>
> 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
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