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    SubjectRe: [PATCH] pata_it821x: sync with IDE it821x driver
    Date

    Hello,

    On Saturday 09 June 2007, Tejun Heo wrote:
    > Hello,
    >
    > Bartlomiej Zolnierkiewicz wrote:
    > > * (partially) fix DMA in RAID mode
    > >
    > > Code intended to check DMA status was checking DMA command register.
    > > Moreover firmware seems to "forget" to set DMA capable bit for the
    > > slave device (at least in RAID mode but without ITE RAID volumes) so
    > > check device ID for DMA capable bit when deciding whether to use DMA
    > > and remove DMA status check completely.
    > >
    > > Thanks to Pavol Šimo for the bugreport and testing the initial fix.
    >
    > Ah... This is the mysterious mwdma configuration in smart mode, right?

    Yep.

    > Thanks for fixing this.
    >
    > > This change unfortunately still doesn't fix DMA in RAID mode (which
    > > works fine with IDE it821x) but Alan is working on the missing pieces
    > > (pata_it821x vs libata EH issues).
    >
    > This is the lbal/nsect SRST problem, right?

    I think so, due to lack of time I'm not following libata discussions closely.

    > > @@ -258,8 +259,14 @@ static void it821x_passthru_set_piomode(
    > > static const u8 pio_want[] = { ATA_66, ATA_66, ATA_66, ATA_66, ATA_ANY };
    > >
    > > struct it821x_dev *itdev = ap->private_data;
    > > + struct ata_device *pair = ata_dev_pair(adev);
    > > int unit = adev->devno;
    > > - int mode_wanted = adev->pio_mode - XFER_PIO_0;
    > > + int mode_wanted = adev->pio_mode;
    > > +
    > > + if (pair && adev->pio_mode > pair->pio_mode)
    > > + mode_wanted = pair->pio_mode;
    > > +
    > > + mode_wanted -= XFER_PIO_0;
    >
    > I think this is better done by mode_filter callback which is guaranteed
    > to be called before any actual mode configuration is performed and in
    > device order (master then slave).

    I was thinking about using ->mode_filter but since all other PATA host
    drivers are doing PIO filtering in ->set_piomode methods and also since it
    seemed that using ->mode_filter method would result in slightly more complex
    code I opted for coherency / simplicity. However if you (or somebody else)
    want to make a follow-up change to this driver (and preferably other PATA
    host drivers ie. pata_sil680) to use ->mode_filter I'm also fine with that.

    Thanks,
    Bart
    -
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