Re: [PATCH v3 2/2] dt-bindings: iio: frequency: add admv1013 doc

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Fri, 5 Nov 2021 08:38:42 +0000
"Miclaus, Antoniu" <Antoniu.Miclaus@analog.com> wrote:

> > -----Original Message-----
> > From: Jonathan Cameron <jic23@kernel.org>
> > Sent: Thursday, November 4, 2021 8:27 PM
> > To: Miclaus, Antoniu <Antoniu.Miclaus@analog.com>
> > Cc: Rob Herring <robh@kernel.org>; linux-iio@vger.kernel.org;
> > devicetree@vger.kernel.org; linux-kernel@vger.kernel.org; Sa, Nuno
> > <Nuno.Sa@analog.com>
> > Subject: Re: [PATCH v3 2/2] dt-bindings: iio: frequency: add admv1013 doc
> > 
> > [External]
> > 
> > On Wed, 3 Nov 2021 14:30:56 +0000
> > "Miclaus, Antoniu" <Antoniu.Miclaus@analog.com> wrote:
> >   
> > > Example:
> > > In the setup that we tested the driver, we had a clock chip that was  
> > hardware-routed only to the positive side of the local oscillator input (LOP
> > pin) from admv1013.  
> > >
> > > Therefore, I think keeping the property in the DT might be useful.  
> > 
> > I think Rob's question was more general than that one property... See below.  
> > >
> > > Regards,
> > > --
> > > Antoniu Miclăuş
> > >  
> > > > -----Original Message-----
> > > > From: Miclaus, Antoniu
> > > > Sent: Wednesday, November 3, 2021 10:09 AM
> > > > To: Rob Herring <robh@kernel.org>
> > > > Cc: jic23@kernel.org; linux-iio@vger.kernel.org;  
> > devicetree@vger.kernel.org;  
> > > > linux-kernel@vger.kernel.org; Sa, Nuno <Nuno.Sa@analog.com>
> > > > Subject: RE: [PATCH v3 2/2] dt-bindings: iio: frequency: add admv1013  
> > doc  
> > > >
> > > > Hello Rob,
> > > >
> > > > These properties are fixed and available in the datasheet (binary format):
> > > > https://www.analog.com/media/en/technical-documentation/data-
> > > > sheets/ADMV1013.pdf
> > > >
> > > > Please see Page 37 of 39, Table 15, QUAD_SE_MODE.
> > > >
> > > > Regards,
> > > > --
> > > > Antoniu Miclăuş
> > > >  
> > > > > -----Original Message-----
> > > > > From: Rob Herring <robh@kernel.org>
> > > > > Sent: Tuesday, November 2, 2021 7:51 PM
> > > > > To: Miclaus, Antoniu <Antoniu.Miclaus@analog.com>
> > > > > Cc: jic23@kernel.org; linux-iio@vger.kernel.org;  
> > > > devicetree@vger.kernel.org;  
> > > > > linux-kernel@vger.kernel.org; Sa, Nuno <Nuno.Sa@analog.com>
> > > > > Subject: Re: [PATCH v3 2/2] dt-bindings: iio: frequency: add admv1013  
> > doc  
> > > > >
> > > > > [External]
> > > > >
> > > > > On Mon, Nov 01, 2021 at 12:04:20PM +0200, Antoniu Miclaus wrote:  
> > > > > > Add device tree bindings for the ADMV1013 Upconverter.
> > > > > >
> > > > > > Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
> > > > > > ---
> > > > > >  .../bindings/iio/frequency/adi,admv1013.yaml  | 119  
> > > > > ++++++++++++++++++  
> > > > > >  1 file changed, 119 insertions(+)
> > > > > >  create mode 100644  
> > > > > Documentation/devicetree/bindings/iio/frequency/adi,admv1013.yaml  
> > > > > >
> > > > > > diff --git  
> > > > >  
> > a/Documentation/devicetree/bindings/iio/frequency/adi,admv1013.yaml  
> > > > >  
> > b/Documentation/devicetree/bindings/iio/frequency/adi,admv1013.yaml  
> > > > > > new file mode 100644
> > > > > > index 000000000000..47993253a586
> > > > > > --- /dev/null
> > > > > > +++  
> > > > >  
> > b/Documentation/devicetree/bindings/iio/frequency/adi,admv1013.yaml  
> > > > > > @@ -0,0 +1,119 @@
> > > > > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > > > > +%YAML 1.2
> > > > > > +---
> > > > > > +$id:  
> > > > >  
> > > >  
> > https://urldefense.com/v3/__http://devicetree.org/schemas/iio/frequency  
> > > > >  
> > > >  
> > /adi,admv1013.yaml*__;Iw!!A3Ni8CS0y2Y!uTDPalOgj6YS_vZ6bsDSbA_Qna6Q  
> > > > > OwMpoRxzo6nn06i5TNuGWZEk9PvtbC6SKQGXrugy$  
> > > > > > +$schema:  
> > https://urldefense.com/v3/__http://devicetree.org/meta-  
> > > > >  
> > > >  
> > schemas/core.yaml*__;Iw!!A3Ni8CS0y2Y!uTDPalOgj6YS_vZ6bsDSbA_Qna6Q  
> > > > > OwMpoRxzo6nn06i5TNuGWZEk9PvtbC6SKYugV1fM$  
> > > > > > +
> > > > > > +title: ADMV1013 Microwave Upconverter
> > > > > > +
> > > > > > +maintainers:
> > > > > > +  - Antoniu Miclaus <antoniu.miclaus@analog.com>
> > > > > > +
> > > > > > +description: |
> > > > > > +   Wideband, microwave upconverter optimized for point to point  
> > > > > microwave  
> > > > > > +   radio designs operating in the 24 GHz to 44 GHz frequency range.
> > > > > > +
> > > > > > +   https://www.analog.com/en/products/admv1013.html
> > > > > > +
> > > > > > +properties:
> > > > > > +  compatible:
> > > > > > +    enum:
> > > > > > +      - adi,admv1013
> > > > > > +
> > > > > > +  reg:
> > > > > > +    maxItems: 1
> > > > > > +
> > > > > > +  spi-max-frequency:
> > > > > > +    maximum: 1000000
> > > > > > +
> > > > > > +  clocks:
> > > > > > +    description:
> > > > > > +      Definition of the external clock.
> > > > > > +    minItems: 1
> > > > > > +
> > > > > > +  clock-names:
> > > > > > +    items:
> > > > > > +      - const: lo_in
> > > > > > +
> > > > > > +  clock-output-names:
> > > > > > +    maxItems: 1
> > > > > > +
> > > > > > +  vcm-supply:
> > > > > > +    description:
> > > > > > +      Analog voltage regulator.
> > > > > > +
> > > > > > +  adi,vga-powerdown:
> > > > > > +    description:
> > > > > > +      Power Down the Voltage Gain Amplifier Circuit available at
> > > > > > +      BG_RBIAS2 pin.
> > > > > > +    type: boolean  
> > 
> > What wiring would make it sensible to always have this powered down?
> > If we can describe that rather than vga-powerdown then that is what should
> > be in the binding.  If there isn't any wiring based justification and this
> > is just turning off part of the device, then it should not be in the binding.
> >   
> This part is similar to ADRF6780 that has also an Enable Register that can power down circuit blocks within the part:
> https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/tree/drivers/iio/frequency/adrf6780.c?h=togreg
> 

