be2net: fix spurious interrupt handling in intx mode

Occasionally we may see an interrupt without an event in the eq.
In intx, we currently see the event queue and return IRQ_NONE causing
a the irq to be disabled ("no one cared".) Instead, read the CEV_ISR
reg to check the existence of the interrupt.
Signed-off-by: Sathya Perla <sathyap@serverengines.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/benet/be_hw.h

@@ -55,6 +55,10 @@
 #define MEMBAR_CTRL_INT_CTRL_PFUNC_MASK  	0x7 	/* bits 26 - 28 */
 #define MEMBAR_CTRL_INT_CTRL_PFUNC_SHIFT	26
 
+/********* ISR0 Register offset **********/
+#define CEV_ISR0_OFFSET 			0xC18
+#define CEV_ISR_SIZE				4
+
 /********* Event Q door bell *************/
 #define DB_EQ_OFFSET			DB_CQ_OFFSET
 #define DB_EQ_RING_ID_MASK		0x1FF	/* bits 0 - 8 */

drivers/net/benet/be_main.c

@@ -1274,15 +1274,17 @@ static irqreturn_t be_intx(int irq, void *dev)
 {
 	struct be_adapter *adapter = dev;
 	struct be_ctrl_info *ctrl = &adapter->ctrl;
-	int rx, tx;
+        int isr;
 
-	tx = event_handle(ctrl, &adapter->tx_eq);
-	rx = event_handle(ctrl, &adapter->rx_eq);
+	isr = ioread32(ctrl->csr + CEV_ISR0_OFFSET +
+                      ctrl->pci_func * CEV_ISR_SIZE);
+	if (!isr)
+                return IRQ_NONE;
+
+        event_handle(ctrl, &adapter->tx_eq);
+        event_handle(ctrl, &adapter->rx_eq);
 
-	if (rx || tx)
         return IRQ_HANDLED;
-	else
-		return IRQ_NONE;
 }
 
 static irqreturn_t be_msix_rx(int irq, void *dev)