Re: [PATCH 2/2] i2c: rcar: add FastMode+ support for Gen4

[Wolfram Sang]

> > +               /* FM+ needs lower SMD and no filters */
> > +               priv->smd /= 2;
> > +               cdf = 0;
> 
> Is this documented somewhere in the R-Car Gen4 docs?

Sadly, there are no recommended values for FM+ in the docs. With cdf=6,
I got speeds around 800kHz. After seeing the BSP also uses cdf=0, I got
speeds close to 1MHz. There is a note in Gen3 and later docs for ICCCR2
saying that cdf=0 is recommended for devices with a data hold time less
than 100ns. I don't have the PMIC docs here to verify if that is the
case here.

However, I recalled there are some generic filter bindings for I2C. I
will check if we can make use of them here.

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