[PATCH linux dev-4.10 v2 4/6] drivers: i2c: Add I2C master locking to FSI algorithm

[Eddie James <eajames@linux.vnet.ibm.com>]

From: "Edward A. James" <eajames@us.ibm.com>

Since there are many ports per master, each with it's own adapter and
chardev, we need some locking to prevent xfers from changing the master
state while other xfers are in progress.

Signed-off-by: Edward A. James <eajames@us.ibm.com>
---
 drivers/i2c/busses/i2c-fsi.c | 41 +++++++++++++++++++++++++++++++++++++----
 1 file changed, 37 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/busses/i2c-fsi.c b/drivers/i2c/busses/i2c-fsi.c
index f690b16..d757aee 100644
--- a/drivers/i2c/busses/i2c-fsi.c
+++ b/drivers/i2c/busses/i2c-fsi.c
@@ -136,6 +136,8 @@ struct fsi_i2c_master {
 	u8			fifo_size;
 	struct list_head	ports;
 	struct ida		ida;
+	wait_queue_head_t	wait;
+	struct semaphore	lock;
 };
 
 struct fsi_i2c_port {
@@ -171,6 +173,29 @@ static int fsi_i2c_write_reg(struct fsi_device *fsi, unsigned int reg,
 	return fsi_device_write(fsi, reg, &raw_data, sizeof(raw_data));
 }
 
+static int fsi_i2c_lock_master(struct fsi_i2c_master *i2c, int timeout)
+{
+	int rc;
+
+	rc = down_trylock(&i2c->lock);
+	if (!rc)
+		return 0;
+
+	rc = wait_event_interruptible_timeout(i2c->wait,
+					      !down_trylock(&i2c->lock),
+					      timeout);
+	if (rc > 0)
+		return 0;
+
+	return -EBUSY;
+}
+
+static void fsi_i2c_unlock_master(struct fsi_i2c_master *i2c)
+{
+	up(&i2c->lock);
+	wake_up(&i2c->wait);
+}
+
 static int fsi_i2c_dev_init(struct fsi_i2c_master *i2c)
 {
 	int rc;
@@ -410,25 +435,31 @@ static int fsi_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 	struct fsi_i2c_port *port = adap->algo_data;
 	struct i2c_msg *msg;
 
-	rc = fsi_i2c_set_port(port);
+	rc = fsi_i2c_lock_master(port->master, adap->timeout);
 	if (rc)
 		return rc;
 
+	rc = fsi_i2c_set_port(port);
+	if (rc)
+		goto unlock;
+
 	for (i = 0; i < num; ++i) {
 		msg = msgs + i;
 		start_time = jiffies;
 
 		rc = fsi_i2c_start(port, msg, i == num - 1);
 		if (rc)
-			return rc;
+			goto unlock;
 
 		rc = fsi_i2c_wait(port, msg,
 				  adap->timeout - (jiffies - start_time));
 		if (rc)
-			return rc;
+			goto unlock;
 	}
 
-	return 0;
+unlock:
+	fsi_i2c_unlock_master(port->master);
+	return rc;
 }
 
 static u32 fsi_i2c_functionality(struct i2c_adapter *adap)
@@ -453,6 +484,8 @@ static int fsi_i2c_probe(struct device *dev)
 	if (!i2c)
 		return -ENOMEM;
 
+	init_waitqueue_head(&i2c->wait);
+	sema_init(&i2c->lock, 1);
 	i2c->fsi = to_fsi_dev(dev);
 	i2c->idx = ida_simple_get(&fsi_i2c_ida, 1, INT_MAX, GFP_KERNEL);
 	ida_init(&i2c->ida);
-- 
1.8.3.1