1 files changed, 52 insertions, 0 deletions

diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index 3ddfbe1b86c..68fa64d2472 100644
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -65,6 +65,8 @@ static unsigned int ata_dev_init_params(struct ata_port *ap,
                                         struct ata_device *dev,
                                         u16 heads,
                                         u16 sectors);
+static int ata_down_xfermask_limit(struct ata_port *ap, struct ata_device *dev,
+                                   int force_pio0);
 static int ata_down_sata_spd_limit(struct ata_port *ap);
 static int ata_set_mode(struct ata_port *ap, struct ata_device **r_failed_dev);
 static unsigned int ata_dev_set_xfermode(struct ata_port *ap,
@@ -1859,6 +1861,56 @@ int ata_timing_compute(struct ata_device *adev, unsigned short speed,
         return 0;
 }
 
+/**
+ *      ata_down_xfermask_limit - adjust dev xfer masks downward
+ *      @ap: Port associated with device @dev
+ *      @dev: Device to adjust xfer masks
+ *      @force_pio0: Force PIO0
+ *
+ *      Adjust xfer masks of @dev downward.  Note that this function
+ *      does not apply the change.  Invoking ata_set_mode() afterwards
+ *      will apply the limit.
+ *
+ *      LOCKING:
+ *      Inherited from caller.
+ *
+ *      RETURNS:
+ *      0 on success, negative errno on failure
+ */
+static int ata_down_xfermask_limit(struct ata_port *ap, struct ata_device *dev,
+                                   int force_pio0)
+{
+        unsigned long xfer_mask;
+        int highbit;
+
+        xfer_mask = ata_pack_xfermask(dev->pio_mask, dev->mwdma_mask,
+                                      dev->udma_mask);
+
+        if (!xfer_mask)
+                goto fail;
+        /* don't gear down to MWDMA from UDMA, go directly to PIO */
+        if (xfer_mask & ATA_MASK_UDMA)
+                xfer_mask &= ~ATA_MASK_MWDMA;
+
+        highbit = fls(xfer_mask) - 1;
+        xfer_mask &= ~(1 << highbit);
+        if (force_pio0)
+                xfer_mask &= 1 << ATA_SHIFT_PIO;
+        if (!xfer_mask)
+                goto fail;
+
+        ata_unpack_xfermask(xfer_mask, &dev->pio_mask, &dev->mwdma_mask,
+                            &dev->udma_mask);
+
+        printk(KERN_WARNING "ata%u: dev %u limiting speed to %s\n",
+               ap->id, dev->devno, ata_mode_string(xfer_mask));
+
+        return 0;
+
+ fail:
+        return -EINVAL;
+}
+
 static int ata_dev_set_mode(struct ata_port *ap, struct ata_device *dev)
 {
         unsigned int err_mask;