On 01/11/2017 02:11 PM, Geert Uytterhoeven wrote:
> 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.
Yep, it's kinda doing SPI behind the scenes.
> 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.
Yes.
> 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.
Right
>> 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 ;-)
So we go with this ? I'm not completely sure about the new
"renesas,adc-master" property, are we OK with it ?
--
Best regards,
Marek Vasut
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