[U-Boot] [PATCH 2/2] fsl_i2c: Add CONFIG_FSL_I2C_CUSTOM_DFSR

[Wolfgang Grandegger]

Joakim Tjernlund wrote:
>> Timur Tabi <timur at freescale.com> wrote on 15/09/2009 21:04:47:
>>> Joakim Tjernlund wrote:
>>>
>>>> No, the impact on speed from DFSR is pretty small so it will
>>>> be close enough.
>>> How small?
>> From the app note:
>>   divisor = B * (A + ((3*C)/B)*2);
>>
>> C is dfsr and 10 <= A <= 30, 16 <= B <= 2048
>> Considering the actual speed may be way lower the requested speed
>> I think this is small enough.
> 
> Once we have the new procedure in place, we can calculate the exact
> divisor so the need for extra CONFIG_ options goes away.

As Timur pointed out, a new table/algorithm would require some real
testing and also some feedback from the users. Who knows if "your"
values do not make trouble. Therefore I vote for using custom
settings for maximum flexibility:

  CONFIG_FSL_I2C_CUSTOM_FDR
  CONFIG_FSL_I2C_CUSTOM_DFSR

  or

  CONFIG_FSL_I2C_CUSTOM_DFSR_FDR

Wolfgang.