Re: [PATCH] ata_piix: fix ghost device probing by honoring PCS present bits

["Unicorn Chang" <unicorn.mail@gmail.com>]

I tested this patch on IBM Intellistation M Pro with Quantum GoVault
(kernel 2.6.18-rc4),
it works fine !

SATA controller is configured to "Compatible" mode.
Intel Corporation 82801GB/GR/GH (ICH7 Family) Serial ATA Storage
Controllers cc=IDE (rev 01)

--
Unicorn

On 8/10/06, Tejun Heo <htejun@gmail.com> wrote:
> Move out PCS handling from piix_sata_prereset() into
> piix_sata_present_mask() and use it from newly implemented
> piix_sata_softreset().  Class codes for devices which are indicated to
> be absent by PCS are cleared to ATA_DEV_NONE.  This fixes ghost device
> problem reported on ICH6 and 7 (and probably 8).
>
> This patch moves PCS handling from prereset to softreset, which makes
> ata_piix perform softreset even when PCS indicates no device.
>
> Signed-off-by: Tejun Heo <htejun@gmail.com>
>
> diff --git a/drivers/scsi/ata_piix.c b/drivers/scsi/ata_piix.c
> index 19745a3..ad880b8 100644
> --- a/drivers/scsi/ata_piix.c
> +++ b/drivers/scsi/ata_piix.c
> @@ -531,27 +531,25 @@ static void piix_pata_error_handler(stru
>  }
>
>  /**
> - *     piix_sata_prereset - prereset for SATA host controller
> + *     piix_sata_present_mask - determine present mask for SATA host controller
>   *     @ap: Target port
>   *
> - *     Reads and configures SATA PCI device's PCI config register
> - *     Port Configuration and Status (PCS) to determine port and
> - *     device availability.  Return -ENODEV to skip reset if no
> - *     device is present.
> + *     Reads SATA PCI device's PCI config register Port Configuration
> + *     and Status (PCS) to determine port and device availability.
>   *
>   *     LOCKING:
>   *     None (inherited from caller).
>   *
>   *     RETURNS:
> - *     0 if device is present, -ENODEV otherwise.
> + *     determined present_mask
>   */
> -static int piix_sata_prereset(struct ata_port *ap)
> +static unsigned int piix_sata_present_mask(struct ata_port *ap)
>  {
>         struct pci_dev *pdev = to_pci_dev(ap->host_set->dev);
>         struct piix_host_priv *hpriv = ap->host_set->private_data;
>         const unsigned int *map = hpriv->map;
>         int base = 2 * ap->hard_port_no;
> -       unsigned int present = 0;
> +       unsigned int present_mask = 0;
>         int port, i;
>         u16 pcs;
>
> @@ -564,24 +562,52 @@ static int piix_sata_prereset(struct ata
>                         continue;
>                 if ((ap->flags & PIIX_FLAG_IGNORE_PCS) ||
>                     (pcs & 1 << (hpriv->map_db->present_shift + port)))
> -                       present = 1;
> +                       present_mask |= 1 << i;
>         }
>
>         DPRINTK("ata%u: LEAVE, pcs=0x%x present_mask=0x%x\n",
>                 ap->id, pcs, present_mask);
>
> -       if (!present) {
> -               ata_port_printk(ap, KERN_INFO, "SATA port has no device.\n");
> -               ap->eh_context.i.action &= ~ATA_EH_RESET_MASK;
> -               return 0;
> +       return present_mask;
> +}
> +
> +/**
> + *     piix_sata_softreset - reset SATA host port via ATA SRST
> + *     @ap: port to reset
> + *     @classes: resulting classes of attached devices
> + *
> + *     Reset SATA host port via ATA SRST.  On controllers with
> + *     reliable PCS present bits, the bits are used to determine
> + *     device presence.
> + *
> + *     LOCKING:
> + *     Kernel thread context (may sleep)
> + *
> + *     RETURNS:
> + *     0 on success, -errno otherwise.
> + */
> +static int piix_sata_softreset(struct ata_port *ap, unsigned int *classes)
> +{
> +       unsigned int present_mask;
> +       int i, rc;
> +
> +       present_mask = piix_sata_present_mask(ap);
> +
> +       rc = ata_std_softreset(ap, classes);
> +       if (rc)
> +               return rc;
> +
> +       for (i = 0; i < ATA_MAX_DEVICES; i++) {
> +               if (!(present_mask & (1 << i)))
> +                       classes[i] = ATA_DEV_NONE;
>         }
>
> -       return ata_std_prereset(ap);
> +       return 0;
>  }
>
>  static void piix_sata_error_handler(struct ata_port *ap)
>  {
> -       ata_bmdma_drive_eh(ap, piix_sata_prereset, ata_std_softreset, NULL,
> +       ata_bmdma_drive_eh(ap, ata_std_prereset, piix_sata_softreset, NULL,
>                            ata_std_postreset);
>  }
>
> -
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