Merge branch 'u-boot-ti/master' into 'u-boot-arm/master'

[platform/kernel/u-boot.git] / drivers / i2c / mxs_i2c.c

diff --git a/drivers/i2c/mxs_i2c.c b/drivers/i2c/mxs_i2c.c
index 73a6659..b907f7b 100644 (file)
--- a/drivers/i2c/mxs_i2c.c
+++ b/drivers/i2c/mxs_i2c.c
@@ -28,6 +28,7 @@
 
 #include <common.h>
 #include <malloc.h>
+#include <i2c.h>
 #include <asm/errno.h>
 #include <asm/io.h>
 #include <asm/arch/clock.h>
@@ -213,62 +214,39 @@ int i2c_probe(uchar chip)
        return ret;
 }
 
-static struct mxs_i2c_speed_table {
-       uint32_t        speed;
-       uint32_t        timing0;
-       uint32_t        timing1;
-} mxs_i2c_tbl[] = {
-       {
-               100000,
-               (0x0078 << I2C_TIMING0_HIGH_COUNT_OFFSET) |
-               (0x0030 << I2C_TIMING0_RCV_COUNT_OFFSET),
-               (0x0080 << I2C_TIMING1_LOW_COUNT_OFFSET) |
-               (0x0030 << I2C_TIMING1_XMIT_COUNT_OFFSET)
-       },
-       {
-               400000,
-               (0x000f << I2C_TIMING0_HIGH_COUNT_OFFSET) |
-               (0x0007 << I2C_TIMING0_RCV_COUNT_OFFSET),
-               (0x001f << I2C_TIMING1_LOW_COUNT_OFFSET) |
-               (0x000f << I2C_TIMING1_XMIT_COUNT_OFFSET),
-       }
-};
-
-static struct mxs_i2c_speed_table *mxs_i2c_speed_to_cfg(uint32_t speed)
-{
-       int i;
-       for (i = 0; i < ARRAY_SIZE(mxs_i2c_tbl); i++)
-               if (mxs_i2c_tbl[i].speed == speed)
-                       return &mxs_i2c_tbl[i];
-       return NULL;
-}
-
-static uint32_t mxs_i2c_cfg_to_speed(uint32_t timing0, uint32_t timing1)
-{
-       int i;
-       for (i = 0; i < ARRAY_SIZE(mxs_i2c_tbl); i++) {
-               if (mxs_i2c_tbl[i].timing0 != timing0)
-                       continue;
-               if (mxs_i2c_tbl[i].timing1 != timing1)
-                       continue;
-               return mxs_i2c_tbl[i].speed;
-       }
-
-       return 0;
-}
-
 int i2c_set_bus_speed(unsigned int speed)
 {
        struct mxs_i2c_regs *i2c_regs = (struct mxs_i2c_regs *)MXS_I2C0_BASE;
-       struct mxs_i2c_speed_table *spd = mxs_i2c_speed_to_cfg(speed);
+       /*
+        * The timing derivation algorithm. There is no documentation for this
+        * algorithm available, it was derived by using the scope and fiddling
+        * with constants until the result observed on the scope was good enough
+        * for 20kHz, 50kHz, 100kHz, 200kHz, 300kHz and 400kHz. It should be
+        * possible to assume the algorithm works for other frequencies as well.
+        *
+        * Note it was necessary to cap the frequency on both ends as it's not
+        * possible to configure completely arbitrary frequency for the I2C bus
+        * clock.
+        */
+       uint32_t clk = mxc_get_clock(MXC_XTAL_CLK);
+       uint32_t base = ((clk / speed) - 38) / 2;
+       uint16_t high_count = base + 3;
+       uint16_t low_count = base - 3;
+       uint16_t rcv_count = (high_count * 3) / 4;
+       uint16_t xmit_count = low_count / 4;
+
+       if (speed > 540000) {
+               printf("MXS I2C: Speed too high (%d Hz)\n", speed);
+               return -EINVAL;
+       }
 
-       if (!spd) {
-               printf("MXS I2C: Invalid speed selected (%d Hz)\n", speed);
+       if (speed < 12000) {
+               printf("MXS I2C: Speed too low (%d Hz)\n", speed);
                return -EINVAL;
        }
 
-       writel(spd->timing0, &i2c_regs->hw_i2c_timing0);
-       writel(spd->timing1, &i2c_regs->hw_i2c_timing1);
+       writel((high_count << 16) | rcv_count, &i2c_regs->hw_i2c_timing0);
+       writel((low_count << 16) | xmit_count, &i2c_regs->hw_i2c_timing1);
 
        writel((0x0030 << I2C_TIMING2_BUS_FREE_OFFSET) |
                (0x0030 << I2C_TIMING2_LEADIN_COUNT_OFFSET),
@@ -280,12 +258,15 @@ int i2c_set_bus_speed(unsigned int speed)
 unsigned int i2c_get_bus_speed(void)
 {
        struct mxs_i2c_regs *i2c_regs = (struct mxs_i2c_regs *)MXS_I2C0_BASE;
-       uint32_t timing0, timing1;
+       uint32_t clk = mxc_get_clock(MXC_XTAL_CLK);
+       uint32_t timing0;
 
        timing0 = readl(&i2c_regs->hw_i2c_timing0);
-       timing1 = readl(&i2c_regs->hw_i2c_timing1);
-
-       return mxs_i2c_cfg_to_speed(timing0, timing1);
+       /*
+        * This is a reverse version of the algorithm presented in
+        * i2c_set_bus_speed(). Please refer there for details.
+        */
+       return clk / ((((timing0 >> 16) - 3) * 2) + 38);
 }
 
 void i2c_init(int speed, int slaveadd)