Re: 2.6.32.2 SATA link detect failed, 2.6.32.1 works fine

[Tejun Heo <tj@kernel.org>]

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On 12/25/2009 10:35 AM, fengxiangjun wrote:
>> Hmmm... SControl DET hasn't been cleared.  Does the attached patch
>> make any difference?
> 
> After 5 successful reboots, I think the patch does fix the problem.
> Thank you very much.

Can you please try this one?  Retry logic was wrong in the original
patch.  With this patch, you should see one "link resume succeeded
after %d retries" message when the original kernel would have failed
probe.  Can you please test this patch and post boot log with such
message?

Thanks.

-- 
tejun

[-- Attachment #2: retry-link-resume.patch --]
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diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 22ff51b..40940dd 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -3790,21 +3790,40 @@ 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;
+	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,