i2c-designware: Disable TX_EMPTY when all i2c_msg msgs has been processed

Currently we disable TX_EMPTY interrupt when buf_len is zero, but this
is wrong.  (buf_len == 0) means that all transmit data in the current
i2c_msg message has been sent out, but that doesn't necessarily mean
all i2c_msg messages have been processed.

TX_EMPTY interrupt is used as the driving force of DW I2C transactions,
so we need to keep it enabled as long as i2c_msg messages are available.
Signed-off-by: NShinya Kuribayashi <shinya.kuribayashi@necel.com>
Signed-off-by: NBen Dooks <ben-linux@fluff.org>

drivers/i2c/busses/i2c-designware.c

@@ -415,12 +415,17 @@ i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
 			/* more bytes to be written */
 			dev->status |= STATUS_WRITE_IN_PROGRESS;
 			break;
-		} else {
+		} else
 			dev->status &= ~STATUS_WRITE_IN_PROGRESS;
-			intr_mask &= ~DW_IC_INTR_TX_EMPTY;
-		}
 	}
 
+	/*
+	 * If i2c_msg index search is completed, we don't need TX_EMPTY
+	 * interrupt any more.
+	 */
+	if (dev->msg_write_idx == dev->msgs_num)
+		intr_mask &= ~DW_IC_INTR_TX_EMPTY;
+
 	writel(intr_mask, dev->base + DW_IC_INTR_MASK);
 }