[PATCH] libata: implement ata_down_xfermask_limit()

Implement ata_down_xfermask_limit().  This function manipulates
@dev->pio/mwdma/udma_mask such that the next lower transfer mode is
selected.  This will be used to improve ata_bus_probe() failure
handling and later by EH.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index 3ddfbe1..68fa64d 100644 (file)
--- 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;