[U-Boot-Users] [PATCH] Add support for setting the I2C bus speed in fsl_i2c.c

Timur Tabi
2008-03-14T22:45:29Z

Add support to the Freescale I2C driver (fsl_i2c.c) for setting and querying
the I2C bus speed. Current 8[356]xx boards define the CFG_I2C_SPEED macro,
but fsl_i2c.c ignores it and uses conservative value when programming the
I2C bus speed.

Signed-off-by: Timur Tabi <timur@freescale.com>
---

This patch is for U-Boot 1.3.3. It affects 83xx, 85xx, and 86xx.

drivers/i2c/fsl_i2c.c | 114 +++++++++++++++++++++++++++++++++++++++++++++----
1 files changed, 105 insertions(+), 9 deletions(-)

diff --git a/drivers/i2c/fsl_i2c.c b/drivers/i2c/fsl_i2c.c
index 22485ea..dde0571 100644
--- a/drivers/i2c/fsl_i2c.c
+++ b/drivers/i2c/fsl_i2c.c
@@ -32,6 +32,8 @@
#define I2C_READ_BIT 1
#define I2C_WRITE_BIT 0

+DECLARE_GLOBAL_DATA_PTR;
+
/* Initialize the bus pointer to whatever one the SPD EEPROM is on.
* Default is bus 0. This is necessary because the DDR initialization
* runs from ROM, and we can't switch buses because we can't modify
@@ -43,24 +45,111 @@ static unsigned int i2c_bus_num __attribute__ ((section ("data"))) = CFG_SPD_BUS
static unsigned int i2c_bus_num __attribute__ ((section ("data"))) = 0;
#endif

-static volatile struct fsl_i2c *i2c_dev[2] = {
+static unsigned int i2c_bus_speed[2] = {CFG_I2C_SPEED, CFG_I2C_SPEED};
+
+static const struct fsl_i2c *i2c_dev[2] = {
(struct fsl_i2c *) (CFG_IMMR + CFG_I2C_OFFSET),
#ifdef CFG_I2C2_OFFSET
(struct fsl_i2c *) (CFG_IMMR + CFG_I2C2_OFFSET)
#endif
};

+/* I2C speed map for a DFSR value of 1 */
+
+/*
+ * Map I2C frequency dividers to FDR and DFSR values
+ *
+ * This structure is used to define the elements of a table that maps I2C
+ * frequency divider (I2C clock rate divided by I2C bus speed) to a value to be
+ * programmed into the Frequency Divider Ratio (FDR) and Digital Filter
+ * Sampling Rate (DFSR) registers.
+ *
+ * The actual table should be defined in the board file, and it must be called
+ * fsl_i2c_speed_map[].
+ *
+ * The last entry of the table must have a value of {-1, X}, where X is same
+ * FDR/DFSR values as the second-to-last entry. This guarantees that any
+ * search through the array will always find a match.
+ *
+ * The values of the divider must be in increasing numerical order, i.e.
+ * fsl_i2c_speed_map[x+1].divider > fsl_i2c_speed_map[x].divider.
+ *
+ * For this table, the values are based on a value of 1 for the DFSR
+ * register. See the application note AN2919 "Determining the I2C Frequency
+ * Divider Ratio for SCL"
+ */
+static const struct {
+ unsigned short divider;
+ u8 dfsr;
+ u8 fdr;
+} fsl_i2c_speed_map[] = {
+ {160, 1, 32}, {192, 1, 33}, {224, 1, 34}, {256, 1, 35},
+ {288, 1, 0}, {320, 1, 1}, {352, 6, 1}, {384, 1, 2}, {416, 6, 2},
+ {448, 1, 38}, {480, 1, 3}, {512, 1, 39}, {544, 11, 3}, {576, 1, 4},
+ {608, 22, 3}, {640, 1, 5}, {672, 32, 3}, {704, 11, 5}, {736, 43, 3},
+ {768, 1, 6}, {800, 54, 3}, {832, 11, 6}, {896, 1, 42}, {960, 1, 7},
+ {1024, 1, 43}, {1088, 22, 7}, {1152, 1, 8}, {1216, 43, 7}, {1280, 1, 9},
+ {1408, 22, 9}, {1536, 1, 10}, {1664, 22, 10}, {1792, 1, 46},
+ {1920, 1, 11}, {2048, 1, 47}, {2176, 43, 11}, {2304, 1, 12},
+ {2560, 1, 13}, {2816, 43, 13}, {3072, 1, 14}, {3328, 43, 14},
+ {3584, 1, 50}, {3840, 1, 15}, {4096, 1, 51}, {4608, 1, 16},
+ {5120, 1, 17}, {6144, 1, 18}, {7168, 1, 54}, {7680, 1, 19},
+ {8192, 1, 55}, {9216, 1, 20}, {10240, 1, 21}, {12288, 1, 22},
+ {14336, 1, 58}, {15360, 1, 23}, {16384, 1, 59}, {18432, 1, 24},
+ {20480, 1, 25}, {24576, 1, 26}, {28672, 1, 62}, {30720, 1, 27},
+ {32768, 1, 63}, {36864, 1, 28}, {40960, 1, 29}, {49152, 1, 30},
+ {61440, 1, 31}, {-1, 1, 31}
+};
+
+/**
+ * Set the I2C bus speed for a given I2C device
+ *
+ * @param dev: the I2C device
+ * @i2c_clk: I2C bus clock frequency
+ * @speed: the desired speed of the bus
+ *
+ * The I2C device must be stopped before calling this function.
+ *
+ * The return value is the actual bus speed that is set.
+ */
+static unsigned int set_i2c_bus_speed(const struct fsl_i2c *dev,
+ unsigned int i2c_clk, unsigned int speed)
+{
+ unsigned short divider = min(i2c_clk / speed, (unsigned short) -1);
+ unsigned int i;
+ u8 fdr, dfsr;
+
+ /*
+ * We want to choose an FDR/DFSR that generates an I2C bus speed that
+ * is equal to or lower than the requested speed. That means that we
+ * want the first divider that is equal to or greater than the
+ * calculated divider.
+ */
+
+ for (i = 0; i < ARRAY_SIZE(fsl_i2c_speed_map); i++)
+ if (fsl_i2c_speed_map[i].divider >= divider) {
+ dfsr = fsl_i2c_speed_map[i].dfsr;
+ fdr = fsl_i2c_speed_map[i].fdr;
+ speed = i2c_clk / fsl_i2c_speed_map[i].divider;
+ break;
+ }
+
+ writeb(fdr, &dev->fdr); /* set bus speed */
+ writeb(dfsr, &dev->dfsrr); /* set default filter */
+
+ return speed;
+}
+
void
i2c_init(int speed, int slaveadd)
{
- volatile struct fsl_i2c *dev;
+ struct fsl_i2c *dev;

