linux-kernel - [PATCH v2] ata: increase retry count but shorten duration for Calxeda controller

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Message-Id: <1369923509-3246-1-git-send-email-mark.langsdorf@calxeda.com>
Date:	Thu, 30 May 2013 09:18:29 -0500
From:	Mark Langsdorf <mark.langsdorf@...xeda.com>
To:	timur@...i.org, tj@...nel.org, linux-kernel@...r.kernel.org,
	linux-ide@...r.kernel.org
Cc:	Mark Langsdorf <mark.langsdorf@...xeda.com>
Subject: [PATCH v2] ata: increase retry count but shorten duration for Calxeda controller

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. Shorten the Linux time-out value for this driver to 500 ms and
keep the other timing constants 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.

Signed-off-by: Mark Langsdorf <mark.langsdorf@...xeda.com>
---
Changes from v1
	Add const to the timing variable definition
	Added more detail in why the various numbers were chosen

 drivers/ata/sata_highbank.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/ata/sata_highbank.c b/drivers/ata/sata_highbank.c
index b20aa96..005cb13 100644
--- a/drivers/ata/sata_highbank.c
+++ b/drivers/ata/sata_highbank.c
@@ -199,7 +199,7 @@ static int highbank_initialize_phys(struct device *dev, void __iomem *addr)
 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);
+	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 +207,7 @@ 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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