drivers: i2c: mxc: Add early init

Add early i2c init function with conservative divider when the exact
clock rate is not available.

Signed-off-by: Yuan Yao <yao.yuan@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>

drivers/i2c/i2c_core.c

@@ -233,6 +233,11 @@ __weak void i2c_init_board(void)
 {
 }
 
+/* implement possible for i2c specific early i2c init */
+__weak void i2c_early_init_f(void)
+{
+}
+
 /*
  * i2c_init_all():
  *

drivers/i2c/mxc_i2c.c

@@ -32,6 +32,14 @@ DECLARE_GLOBAL_DATA_PTR;
 
 #define IMX_I2C_REGSHIFT	2
 #define VF610_I2C_REGSHIFT	0
+
+#define I2C_EARLY_INIT_INDEX		0
+#ifdef CONFIG_SYS_I2C_IFDR_DIV
+#define I2C_IFDR_DIV_CONSERVATIVE	CONFIG_SYS_I2C_IFDR_DIV
+#else
+#define I2C_IFDR_DIV_CONSERVATIVE	0x7e
+#endif
+
 /* Register index */
 #define IADR	0
 #define IFDR	1
@@ -659,6 +667,25 @@ void bus_i2c_init(int index, int speed, int unused,
 	bus_i2c_set_bus_speed(&mxc_i2c_buses[index], speed);
 }
 
+/*
+ * Early init I2C for prepare read the clk through I2C.
+ */
+void i2c_early_init_f(void)
+{
+	ulong base = mxc_i2c_buses[I2C_EARLY_INIT_INDEX].base;
+	bool quirk = mxc_i2c_buses[I2C_EARLY_INIT_INDEX].driver_data
+					& I2C_QUIRK_FLAG ? true : false;
+	int reg_shift = quirk ? VF610_I2C_REGSHIFT : IMX_I2C_REGSHIFT;
+
+	/* Set I2C divider value */
+	writeb(I2C_IFDR_DIV_CONSERVATIVE, base + (IFDR << reg_shift));
+	/* Reset module */
+	writeb(I2CR_IDIS, base + (I2CR << reg_shift));
+	writeb(0, base + (I2SR << reg_shift));
+	/* Enable I2C */
+	writeb(I2CR_IEN, base + (I2CR << reg_shift));
+}
+
 /*
  * Init I2C Bus
  */

include/i2c.h

@@ -701,6 +701,9 @@ extern struct i2c_bus_hose	i2c_bus[];
  * Initialization, must be called once on start up, may be called
  * repeatedly to change the speed and slave addresses.
  */
+#ifdef CONFIG_SYS_I2C_EARLY_INIT
+void i2c_early_init_f(void);
+#endif
 void i2c_init(int speed, int slaveaddr);
 void i2c_init_board(void);
 #ifdef CONFIG_SYS_I2C_BOARD_LATE_INIT