Hmm.  Guess we weren't super awake with that one :( 

> I preferred to expose these properties in the device tree, rather than creating custom device attributes in the driver.
> 
> But I guess these properties can be managed also only from debug fs.

The ideal situation is to control these based on what the device is being used for
and not provide explicit control to userspace or via dt.

So if it doesn't make sense to power up a unit because it isn't wired to anything
then express the wiring in DT.

If it makes sense to power down a unit because it isn't being used currently
due to what features are in use, then power it down automatically.  Runtime pm
handles a lot of these cases by letting you do autopowerdown if not used after
a certain period.  That way, we don't end up powering up and down rapidly but
only do it if we have go reason to believe it is worth powering down.

Could we use either of these approaches here?

Jonathan
> 
> I can adapt the code based on your decision. Looking forward to your feedback.
> > > > > > +
> > > > > > +  adi,mixer-powerdown:
> > > > > > +    description:
> > > > > > +      Power Down the Mixer Circuit. Enable to put the block in
> > > > > > +      a power down state.  
> > 
> > Same for all these other power downs.
> >   
> > > > > > +    type: boolean
> > > > > > +
> > > > > > +  adi,quad-powerdown:
> > > > > > +    description:
> > > > > > +      Power Down the Quadrupler. Enable to put the block in
> > > > > > +      a power down state.
> > > > > > +    type: boolean
> > > > > > +
> > > > > > +  adi,bg-powerdown:
> > > > > > +    description:
> > > > > > +      Power Down the Transmitter Band Gap. Enable to put the part in
> > > > > > +      a power down state.
> > > > > > +    type: boolean
> > > > > > +
> > > > > > +  adi,mixer-if-enable:
> > > > > > +    description:
> > > > > > +      Enable the Intermediate Frequency Mode. Either IF Mode or I/Q  
> > > > Mode  
> > > > > > +      can be enabled at a time.
> > > > > > +    type: boolean
> > > > > > +
> > > > > > +  adi,detector-enable:
> > > > > > +    description:
> > > > > > +      Enable the Envelope Detector available at output pins VENV_P  
> > and  
> > > > > > +      VENV_N. Disable to reduce power consumption.
> > > > > > +    type: boolean
> > > > > > +
> > > > > > +  adi,quad-se-mode:
> > > > > > +    description:
> > > > > > +      Switch the LO path from differential to single-ended operation.
> > > > > > +      Set value 6 for Single-Ended Mode, Negative Side Disabled.
> > > > > > +      Set value 9 for Single-Ended Mode, Positive Side Disabled.
> > > > > > +      Set value 12 for Differential Mode.
> > > > > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > > > > +    enum: [6, 9, 12]  
> > > > >
> > > > > All these vendor properties are fixed based on the board design or
> > > > > something a user may want to change? The latter does not belong in  
> > DT.  
> > > > >
> > > > > Rob  
>