>From 4ca53a1cda2a25fbca3b955816f5e3b684f08e2e Mon Sep 17 00:00:00 2001
From: Tom Rix <Tom.Rix@windriver.com>
Date: Sat, 6 Jun 2009 09:17:55 -0500
Subject: [PATCH 1/4] OMAP3 I2C Fix the sampling clock.

This problem is seen on Zoom1 and Zoom2 in the startup and
when i2c probe is used

Before :

In:    serial
Out:   serial
Err:   serial
timed out in wait_for_bb: I2C_STAT=1000
timed out in wait_for_bb: I2C_STAT=1000
timed out in wait_for_bb: I2C_STAT=1000
timed out in wait_for_pin: I2C_STAT=1000
I2C read: I/O error
timed out in wait_for_bb: I2C_STAT=1000
timed out in wait_for_bb: I2C_STAT=1000
Die ID #327c00020000000004013ddd05026013
Hit any key to stop autoboot:  0
OMAP3 Zoom1# i2c probe
Valid chip addresses:timed out in wait_for_bb: I2C_STAT=1000
 02 03 04 05 06 07 08 09 0A 0B 0C 0D <snip>

After :

In:    serial
Out:   serial
Err:   serial
Die ID #327c00020000000004013ddd05026013
Hit any key to stop autoboot:  0
OMAP3 Zoom1# i2c probe
Valid chip addresses: 48 49 4A 4B

The addresses are for the twl4030.

The prescalar that converts the function clock to the sampling
clock is hardcoded to 0.  The reference manual recommends 7
if the function clock is 96MHz.

Instead of just changing the hardcoded values, the prescalar
is calculated from the value I2C_IP_CLK.

The i2c #defines are in kHz.  The speed passed into the
i2c init routine is in Hz.  To be consistent, change the
defines to be in Hz.

The timing calculations are based on what is done in the
linux 2.6.30 kernel in drivers/i2c/buses/i2c_omap.c as
apposed to what is done in TRM.

The major variables in the timing caculations are
specified as #defines that can be overriden as required.

The variables and their defaults are

I2C_IP_CLK			SYSTEM_CLOCK_96
I2C_INTERNAL_SAMPLING_CLK	19200000
I2C_SCLL_TRIM			6
I2C_SCLH_TRIM			6

This was runtime verified on Zoom1, Zoom2, Beagle and Overo.
The 400kHz case was verifed on a test Zoom1 configuration.

Signed-off-by: Tom Rix <Tom.Rix@windriver.com>
---
 drivers/i2c/omap24xx_i2c.c       |   34 +++++++++++++++++++-----
 include/asm-arm/arch-omap3/i2c.h |   54 +++++++++++++++++++++++++++++++++-----
 2 files changed, 74 insertions(+), 14 deletions(-)

diff --git a/drivers/i2c/omap24xx_i2c.c b/drivers/i2c/omap24xx_i2c.c
index 6784603..4ab0ed0 100644
--- a/drivers/i2c/omap24xx_i2c.c
+++ b/drivers/i2c/omap24xx_i2c.c
@@ -31,7 +31,29 @@ static void flush_fifo(void);
 
 void i2c_init (int speed, int slaveadd)
 {
-	u16 scl;
+	int psc, iclk, scll, sclh;
+
+	/* Only handle standard and fast speeds */
+	if ((speed != OMAP_I2C_STANDARD) &&
+	    (speed != OMAP_I2C_FAST_MODE)) {
+		printf("Error : I2C unsupported speed %d\n", speed);
+		return;
+	}
+
+	psc = I2C_IP_CLK / I2C_INTERNAL_SAMPLING_CLK;
+	psc -= 1;
+	if (psc < I2C_PSC_MIN) {
+		printf("Error : I2C unsupported prescalar %d\n", psc);
+		return;
+	}
+
+	scll = sclh = I2C_INTERNAL_SAMPLING_CLK / (2 * speed);
+	scll -= I2C_SCLL_TRIM;
+	sclh -= I2C_SCLH_TRIM;
+	if ((scll < 0) || (sclh < 0)) {
+		printf("Error : I2C initializing clock\n");
+		return;
+	}
 
 	writew(0x2, I2C_SYSC); /* for ES2 after soft reset */
 	udelay(1000);
@@ -42,12 +64,10 @@ void i2c_init (int speed, int slaveadd)
 		udelay (50000);
 	}
 
