usb: typec: ucsi: Rework ppm_lock handling

The ppm_lock really only needs to be hold during 2 functions:
ucsi_reset_ppm() and ucsi_run_command().

Push the taking of the lock down into these 2 functions, renaming
ucsi_run_command() to ucsi_send_command() which was an existing
wrapper already taking the lock for its callers.

This simplifies things for the callers and removes the difference
between ucsi_send_command() and ucsi_run_command() which has led
to various locking bugs in the past.

Cc: stable@vger.kernel.org
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20200809141904.4317-4-hdegoede@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/typec/ucsi/ucsi.c

@@ -146,42 +146,33 @@ static int ucsi_exec_command(struct ucsi *ucsi, u64 cmd)
 	return UCSI_CCI_LENGTH(cci);
 }
 
-static int ucsi_run_command(struct ucsi *ucsi, u64 command,
-			    void *data, size_t size)
+int ucsi_send_command(struct ucsi *ucsi, u64 command,
+		      void *data, size_t size)
 {
 	u8 length;
 	int ret;
 
-	WARN_ON(!mutex_is_locked(&ucsi->ppm_lock));
+	mutex_lock(&ucsi->ppm_lock);
 
 	ret = ucsi_exec_command(ucsi, command);
 	if (ret < 0)
-		return ret;
+		goto out;
 
 	length = ret;
 
 	if (data) {
 		ret = ucsi->ops->read(ucsi, UCSI_MESSAGE_IN, data, size);
 		if (ret)
-			return ret;
+			goto out;
 	}
 
 	ret = ucsi_acknowledge_command(ucsi);
 	if (ret)
-		return ret;
+		goto out;
 
-	return length;
-}
-
-int ucsi_send_command(struct ucsi *ucsi, u64 command,
-		      void *retval, size_t size)
-{
-	int ret;
-
-	mutex_lock(&ucsi->ppm_lock);
-	ret = ucsi_run_command(ucsi, command, retval, size);
+	ret = length;
+out:
 	mutex_unlock(&ucsi->ppm_lock);
-
 	return ret;
 }
 EXPORT_SYMBOL_GPL(ucsi_send_command);
@@ -738,20 +729,24 @@ static int ucsi_reset_ppm(struct ucsi *ucsi)
 	u32 cci;
 	int ret;
 
+	mutex_lock(&ucsi->ppm_lock);
+
 	ret = ucsi->ops->async_write(ucsi, UCSI_CONTROL, &command,
 				     sizeof(command));
 	if (ret < 0)
-		return ret;
+		goto out;
 
 	tmo = jiffies + msecs_to_jiffies(UCSI_TIMEOUT_MS);
 
 	do {
-		if (time_is_before_jiffies(tmo))
-			return -ETIMEDOUT;
+		if (time_is_before_jiffies(tmo)) {
+			ret = -ETIMEDOUT;
+			goto out;
+		}
 
 		ret = ucsi->ops->read(ucsi, UCSI_CCI, &cci, sizeof(cci));
 		if (ret)
-			return ret;
+			goto out;
 
 		/* If the PPM is still doing something else, reset it again. */
 		if (cci & ~UCSI_CCI_RESET_COMPLETE) {
@@ -759,13 +754,15 @@ static int ucsi_reset_ppm(struct ucsi *ucsi)
 						     &command,
 						     sizeof(command));
 			if (ret < 0)
-				return ret;
+				goto out;
 		}
 
 		msleep(20);
 	} while (!(cci & UCSI_CCI_RESET_COMPLETE));
 
-	return 0;
+out:
+	mutex_unlock(&ucsi->ppm_lock);
+	return ret;
 }
 
 static int ucsi_role_cmd(struct ucsi_connector *con, u64 command)
@@ -777,9 +774,7 @@ static int ucsi_role_cmd(struct ucsi_connector *con, u64 command)
 		u64 c;
 
 		/* PPM most likely stopped responding. Resetting everything. */
-		mutex_lock(&con->ucsi->ppm_lock);
 		ucsi_reset_ppm(con->ucsi);
-		mutex_unlock(&con->ucsi->ppm_lock);
 
 		c = UCSI_SET_NOTIFICATION_ENABLE | con->ucsi->ntfy;
 		ucsi_send_command(con->ucsi, c, NULL, 0);
@@ -1010,8 +1005,6 @@ static int ucsi_init(struct ucsi *ucsi)
 	int ret;
 	int i;
 
-	mutex_lock(&ucsi->ppm_lock);
-
 	/* Reset the PPM */
 	ret = ucsi_reset_ppm(ucsi);
 	if (ret) {
@@ -1022,13 +1015,13 @@ static int ucsi_init(struct ucsi *ucsi)
 	/* Enable basic notifications */
 	ucsi->ntfy = UCSI_ENABLE_NTFY_CMD_COMPLETE | UCSI_ENABLE_NTFY_ERROR;
 	command = UCSI_SET_NOTIFICATION_ENABLE | ucsi->ntfy;
-	ret = ucsi_run_command(ucsi, command, NULL, 0);
+	ret = ucsi_send_command(ucsi, command, NULL, 0);
 	if (ret < 0)
 		goto err_reset;
 
 	/* Get PPM capabilities */
 	command = UCSI_GET_CAPABILITY;
-	ret = ucsi_run_command(ucsi, command, &ucsi->cap, sizeof(ucsi->cap));
+	ret = ucsi_send_command(ucsi, command, &ucsi->cap, sizeof(ucsi->cap));
 	if (ret < 0)
 		goto err_reset;
 
@@ -1045,8 +1038,6 @@ static int ucsi_init(struct ucsi *ucsi)
 		goto err_reset;
 	}
 
-	mutex_unlock(&ucsi->ppm_lock);
-
 	/* Register all connectors */
 	for (i = 0; i < ucsi->cap.num_connectors; i++) {
 		ret = ucsi_register_port(ucsi, i);
@@ -1072,12 +1063,9 @@ err_unregister:
 		con->port = NULL;
 	}
 
-	mutex_lock(&ucsi->ppm_lock);
 err_reset:
 	ucsi_reset_ppm(ucsi);
 err:
-	mutex_unlock(&ucsi->ppm_lock);
-
 	return ret;
 }