sky2: check for more work before leaving NAPI

Backport of commit 5c11ce70

This patch avoids generating another IRQ if more packets
arrive while in the NAPI poll routine. Before marking device as
finished, it rechecks that the status ring is empty.
Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/net/sky2.c

@@ -2428,8 +2428,7 @@ static void sky2_err_intr(struct sky2_hw *hw, u32 status)
 static int sky2_poll(struct net_device *dev0, int *budget)
 {
 	struct sky2_hw *hw = ((struct sky2_port *) netdev_priv(dev0))->hw;
-	int work_limit = min(dev0->quota, *budget);
-	int work_done = 0;
+	int work_done;
 	u32 status = sky2_read32(hw, B0_Y2_SP_EISR);
 
 	if (unlikely(status & Y2_IS_ERROR))
@@ -2441,25 +2440,25 @@ static int sky2_poll(struct net_device *dev0, int *budget)
 	if (status & Y2_IS_IRQ_PHY2)
 		sky2_phy_intr(hw, 1);
 
-	work_done = sky2_status_intr(hw, work_limit);
-	if (work_done < work_limit) {
-		/* Bug/Errata workaround?
-		 * Need to kick the TX irq moderation timer.
-		 */
-		if (sky2_read8(hw, STAT_TX_TIMER_CTRL) == TIM_START) {
-			sky2_write8(hw, STAT_TX_TIMER_CTRL, TIM_STOP);
-			sky2_write8(hw, STAT_TX_TIMER_CTRL, TIM_START);
-		}
-		netif_rx_complete(dev0);
+	work_done = sky2_status_intr(hw, min(dev0->quota, *budget));
+	*budget -= work_done;
+	dev0->quota -= work_done;
 
-		/* end of interrupt, re-enables also acts as I/O synchronization */
-		sky2_read32(hw, B0_Y2_SP_LISR);
-		return 0;
-	} else {
-		*budget -= work_done;
-		dev0->quota -= work_done;
+	/* More work? */
+ 	if (hw->st_idx != sky2_read16(hw, STAT_PUT_IDX))
 		return 1;
+
+	/* Bug/Errata workaround?
+	 * Need to kick the TX irq moderation timer.
+	 */
+	if (sky2_read8(hw, STAT_TX_TIMER_CTRL) == TIM_START) {
+		sky2_write8(hw, STAT_TX_TIMER_CTRL, TIM_STOP);
+		sky2_write8(hw, STAT_TX_TIMER_CTRL, TIM_START);
 	}
+	netif_rx_complete(dev0);
+
+	sky2_read32(hw, B0_Y2_SP_LISR);
+	return 0;
 }
 
 static irqreturn_t sky2_intr(int irq, void *dev_id)