p8-i2c: Limit number of retry attempts

Current we will attempt to start an I2C transaction until it succeeds.
In the event that the OCC does not release the lock on an I2C bus this
results in an async token being held forever and the kernel thread that
started the transaction will block forever while waiting for an async
completion message. Fix this by limiting the number of attempts to
start the transaction.

Signed-off-by: Oliver O'Halloran <[email protected]>
Signed-off-by: Stewart Smith <[email protected]>

Author: oohal

hw/p8-i2c.c

@@ -1303,8 +1303,16 @@ static void p8_i2c_check_work(struct p8_i2c_master *master)
 	while (master->state == state_idle && !list_empty(&master->req_list)) {
 		req = list_top(&master->req_list, struct i2c_request, link);
 		rc = p8_i2c_start_request(master, req);
-		if (rc && rc != OPAL_BUSY)
-			p8_i2c_complete_request(master, req, rc);
+		if (rc) {
+			/*
+			 * If it didn't work the first three times then
+			 * odds are it's not going to work on the 4th.
+			 */
+			if (rc && req->retries > 3)
+				p8_i2c_complete_request(master, req, rc);
+			else
+				req->retries++;
+		}
 	}
 }
 

include/i2c.h

@@ -64,6 +64,7 @@ struct i2c_request {
 	void			(*completion)(	/* Completion callback */
 					      int rc, struct i2c_request *req);
 	void			*user_data;	/* Client data */
+	int			retries;
 };
 
 /* Generic i2c */