linux-kernel - [PATCH 4/7] staging: typec: tcpm: Drop duplicate PD messages

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Message-Id: <1494345899-14283-4-git-send-email-linux@roeck-us.net>
Date:   Tue,  9 May 2017 09:04:56 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Yueyao Zhu <yueyao.zhu@...il.com>, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>
Subject: [PATCH 4/7] staging: typec: tcpm: Drop duplicate PD messages

Per USB PD standard, we have to drop duplicate PD messages.
We can not expect lower protocol layers to drop such messages,
since lower layers don't know if a message was dropped somewhere
else in the stack.

Originally-from: Puma Hsu <puma_hsu@....com>
Cc: Yueyao Zhu <yueyao.zhu@...il.com>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
---
 drivers/staging/typec/pd.h   | 10 ++++++++++
 drivers/staging/typec/tcpm.c | 29 +++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/drivers/staging/typec/pd.h b/drivers/staging/typec/pd.h
index 8d97bdb95f23..510ef7279900 100644
--- a/drivers/staging/typec/pd.h
+++ b/drivers/staging/typec/pd.h
@@ -92,6 +92,16 @@ static inline unsigned int pd_header_type_le(__le16 header)
 	return pd_header_type(le16_to_cpu(header));
 }
 
+static inline unsigned int pd_header_msgid(u16 header)
+{
+	return (header >> PD_HEADER_ID_SHIFT) & PD_HEADER_ID_MASK;
+}
+
+static inline unsigned int pd_header_msgid_le(__le16 header)
+{
+	return pd_header_msgid(le16_to_cpu(header));
+}
+
 #define PD_MAX_PAYLOAD		7
 
 struct pd_message {
diff --git a/drivers/staging/typec/tcpm.c b/drivers/staging/typec/tcpm.c
index abba655ba00a..c5d8b129c4f4 100644
--- a/drivers/staging/typec/tcpm.c
+++ b/drivers/staging/typec/tcpm.c
@@ -238,6 +238,7 @@ struct tcpm_port {
 	unsigned int hard_reset_count;
 	bool pd_capable;
 	bool explicit_contract;
+	unsigned int rx_msgid;
 
 	/* Partner capabilities/requests */
 	u32 sink_request;
@@ -1415,6 +1416,7 @@ static void tcpm_pd_ctrl_request(struct tcpm_port *port,
 			break;
 		case SOFT_RESET_SEND:
 			port->message_id = 0;
+			port->rx_msgid = -1;
 			if (port->pwr_role == TYPEC_SOURCE)
 				next_state = SRC_SEND_CAPABILITIES;
 			else
@@ -1503,6 +1505,22 @@ static void tcpm_pd_rx_handler(struct work_struct *work)
 		 port->attached);
 
 	if (port->attached) {
+		enum pd_ctrl_msg_type type = pd_header_type_le(msg->header);
+		unsigned int msgid = pd_header_msgid_le(msg->header);
+
+		/*
+		 * USB PD standard, 6.6.1.2:
+		 * "... if MessageID value in a received Message is the
+		 * same as the stored value, the receiver shall return a
+		 * GoodCRC Message with that MessageID value and drop
+		 * the Message (this is a retry of an already received
+		 * Message). Note: this shall not apply to the Soft_Reset
+		 * Message which always has a MessageID value of zero."
+		 */
+		if (msgid == port->rx_msgid && type != PD_CTRL_SOFT_RESET)
+			goto done;
+		port->rx_msgid = msgid;
+
 		/*
 		 * If both ends believe to be DFP/host, we have a data role
 		 * mismatch.
@@ -1520,6 +1538,7 @@ static void tcpm_pd_rx_handler(struct work_struct *work)
 		}
 	}
 
+done:
 	mutex_unlock(&port->lock);
 	kfree(event);
 }
@@ -1957,6 +1976,12 @@ static void tcpm_reset_port(struct tcpm_port *port)
 	port->attached = false;
 	port->pd_capable = false;
 
+	/*
+	 * First Rx ID should be 0; set this to a sentinel of -1 so that
+	 * we can check tcpm_pd_rx_handler() if we had seen it before.
+	 */
+	port->rx_msgid = -1;
+
 	port->tcpc->set_pd_rx(port->tcpc, false);
 	tcpm_init_vbus(port);	/* also disables charging */
 	tcpm_init_vconn(port);
@@ -2170,6 +2195,7 @@ static void run_state_machine(struct tcpm_port *port)
 		port->pwr_opmode = TYPEC_PWR_MODE_USB;
 		port->caps_count = 0;
 		port->message_id = 0;
+		port->rx_msgid = -1;
 		port->explicit_contract = false;
 		tcpm_set_state(port, SRC_SEND_CAPABILITIES, 0);
 		break;
@@ -2329,6 +2355,7 @@ static void run_state_machine(struct tcpm_port *port)
 		typec_set_pwr_opmode(port->typec_port, TYPEC_PWR_MODE_USB);
 		port->pwr_opmode = TYPEC_PWR_MODE_USB;
 		port->message_id = 0;
+		port->rx_msgid = -1;
 		port->explicit_contract = false;
 		tcpm_set_state(port, SNK_DISCOVERY, 0);
 		break;
@@ -2496,6 +2523,7 @@ static void run_state_machine(struct tcpm_port *port)
 	/* Soft_Reset states */
 	case SOFT_RESET:
 		port->message_id = 0;
+		port->rx_msgid = -1;
 		tcpm_pd_send_control(port, PD_CTRL_ACCEPT);
 		if (port->pwr_role == TYPEC_SOURCE)
 			tcpm_set_state(port, SRC_SEND_CAPABILITIES, 0);
@@ -2504,6 +2532,7 @@ static void run_state_machine(struct tcpm_port *port)
 		break;
 	case SOFT_RESET_SEND:
 		port->message_id = 0;
+		port->rx_msgid = -1;
 		if (tcpm_pd_send_control(port, PD_CTRL_SOFT_RESET))
 			tcpm_set_state_cond(port, hard_reset_state(port), 0);
 		else
-- 
2.7.4