TCPMv2: Notify transmit engines of incoming messages more often

By spec, we should be running PRL_TX discard on every incoming message,
and also running TCH_Message_Received when incoming messages come during
TCH runs. However, there are some tricky points following spec closely
here since our systems use TCPCs, which can cause message receipt and
transmission confirmation to often appear simultaneous.

This change discards as often as we can without disrupting incoming
transmissions.

BRANCH=None
BUG=b:155229288,b:158248741,b:158613480
TEST=on waddledoo, confirm:
- moshi no longer gets stuck replying to DR swap
- PRL_Tx discards when incoming message comes from Starteck dock

No regressions running PD 3.0 or PD 2.0 with:
- PD 2.0 charger (tested Apple 87W)
- PD 2.0 dual role partners (tested Apple 3-in-1, Acer dock)
- PD 3.0 charger (tested 45W Chicony)
- PD 3.0 dual role partners (tested Starteck TBT dock, Moshi, HooToo)

Signed-off-by: Diana Z <dzigterman@chromium.org>
Change-Id: Iec56635755b0d5dbaf9de80b29c3d81c34689e68
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2241178
Reviewed-by: Jett Rink <jettrink@chromium.org>

1 files changed, 66 insertions, 12 deletions

diff --git a/common/usbc/usb_prl_sm.c b/common/usbc/usb_prl_sm.c
index 8585fa93a1..f9102ca80c 100644
--- a/common/usbc/usb_prl_sm.c
+++ b/common/usbc/usb_prl_sm.c
@@ -741,9 +741,8 @@ static void prl_tx_phy_layer_reset_entry(const int port)
 	 || IS_ENABLED(CONFIG_USB_VPD)) {
 		vpd_rx_enable(pd_is_connected(port));
 	} else {
-		/* Purge any outstanding TX message */
-		PRL_TX_CLR_FLAG(port, PRL_FLAGS_MSG_XMIT);
-		/* TODO(b/157228506): notify pe if needed */
+		/* Note: can't clear PHY messages due to TCPC architecture */
+		/* Enable communications*/
 		tcpm_set_rx_enable(port, pd_is_connected(port));
 	}
 	set_state_prl_tx(port, PRL_TX_WAIT_FOR_MESSAGE_REQUEST);
@@ -844,8 +843,17 @@ static void prl_tx_discard_message_entry(const int port)
 {
 	print_current_prl_tx_state(port);
 
-	/* Increment msgidCounter */
-	increment_msgid_counter(port);
+	/*
+	 * Discard queued message
+	 * Note: We differ from spec here, which allows us to not discard on
+	 * incoming SOP' or SOP''.  However this would get the TCH out of sync.
+	 */
+	if (PRL_TX_CHK_FLAG(port, PRL_FLAGS_MSG_XMIT)) {
+		increment_msgid_counter(port);
+		PRL_TX_CLR_FLAG(port, PRL_FLAGS_MSG_XMIT);
+		/* TODO(b/157228506): notify pe if needed */
+	}
+
 	set_state_prl_tx(port, PRL_TX_PHY_LAYER_RESET);
 }
 
@@ -1680,6 +1688,7 @@ static void tch_wait_for_transmission_complete_run(const int port)
 	if (PDMSG_CHK_FLAG(port, PRL_FLAGS_TX_COMPLETE)) {
 		PDMSG_CLR_FLAG(port, PRL_FLAGS_TX_COMPLETE);
 		set_state_tch(port, TCH_MESSAGE_SENT);
+		return;
 	}
 	/*
 	 * Inform Policy Engine of Tx Error
@@ -1688,6 +1697,19 @@ static void tch_wait_for_transmission_complete_run(const int port)
 		PDMSG_CLR_FLAG(port, PRL_FLAGS_TX_ERROR);
 		tch[port].error = ERR_TCH_XMIT;
 		set_state_tch(port, TCH_REPORT_ERROR);
+		return;
+	}
+	/*
+	 * Any message received and not in state TCH_Wait_Chunk_Request
+	 * MUST be checked after transmission status due to our TCPC
+	 * architecture, and should not be checked if prl_tx is still waiting on
+	 * the TCPC.
+	 */
+	if (TCH_CHK_FLAG(port, PRL_FLAGS_MSG_RECEIVED) &&
+	     prl_tx_get_state(port) !=  PRL_TX_WAIT_FOR_PHY_RESPONSE) {
+		TCH_CLR_FLAG(port, PRL_FLAGS_MSG_RECEIVED);
+		set_state_tch(port, TCH_MESSAGE_RECEIVED);
+		return;
 	}
 }
 
