forcedeth: fix irq clearing and napi spin lock changes

This patch clears the irqstatus register with the exact same events it
has read from it. Since the read-write operation is not atomic, a new
irqstatus bit could have been set in between these operations and would
then be cleared accidentally.

Secondly, we now don't need any spin lock protection when
scheduling/completing napi poll as the isr will not execute anymore (as
we turn off all interrupts now).

Signed-off-by: Ayaz Abdulla <aabdulla@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/forcedeth.c

@@ -3464,10 +3464,10 @@ static irqreturn_t nv_nic_irq(int foo, void *data)
 
 	if (!(np->msi_flags & NV_MSI_X_ENABLED)) {
 		np->events = readl(base + NvRegIrqStatus);
-		writel(NVREG_IRQSTAT_MASK, base + NvRegIrqStatus);
+		writel(np->events, base + NvRegIrqStatus);
 	} else {
 		np->events = readl(base + NvRegMSIXIrqStatus);
-		writel(NVREG_IRQSTAT_MASK, base + NvRegMSIXIrqStatus);
+		writel(np->events, base + NvRegMSIXIrqStatus);
 	}
 	dprintk(KERN_DEBUG "%s: irq: %08x\n", dev->name, np->events);
 	if (!(np->events & np->irqmask))
@@ -3476,15 +3476,12 @@ static irqreturn_t nv_nic_irq(int foo, void *data)
 	nv_msi_workaround(np);
 
 #ifdef CONFIG_FORCEDETH_NAPI
-	spin_lock(&np->lock);
 	napi_schedule(&np->napi);
 
 	/* Disable furthur irq's
 	   (msix not enabled with napi) */
 	writel(0, base + NvRegIrqMask);
 
-	spin_unlock(&np->lock);
-
 #else
 	do
 	{
@@ -3568,10 +3565,10 @@ static irqreturn_t nv_nic_irq_optimized(int foo, void *data)
 
 	if (!(np->msi_flags & NV_MSI_X_ENABLED)) {
 		np->events = readl(base + NvRegIrqStatus);
-		writel(NVREG_IRQSTAT_MASK, base + NvRegIrqStatus);
+		writel(np->events, base + NvRegIrqStatus);
 	} else {
 		np->events = readl(base + NvRegMSIXIrqStatus);
-		writel(NVREG_IRQSTAT_MASK, base + NvRegMSIXIrqStatus);
+		writel(np->events, base + NvRegMSIXIrqStatus);
 	}
 	dprintk(KERN_DEBUG "%s: irq: %08x\n", dev->name, np->events);
 	if (!(np->events & np->irqmask))
@@ -3580,15 +3577,12 @@ static irqreturn_t nv_nic_irq_optimized(int foo, void *data)
 	nv_msi_workaround(np);
 
 #ifdef CONFIG_FORCEDETH_NAPI
-	spin_lock(&np->lock);
 	napi_schedule(&np->napi);
 
 	/* Disable furthur irq's
 	   (msix not enabled with napi) */
 	writel(0, base + NvRegIrqMask);
 
-	spin_unlock(&np->lock);
-
 #else
 	do
 	{
@@ -3758,13 +3752,9 @@ static int nv_napi_poll(struct napi_struct *napi, int budget)
 	if (rx_work < budget) {
 		/* re-enable interrupts
 		   (msix not enabled in napi) */
-		spin_lock_irqsave(&np->lock, flags);
-
 		__napi_complete(napi);
 
 		writel(np->irqmask, base + NvRegIrqMask);
-
-		spin_unlock_irqrestore(&np->lock, flags);
 	}
 	return rx_work;
 }