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Subject[PATCH] libata: warn if speed limited due to 40-wire cable (v2)
Here's a revised version of my previous patch to warn the user if a
drive's transfer rate is limited because of a 40-wire cable detection.
This one hopefully addresses Alan's previous comments - we now do this
at the very end of the function, and the ugly if condition has been
cleaned up somewhat. Also, it's been inadvertently tested (it seems that
pata_amd Nvidia cable detection is broken in current -git..)

Signed-off-by: Robert Hancock <hancockr@shaw.ca>

--- linux-2.6.20-git6/drivers/ata/libata-core.c 2007-02-11 17:31:19.000000000 -0600
+++ linux-2.6.20-git6edit/drivers/ata/libata-core.c 2007-02-13 19:15:58.000000000 -0600
@@ -3305,19 +3305,7 @@ static void ata_dev_xfermask(struct ata_
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);
@@ -3348,6 +3336,25 @@ static void ata_dev_xfermask(struct ata_
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);
}
-
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