Robert Hancock wrote:
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 <[EMAIL PROTECTED]>

--- 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);
+        }

it seems broken to manipulate xfer_mask after returning from the driver's ->mode_filter hook.

this patch is more than just a speed-limited warning printk, afaics


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