linux-kernel - [PATCH 007/145] sata_highbank: increase retry count but shorten duration for Calxeda controller

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Message-Id: <1374101277-7915-8-git-send-email-kamal@canonical.com>
Date:	Wed, 17 Jul 2013 15:45:39 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Mark Langsdorf <mark.langsdorf@...xeda.com>,
	Tejun Heo <tj@...nel.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 007/145] sata_highbank: increase retry count but shorten duration for Calxeda controller

3.8.13.5 -stable review patch.  If anyone has any objections, please let me know.

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

From: Mark Langsdorf <mark.langsdorf@...xeda.com>

commit ddfef5de3d716f77bad32dbbba6b280158dfd721 upstream.

Increase the retry count for the hard reset function to 100 but
shorten the time out period to 500 ms. See the comment for
ahci_highbank_hardreset for the reasons why those vaulues were
chosen.

Signed-off-by: Mark Langsdorf <mark.langsdorf@...xeda.com>
Signed-off-by: Tejun Heo <tj@...nel.org>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/ata/sata_highbank.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/ata/sata_highbank.c b/drivers/ata/sata_highbank.c
index b1a664a..ecaf1ff 100644
--- a/drivers/ata/sata_highbank.c
+++ b/drivers/ata/sata_highbank.c
@@ -196,10 +196,26 @@ static int highbank_initialize_phys(struct device *dev, void __iomem *addr)
 	return 0;
 }
 
+/*
+ * The Calxeda SATA phy intermittently fails to bring up a link with Gen3
+ * Retrying the phy hard reset can work around the issue, but the drive
+ * may fail again. In less than 150 out of 15000 test runs, it took more
+ * than 10 tries for the link to be established (but never more than 35).
+ * Triple the maximum observed retry count to provide plenty of margin for
+ * rare events and to guarantee that the link is established.
+ *
+ * Also, the default 2 second time-out on a failed drive is too long in
+ * this situation. The uboot implementation of the same driver function
+ * uses a much shorter time-out period and never experiences a time out
+ * issue. Reducing the time-out to 500ms improves the responsiveness.
+ * The other timing constants were kept the same as the stock AHCI driver.
+ * This change was also tested 15000 times on 24 drives and none of them
+ * experienced a time out.
+ */
 static int ahci_highbank_hardreset(struct ata_link *link, unsigned int *class,
 				unsigned long deadline)
 {
-	const unsigned long *timing = sata_ehc_deb_timing(&link->eh_context);
+	static const unsigned long timing[] = { 5, 100, 500};
 	struct ata_port *ap = link->ap;
 	struct ahci_port_priv *pp = ap->private_data;
 	u8 *d2h_fis = pp->rx_fis + RX_FIS_D2H_REG;
@@ -207,7 +223,7 @@ static int ahci_highbank_hardreset(struct ata_link *link, unsigned int *class,
 	bool online;
 	u32 sstatus;
 	int rc;
-	int retry = 10;
+	int retry = 100;
 
 	ahci_stop_engine(ap);
 
-- 
1.8.1.2

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