forcedeth: msi interrupts

Add a workaround for lost MSI interrupts.  There is a race condition in
the HW in which future interrupts could be missed.  The workaround is to
toggle the MSI irq mask.

Added cleanup based on comments from Andrew Morton.

Signed-off-by: Ayaz Abdulla <aabdulla@nvidia.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: Jeff Garzik <jeff@garzik.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/net/forcedeth.c

@@ -3273,6 +3273,20 @@ static void nv_link_irq(struct net_device *dev)
 	dprintk(KERN_DEBUG "%s: link change notification done.\n", dev->name);
 }
 
+static void nv_msi_workaround(struct fe_priv *np)
+{
+
+	/* Need to toggle the msi irq mask within the ethernet device,
+	 * otherwise, future interrupts will not be detected.
+	 */
+	if (np->msi_flags & NV_MSI_ENABLED) {
+		u8 __iomem *base = np->base;
+
+		writel(0, base + NvRegMSIIrqMask);
+		writel(NVREG_MSI_VECTOR_0_ENABLED, base + NvRegMSIIrqMask);
+	}
+}
+
 static irqreturn_t nv_nic_irq(int foo, void *data)
 {
 	struct net_device *dev = (struct net_device *) data;
@@ -3295,6 +3309,8 @@ static irqreturn_t nv_nic_irq(int foo, void *data)
 		if (!(events & np->irqmask))
 			break;
 
+		nv_msi_workaround(np);
+
 		spin_lock(&np->lock);
 		nv_tx_done(dev);
 		spin_unlock(&np->lock);
@@ -3410,6 +3426,8 @@ static irqreturn_t nv_nic_irq_optimized(int foo, void *data)
 		if (!(events & np->irqmask))
 			break;
 
+		nv_msi_workaround(np);
+
 		spin_lock(&np->lock);
 		nv_tx_done_optimized(dev, TX_WORK_PER_LOOP);
 		spin_unlock(&np->lock);
@@ -3750,6 +3768,8 @@ static irqreturn_t nv_nic_irq_test(int foo, void *data)
 	if (!(events & NVREG_IRQ_TIMER))
 		return IRQ_RETVAL(0);
 
+	nv_msi_workaround(np);
+
 	spin_lock(&np->lock);
 	np->intr_test = 1;
 	spin_unlock(&np->lock);