[PATCH 4/4] usb: typec: tcpm: fix source caps may lost after soft reset

[Frank Wang]

Invoke set_pd_rx() may flush the RX FIFO of PD controller, so do
set_pd_rx() before sending Soft Reset in case Source caps may be flushed
at debounce time between SOFT_RESET_SEND and SNK_WAIT_CAPABILITIES state.

Without this patch, in PD charger stress test, the FUSB302 driver may
occur the following exceptions in power negotiation stage.

[ ...]
[ 4.512252] fusb302_irq_intn
[ 4.512260] AMS SOFT_RESET_AMS finished
[ 4.512269] state change SOFT_RESET_SEND ->SNK_WAIT_CAPABILITIES [rev3 NONE_AMS]
[ 4.514511] pd := on
[ 4.514516] pending state change SNK_WAIT_CAPABILITIES ->HARD_RESET_SEND @ 310 ms [rev3 NONE_AMS]
[ 4.515428] IRQ: 0x51, a: 0x00, b: 0x01, status0: 0x93
[ 4.515431] IRQ: BC_LVL, handler pending
[ 4.515435] IRQ: PD sent good CRC
[ 4.516434] PD message header: 0
[ 4.516437] PD message len: 0
[ 4.516444] PD RX, header: 0x0 [1]

Signed-off-by: Frank Wang <frank.wang@xxxxxxxxxxxxxx>
---
 drivers/usb/typec/tcpm/tcpm.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
index 9e583060e64fc..ba6bf71838eed 100644
--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c
@@ -4321,10 +4321,12 @@ static void run_state_machine(struct tcpm_port *port)
 		tcpm_set_state(port, unattached_state(port), 0);
 		break;
 	case SNK_WAIT_CAPABILITIES:
-		ret = port->tcpc->set_pd_rx(port->tcpc, true);
-		if (ret < 0) {
-			tcpm_set_state(port, SNK_READY, 0);
-			break;
+		if (port->prev_state != SOFT_RESET_SEND) {
+			ret = port->tcpc->set_pd_rx(port->tcpc, true);
+			if (ret < 0) {
+				tcpm_set_state(port, SNK_READY, 0);
+				break;
+			}
 		}
 		/*
 		 * If VBUS has never been low, and we time out waiting
@@ -4603,6 +4605,7 @@ static void run_state_machine(struct tcpm_port *port)
 	case SOFT_RESET_SEND:
 		port->message_id = 0;
 		port->rx_msgid = -1;
+		port->tcpc->set_pd_rx(port->tcpc, true);
 		if (tcpm_pd_send_control(port, PD_CTRL_SOFT_RESET))
 			tcpm_set_state_cond(port, hard_reset_state(port), 0);
 		else
-- 
2.17.1