Re: [PATCH 1/3] pata_pdc202xx_old: fix UDMA mode for Promise UDMA33cards

[Jeff Garzik]

On 02/13/2010 08:35 AM, Bartlomiej Zolnierkiewicz wrote:
> From: Bartlomiej Zolnierkiewicz<bzolnier@xxxxxxxxx>
> Subject: [PATCH] pata_pdc202xx_old: fix UDMA mode for Promise UDMA33 cards
>
> On Monday 04 January 2010 02:30:24 pm Russell King wrote:
>
> > Found the problem - getting rid of the read of the alt status register
> > after the command has been written fixes the UDMA CRC errors on write:
> >
> > @@ -676,7 +676,8 @@ void ata_sff_exec_command(struct ata_port *ap, const struct
> > ata_taskfile *tf)
> >          DPRINTK("ata%u: cmd 0x%X\n", ap->print_id, tf->command);
> >
> >          iowrite8(tf->command, ap->ioaddr.command_addr);
> > -       ata_sff_pause(ap);
> > +       ndelay(400);
> > +//     ata_sff_pause(ap);
> >   }
> >   EXPORT_SYMBOL_GPL(ata_sff_exec_command);
> >
> >
> > This rather makes sense.  The PDC20247 handles the UDMA part of the
> > protocol.  It has no way to tell the PDC20246 to wait while it suspends
> > UDMA, so that a normal register access can take place - the 246 ploughs
> > on with the register access without any regard to the state of the 247.
> >
> > If the drive immediately starts the UDMA protocol after a write to the
> > command register (as it probably will for the DMA WRITE command), then
> > we'll be accessing the taskfile in the middle of the UDMA setup, which
> > can't be good.  It's certainly a violation of the ATA specs.
>
> Fix it by adding custom ->sff_exec_command method for UDMA33 chipsets.
>
> Debugged-by: Russell King<rmk@xxxxxxxxxxxxxxxx>
> Signed-off-by: Bartlomiej Zolnierkiewicz<bzolnier@xxxxxxxxx>
> ---
>   drivers/ata/pata_pdc202xx_old.c |   13 ++++++++++++-
>   1 file changed, 12 insertions(+), 1 deletion(-)

applied


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