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    SubjectRe: [smartmontools-support] inactive SATA drives won't stay in standby or sleep, PATA models did. (fwd)
    On Mon, 20 Oct 2008 01:40:21 +0200, Mikael Pettersson wrote:
    >On Mon, 13 Oct 2008 14:16:24 +0900, Tejun Heo wrote:
    >>Mikael Pettersson wrote:
    >>> - hardreset in sata_promise seems broken. I'll take a closer look
    >>> at that in about a week's time (I'll be busy with other work the
    >>> next couple of days).
    >>This looks like a rather serious problem, so please take a look at
    >I've done more tests now, and the problem is that errors detected
    >outside of sata_promise itself, typically timeouts, don't trigger
    >the pdc_reset_port() call needed to bring the ATA engine behind the
    >port back to sanity.

    I did a round of regression tests which identified another
    related but different problem.

    In kernels 2.6.24 and 2.6.25 sata_promise would actually recover
    from the timeouts, while in kernels 2.6.26 and 2.6.27 it would not.
    Before 2.6.26 sata_promise explicitly used sata_std_hardreset, but
    in the "make reset related methods proper port operations" commit
    (a1efdaba2dbd6fb89e23a87b66d3f4dd92c9f5af), Tejun changed sata_promise
    to use the hardreset it now inherits from ata_sff_port_ops, namely
    sata_sff_hardreset. This change looks accidental. The main difference
    between these two procedures is that the sff version will poll the
    legacy status register until the port becomes ready.

    Changing sata_promise to use sata_std_hardreset in 2.6.26/.27
    makes the EH after the timeouts much more reliable. Not as
    tidy as with the previous ->prereset fix, but still working.


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