4 files changed, 22 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)
diff --git a/include/linux/ide.h b/include/linux/ide.h
index 54525be4b5f8..010fb26a1579 100644
--- a/include/linux/ide.h
+++ b/include/linux/ide.h
@@ -1296,6 +1296,13 @@ extern int __ide_pci_register_driver(struct pci_driver *driver, struct module *o
 #define ide_pci_register_driver(d) pci_register_driver(d)
 #endif
 
+static inline int ide_pci_is_in_compatibility_mode(struct pci_dev *dev)
+{
+        if ((dev->class >> 8) == PCI_CLASS_STORAGE_IDE && (dev->class & 5) != 5)
+                return 1;
+        return 0;
+}
+
 void ide_pci_setup_ports(struct pci_dev *, const struct ide_port_info *, int,
                          hw_regs_t *, hw_regs_t **);
 void ide_setup_pci_noise(struct pci_dev *, const struct ide_port_info *);
@@ -1375,6 +1382,7 @@ enum {
         IDE_HFLAG_IO_32BIT              = (1 << 24),
         /* unmask IRQs */
         IDE_HFLAG_UNMASK_IRQS           = (1 << 25),
+        IDE_HFLAG_BROKEN_ALTSTATUS      = (1 << 26),
         /* serialize ports if DMA is possible (for sl82c105) */
         IDE_HFLAG_SERIALIZE_DMA         = (1 << 27),
         /* force host out of "simplex" mode */