3 files changed, 14 insertions, 3 deletions
diff --git a/drivers/ide/amd74xx.c b/drivers/ide/amd74xx.c
index 81ec73134eda..c6bcd3014a29 100644
--- a/drivers/ide/amd74xx.c
+++ b/drivers/ide/amd74xx.c
@@ -3,7 +3,7 @@
  * IDE driver for Linux.
  *
  * Copyright (c) 2000-2002 Vojtech Pavlik
- * Copyright (c) 2007 Bartlomiej Zolnierkiewicz
+ * Copyright (c) 2007-2008 Bartlomiej Zolnierkiewicz
  *
  * Based on the work of:
  *      Andre Hedrick
@@ -263,6 +263,15 @@ static int __devinit amd74xx_probe(struct pci_dev *dev, const struct pci_device_
 			d.udma_mask = ATA_UDMA5;
 	}
 
+	/*
+	 * It seems that on some nVidia controllers using AltStatus
+	 * register can be unreliable so default to Status register
+	 * if the device is in Compatibility Mode.
+	 */
+	if (dev->vendor == PCI_VENDOR_ID_NVIDIA &&
+	    ide_pci_is_in_compatibility_mode(dev))
+		d.host_flags |= IDE_HFLAG_BROKEN_ALTSTATUS;
+
 	printk(KERN_INFO "%s %s: UDMA%s controller\n",
 		d.name, pci_name(dev), amd_dma[fls(d.udma_mask) - 1]);
 
diff --git a/drivers/ide/ide-iops.c b/drivers/ide/ide-iops.c
index 5d6ba14e211d..142b9573d64c 100644
--- a/drivers/ide/ide-iops.c
+++ b/drivers/ide/ide-iops.c
@@ -468,7 +468,8 @@ int drive_is_ready (ide_drive_t *drive)
 	 * an interrupt with another pci card/device.  We make no assumptions
 	 * about possible isa-pnp and pci-pnp issues yet.
 	 */
-	if (hwif->io_ports.ctl_addr)
+	if (hwif->io_ports.ctl_addr &&
+	    (hwif->host_flags & IDE_HFLAG_BROKEN_ALTSTATUS) == 0)
 		stat = hwif->tp_ops->read_altstatus(hwif);
 	else
 		/* Note: this may clear a pending IRQ!! */
diff --git a/drivers/ide/ide-probe.c b/drivers/ide/ide-probe.c
index 1649ea54f76c..c55bdbd22314 100644
--- a/drivers/ide/ide-probe.c
+++ b/drivers/ide/ide-probe.c
@@ -266,7 +266,8 @@ static int actual_try_to_identify (ide_drive_t *drive, u8 cmd)
 	/* take a deep breath */
 	msleep(50);
 
-	if (io_ports->ctl_addr) {
+	if (io_ports->ctl_addr &&
+	    (hwif->host_flags & IDE_HFLAG_BROKEN_ALTSTATUS) == 0) {
 		a = tp_ops->read_altstatus(hwif);
 		s = tp_ops->read_status(hwif);
 		if ((a ^ s) & ~ATA_IDX)