ide: fix handling of unexpected IRQs vs request_irq()

Add ide_host_enable_irqs() helper and use it in ide_host_register()
before registering ports.  Then remove no longer needed IRQ unmasking
from in init_irq().

This should fix the problem with "screaming" shared IRQ on the first
port (after request_irq() call while we have the unexpected IRQ pending
on the second port) which was uncovered by my rework of the serialized
interfaces support.
Reported-by: NFrans Pop <elendil@planet.nl>
Tested-by: NFrans Pop <elendil@planet.nl>
Signed-off-by: NBartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/ide/ide-probe.c

@@ -818,6 +818,24 @@ static int ide_port_setup_devices(ide_hwif_t *hwif)
 	return j;
 }
 
+static void ide_host_enable_irqs(struct ide_host *host)
+{
+	ide_hwif_t *hwif;
+	int i;
+
+	ide_host_for_each_port(i, hwif, host) {
+		if (hwif == NULL)
+			continue;
+
+		/* clear any pending IRQs */
+		hwif->tp_ops->read_status(hwif);
+
+		/* unmask IRQs */
+		if (hwif->io_ports.ctl_addr)
+			hwif->tp_ops->write_devctl(hwif, ATA_DEVCTL_OBS);
+	}
+}
+
 /*
  * This routine sets up the IRQ for an IDE interface.
  */
@@ -831,9 +849,6 @@ static int init_irq (ide_hwif_t *hwif)
 	if (irq_handler == NULL)
 		irq_handler = ide_intr;
 
-	if (io_ports->ctl_addr)
-		hwif->tp_ops->write_devctl(hwif, ATA_DEVCTL_OBS);
-
 	if (request_irq(hwif->irq, irq_handler, sa, hwif->name, hwif))
 		goto out_up;
 
@@ -1404,6 +1419,8 @@ int ide_host_register(struct ide_host *host, const struct ide_port_info *d,
 			ide_port_tune_devices(hwif);
 	}
 
+	ide_host_enable_irqs(host);
+
 	ide_host_for_each_port(i, hwif, host) {
 		if (hwif == NULL)
 			continue;