i2c: xiic: improve error message when transfer fails to start

xiic_start_xfer can fail for different reasons:

- EBUSY: bus is busy or i2c messages still in tx_msg or rx_msg
- ETIMEDOUT: timed-out trying to clear the RX fifo
- EINVAL: wrong clock settings

Both EINVAL and ETIMEDOUT will currently print a specific error
message followed by a generic one, for example:

    Failed to clear rx fifo
    Error xiic_start_xfer

however EBUSY will simply output the generic message:

    Error xiic_start_xfer

which is not really helpful.

This commit adds a new error message when a busy condition is detected
and also removes the generic message since it does not provide any
relevant information to the user.

Signed-off-by: Marc Ferland <marc.ferland@sonatest.com>
Acked-by: Michal Simek <michal.simek@amd.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>

drivers/i2c/busses/i2c-xiic.c

@@ -1105,8 +1105,11 @@ static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num)
 	mutex_lock(&i2c->lock);
 
 	ret = xiic_busy(i2c);
-	if (ret)
+	if (ret) {
+		dev_err(i2c->adap.dev.parent,
+			"cannot start a transfer while busy\n");
 		goto out;
+	}
 
 	i2c->tx_msg = msgs;
 	i2c->rx_msg = NULL;
@@ -1164,10 +1167,8 @@ static int xiic_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 		return err;
 
 	err = xiic_start_xfer(i2c, msgs, num);
-	if (err < 0) {
-		dev_err(adap->dev.parent, "Error xiic_start_xfer\n");
+	if (err < 0)
 		goto out;
-	}
 
 	err = wait_for_completion_timeout(&i2c->completion, XIIC_XFER_TIMEOUT);
 	mutex_lock(&i2c->lock);