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Subject[52/74] libata: retry link resume if necessary
2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Tejun Heo <tj@kernel.org>

commit 5040ab67a2c6d5710ba497dc52a8f7035729d7b0 upstream.

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>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -3790,21 +3790,45 @@ int sata_link_debounce(struct ata_link *link, const unsigned long *params,
int sata_link_resume(struct ata_link *link, const unsigned long *params,
unsigned long deadline)
{
+ int tries = ATA_LINK_RESUME_TRIES;
u32 scontrol, serror;
int rc;

if ((rc = sata_scr_read(link, SCR_CONTROL, &scontrol)))
return rc;

- scontrol = (scontrol & 0x0f0) | 0x300;
+ /*
+ * Writes to SControl sometimes get ignored under certain
+ * controllers (ata_piix SIDPR). Make sure DET actually is
+ * cleared.
+ */
+ do {
+ scontrol = (scontrol & 0x0f0) | 0x300;
+ if ((rc = sata_scr_write(link, SCR_CONTROL, scontrol)))
+ return rc;
+ /*
+ * Some PHYs react badly if SStatus is pounded
+ * immediately after resuming. Delay 200ms before
+ * debouncing.
+ */
+ msleep(200);

- if ((rc = sata_scr_write(link, SCR_CONTROL, scontrol)))
- return rc;
+ /* is SControl restored correctly? */
+ if ((rc = sata_scr_read(link, SCR_CONTROL, &scontrol)))
+ return rc;
+ } while ((scontrol & 0xf0f) != 0x300 && --tries);

- /* Some PHYs react badly if SStatus is pounded immediately
- * after resuming. Delay 200ms before debouncing.
- */
- msleep(200);
+ if ((scontrol & 0xf0f) != 0x300) {
+ ata_link_printk(link, KERN_ERR,
+ "failed to resume link (SControl %X)\n",
+ scontrol);
+ return 0;
+ }
+
+ if (tries < ATA_LINK_RESUME_TRIES)
+ ata_link_printk(link, KERN_WARNING,
+ "link resume succeeded after %d retries\n",
+ ATA_LINK_RESUME_TRIES - tries);

if ((rc = sata_link_debounce(link, params, deadline)))
return rc;
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 6a9c4dd..7311225 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,



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