staging: typec: tcpm: Improve role swap with non PD capable partners

If the partner is not PD capable, we can not use a power role set request
to swap roles. Use the data role set request instead.

Also, if a partner is not PD capable, it does not really make sense to send
a PD message to trigger a role swap. On top of that, we should really wait
for the attempted role change to complete. Otherwise, it may well be that
user space requests another role change immediately afterwards which will
fail because the port is not yet in ready state.

Trigger the role swap from data role change requests and introduce new
state PORT_RESET and use it to solve the problem. This new state is
mostly identical to ERROR_RECOVERY, only it does not cause a pending
role change to fail. Use this new state also when initializing the driver.
Rename ERROR_RECOVERY_WAIT_OFF to PORT_RESET_WAIT_OFF to better reflect
its new meaning.
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/typec/tcpm.c

@@ -115,7 +115,8 @@
 	S(BIST_RX),				\
 						\
 	S(ERROR_RECOVERY),			\
-	S(ERROR_RECOVERY_WAIT_OFF)
+	S(PORT_RESET),				\
+	S(PORT_RESET_WAIT_OFF)
 
 #define GENERATE_ENUM(e)	e
 #define GENERATE_STRING(s)	#s
@@ -230,6 +231,7 @@ struct tcpm_port {
 
 	struct mutex swap_lock;		/* swap command lock */
 	bool swap_pending;
+	bool non_pd_role_swap;
 	struct completion swap_complete;
 	int swap_status;
 
@@ -2123,6 +2125,7 @@ static void tcpm_swap_complete(struct tcpm_port *port, int result)
 	if (port->swap_pending) {
 		port->swap_status = result;
 		port->swap_pending = false;
+		port->non_pd_role_swap = false;
 		complete(&port->swap_complete);
 	}
 }
@@ -2137,7 +2140,8 @@ static void run_state_machine(struct tcpm_port *port)
 		break;
 	/* SRC states */
 	case SRC_UNATTACHED:
-		tcpm_swap_complete(port, -ENOTCONN);
+		if (!port->non_pd_role_swap)
+			tcpm_swap_complete(port, -ENOTCONN);
 		tcpm_src_detach(port);
 		if (tcpm_start_drp_toggling(port)) {
 			tcpm_set_state(port, DRP_TOGGLING, 0);
@@ -2292,7 +2296,8 @@ static void run_state_machine(struct tcpm_port *port)
 
 	/* SNK states */
 	case SNK_UNATTACHED:
-		tcpm_swap_complete(port, -ENOTCONN);
+		if (!port->non_pd_role_swap)
+			tcpm_swap_complete(port, -ENOTCONN);
 		tcpm_snk_detach(port);
 		if (tcpm_start_drp_toggling(port)) {
 			tcpm_set_state(port, DRP_TOGGLING, 0);
@@ -2703,13 +2708,15 @@ static void run_state_machine(struct tcpm_port *port)
 		break;
 	case ERROR_RECOVERY:
 		tcpm_swap_complete(port, -EPROTO);
+		tcpm_set_state(port, PORT_RESET, 0);
+		break;
+	case PORT_RESET:
 		tcpm_reset_port(port);
-
 		tcpm_set_cc(port, TYPEC_CC_OPEN);
-		tcpm_set_state(port, ERROR_RECOVERY_WAIT_OFF,
+		tcpm_set_state(port, PORT_RESET_WAIT_OFF,
 			       PD_T_ERROR_RECOVERY);
 		break;
-	case ERROR_RECOVERY_WAIT_OFF:
+	case PORT_RESET_WAIT_OFF:
 		tcpm_set_state(port,
 			       tcpm_default_state(port),
 			       port->vbus_present ? PD_T_PS_SOURCE_OFF : 0);
@@ -3041,7 +3048,7 @@ static void _tcpm_pd_vbus_off(struct tcpm_port *port)
 		/* Do nothing, expected */
 		break;
 
-	case ERROR_RECOVERY_WAIT_OFF:
+	case PORT_RESET_WAIT_OFF:
 		tcpm_set_state(port, tcpm_default_state(port), 0);
 		break;
 
@@ -3138,7 +3145,7 @@ static int tcpm_dr_set(const struct typec_capability *cap,
 	mutex_lock(&port->swap_lock);
 	mutex_lock(&port->lock);
 
-	if (port->typec_caps.type != TYPEC_PORT_DRP || !port->pd_capable) {
+	if (port->typec_caps.type != TYPEC_PORT_DRP) {
 		ret = -EINVAL;
 		goto port_unlock;
 	}
@@ -3159,10 +3166,26 @@ static int tcpm_dr_set(const struct typec_capability *cap,
 	 * Reject data role swap request in this case.
 	 */
 
+	if (!port->pd_capable) {
+		/*
+		 * If the partner is not PD capable, reset the port to
+		 * trigger a role change. This can only work if a preferred
+		 * role is configured, and if it matches the requested role.
+		 */
+		if (port->try_role == TYPEC_NO_PREFERRED_ROLE ||
+		    port->try_role == port->pwr_role) {
+			ret = -EINVAL;
+			goto port_unlock;
+		}
+		port->non_pd_role_swap = true;
+		tcpm_set_state(port, PORT_RESET, 0);
+	} else {
+		tcpm_set_state(port, DR_SWAP_SEND, 0);
+	}
+
 	port->swap_status = 0;
 	port->swap_pending = true;
 	reinit_completion(&port->swap_complete);
-	tcpm_set_state(port, DR_SWAP_SEND, 0);
 	mutex_unlock(&port->lock);
 
 	if (!wait_for_completion_timeout(&port->swap_complete,
@@ -3171,6 +3194,7 @@ static int tcpm_dr_set(const struct typec_capability *cap,
 	else
 		ret = port->swap_status;
 
+	port->non_pd_role_swap = false;
 	goto swap_unlock;
 
 port_unlock:
@@ -3203,22 +3227,6 @@ static int tcpm_pr_set(const struct typec_capability *cap,
 		goto port_unlock;
 	}
 
-	if (!port->pd_capable) {
-		/*
-		 * If the partner is not PD capable, reset the port to
-		 * trigger a role change. This can only work if a preferred
-		 * role is configured, and if it matches the requested role.
-		 */
-		if (port->try_role == TYPEC_NO_PREFERRED_ROLE ||
-		    port->try_role == port->pwr_role) {
-			ret = -EINVAL;
-			goto port_unlock;
-		}
-		tcpm_set_state(port, HARD_RESET_SEND, 0);
-		ret = 0;
-		goto port_unlock;
-	}
-
 	port->swap_status = 0;
 	port->swap_pending = true;
 	reinit_completion(&port->swap_complete);
@@ -3324,7 +3332,7 @@ static void tcpm_init(struct tcpm_port *port)
 	 * Some adapters need a clean slate at startup, and won't recover
 	 * otherwise. So do not try to be fancy and force a clean disconnect.
 	 */
-	tcpm_set_state(port, ERROR_RECOVERY, 0);
+	tcpm_set_state(port, PORT_RESET, 0);
 }
 
 void tcpm_tcpc_reset(struct tcpm_port *port)