r6040: save and restore MIER correctly in the interrupt routine

This patch saves the MIER register contents before treating
interrupts, then restores them correcty at the end of the
interrupt routine.

Signed-off-by: Joe Chou <Joe.Chou@rdc.com.tw>
Signed-off-by: Florian Fainelli <florian@openwrt.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/r6040.c b/drivers/net/r6040.c
index cc5e316..9906123 100644
--- a/drivers/net/r6040.c
+++ b/drivers/net/r6040.c
@@ -680,8 +680,10 @@
 	struct net_device *dev = dev_id;
 	struct r6040_private *lp = netdev_priv(dev);
 	void __iomem *ioaddr = lp->base;
-	u16 status;
+	u16 misr, status;
 
+	/* Save MIER */
+	misr = ioread16(ioaddr + MIER);
 	/* Mask off RDC MAC interrupt */
 	iowrite16(MSK_INT, ioaddr + MIER);
 	/* Read MISR status and clear */
@@ -701,7 +703,7 @@
 			dev->stats.rx_fifo_errors++;
 
 		/* Mask off RX interrupt */
-		iowrite16(ioread16(ioaddr + MIER) & ~RX_INTS, ioaddr + MIER);
+		misr &= ~RX_INTS;
 		netif_rx_schedule(dev, &lp->napi);
 	}
 
@@ -709,6 +711,9 @@
 	if (status & TX_INTS)
 		r6040_tx(dev);
 
+	/* Restore RDC MAC interrupt */
+	iowrite16(misr, ioaddr + MIER);
+
 	return IRQ_HANDLED;
 }