linux-kernel - Re: [PATCH v3 04/10] dt-bindings: iio: dac: ad3552r: add io-backend support

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Message-ID: <ipnqs4uektoysenkr7jvf6ic2rh56n3e5fmmheay323yhavs7u@th7qmxwmkiqo>
Date: Mon, 30 Sep 2024 17:08:48 +0200
From: Angelo Dureghello <adureghello@...libre.com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: Jonathan Cameron <jic23@...nel.org>, 
	Lars-Peter Clausen <lars@...afoo.de>, Michael Hennerich <Michael.Hennerich@...log.com>, 
	Nuno Sa <nuno.sa@...log.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Olivier Moysan <olivier.moysan@...s.st.com>, linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
	devicetree@...r.kernel.org, dlechner@...libre.com
Subject: Re: [PATCH v3 04/10] dt-bindings: iio: dac: ad3552r: add io-backend
 support

On 30.09.2024 15:49, Jonathan Cameron wrote:
> On Mon, 30 Sep 2024 16:15:41 +0200
> Angelo Dureghello <adureghello@...libre.com> wrote:
> 
> > On 29.09.2024 11:51, Jonathan Cameron wrote:
> > > On Thu, 19 Sep 2024 11:20:00 +0200
> > > Angelo Dureghello <adureghello@...libre.com> wrote:
> > >   
> > > > From: Angelo Dureghello <adureghello@...libre.com>
> > > > 
> > > > There is a version AXI DAC IP block (for FPGAs) that provides
> > > > a physical bus for AD3552R and similar chips, and acts as
> > > > an SPI controller.  
> > > 
> > > Wrap is a bit short. Aim for < 75 chars for patch descriptions.
> > >   
> > > > 
> > > > For this case, the binding is modified to include some
> > > > additional properties.
> > > > 
> > > > Signed-off-by: Angelo Dureghello <adureghello@...libre.com>
> > > > ---
> > > >  .../devicetree/bindings/iio/dac/adi,ad3552r.yaml   | 42 ++++++++++++++++++++++
> > > >  1 file changed, 42 insertions(+)
> > > > 
> > > > diff --git a/Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml b/Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml
> > > > index 41fe00034742..aca4a41c2633 100644
> > > > --- a/Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml
> > > > +++ b/Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml
> > > > @@ -60,6 +60,18 @@ properties:
> > > >      $ref: /schemas/types.yaml#/definitions/uint32
> > > >      enum: [0, 1, 2, 3]
> > > >  
> > > > +  io-backends:
> > > > +    description: The iio backend reference.  
> > > 
> > > Give a description of what the backend does in this case.  I.e. that it is
> > > a qspi DDR backend with ...
> > >   
> > > > +      An example backend can be found at
> > > > +        https://analogdevicesinc.github.io/hdl/library/axi_ad3552r/index.html
> > > > +    maxItems: 1
> > > > +
> > > > +  adi,synchronous-mode:
> > > > +    description: Enable waiting for external synchronization signal.
> > > > +      Some AXI IP configuration can implement a dual-IP layout, with internal
> > > > +      wirings for streaming synchronization.  
> > > 
> > > I've no idea what a dual-IP layout is.  Can you provide a little more info
> > > here?  What are the two IPs?
> > >  
> > IP is a term used in fpga design as "intellectual property", that is
> > intended as a functional block of logic or data used to make a 
> > field-programmable gate array module.
> > 
> > A dual layout is just 2 same fpga modules in place of one.
> >  
> > I can add a "fpga" regerence to be more clear.
> 
> IP I was familiar with.  I'm more interested in what each IP is doing in this
> case.  Or at least an example of what sort of split of functionality might
> make use of this.
>

I have an image of the project (that is under development or testing now),
not sure how to attach the image here, btw, something as
 
          axi_ad3552r_0  ----------->---- qspi0
              sync_ext_device --.
       .- external_sync          |
       |                         |
       |-------------<-----------                        
       |
       |   axi_ad3552r_1 ----------->---- qspi1
       `- external_sync
 
My understanding is that it's just a method to use a octal spi,
duplicating the transfer rate. I can collect more info in case.


> Jonathan

Regards,
Angelo

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