usb: musb: dsps: fix otg state machine

Due to lack of ID pin interrupt event on AM335x devices, the musb dsps
driver uses polling to detect usb device attach for dual-role port.

But in the case if a micro-A cable adapter is attached without a USB device
attached to the cable, the musb state machine gets stuck in a_wait_vrise
state waiting for the MUSB_CONNECT interrupt which won't happen due to the
usb device is not attached. The state is stuck in a_wait_vrise even after
the micro-A cable is detached, which could cause VBUS retention if then the
dual-role port is attached to a host port.

To fix the problem, make a_wait_vrise as a transient state, then move the
state to either a_wait_bcon for host port or a_idle state for dual-role
port, if no usb device is attached to the port.

Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/musb/musb_dsps.c

@@ -227,8 +227,13 @@ static int dsps_check_status(struct musb *musb, void *unused)
 
 	switch (musb->xceiv->otg->state) {
 	case OTG_STATE_A_WAIT_VRISE:
-		dsps_mod_timer_optional(glue);
-		break;
+		if (musb->port_mode == MUSB_HOST) {
+			musb->xceiv->otg->state = OTG_STATE_A_WAIT_BCON;
+			dsps_mod_timer_optional(glue);
+			break;
+		}
+		/* fall through */
+
 	case OTG_STATE_A_WAIT_BCON:
 		/* keep VBUS on for host-only mode */
 		if (musb->port_mode == MUSB_HOST) {