i2c-davinci: Ensure clock between 7-12 MHz

Ensure psc value gives a clock between 7-12 MHz

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
Signed-off-by: Kevin Hilman <khilman@mvista.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

1 files changed, 11 insertions, 4 deletions

diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c
index 7ecbfc429b19..7fdbca17d4a8 100644
--- a/drivers/i2c/busses/i2c-davinci.c
+++ b/drivers/i2c/busses/i2c-davinci.c
@@ -142,6 +142,7 @@ static int i2c_davinci_init(struct davinci_i2c_dev *dev)
         struct davinci_i2c_platform_data *pdata = dev->dev->platform_data;
         u16 psc;
         u32 clk;
+        u32 d;
         u32 clkh;
         u32 clkl;
         u32 input_clock = clk_get_rate(dev->clk);
@@ -171,23 +172,29 @@ static int i2c_davinci_init(struct davinci_i2c_dev *dev)
          *       if PSC > 1 , d = 5
          */
 
-        psc = 26; /* To get 1MHz clock */
+        /* get minimum of 7 MHz clock, but max of 12 MHz */
+        psc = (input_clock / 7000000) - 1;
+        if ((input_clock / (psc + 1)) > 12000000)
+                psc++;  /* better to run under spec than over */
+        d = (psc >= 2) ? 5 : 7 - psc;
 
-        clk = ((input_clock / (psc + 1)) / (pdata->bus_freq * 1000)) - 10;
-        clkh = (50 * clk) / 100;
+        clk = ((input_clock / (psc + 1)) / (pdata->bus_freq * 1000)) - (d << 1);
+        clkh = clk >> 1;
         clkl = clk - clkh;
 
         davinci_i2c_write_reg(dev, DAVINCI_I2C_PSC_REG, psc);
         davinci_i2c_write_reg(dev, DAVINCI_I2C_CLKH_REG, clkh);
         davinci_i2c_write_reg(dev, DAVINCI_I2C_CLKL_REG, clkl);
 
-        dev_dbg(dev->dev, "CLK  = %d\n", clk);
+        dev_dbg(dev->dev, "input_clock = %d, CLK = %d\n", input_clock, clk);
         dev_dbg(dev->dev, "PSC  = %d\n",
                 davinci_i2c_read_reg(dev, DAVINCI_I2C_PSC_REG));
         dev_dbg(dev->dev, "CLKL = %d\n",
                 davinci_i2c_read_reg(dev, DAVINCI_I2C_CLKL_REG));
         dev_dbg(dev->dev, "CLKH = %d\n",
                 davinci_i2c_read_reg(dev, DAVINCI_I2C_CLKH_REG));
+        dev_dbg(dev->dev, "bus_freq = %dkHz, bus_delay = %d\n",
+                pdata->bus_freq, pdata->bus_delay);
 
         /* Take the I2C module out of reset: */
         w = davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG);