On Mon, 9 May 2022 22:48:26 -0700 Gwendal Grignou <gwendal@xxxxxxxxxxxx> wrote: > On Sun, May 1, 2022 at 10:09 AM Jonathan Cameron <jic23@xxxxxxxxxx> wrote: > > > > On Fri, 29 Apr 2022 15:01:41 -0700 > > Gwendal Grignou <gwendal@xxxxxxxxxxxx> wrote: > > > > > Allow setting the configure the input analog gain. > > > > > > Signed-off-by: Gwendal Grignou <gwendal@xxxxxxxxxxxx> > > > > Hi Gwendal. > > > > So, my immediate thought on this is whether it make sense as a > > dt controlled thing or not. It's the sort of thing hardwaregain > > is for in the userspace ABI. However, I see that's already > > in use for the digital gain. This one also unhelpfully applies > > to all changes whereas the digital gain is pair wise. Hence > > there is basically no way we can map the two controls to a > > single ABI element. > > > > So, how would we expect a board designer to set this value? > > > > If the answer is we basically have no idea but some boards do > > want it set then I'm fine with this basically being a somewhat magic > > value that is in some vague way associated with the antenna setup... > More or less :-). All these parameters are set with the help of > Semtech application engineers. The input analog gain is directly > linked to the antenna design, as it is used by the AFE (Analog Front > End). The hardwaregain (aka digital gain) comes second during the > digital processing. We could have put all the settings in the device > tree, as we don't expect changes once the values are satisfactory to > pass regulatory testings, but the hybrid approach still allows some > tinkering: I've use to get a sense of the data amplitude when > collecting data with /dev/iio:devoceX. Fair enough. Applied, Thanks, Jonathan > > > > Jonathan > > > > > --- > > > New in v5. > > > > > > .../bindings/iio/proximity/semtech,sx9324.yaml | 11 +++++++++++ > > > 1 file changed, 11 insertions(+) > > > > > > diff --git a/Documentation/devicetree/bindings/iio/proximity/semtech,sx9324.yaml b/Documentation/devicetree/bindings/iio/proximity/semtech,sx9324.yaml > > > index 0be87ac05b97a..d265eb5258c84 100644 > > > --- a/Documentation/devicetree/bindings/iio/proximity/semtech,sx9324.yaml > > > +++ b/Documentation/devicetree/bindings/iio/proximity/semtech,sx9324.yaml > > > @@ -143,6 +143,17 @@ properties: > > > description: > > > Pre-charge input resistance in Ohm. > > > > > > + semtech,input-analog-gain: > > > + $ref: /schemas/types.yaml#/definitions/uint32 > > > + minimum: 0 > > > + maximum: 3 > > > + description: | > > > + Defines the input antenna analog gain > > > + 0: x1.247 > > > + 1: x1 (default) > > > + 2: x0.768 > > > + 3: x0.552 > > > + > > > required: > > > - compatible > > > - reg > >
