[U-Boot] [PATCH 1/1] OMAP3 I2C Fix the sampling clock.
Tom Rix
Tom.Rix at windriver.com
Thu Jun 11 21:44:32 CEST 2009
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 and follows the setup
recommend by the reference manual.
To support boards with custom timing setups, the time is done
with a weakly linked function, omap_i2c_timing. If a board
does not override this function with its own, the reference manual
setup is used.
As an example, if Zoom1 needed to override the function it
would add this to Zoom1.c
int omap_i2c_timing (int speed, int *psc, int *scll, int *sclh)
{
*psc = 7;
*scll = 53;
*sclh = 57;
return 0;
}
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.
This was runtime verified on Zoom1, Zoom2, Beagle and Overo.
The 400kHz case was verifed on a test Zoom2 configuration.
Signed-off-by: Tom Rix <Tom.Rix at windriver.com>
---
drivers/i2c/omap24xx_i2c.c | 84 ++++++++++++++++++++++++++++++++++---
include/asm-arm/arch-omap3/i2c.h | 16 ++++----
2 files changed, 85 insertions(+), 15 deletions(-)
diff --git a/drivers/i2c/omap24xx_i2c.c b/drivers/i2c/omap24xx_i2c.c
index 6784603..13e2f4c 100644
--- a/drivers/i2c/omap24xx_i2c.c
+++ b/drivers/i2c/omap24xx_i2c.c
@@ -29,9 +29,81 @@ static void wait_for_bb (void);
static u16 wait_for_pin (void);
static void flush_fifo(void);
+/*
+ * This sets up the the default timing as specified by the omap3xxx reference
+ * manual. If your board has a custom timing, define the function
+ * omap_i2c_timings in the board file.
+ */
+int __omap_i2c_timing(int speed, int *psc, int *scll, int *sclh)
+{
+ int ret = -1;
+ int iclk, _psc, _scll, _sclh;
+
+ /*
+ * Calculate the prescalar to go from from the function clock
+ * to the internal sampling clock, 12MHz.
+ */
+ _psc = I2C_PSC_MAX;
+ while (_psc >= I2C_PSC_MIN) {
+ iclk = I2C_IP_CLK / (_psc + 1);
+ if (12000000 <= iclk)
+ break;
+ _psc--;
+ }
+ if (_psc < I2C_PSC_MIN) {
+ printf("Error : I2C unsupported prescalar %d\n", _psc);
+ return ret;
+ }
+
+ /*
+ * How the low and high time periods are calculated
+ * See the OMAP3xxx Reference Manual for more details
+ *
+ * tlow + thigh = 1 / speed
+ * thigh = tlow, nice square wave..
+ *
+ * tlow = 1 / (2 * speed) = (scll + 7) / iclk;
+ * scll + 7 = iclk / 2 * speed
+ * sclh + 5 = iclk / 2 * speed
+ */
+ _scll = _sclh = iclk / (2 * speed);
+ _scll -= 7;
+ _sclh -= 5;
+ if ((_scll < 0) || (_sclh < 0)) {
+ printf("Error : I2C initializing clock\n");
+ return ret;
+ }
+
+ *psc = _psc;
+ *scll = _scll;
+ *sclh = _sclh;
+
+ ret = 0;
+ return ret;
+}
+
+/*
+ * This function sets the i2c timing. It is weakly linked to use
+ * __omap_i2c_timing. The intent is for boards with custom i2c timing
+ * setups to do them by redefining this function in their board file.
+ */
+int omap_i2c_timing(int speed, int *psc, int *scll, int *sclh) __attribute__((weak, alias("__omap_i2c_timing")));
+
void i2c_init (int speed, int slaveadd)
{
- u16 scl;
+ int psc, 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;
+ }
+
+ if (omap_i2c_timing(speed, &psc, &scll, &sclh)) {
+ printf("Error : I2C failed to set timings\n");
+ return;
+ }
writew(0x2, I2C_SYSC); /* for ES2 after soft reset */
udelay(1000);
@@ -42,12 +114,10 @@ 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..09afca0 100644
--- a/include/asm-arm/arch-omap3/i2c.h
+++ b/include/asm-arm/arch-omap3/i2c.h
@@ -112,14 +112,14 @@
#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 SYSTEM_CLOCK_12 12000
-#define SYSTEM_CLOCK_13 13000
-#define SYSTEM_CLOCK_192 19200
-#define SYSTEM_CLOCK_96 96000
+#define OMAP_I2C_STANDARD 100000
+#define OMAP_I2C_FAST_MODE 400000
+#define OMAP_I2C_HIGH_SPEED 3400000
+
+#define SYSTEM_CLOCK_12 12000000
+#define SYSTEM_CLOCK_13 13000000
+#define SYSTEM_CLOCK_192 19200000
+#define SYSTEM_CLOCK_96 96000000
#define I2C_IP_CLK SYSTEM_CLOCK_96
#define I2C_PSC_MAX 0x0f
--
1.6.0.5
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