062300.1945009-2-kyletso@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/typec/tcpm/tcpm.c

@@ -259,6 +259,7 @@ enum frs_typec_current {
 #define ALTMODE_DISCOVERY_MAX	(SVID_DISCOVERY_MAX * MODE_DISCOVERY_MAX)
 
 #define GET_SINK_CAP_RETRY_MS	100
+#define SEND_DISCOVER_RETRY_MS	100
 
 struct pd_mode_data {
 	int svid_index;		/* current SVID index		*/
@@ -366,6 +367,8 @@ struct tcpm_port {
 	struct kthread_work vdm_state_machine;
 	struct hrtimer enable_frs_timer;
 	struct kthread_work enable_frs;
+	struct hrtimer send_discover_timer;
+	struct kthread_work send_discover_work;
 	bool state_machine_running;
 	bool vdm_sm_running;
 
@@ -1178,6 +1181,16 @@ static void mod_enable_frs_delayed_work(struct tcpm_port *port, unsigned int del
 	}
 }
 
+static void mod_send_discover_delayed_work(struct tcpm_port *port, unsigned int delay_ms)
+{
+	if (delay_ms) {
+		hrtimer_start(&port->send_discover_timer, ms_to_ktime(delay_ms), HRTIMER_MODE_REL);
+	} else {
+		hrtimer_cancel(&port->send_discover_timer);
+		kthread_queue_work(port->wq, &port->send_discover_work);
+	}
+}
+
 static void tcpm_set_state(struct tcpm_port *port, enum tcpm_state state,
 			   unsigned int delay_ms)
 {
@@ -1855,6 +1868,9 @@ static void vdm_run_state_machine(struct tcpm_port *port)
 				res = tcpm_ams_start(port, DISCOVER_IDENTITY);
 				if (res == 0)
 					port->send_discover = false;
+				else if (res == -EAGAIN)
+					mod_send_discover_delayed_work(port,
+								       SEND_DISCOVER_RETRY_MS);
 				break;
 			case CMD_DISCOVER_SVID:
 				res = tcpm_ams_start(port, DISCOVER_SVIDS);
@@ -1880,6 +1896,7 @@ static void vdm_run_state_machine(struct tcpm_port *port)
 			}
 
 			if (res < 0) {
+				port->vdm_state = VDM_STATE_ERR_BUSY;
 				port->vdm_sm_running = false;
 				return;
 			}
@@ -3682,14 +3699,6 @@ static inline enum tcpm_state unattached_state(struct tcpm_port *port)
 	return SNK_UNATTACHED;
 }
 
-static void tcpm_check_send_discover(struct tcpm_port *port)
-{
-	if ((port->data_role == TYPEC_HOST || port->negotiated_rev > PD_REV20) &&
-	    port->send_discover && port->pd_capable)
-		tcpm_send_vdm(port, USB_SID_PD, CMD_DISCOVER_IDENT, NULL, 0);
-	port->send_discover = false;
-}
-
 static void tcpm_swap_complete(struct tcpm_port *port, int result)
 {
 	if (port->swap_pending) {
@@ -3926,7 +3935,18 @@ static void run_state_machine(struct tcpm_port *port)
 			break;
 		}
 
-		tcpm_check_send_discover(port);
+		/*
+		 * 6.4.4.3.1 Discover Identity
+		 * "The Discover Identity Command Shall only be sent to SOP when there is an
+		 * Explicit Contract."
+		 * For now, this driver only supports SOP for DISCOVER_IDENTITY, thus using
+		 * port->explicit_contract to decide whether to send the command.
+		 */
+		if (port->explicit_contract)
+			mod_send_discover_delayed_work(port, 0);
+		else
+			port->send_discover = false;
+
 		/*
 		 * 6.3.5
 		 * Sending ping messages is not necessary if
@@ -4194,7 +4214,18 @@ static void run_state_machine(struct tcpm_port *port)
 			break;
 		}
 
-		tcpm_check_send_discover(port);
+		/*
+		 * 6.4.4.3.1 Discover Identity
+		 * "The Discover Identity Command Shall only be sent to SOP when there is an
+		 * Explicit Contract."
+		 * For now, this driver only supports SOP for DISCOVER_IDENTITY, thus using
+		 * port->explicit_contract.
+		 */
+		if (port->explicit_contract)
+			mod_send_discover_delayed_work(port, 0);
+		else
+			port->send_discover = false;
+
 		power_supply_changed(port->psy);
 		break;
 
@@ -5288,6 +5319,29 @@ unlock:
 	mutex_unlock(&port->lock);
 }
 
+static void tcpm_send_discover_work(struct kthread_work *work)
+{
+	struct tcpm_port *port = container_of(work, struct tcpm_port, send_discover_work);
+
+	mutex_lock(&port->lock);
+	/* No need to send DISCOVER_IDENTITY anymore */
+	if (!port->send_discover)
+		goto unlock;
+
+	/* Retry if the port is not idle */
+	if ((port->state != SRC_READY && port->state != SNK_READY) || port->vdm_sm_running) {
+		mod_send_discover_delayed_work(port, SEND_DISCOVER_RETRY_MS);
+		goto unlock;
+	}
+
+	/* Only send the Message if the port is host for PD rev2.0 */
+	if (port->data_role == TYPEC_HOST || port->negotiated_rev > PD_REV20)
+		tcpm_send_vdm(port, USB_SID_PD, CMD_DISCOVER_IDENT, NULL, 0);
+
+unlock:
+	mutex_unlock(&port->lock);
+}
+
 static int tcpm_dr_set(struct typec_port *p, enum typec_data_role data)
 {
 	struct tcpm_port *port = typec_get_drvdata(p);
@@ -6093,6 +6147,14 @@ static enum hrtimer_restart enable_frs_timer_handler(struct hrtimer *timer)
 	return HRTIMER_NORESTART;
 }
 
+static enum hrtimer_restart send_discover_timer_handler(struct hrtimer *timer)
+{
+	struct tcpm_port *port = container_of(timer, struct tcpm_port, send_discover_timer);
+
+	kthread_queue_work(port->wq, &port->send_discover_work);
+	return HRTIMER_NORESTART;
+}
+
 struct tcpm_port *tcpm_register_port(struct device *dev, struct tcpc_dev *tcpc)
 {
 	struct tcpm_port *port;
@@ -6123,12 +6185,15 @@ struct tcpm_port *tcpm_register_port(struct device *dev, struct tcpc_dev *tcpc)
 	kthread_init_work(&port->vdm_state_machine, vdm_state_machine_work);
 	kthread_init_work(&port->event_work, tcpm_pd_event_handler);
 	kthread_init_work(&port->enable_frs, tcpm_enable_frs_work);
+	kthread_init_work(&port->send_discover_work, tcpm_send_discover_work);
 	hrtimer_init(&port->state_machine_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	port->state_machine_timer.function = state_machine_timer_handler;
 	hrtimer_init(&port->vdm_state_machine_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	port->vdm_state_machine_timer.function = vdm_state_machine_timer_handler;
 	hrtimer_init(&port->enable_frs_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	port->enable_frs_timer.function = enable_frs_timer_handler;
+	hrtimer_init(&port->send_discover_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	port->send_discover_timer.function = send_discover_timer_handler;
 
 	spin_lock_init(&port->pd_event_lock);