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SubjectRe: [PATCH] libata: Cable detection fixes
Alan wrote:
> 2.6.21-rc has horrible problems with libata and PATA cable types (and
> thus speeds). This occurs because Tejun fixed a pile of other bugs and
> we now do cable detect enforcement for drive side detection properly.
>
> Unfortunately we don't do the process around cable detection right. Tejun
> identified the problem and pointed to the right Annex in the spec, this patch
> implements the needed changes.
>
> The basic requirement is that we have to identify the slave before the
> master.
>
> The patch switches the identify order so that we can do the drive side
> detection correctly.
>
> Secondly we add a ->cable_detect() method called after the identify
> sequence which allows a host to do host side detection at this point
> should it wish, or to modify the results of the drive side identify.
[...]

> @@ -1850,8 +1900,11 @@
> for (i = 0; i < ATA_MAX_DEVICES; i++)
> ap->device[i].pio_mode = XFER_PIO_0;
>
> - /* read IDENTIFY page and configure devices */
> - for (i = 0; i < ATA_MAX_DEVICES; i++) {
> + /* read IDENTIFY page and configure devices. We have to do the identify
> + specific sequence bass-ackwards so that PDIAG- is released by
> + the slave device */
> +
> + for (i = ATA_MAX_DEVICES - 1; i >= 0; i--) {
> dev = &ap->device[i];
>
> if (tries[i])
> @@ -1864,6 +1917,19 @@
> dev->id);
> if (rc)
> goto fail;
> + }
> +
> + /* Now ask for the cable type as PDIAG- should have been released */
> + if (ap->ops->cable_detect)
> + ap->cbl = ap->ops->cable_detect(ap);
> +
> + /* After the identify sequence we can now set up the devices. We do
> + this in the normal order so that the user doesn't get confused */
> +
> + for(i = 0; i < ATA_MAX_DEVICES; i++) {
> + dev = &ap->device[i];
> + if (!ata_dev_enabled(dev))
> + continue;
>
> ap->eh_context.i.flags |= ATA_EHI_PRINTINFO;
> rc = ata_dev_configure(dev);


ACK pending positive testing reports

However, given that we are in -rc cycle, and the wide impact of this
change, this patch wants splitting. The ->cable_detect stuff should be
in a separate patch from the IDENTIFY DEVICE ordering stuff. This
ensures sanity when git-bisecting changes, and allows fast-tracking of
the identify-ordering change.

At present, adding the new ->cable_detect hook looks like 2.6.22
material (#upstream) rather than 2.6.21-rc (#upstream-fixes).

Jeff


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