[POWERPC] mpc5200: Fix FEC error handling on FIFO errors

The error handling for the mpc5200 fec interrupt is broken. The intended
behaviour is like this:

* If one of FEC_IEVENT_RFIFO_ERROR and FEC_IEVENT_XFIFO_ERROR happens,
  the datasheet says (MPC5200B User's Guide R1.2, p. 14-13): "When this
  occurs, software must ensure both the FIFO Controller and BestComm are
  soft-reset".

* On any other error (non-TFINT) interrupt, just issue a debug message.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/net/fec_mpc52xx.c

@@ -491,20 +491,23 @@ static irqreturn_t mpc52xx_fec_interrupt(int irq, void *dev_id)
 
 	out_be32(&fec->ievent, ievent);		/* clear pending events */
 
-	if (ievent & ~(FEC_IEVENT_RFIFO_ERROR | FEC_IEVENT_XFIFO_ERROR)) {
-		if (ievent & ~FEC_IEVENT_TFINT)
-			dev_dbg(&dev->dev, "ievent: %08x\n", ievent);
+	/* on fifo error, soft-reset fec */
+	if (ievent & (FEC_IEVENT_RFIFO_ERROR | FEC_IEVENT_XFIFO_ERROR)) {
+
+		if (net_ratelimit() && (ievent & FEC_IEVENT_RFIFO_ERROR))
+			dev_warn(&dev->dev, "FEC_IEVENT_RFIFO_ERROR\n");
+		if (net_ratelimit() && (ievent & FEC_IEVENT_XFIFO_ERROR))
+			dev_warn(&dev->dev, "FEC_IEVENT_XFIFO_ERROR\n");
+
+		mpc52xx_fec_reset(dev);
+
+		netif_wake_queue(dev);
 		return IRQ_HANDLED;
 	}
 
-	if (net_ratelimit() && (ievent & FEC_IEVENT_RFIFO_ERROR))
-		dev_warn(&dev->dev, "FEC_IEVENT_RFIFO_ERROR\n");
-	if (net_ratelimit() && (ievent & FEC_IEVENT_XFIFO_ERROR))
-		dev_warn(&dev->dev, "FEC_IEVENT_XFIFO_ERROR\n");
+	if (ievent & ~FEC_IEVENT_TFINT)
+		dev_dbg(&dev->dev, "ievent: %08x\n", ievent);
 
-	mpc52xx_fec_reset(dev);
-
-	netif_wake_queue(dev);
 	return IRQ_HANDLED;
 }