[PATCH v4] i2c: rk3x: adjust the LOW divison based on characteristics of SCL

[Doug Anderson]

Max,

On Sun, Oct 12, 2014 at 5:10 AM, Max Schwarz <max.schwarz at online.de> wrote:
>> +     /* Adjust to avoid overflow */
>> +     i2c_rate_khz = DIV_ROUND_UP(i2c_rate, 1000);
>> +     scl_rate_khz = DIV_ROUND_UP(scl_rate, 1000);
>
> I'm not really comfortable with using DIV_ROUND_UP on the last line, since
> this may violate the user's set SCL rate. Rounding up 1.1kHz SCL rate to 2kHz
> is not good.

Ah, good point.  So we round up for i2c_rate and down for scl_rate:

  i2c_rate_khz = DIV_ROUND_UP(i2c_rate, 1000);
  scl_rate_khz = scl_rate / 1000;


> I suggest using scl_rate / 1000 and placing a
>
> if(WARN_ON(scl_rate < 1000))
>   scl_rate = 1000;
>
> somewhere to prevent scl_rate_khz from becoming 0.

Ah, makes sense.  Yeah, that should be at the top.