[U-Boot] fsl_i2c: increase I2C timeout values and make them configurable

[Joakim Tjernlund]

>
> Timur Tabi wrote:
> > Wolfgang Grandegger wrote:
> >
> >> I did not follow the thread yet, sorry. I implemented AN2819 for Linux
> >> (see http://lxr.linux.no/#linux+v2.6.31/drivers/i2c/busses/i2c-mpc.c)
> >> some time ago using Timur's table approach. But there is no difference
> >> between the table and the algorithm to calculate the value. The table is
> >> actually derived from the same algorithm.
> >
> > The problem with the table is that it does not allow for flexibility in
> choosing dfsr.  When I implemented the table code, I did not think that this
> was a problem, but apparently it is.
>
> What would be the criteria to choose dfsr, especially for a defined bus
> frequency.

It is in the new AN2919:
   • Condition 1: C ≤ 50 ÷ T.
This means that the product of the decimal equivalent of the value in the DFSR and the source clock period
must not exceed 50 ns. Thus, given a specific source clock period, the value in the DFSR must not be so
high that it violates this condition.

I just compared the u-boot fsl-i2c.c driver with the kernel one and I think u-boot is buggy.
One cannot disable I2C directly after a read/write of last byte. There has to be some time
for the controller to generate STOP.
There are other differences too that I am not sure if they are significant or not.

          Jocke