libata: assume ATA_DEV_ATA on diagnostic failure

Certain device which reports diagnostic failure also reports invalid
device signature.  Assume ATA_DEV_ATA on diagnostic failure if reset
indicates device presence.

This is fix for bugzilla bug 8784.

  http://bugzilla.kernel.org/show_bug.cgi?id=8784

Signed-off-by: Tejun Heo <htejun@gmail.com>
Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Edward Amsden <amsden_linux@earthlink.net>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 14 insertions, 4 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index ea8c07b04f29..2116f2794580 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -751,10 +751,20 @@ unsigned int ata_dev_try_classify(struct ata_device *dev, int present,
         /* determine if device is ATA or ATAPI */
         class = ata_dev_classify(&tf);
 
-        if (class == ATA_DEV_UNKNOWN)
-                return ATA_DEV_NONE;
-        if ((class == ATA_DEV_ATA) && (ata_chk_status(ap) == 0))
-                return ATA_DEV_NONE;
+        if (class == ATA_DEV_UNKNOWN) {
+                /* If the device failed diagnostic, it's likely to
+                 * have reported incorrect device signature too.
+                 * Assume ATA device if the device seems present but
+                 * device signature is invalid with diagnostic
+                 * failure.
+                 */
+                if (present && (dev->horkage & ATA_HORKAGE_DIAGNOSTIC))
+                        class = ATA_DEV_ATA;
+                else
+                        class = ATA_DEV_NONE;
+        } else if ((class == ATA_DEV_ATA) && (ata_chk_status(ap) == 0))
+                class = ATA_DEV_NONE;
+
         return class;
 }