[libata] pata_atiixp: add locking for parallel scanning

This is similar change as commit 60c3be38 for ata_piix host driver
and while pata_atiixp doesn't enable parallel scan yet the race
could probably also be triggered by requesting re-scanning of both
ports at the same time using SCSI sysfs interface.

[Ported to current tree without other patch dependancies by Alan Cox]

Original is
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

This one is
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/pata_atiixp.c

 /*
  * pata_atiixp.c 	- ATI PATA for new ATA layer
  *			  (C) 2005 Red Hat Inc
- *			  (C) 2009 Bartlomiej Zolnierkiewicz
+ *			  (C) 2009-2010 Bartlomiej Zolnierkiewicz
  *
  * Based on
  *
@@ -46,6 +46,8 @@ static int atiixp_cable_detect(struct ata_port *ap)
 	return ATA_CBL_PATA40;
 }
 
+static DEFINE_SPINLOCK(atiixp_lock);
+
 /**
  *	atiixp_set_pio_timing	-	set initial PIO mode data
  *	@ap: ATA interface
@@ -88,7 +90,10 @@ static void atiixp_set_pio_timing(struct ata_port *ap, struct ata_device *adev,
 
 static void atiixp_set_piomode(struct ata_port *ap, struct ata_device *adev)
 {
+	unsigned long flags;
+	spin_lock_irqsave(&atiixp_lock, flags);
 	atiixp_set_pio_timing(ap, adev, adev->pio_mode - XFER_PIO_0);
+	spin_unlock_irqrestore(&atiixp_lock, flags);
 }
 
 /**
@@ -108,6 +113,9 @@ static void atiixp_set_dmamode(struct ata_port *ap, struct ata_device *adev)
 	int dma = adev->dma_mode;
 	int dn = 2 * ap->port_no + adev->devno;
 	int wanted_pio;
+	unsigned long flags;
+
+	spin_lock_irqsave(&atiixp_lock, flags);
 
 	if (adev->dma_mode >= XFER_UDMA_0) {
 		u16 udma_mode_data;
@@ -145,6 +153,7 @@ static void atiixp_set_dmamode(struct ata_port *ap, struct ata_device *adev)
 
 	if (adev->pio_mode != wanted_pio)
 		atiixp_set_pio_timing(ap, adev, wanted_pio);
+	spin_unlock_irqrestore(&atiixp_lock, flags);
 }
 
 /**