staging: typec: tcpm: Comply with TryWait.SNK State

According to the spec:
"4.5.2.2.10.2 Exiting from TryWait.SNK State
The port shall transition to Attached.SNK after tCCDebounce if or when VBUS
is detected. Note the Source may initiate USB PD communications which will
cause brief periods of the SNK.Open state on both the CC1 and CC2 pins,
but this event will not exceed tPDDebounce. The port shall transition to
Unattached.SNK when the state of both of the CC1 and CC2 pins is SNK.Open
for at least tPDDebounce."
Signed-off-by: Badhri Jagan Sridharan <Badhri@google.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/typec/tcpm.c

@@ -2408,26 +2408,24 @@ static void run_state_machine(struct tcpm_port *port)
 		break;
 	case SNK_TRYWAIT:
 		tcpm_set_cc(port, TYPEC_CC_RD);
-		tcpm_set_state(port, SNK_TRYWAIT_DEBOUNCE, PD_T_CC_DEBOUNCE);
+		tcpm_set_state(port, SNK_TRYWAIT_VBUS, PD_T_CC_DEBOUNCE);
 		break;
-	case SNK_TRYWAIT_DEBOUNCE:
-		if (port->vbus_present) {
+	case SNK_TRYWAIT_VBUS:
+		/*
+		 * TCPM stays in this state indefinitely until VBUS
+		 * is detected as long as Rp is not detected for
+		 * more than a time period of tPDDebounce.
+		 */
+		if (port->vbus_present && tcpm_port_is_sink(port)) {
 			tcpm_set_state(port, SNK_ATTACHED, 0);
 			break;
 		}
-		if (tcpm_port_is_disconnected(port)) {
-			tcpm_set_state(port, SNK_UNATTACHED,
-				       PD_T_PD_DEBOUNCE);
-			break;
-		}
-		if (tcpm_port_is_source(port))
-			tcpm_set_state(port, SRC_ATTACHED, 0);
-		/* XXX Are we supposed to stay in this state ? */
+		if (!tcpm_port_is_sink(port))
+			tcpm_set_state(port, SNK_TRYWAIT_DEBOUNCE, 0);
 		break;
-	case SNK_TRYWAIT_VBUS:
-		tcpm_set_state(port, SNK_ATTACHED, PD_T_CC_DEBOUNCE);
+	case SNK_TRYWAIT_DEBOUNCE:
+		tcpm_set_state(port, SNK_UNATTACHED, PD_T_PD_DEBOUNCE);
 		break;
-
 	case SNK_ATTACHED:
 		ret = tcpm_snk_attach(port);
 		if (ret < 0)
@@ -2965,19 +2963,16 @@ static void _tcpm_cc_change(struct tcpm_port *port, enum typec_cc_status cc1,
 		tcpm_set_state(port, SRC_TRY_WAIT, 0);
 		break;
 	case SNK_TRYWAIT_DEBOUNCE:
-		if (port->vbus_present) {
-			tcpm_set_state(port, SNK_ATTACHED, 0);
-			break;
-		}
-		if (tcpm_port_is_source(port)) {
-			tcpm_set_state(port, SRC_ATTACHED, 0);
-			break;
-		}
-		if (tcpm_port_is_disconnected(port) &&
-		    port->delayed_state != SNK_UNATTACHED)
+		if (tcpm_port_is_sink(port))
+			tcpm_set_state(port, SNK_TRYWAIT_VBUS, 0);
+		break;
+	case SNK_TRYWAIT_VBUS:
+		if (!tcpm_port_is_sink(port))
 			tcpm_set_state(port, SNK_TRYWAIT_DEBOUNCE, 0);
 		break;
-
+	case SNK_TRYWAIT:
+		/* Do nothing, waiting for tCCDebounce */
+		break;
 	case PR_SWAP_SNK_SRC_SINK_OFF:
 	case PR_SWAP_SRC_SNK_TRANSITION_OFF:
 	case PR_SWAP_SRC_SNK_SOURCE_OFF:
@@ -3035,7 +3030,14 @@ static void _tcpm_pd_vbus_on(struct tcpm_port *port)
 		/* Do nothing, waiting for PD_DEBOUNCE to do be done */
 		break;
 	case SNK_TRYWAIT:
-		tcpm_set_state(port, SNK_TRYWAIT_VBUS, 0);
+		/* Do nothing, waiting for tCCDebounce */
+		break;
+	case SNK_TRYWAIT_VBUS:
+		if (tcpm_port_is_sink(port))
+			tcpm_set_state(port, SNK_ATTACHED, 0);
+		break;
+	case SNK_TRYWAIT_DEBOUNCE:
+		/* Do nothing, waiting for Rp */
 		break;
 	case SRC_TRY_WAIT:
 	case SRC_TRY_DEBOUNCE:
@@ -3072,10 +3074,10 @@ static void _tcpm_pd_vbus_off(struct tcpm_port *port)
 	case SNK_TRY_WAIT_DEBOUNCE:
 		/* Do nothing, waiting for PD_DEBOUNCE to do be done */
 		break;
+	case SNK_TRYWAIT:
 	case SNK_TRYWAIT_VBUS:
-		tcpm_set_state(port, SNK_TRYWAIT, 0);
+	case SNK_TRYWAIT_DEBOUNCE:
 		break;
-
 	case SNK_ATTACH_WAIT:
 		tcpm_set_state(port, SNK_UNATTACHED, 0);
 		break;