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SubjectRe: [PATCH v6 8/9] dt-bindings: mux-adg792a: document devicetree bindings for ADG792A/G mux
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On 02/01/17 16:01, Peter Rosin wrote:
> On 2017-01-01 12:00, Jonathan Cameron wrote:
>> On 30/11/16 08:17, Peter Rosin wrote:
>>> Analog Devices ADG792A/G is a triple 4:1 mux.
>>>
>>> Signed-off-by: Peter Rosin <peda@axentia.se>
>> Few comments inline. Worth adding anything about the gpio (output pins) to
>> the binding at this stage as well? Would certainly be nice to support
>> them.
>
> I'll add optional properties "gpio-controller;" and "#gpio-cells = <2>;"
> with the usual interpretation in v7 (but no implementation...) Is that
> enough?
>
>> Jonathan
>>> ---
>>> .../devicetree/bindings/misc/mux-adg792a.txt | 64 ++++++++++++++++++++++
>>> 1 file changed, 64 insertions(+)
>>> create mode 100644 Documentation/devicetree/bindings/misc/mux-adg792a.txt
>>>
>>> diff --git a/Documentation/devicetree/bindings/misc/mux-adg792a.txt b/Documentation/devicetree/bindings/misc/mux-adg792a.txt
>>> new file mode 100644
>>> index 000000000000..4677f9ab1c55
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/misc/mux-adg792a.txt
>>> @@ -0,0 +1,64 @@
>>> +Bindings for Analog Devices ADG792A/G Triple 4:1 Multiplexers
>>> +
>>> +Required properties:
>>> +- compatible : "adi,adg792a" or "adi,adg792g"
>>> +- #mux-control-cells : <0> if parallel, or <1> if not.
>>> +* Standard mux-controller bindings as decribed in mux-controller.txt
>>> +
>>> +Optional properties:
>>> +- adi,parallel : if present, the three muxes are bound together with a single
>>> + mux controller, controlling all three muxes in parallel.
>>> +- adi,idle-state : if present, array of states the three mux controllers will
>>> + have when idle (or, if parallel, a single idle-state).
>> Hmm. These are actually a policy decision. As only one policy will make
>> sense for a given set of hardware probably fine to have it in here I guess.
>> Might be worth adding a note to say this though.
>
> I don't really know what you want me to add, do you have a suggestion for the
> wording?
>
>>> +
>>> +Mux controller states 0 through 3 correspond to signals A through D in the
>>> +datasheet. Mux controller states 4 and 5 are only available as possible idle
>>> +states. State 4 represents that nothing is connected, and state 5 represents
>>> +that the mux controller keeps the mux in its previously selected state during
>>> +the idle period. State 5 is the default idle state.
>> I'm never a great fan of magic numbers. Can we represent this more cleanly by
>> breaking it into multiple properties?
>> Optional:
>> adi,idle-switch-to-channel : switch to this channel when idle.
>> adi,idle-high-impedance : <boolean> the nothing connected state?
>>
>> If neither present leaves it in previous state?
>
> It's not that easy. adi,idle-state is an array when there are three single
> pole quadruple throw muxes, so there really needs to be a number for each
> desired idle-behavior. Unless you have a better idea for how to describe
> that?
The above with arrays for each of the two parameters?
Though then you need a priority documented - I'd say high impedance overrides
the channel selection if both are present.
>
> Cheers,
> peda
>
>>> +
>>> +Example:
>>> +
>>> + /* three independent mux controllers (of which one is used) */
>>> + &i2c0 {
>>> + mux: adg792a@50 {
>>> + compatible = "adi,adg792a";
>>> + reg = <0x50>;
>>> + #mux-control-cells = <1>;
>>> + };
>>> + };
>>> +
>>> + adc-mux {
>>> + compatible = "iio-mux";
>>> + io-channels = <&adc 0>;
>>> + io-channel-names = "parent";
>>> +
>>> + mux-controls = <&mux 1>;
>>> +
>>> + channels = "sync-1", "", "out";
>>> + };
>>> +
>>> +
>>> + /*
>>> + * Three parallel muxes with one mux controller, useful e.g. if
>>> + * the adc is differential, thus needing two signals to be muxed
>>> + * simultaneously for correct operation.
>>> + */
>>> + &i2c0 {
>>> + pmux: adg792a@50 {
>>> + compatible = "adi,adg792a";
>>> + reg = <0x50>;
>>> + #mux-control-cells = <0>;
>>> + adi,parallel;
>>> + };
>>> + };
>>> +
>>> + diff-adc-mux {
>>> + compatible = "iio-mux";
>>> + io-channels = <&adc 0>;
>>> + io-channel-names = "parent";
>>> +
>>> + mux-controls = <&pmux>;
>>> +
>>> + channels = "sync-1", "", "out";
>>> + };
>>>
>>
>

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