MLK-21023 i2c: rpmsg-imx: add mutex lock when transfer i2c messages

I2c_lock_bus function in i2c-core-base will not stop the transfer to
different devices on different buses at the same time.

Since the multiple rpmsg i2c buses share one rpmsg channel, so it has to
add mutex to protect rpmsg resource accessing.

Signed-off-by: Clark Wang <xiaoning.wang@nxp.com>

drivers/i2c/busses/i2c-rpmsg-imx.c

@@ -108,6 +108,7 @@ struct i2c_rpmsg_info {
 	struct device *dev;
 	struct i2c_rpmsg_msg *msg;
 	struct completion cmd_complete;
+	struct mutex lock;
 };
 
 static struct i2c_rpmsg_info i2c_rpmsg;
@@ -271,6 +272,7 @@ static int i2c_rpmsg_probe(struct rpmsg_device *rpdev)
 
 	i2c_rpmsg.rpdev = rpdev;
 
+	mutex_init(&i2c_rpmsg.lock);
 	init_completion(&i2c_rpmsg.cmd_complete);
 
 	dev_info(&rpdev->dev, "new channel: 0x%x -> 0x%x!\n",
@@ -309,6 +311,8 @@ static int i2c_rpbus_xfer(struct i2c_adapter *adapter,
 	int i, ret;
 	bool is_last = false;
 
+	mutex_lock(&i2c_rpmsg.lock);
+
 	for (i = 0; i < num; i++) {
 		if (i == num - 1)
 			is_last = true;
@@ -318,18 +322,23 @@ static int i2c_rpbus_xfer(struct i2c_adapter *adapter,
 		if (pmsg->flags & I2C_M_RD) {
 			ret = i2c_rpmsg_read(pmsg, &i2c_rpmsg,
 						rdata->adapter.nr, is_last);
-			if (ret < 0)
+			if (ret < 0) {
+				mutex_unlock(&i2c_rpmsg.lock);
 				return ret;
+			}
 
 			pmsg->len = ret;
 		} else {
 			ret = i2c_rpmsg_write(pmsg, &i2c_rpmsg,
 						rdata->adapter.nr, is_last);
-			if (ret < 0)
+			if (ret < 0) {
+				mutex_unlock(&i2c_rpmsg.lock);
 				return ret;
+			}
 		}
 	}
 
+	mutex_unlock(&i2c_rpmsg.lock);
 	return num;
 }