libata: warn if speed limited due to 40-wire cable

Warn the user if a drive's transfer rate is limited because of a 40-wire
cable detection.

Signed-off-by: Robert Hancock <hancockr@shaw.ca>
Cc: Jeff Garzik <jeff@garzik.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 20 insertions, 13 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 99a881558e8..93e7b99d781 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -3425,19 +3425,7 @@ static void ata_dev_xfermask(struct ata_device *dev)
         xfer_mask = ata_pack_xfermask(ap->pio_mask,
                                       ap->mwdma_mask, ap->udma_mask);
 
-        /* Apply cable rule here.  Don't apply it early because when
-         * we handle hot plug the cable type can itself change.
-         */
-        if (ap->cbl == ATA_CBL_PATA40)
-                xfer_mask &= ~(0xF8 << ATA_SHIFT_UDMA);
-        /* Apply drive side cable rule. Unknown or 80 pin cables reported
-         * host side are checked drive side as well. Cases where we know a
-         * 40wire cable is used safely for 80 are not checked here.
-         */
-        if (ata_drive_40wire(dev->id) && (ap->cbl == ATA_CBL_PATA_UNK || ap->cbl == ATA_CBL_PATA80))
-                xfer_mask &= ~(0xF8 << ATA_SHIFT_UDMA);
-
-
+        /* drive modes available */
         xfer_mask &= ata_pack_xfermask(dev->pio_mask,
                                        dev->mwdma_mask, dev->udma_mask);
         xfer_mask &= ata_id_xfermask(dev->id);
@@ -3469,6 +3457,25 @@ static void ata_dev_xfermask(struct ata_device *dev)
         if (ap->ops->mode_filter)
                 xfer_mask = ap->ops->mode_filter(ap, dev, xfer_mask);
 
+        /* Apply cable rule here.  Don't apply it early because when
+         * we handle hot plug the cable type can itself change.
+         * Check this last so that we know if the transfer rate was
+         * solely limited by the cable.
+         * Unknown or 80 wire cables reported host side are checked
+         * drive side as well. Cases where we know a 40wire cable
+         * is used safely for 80 are not checked here.
+         */
+        if (xfer_mask & (0xF8 << ATA_SHIFT_UDMA))
+                /* UDMA/44 or higher would be available */
+                if((ap->cbl == ATA_CBL_PATA40) ||
+                    (ata_drive_40wire(dev->id) &&
+                     (ap->cbl == ATA_CBL_PATA_UNK ||
+                     ap->cbl == ATA_CBL_PATA80))) {
+                        ata_dev_printk(dev, KERN_WARNING,
+                                 "limited to UDMA/33 due to 40-wire cable\n");
+                        xfer_mask &= ~(0xF8 << ATA_SHIFT_UDMA);
+                }
+
         ata_unpack_xfermask(xfer_mask, &dev->pio_mask,
                             &dev->mwdma_mask, &dev->udma_mask);
 }