i2c: ocores: generate stop condition after timeout in polling mode

In polling mode, no stop condition is generated after a timeout. This
causes SCL to remain low and thereby block the bus. If this happens
during a transfer it can cause slaves to misinterpret the subsequent
transfer and return wrong values.

To solve this, pass the ETIMEDOUT error up from ocores_process_polling()
instead of setting STATE_ERROR directly. The caller is adjusted to call
ocores_process_timeout() on error both in polling and in IRQ mode, which
will set STATE_ERROR and generate a stop condition.

Fixes: 69c8c0c0 ("i2c: ocores: add polling interface")
Signed-off-by: Gregor Herburger <gregor.herburger@tq-group.com>
Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Acked-by: Peter Korsgaard <peter@korsgaard.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Federico Vaga <federico.vaga@cern.ch>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/busses/i2c-ocores.c

@@ -342,18 +342,18 @@ static int ocores_poll_wait(struct ocores_i2c *i2c)
  * ocores_isr(), we just add our polling code around it.
  *
  * It can run in atomic context
+ *
+ * Return: 0 on success, -ETIMEDOUT on timeout
  */
-static void ocores_process_polling(struct ocores_i2c *i2c)
+static int ocores_process_polling(struct ocores_i2c *i2c)
 {
-	while (1) {
-		irqreturn_t ret;
-		int err;
+	irqreturn_t ret;
+	int err = 0;
 
+	while (1) {
 		err = ocores_poll_wait(i2c);
-		if (err) {
-			i2c->state = STATE_ERROR;
+		if (err)
 			break; /* timeout */
-		}
 
 		ret = ocores_isr(-1, i2c);
 		if (ret == IRQ_NONE)
@@ -364,13 +364,15 @@ static void ocores_process_polling(struct ocores_i2c *i2c)
 					break;
 		}
 	}
+
+	return err;
 }
 
 static int ocores_xfer_core(struct ocores_i2c *i2c,
 			    struct i2c_msg *msgs, int num,
 			    bool polling)
 {
-	int ret;
+	int ret = 0;
 	u8 ctrl;
 
 	ctrl = oc_getreg(i2c, OCI2C_CONTROL);
@@ -388,15 +390,16 @@ static int ocores_xfer_core(struct ocores_i2c *i2c,
 	oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_START);
 
 	if (polling) {
-		ocores_process_polling(i2c);
+		ret = ocores_process_polling(i2c);
 	} else {
-		ret = wait_event_timeout(i2c->wait,
-					 (i2c->state == STATE_ERROR) ||
-					 (i2c->state == STATE_DONE), HZ);
-		if (ret == 0) {
-			ocores_process_timeout(i2c);
-			return -ETIMEDOUT;
-		}
+		if (wait_event_timeout(i2c->wait,
+				       (i2c->state == STATE_ERROR) ||
+				       (i2c->state == STATE_DONE), HZ) == 0)
+			ret = -ETIMEDOUT;
+	}
+	if (ret) {
+		ocores_process_timeout(i2c);
+		return ret;
 	}
 
 	return (i2c->state == STATE_DONE) ? num : -EIO;