RE: [PATCH v2] i2c: riic: remove fixed clock restriction

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Hi Wolfram,

On Friday, October 13, 2017, Wolfram Sang wrote:
> > Technically, to do it right, to calculate the ACTUAL I2C baud rate, you
> > have to take into effect the load resistance and capacitance of the
> > lines in order to factor in the rise and fall times correctly. Of course
> 
> We have those generic bindings upstream:
> 
> - i2c-scl-falling-time-ns
>         Number of nanoseconds the SCL signal takes to fall; t(f) in the
> I2C
>         specification.
> 
> - i2c-scl-internal-delay-ns
>         Number of nanoseconds the IP core additionally needs to setup SCL.
> 
> - i2c-scl-rising-time-ns
>         Number of nanoseconds the SCL signal takes to rise; t(r) in the
> I2C
>         specification.
> 
> - i2c-sda-falling-time-ns
>         Number of nanoseconds the SDA signal takes to fall; t(f) in the
> I2C
>         specification.
> 
> So far, that was all that is needed, however...

So for now, I'm going to take the easy way out and just put in the range
as you suggested.


But, I think later I will revisit this and come up with an algorithm for
calculating the rate/duty at run-time. I want to do that when I have 
more time to verify things with a scope and such.


Thanks,
Chris





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