Hi Marek,
On Wed, Jan 11, 2017 at 1:35 PM, Marek Vasut <marek.vasut@xxxxxxxxx> wrote:
>>> +Required properties for subnodes:
>>> +- compatible: Should be either of:
>>> + "fujitsu,mb88101a"
>>> + - Fujitsu MB88101A compatible mode,
>>> + 12bit sampling, 4 channels
>>
>> For this one, we have to find a better representation in DT.
>> Unlike the other two types, the MB88101A is a 4-channel ADC, and thus only
>> a single instance is supported, providing 4 channels.
>> Hence for MB88101A I suggest to just have a single node "adc", without a
>> unit address or "reg" property.
>
> Hmmmmmm, this doesn't look quite right and it does make the binding
> complicated and the MB88101A into quite the special snow flake. Also,
> what if you have the MB88101A channels 0 and 1 connected only to ie.
> gyroadc channels 2 and 3?
The gyroadc does not have multiple channel inputs, only a single input
pin for serialized data. Supporting multiple channels is done using a
3-bit channel select (CHS) output signal.
In mode 1, the 2 lsb CHS lines are to be connected to the C[01] channel
select pins on the MB88101A.
In other modes, I think you need an external multiplexer to select one of the
8 connected ADCs.
So while you cannot have non-standard channel wirings in mode 1,
you can have a partial (or none at all) multiplexer and less than 8 ADCs,
duplicating data to multiple channels.
> What about something like:
>
> adc2: adc@2 {
> reg = <0>;
> compatible = "fujitsu,mb88101a";
> vref-supply = <&vref_fujitsu_mb88101a>;
> };
>
> adc3: adc@3 {
> reg = <3>;
> renesas,adc-master = <&adc2>;
> };
Hmm, that can be used to describe duplicated channels, too ;-)
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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