[SCSI] ipr: fix possible false positive detection of stuck interrupt

If the driver is getting flooded with interrupts, there's a possibility
that the interrupt service routine could falsely detect a stuck interrupt
condition and reset the adapter.

This patch changes the logic such that the routine will loop back into
the command processing code one more time after detecting the stuck
interrupt signature.  If there are no commands to process after that pass,
and the interrupt is still not cleared, then the driver will print the
"Error clearing HRRQ" message and reset the adapter.
Signed-off-by: Wayne Boyer <wayneb@linux.vnet.ibm.com>
Acked-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <jbottomley@parallels.com>

drivers/scsi/ipr.c

@@ -5149,21 +5149,21 @@ static irqreturn_t ipr_isr(int irq, void *devp)
 
 		if (ipr_cmd != NULL) {
 			/* Clear the PCI interrupt */
+			num_hrrq = 0;
 			do {
 				writel(IPR_PCII_HRRQ_UPDATED, ioa_cfg->regs.clr_interrupt_reg32);
 				int_reg = readl(ioa_cfg->regs.sense_interrupt_reg32);
 			} while (int_reg & IPR_PCII_HRRQ_UPDATED &&
 					num_hrrq++ < IPR_MAX_HRRQ_RETRIES);
 
-			if (int_reg & IPR_PCII_HRRQ_UPDATED) {
-				ipr_isr_eh(ioa_cfg, "Error clearing HRRQ");
-				spin_unlock_irqrestore(ioa_cfg->host->host_lock, lock_flags);
-				return IRQ_HANDLED;
-			}
-
 		} else if (rc == IRQ_NONE && irq_none == 0) {
 			int_reg = readl(ioa_cfg->regs.sense_interrupt_reg32);
 			irq_none++;
+		} else if (num_hrrq == IPR_MAX_HRRQ_RETRIES &&
+			   int_reg & IPR_PCII_HRRQ_UPDATED) {
+			ipr_isr_eh(ioa_cfg, "Error clearing HRRQ");
+			spin_unlock_irqrestore(ioa_cfg->host->host_lock, lock_flags);
+			return IRQ_HANDLED;
 		} else
 			break;
 	}