Re: [PATCH 2/5] I2C: DaVinci: clock between 7-12 Mhz

[Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>]

Hi Troy,

On Thu, 20 Mar 2008 20:06:07 -0700, Troy Kisky wrote:
> Ensure psc value gives a clock between 7-12 Mhz

Correct spelling is MHz.

> Signed-off-by: Troy Kisky <troy.kisky-Q5RJGjKts06CY9SHAMCTRUEOCMrvLtNR@public.gmane.org>
> Signed-off-by: Kevin Hilman <khilman-Igf4POYTYCDQT0dZR+AlfA@public.gmane.org>
> ---
>  drivers/i2c/busses/i2c-davinci.c |   19 ++++++++++++-------
>  1 files changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c
> index fde2634..82d4b7f 100755
> --- 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 7mHz clock, but max of 12mHz */

Correct spelling is MHz.

> +	psc = (input_clock/7000000)-1;

The usual coding style is to leave spaces around all operators. Same
problem below.

Note: if input_clock < 7000000, you're in trouble.

> +	if ((input_clock/(psc+1)) > 12000000)
> +		psc++;

The only case where this will happen as far as I can see is if
input_clock is between 12 and 14 MHz. In this case, you'll get a clock
lower than 7 MHz (worst case is 6 MHz). Is this OK?

> +	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);

As I already wrote in my previous review: please come up with
consistent spacing in this debugging message. Having no space around
the first "=", but two spaced before and one after the second "=",
doesn't look good.

>  	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",

For consistency, you should add a comma after kHz.

> +		pdata->bus_freq, pdata->bus_delay);
>  
>  	/* Take the I2C module out of reset: */
>  	w = davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG);
> @@ -338,12 +345,10 @@ i2c_davinci_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
>  
>  	for (i = 0; i < num; i++) {
>  		ret = i2c_davinci_xfer_msg(adap, &msgs[i], (i == (num - 1)));
> +		dev_dbg(dev->dev, "%s ret: %d\n", __func__, ret);
>  		if (ret < 0)
>  			return ret;
>  	}
> -
> -	dev_dbg(dev->dev, "%s:%d ret: %d\n", __FUNCTION__, __LINE__, ret);
> -
>  	return num;
>  }
>  

Not sure how this last chunk is supposed to belong to this patch?

-- 
Jean Delvare

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