1 files changed, 10 insertions, 1 deletions

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index e00e1b913d28..bb940475d87c 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -170,6 +170,7 @@ enum {
         AHCI_FLAG_IGN_IRQ_IF_ERR        = (1 << 25), /* ignore IRQ_IF_ERR */
         AHCI_FLAG_HONOR_PI              = (1 << 26), /* honor PORTS_IMPL */
         AHCI_FLAG_IGN_SERR_INTERNAL     = (1 << 27), /* ignore SERR_INTERNAL */
+        AHCI_FLAG_32BIT_ONLY            = (1 << 28), /* force 32bit */
 
         AHCI_FLAG_COMMON                = ATA_FLAG_SATA | ATA_FLAG_NO_LEGACY |
                                           ATA_FLAG_MMIO | ATA_FLAG_PIO_DMA |
@@ -354,7 +355,8 @@ static const struct ata_port_info ahci_port_info[] = {
         /* board_ahci_sb600 */
         {
                 .flags          = AHCI_FLAG_COMMON |
-                                  AHCI_FLAG_IGN_SERR_INTERNAL,
+                                  AHCI_FLAG_IGN_SERR_INTERNAL |
+                                  AHCI_FLAG_32BIT_ONLY,
                 .pio_mask       = 0x1f, /* pio0-4 */
                 .udma_mask      = 0x7f, /* udma0-6 ; FIXME */
                 .port_ops       = &ahci_ops,
@@ -492,6 +494,13 @@ static void ahci_save_initial_config(struct pci_dev *pdev,
         hpriv->saved_cap = cap = readl(mmio + HOST_CAP);
         hpriv->saved_port_map = port_map = readl(mmio + HOST_PORTS_IMPL);
 
+        /* some chips lie about 64bit support */
+        if ((cap & HOST_CAP_64) && (pi->flags & AHCI_FLAG_32BIT_ONLY)) {
+                dev_printk(KERN_INFO, &pdev->dev,
+                           "controller can't do 64bit DMA, forcing 32bit\n");
+                cap &= ~HOST_CAP_64;
+        }
+
         /* fixup zero port_map */
         if (!port_map) {
                 port_map = (1 << ahci_nr_ports(hpriv->cap)) - 1;