-	/* 12MHz I2C module clock */
-	writew (0, I2C_PSC);
-	speed = speed/1000;		    /* 100 or 400 */
-	scl = ((12000/(speed*2)) - 7);	/* use 7 when PSC = 0 */
-	writew (scl, I2C_SCLL);
-	writew (scl, I2C_SCLH);
+	writew(psc, I2C_PSC);
+	writew(scll, I2C_SCLL);
+	writew(sclh, I2C_SCLH);
+
 	/* own address */
 	writew (slaveadd, I2C_OA);
 	writew (I2C_CON_EN, I2C_CON);
diff --git a/include/asm-arm/arch-omap3/i2c.h b/include/asm-arm/arch-omap3/i2c.h
index 3937f35..b8f3862 100644
--- a/include/asm-arm/arch-omap3/i2c.h
+++ b/include/asm-arm/arch-omap3/i2c.h
@@ -112,16 +112,56 @@
 #define I2C_SCLH_HSSCLH		8
 #define I2C_SCLH_HSSCLH_M	0xFF
 
-#define OMAP_I2C_STANDARD	100
-#define OMAP_I2C_FAST_MODE	400
-#define OMAP_I2C_HIGH_SPEED	3400
+#define OMAP_I2C_STANDARD	100000
+#define OMAP_I2C_FAST_MODE	400000
+#define OMAP_I2C_HIGH_SPEED	3400000
 
-#define SYSTEM_CLOCK_12		12000
-#define SYSTEM_CLOCK_13		13000
-#define SYSTEM_CLOCK_192	19200
-#define SYSTEM_CLOCK_96		96000
+#define SYSTEM_CLOCK_12		12000000
+#define SYSTEM_CLOCK_13		13000000
+#define SYSTEM_CLOCK_192	19200000
+#define SYSTEM_CLOCK_96		96000000
 
+/* Use the reference value of 96MHz if not explicitly set by the board */
+#ifndef I2C_IP_CLK
 #define I2C_IP_CLK		SYSTEM_CLOCK_96
+#endif
+
+/*
+ * The reference minimum clock for high speed is 19.2MHz.
+ * The linux 2.6.30 kernel uses this value.
+ * The reference minimum clock for fast mode is 9.6MHz
+ * The reference minimum clock for standard mode is 4MHz
+ * In TRM, the value of 12MHz is used.
+ */
+#ifndef I2C_INTERNAL_SAMPLING_CLK
+#define I2C_INTERNAL_SAMPLING_CLK	19200000
+#endif
+
+/*
+ * The equation for the low and high time is
+ * tlow = scll + scll_trim = (sampling clock * tlow_duty) / speed
+ * thigh = sclh + sclh_trim = (sampling clock * (1 - tlow_duty)) / speed
+ *
+ * If the duty cycle is 50%
+ *
+ * tlow = scll + scll_trim = sampling clock / (2 * speed)
+ * thigh = sclh + sclh_trim = sampling clock / (2 * speed)
+ *
+ * In TRM
+ * scll_trim = 7
+ * sclh_trim = 5
+ *
+ * The linux 2.6.30 kernel uses
+ * scll_trim = 6
+ * sclh_trim = 6
+ */
+#ifndef I2C_SCLL_TRIM
+#define I2C_SCLL_TRIM		6
+#endif
+#ifndef I2C_SCLH_TRIM
+#define I2C_SCLH_TRIM		6
+#endif
+
 #define I2C_PSC_MAX		0x0f
 #define I2C_PSC_MIN		0x00
 
-- 
1.6.0.4

