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

[Wolfgang Grandegger]

Joakim Tjernlund wrote:
> Wolfgang Grandegger <wg at denx.de> wrote on 16/09/2009 12:22:05:
>> 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
> 
> Oh well, since you both wanted it I added it.
> Sent 3 patches, the last patch impl. the latest AN2819 spec.
> 
> Would you mind test it a little?

OK, I will do some tests later this week. What CPU do you use and at
what I2C bus frequency do you test?

Wolfgang.