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

[Joakim Tjernlund]

Wolfgang Grandegger <wg at grandegger.com> wrote on 16/09/2009 13:45:03:
>
> 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?

mpc8321, I2C bus is between 34KHz and 100KHz, CSB is 133.332 MHz