@@ -1860,6 +1882,7 @@ static void tch_message_received_entry(const int port)
 	RCH_SET_FLAG(port, PRL_FLAGS_MSG_RECEIVED);
 
 	/* Clear extended message objects */
+	/* TODO: Notify PE of message discard */
 	TCH_CLR_FLAG(port, PRL_FLAGS_MSG_XMIT);
 	pdmsg[port].data_objs = 0;
 }
@@ -1878,6 +1901,19 @@ static void tch_message_sent_entry(const int port)
 
 	/* Tell PE message was sent */
 	pe_message_sent(port);
+
+	/*
+	 * Any message received and not in state TCH_Wait_Chunk_Request
+	 * MUST be checked after notifying PE
+	 */
+	if (TCH_CHK_FLAG(port, PRL_FLAGS_MSG_RECEIVED)) {
+		TCH_CLR_FLAG(port, PRL_FLAGS_MSG_RECEIVED);
+		set_state_tch(port, TCH_MESSAGE_RECEIVED);
+		return;
+	}
+
+
+
 	set_state_tch(port, TCH_WAIT_FOR_MESSAGE_REQUEST_FROM_PE);
 }
 
@@ -1890,6 +1926,18 @@ static void tch_report_error_entry(const int port)
 
 	/* Report Error To Policy Engine */
 	pe_report_error(port, tch[port].error, prl_tx[port].last_xmit_type);
+
+	/*
+	 * Any message received and not in state TCH_Wait_Chunk_Request
+	 * MUST be checked after notifying PE
+	 */
+	if (TCH_CHK_FLAG(port, PRL_FLAGS_MSG_RECEIVED)) {
+		TCH_CLR_FLAG(port, PRL_FLAGS_MSG_RECEIVED);
+		set_state_tch(port, TCH_MESSAGE_RECEIVED);
+		return;
+	}
+
+
 	set_state_tch(port, TCH_WAIT_FOR_MESSAGE_REQUEST_FROM_PE);
 }
 #endif /* CONFIG_USB_PD_REV30 */
@@ -1979,11 +2027,19 @@ static void prl_rx_wait_for_phy_message(const int port, int evt)
 
 	/*
 	 * Discard any pending tx message if this is
-	 * not a ping message
+	 * not a ping message (length must be checked to verify this is a
+	 * control message, rather than data)
 	 */
 	if ((cnt > 0) || (type != PD_CTRL_PING)) {
-		if (prl_tx_get_state(port) == PRL_TX_SRC_PENDING ||
-			prl_tx_get_state(port) == PRL_TX_SNK_PENDING)
+		/*
+		 * Note: Spec dictates that we always go into
+		 * PRL_Tx_Discard_Message upon receivng a message.  However, due
+		 * to our TCPC architecture we may be receiving a transmit
+		 * complete at the same time as a response so only do this if a
+		 * message is pending.
+		 */
+		if (prl_tx_get_state(port) != PRL_TX_WAIT_FOR_PHY_RESPONSE ||
+		    PRL_TX_CHK_FLAG(port, PRL_FLAGS_MSG_XMIT))
 			set_state_prl_tx(port, PRL_TX_DISCARD_MESSAGE);
 	}
 
@@ -2009,10 +2065,8 @@ static void prl_rx_wait_for_phy_message(const int port, int evt)
 		 * queued for sending but a message is received before
 		 * tch_wait_for_message_request_from_pe has been run
 		 */
-		else if ((tch_get_state(port) !=
-				TCH_WAIT_FOR_MESSAGE_REQUEST_FROM_PE &&
-			  tch_get_state(port) !=
-				TCH_WAIT_FOR_TRANSMISSION_COMPLETE) ||
+		else if (tch_get_state(port) !=
+				TCH_WAIT_FOR_MESSAGE_REQUEST_FROM_PE ||
 			 TCH_CHK_FLAG(port, PRL_FLAGS_MSG_XMIT)) {
 			/* NOTE: RTR_TX_CHUNKS State embedded here. */
 			/*