linux-kernel - [PATCH 1/2] i2c-mv64xxx: Fix timing issue on Armada XP (errata FE-8471889)

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Date:	Fri,  7 Jun 2013 17:48:59 +0200
From:	Gregory CLEMENT <gregory.clement@...e-electrons.com>
To:	Wolfram Sang <wsa@...-dreams.de>, linux-i2c@...r.kernel.org
Cc:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	linux-arm-kernel@...ts.infradead.org,
	Jason Cooper <jason@...edaemon.net>,
	Andrew Lunn <andrew@...n.ch>,
	Gregory CLEMENT <gregory.clement@...e-electrons.com>,
	Nicolas Pitre <nico@...xnic.net>,
	Lior Amsalem <alior@...vell.com>,
	Maen Suleiman <maen@...vell.com>,
	Tawfik Bayouk <tawfik@...vell.com>,
	Shadi Ammouri <shadi@...vell.com>,
	Eran Ben-Avi <benavi@...vell.com>,
	Yehuda Yitschak <yehuday@...vell.com>,
	Nadav Haklai <nadavh@...vell.com>,
	Ike Pan <ike.pan@...onical.com>,
	Chris Van Hoof <vanhoof@...onical.com>,
	Dan Frazier <dann.frazier@...onical.com>,
	Leif Lindholm <leif.lindholm@....com>,
	Jon Masters <jcm@...hat.com>,
	David Marlin <dmarlin@...hat.com>,
	linux-kernel@...r.kernel.org, Zbigniew Bodek <zbb@...ihalf.com>
Subject: [PATCH 1/2] i2c-mv64xxx: Fix timing issue on Armada XP (errata FE-8471889)

From: Zbigniew Bodek <zbb@...ihalf.com>

All the Armada XP (mv78230, mv78260 and mv78460) have a silicon issue
in the I2C controller which violate the i2c repeated start
timing. The I2C standard requires a minimum of 4.7us for the repeated
start condition whereas the I2C controller of the Armada XP this time
is 2.9us.

So this patch adds a 5us delay for the start case only if the
mv64xxx_i2c_errata_delay flag is set.

[gregory.clement@...e-electrons.com: Merge the incoming commits into
this single one]
[gregory.clement@...e-electrons.com: Reword the commit log]

Signed-off-by: Gregory CLEMENT <gregory.clement@...e-electrons.com>
Signed-off-by: Zbigniew Bodek <zbb@...ihalf.com>
---
 drivers/i2c/busses/i2c-mv64xxx.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/i2c/busses/i2c-mv64xxx.c b/drivers/i2c/busses/i2c-mv64xxx.c
index 1a3abd6..60cac9f 100644
--- a/drivers/i2c/busses/i2c-mv64xxx.c
+++ b/drivers/i2c/busses/i2c-mv64xxx.c
@@ -23,6 +23,7 @@
 #include <linux/of_i2c.h>
 #include <linux/clk.h>
 #include <linux/err.h>
+#include <linux/delay.h>
 
 /* Register defines */
 #define	MV64XXX_I2C_REG_SLAVE_ADDR			0x00
@@ -59,6 +60,12 @@
 #define	MV64XXX_I2C_STATUS_MAST_RD_ADDR_2_NO_ACK	0xe8
 #define	MV64XXX_I2C_STATUS_NO_STATUS			0xf8
 
+/*
+ * 5us delay in order to avoid repeated start
+ * timing violation on Armada XP SoC.
+ */
+static int mv64xxx_i2c_errata_delay;
+
 /* Driver states */
 enum {
 	MV64XXX_I2C_STATE_INVALID,
@@ -252,6 +259,9 @@ mv64xxx_i2c_do_action(struct mv64xxx_i2c_data *drv_data)
 		writel(drv_data->cntl_bits,
 			drv_data->reg_base + MV64XXX_I2C_REG_CONTROL);
 		drv_data->block = 0;
+		if (mv64xxx_i2c_errata_delay)
+			udelay(5);
+
 		wake_up(&drv_data->waitq);
 		break;
 
@@ -300,6 +310,9 @@ mv64xxx_i2c_do_action(struct mv64xxx_i2c_data *drv_data)
 		writel(drv_data->cntl_bits | MV64XXX_I2C_REG_CONTROL_STOP,
 			drv_data->reg_base + MV64XXX_I2C_REG_CONTROL);
 		drv_data->block = 0;
+		if (mv64xxx_i2c_errata_delay)
+			udelay(5);
+
 		wake_up(&drv_data->waitq);
 		break;
 
@@ -592,6 +605,10 @@ mv64xxx_of_config(struct mv64xxx_i2c_data *drv_data,
 	 * So hard code the value to 1 second.
 	 */
 	drv_data->adapter.timeout = HZ;
+
+	if (!mv64xxx_i2c_errata_delay &&
+	    of_machine_is_compatible("marvell,armadaxp"))
+		mv64xxx_i2c_errata_delay = 1;
 out:
 	return rc;
 #endif
-- 
1.8.1.2

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