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

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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@xxxxxxxxx> 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@xxxxxxxxx>

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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