[PATCH] smc91x: fix one source of spurious interrupts

Not only SMC_ACK_INT(IM_TX_EMPTY_INT) in in smc_hardware_send_pkt)
appears to be unnecessary (tested with an SMC91C94 and SMC91C111), but
it seems to trigger spurious interrupts on some machines as well.
Removed.

While at it, let's log any remaining spurious interrupts if any (and
clean usage of the max IRQ loop count value).
Signed-off-by: NNicolas Pitre <nico@cam.org>
Signed-off-by: NJeff Garzik <jgarzik@pobox.com>

drivers/net/smc91x.c

@@ -154,6 +154,12 @@ MODULE_LICENSE("GPL");
  */
 #define MEMORY_WAIT_TIME	16
 
+/*
+ * The maximum number of processing loops allowed for each call to the
+ * IRQ handler.  
+ */
+#define MAX_IRQ_LOOPS		8
+
 /*
  * This selects whether TX packets are sent one by one to the SMC91x internal
  * memory and throttled until transmission completes.  This may prevent
@@ -684,7 +690,6 @@ static void smc_hardware_send_pkt(unsigned long data)
 
 	/* queue the packet for TX */
 	SMC_SET_MMU_CMD(MC_ENQUEUE);
-	SMC_ACK_INT(IM_TX_EMPTY_INT);
 	smc_special_unlock(&lp->lock);
 
 	dev->trans_start = jiffies;
@@ -1305,7 +1310,7 @@ static irqreturn_t smc_interrupt(int irq, void *dev_id, struct pt_regs *regs)
 	SMC_SET_INT_MASK(0);
 
 	/* set a timeout value, so I don't stay here forever */
-	timeout = 8;
+	timeout = MAX_IRQ_LOOPS;
 
 	do {
 		status = SMC_GET_INT();
@@ -1372,10 +1377,13 @@ static irqreturn_t smc_interrupt(int irq, void *dev_id, struct pt_regs *regs)
 	/* restore register states */
 	SMC_SET_PTR(saved_pointer);
 	SMC_SET_INT_MASK(mask);
-
 	spin_unlock(&lp->lock);
 
-	DBG(3, "%s: Interrupt done (%d loops)\n", dev->name, 8-timeout);
+	if (timeout == MAX_IRQ_LOOPS)
+		PRINTK("%s: spurious interrupt (mask = 0x%02x)\n",
+		       dev->name, mask);
+	DBG(3, "%s: Interrupt done (%d loops)\n",
+	       dev->name, MAX_IRQ_LOOPS - timeout);
 
 	/*
 	 * We return IRQ_HANDLED unconditionally here even if there was