serial: imx: let irq handler return IRQ_NONE if no event was handled

This gives the irq core a chance to disable the serial interrupt in case
an event isn't cleared in the handler.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/imx.c

@@ -737,6 +737,7 @@ static irqreturn_t imx_int(int irq, void *dev_id)
 	struct imx_port *sport = dev_id;
 	unsigned int sts;
 	unsigned int sts2;
+	irqreturn_t ret = IRQ_NONE;
 
 	sts = readl(sport->port.membase + USR1);
 	sts2 = readl(sport->port.membase + USR2);
@@ -746,26 +747,34 @@ static irqreturn_t imx_int(int irq, void *dev_id)
 			imx_dma_rxint(sport);
 		else
 			imx_rxint(irq, dev_id);
+		ret = IRQ_HANDLED;
 	}
 
 	if ((sts & USR1_TRDY &&
 	     readl(sport->port.membase + UCR1) & UCR1_TXMPTYEN) ||
 	    (sts2 & USR2_TXDC &&
-	     readl(sport->port.membase + UCR4) & UCR4_TCEN))
+	     readl(sport->port.membase + UCR4) & UCR4_TCEN)) {
 		imx_txint(irq, dev_id);
+		ret = IRQ_HANDLED;
+	}
 
-	if (sts & USR1_RTSD)
+	if (sts & USR1_RTSD) {
 		imx_rtsint(irq, dev_id);
+		ret = IRQ_HANDLED;
+	}
 
-	if (sts & USR1_AWAKE)
+	if (sts & USR1_AWAKE) {
 		writel(USR1_AWAKE, sport->port.membase + USR1);
+		ret = IRQ_HANDLED;
+	}
 
 	if (sts2 & USR2_ORE) {
 		sport->port.icount.overrun++;
 		writel(USR2_ORE, sport->port.membase + USR2);
+		ret = IRQ_HANDLED;
 	}
 
-	return IRQ_HANDLED;
+	return ret;
 }
 
 /*