i2c: hisi: Avoid redundant interrupts

After issuing all the messages we can disable the TX_EMPTY interrupts
to avoid handling redundant interrupts. For doing a sinlge bus
detection (i2cdetect -y -r 0) we can reduce ~97% interrupts (before
~12000 after ~400).
Signed-off-by: Sheng Feng <fengsheng5@huawei.com>
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/busses/i2c-hisi.c

@@ -316,6 +316,13 @@ static void hisi_i2c_xfer_msg(struct hisi_i2c_controller *ctlr)
 		    max_write == 0)
 			break;
 	}
+
+	/*
+	 * Disable the TX_EMPTY interrupt after finishing all the messages to
+	 * avoid overwhelming the CPU.
+	 */
+	if (ctlr->msg_tx_idx == ctlr->msg_num)
+		hisi_i2c_disable_int(ctlr, HISI_I2C_INT_TX_EMPTY);
 }
 
 static irqreturn_t hisi_i2c_irq(int irq, void *context)