libata: retry link resume if necessary

Interestingly, when SIDPR is used in ata_piix, writes to DET in
SControl sometimes get ignored leading to detection failure.  Update
sata_link_resume() such that it reads back SControl after clearing DET
and retry if it's not clear.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: fengxiangjun <fengxiangjun@neusoft.com>
Reported-by: Jim Faulkner <jfaulkne@ccs.neu.edu>
Cc: stable@kernel.org
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/libata.h b/include/linux/libata.h
index 6a9c4ddd3d9..73112250862 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -354,6 +354,9 @@ enum {
         /* max tries if error condition is still set after ->error_handler */
         ATA_EH_MAX_TRIES        = 5,
 
+        /* sometimes resuming a link requires several retries */
+        ATA_LINK_RESUME_TRIES   = 5,
+
         /* how hard are we gonna try to probe/recover devices */
         ATA_PROBE_MAX_TRIES     = 3,
         ATA_EH_DEV_TRIES        = 3,