dev = (struct fsl_i2c *) (CFG_IMMR + CFG_I2C_OFFSET);

writeb(0, &dev->cr); /* stop I2C controller */
udelay(5); /* let it shutdown in peace */
- writeb(0x3F, &dev->fdr); /* set bus speed */
- writeb(0x3F, &dev->dfsrr); /* set default filter */
+ i2c_bus_speed[0] = set_i2c_bus_speed(dev, gd->i2c1_clk, speed);
writeb(slaveadd << 1, &dev->adr); /* write slave address */
writeb(0x0, &dev->sr); /* clear status register */
writeb(I2C_CR_MEN, &dev->cr); /* start I2C controller */
@@ -70,12 +159,11 @@ i2c_init(int speed, int slaveadd)

writeb(0, &dev->cr); /* stop I2C controller */
udelay(5); /* let it shutdown in peace */
- writeb(0x3F, &dev->fdr); /* set bus speed */
- writeb(0x3F, &dev->dfsrr); /* set default filter */
+ i2c_bus_speed[1] = set_i2c_bus_speed(dev, gd->i2c2_clk, speed);
writeb(slaveadd << 1, &dev->adr); /* write slave address */
writeb(0x0, &dev->sr); /* clear status register */
writeb(I2C_CR_MEN, &dev->cr); /* start I2C controller */
-#endif /* CFG_I2C2_OFFSET */
+#endif
}

static __inline__ int
@@ -279,7 +367,14 @@ int i2c_set_bus_num(unsigned int bus)

int i2c_set_bus_speed(unsigned int speed)
{
- return -1;
+ unsigned int i2c_clk = (i2c_bus_num == 1) ? gd->i2c2_clk : gd->i2c1_clk;
+
+ writeb(0, &i2c_dev[i2c_bus_num]->cr); /* stop controller */
+ i2c_bus_speed[i2c_bus_num] =
+ set_i2c_bus_speed(i2c_dev[i2c_bus_num], i2c_clk, speed);
+ writeb(I2C_CR_MEN, &i2c_dev[i2c_bus_num]->cr); /* start controller */
+
+ return 0;
}

unsigned int i2c_get_bus_num(void)
@@ -289,7 +384,8 @@ unsigned int i2c_get_bus_num(void)

unsigned int i2c_get_bus_speed(void)
{
- return 0;
+ return i2c_bus_speed[i2c_bus_num];
}
+
#endif /* CONFIG_HARD_I2C */
#endif /* CONFIG_FSL_I2C */
--
1.5.4