tcpc: Resume suspended ports after an interval

When it appears that the TCPC queue handling logic may be stuck in an
infinite loop, the EC will break the loop by disabling the port in order
to avoid task starvation.  However, nothing attempts to resume the port,
and it therefore remains disabled until the next EC reset.  Wake back up
after a reasonable interval in order to automatically retry.  On port
suspend, completely drain the TCPM message queue.

BUG=chromium:891713
TEST=On Careena hardware, with analogix TCPC firmware v1.5 and an
electronically marked cable that sends SOP' messages, verify that the EC
auto-retries every second.  After removing the offending cable, and PD
power supply will work.
BRANCH=grunt

Change-Id: I563b763501333eb36ee1f76e6f484ebb3245c82a
Signed-off-by: Jonathan Brandmeyer <jbrandmeyer@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1258571
Reviewed-by: Jett Rink <jettrink@chromium.org>

1 files changed, 11 insertions, 1 deletions

diff --git a/common/usb_pd_tcpc.c b/common/usb_pd_tcpc.c
index 152775bbc0..11bc399b5e 100644
--- a/common/usb_pd_tcpc.c
+++ b/common/usb_pd_tcpc.c
@@ -261,7 +261,12 @@ static struct pd_port_controller {
 
 static int rx_buf_is_full(int port)
 {
-	/* Buffer is full if the tail is 1 ahead of head */
+	/*
+	 * TODO: Refactor these to use the incrementing-counter idiom instead of
+	 * the wrapping-counter idiom to reclaim the last buffer entry.
+	 *
+	 * Buffer is full if the tail is 1 ahead of head.
+	 */
 	int diff = pd[port].rx_buf_tail - pd[port].rx_buf_head;
 	return (diff == 1) || (diff == -RX_BUFFER_SIZE);
 }
@@ -272,6 +277,11 @@ int rx_buf_is_empty(int port)
 	return pd[port].rx_buf_tail == pd[port].rx_buf_head;
 }
 
+void rx_buf_clear(int port)
+{
+	pd[port].rx_buf_tail = pd[port].rx_buf_head;
+}
+
 static void rx_buf_increment(int port, int *buf_ptr)
 {
 	*buf_ptr = *buf_ptr == RX_BUFFER_SIZE ? 0 : *buf_ptr + 1;