linux-kernel - RE: [PATCH v2 1/2] dt-bindings: misc: adi,axi-tdd: Add device-tree binding for TDD engine

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Message-ID: <BN7PR03MB4545090CC2F859333E9C3AB297C5A@BN7PR03MB4545.namprd03.prod.outlook.com>
Date:   Mon, 2 Oct 2023 19:48:42 +0000
From:   "Balas, Eliza" <Eliza.Balas@...log.com>
To:     Conor Dooley <conor@...nel.org>
CC:     Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Derek Kiernan <derek.kiernan@....com>,
        Dragan Cvetic <dragan.cvetic@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: RE: [PATCH v2 1/2] dt-bindings: misc: adi,axi-tdd: Add device-tree
 binding for TDD engine

> -----Original Message-----
> From: Conor Dooley <conor@...nel.org>
> Sent: Monday, October 2, 2023 22:21
> To: Balas, Eliza <Eliza.Balas@...log.com>
> Cc: Rob Herring <robh@...nel.org>; Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>; Conor Dooley <conor+dt@...nel.org>;
> Derek Kiernan <derek.kiernan@....com>; Dragan Cvetic <dragan.cvetic@....com>; Arnd Bergmann <arnd@...db.de>; Greg
> Kroah-Hartman <gregkh@...uxfoundation.org>; linux-kernel@...r.kernel.org; devicetree@...r.kernel.org
> Subject: Re: [PATCH v2 1/2] dt-bindings: misc: adi,axi-tdd: Add device-tree binding for TDD engine
> 
> [External]
> 
> On Mon, Oct 02, 2023 at 04:46:26PM +0000, Balas, Eliza wrote:
> > > -----Original Message-----
> > > From: Rob Herring <robh@...nel.org>
> > > Sent: Monday, October 2, 2023 19:33
> > > To: Balas, Eliza <Eliza.Balas@...log.com>
> > > Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>; Conor Dooley <conor+dt@...nel.org>; Derek Kiernan
> > > <derek.kiernan@....com>; Dragan Cvetic <dragan.cvetic@....com>; Arnd Bergmann <arnd@...db.de>; Greg Kroah-Hartman
> > > <gregkh@...uxfoundation.org>; linux-kernel@...r.kernel.org; devicetree@...r.kernel.org
> > > Subject: Re: [PATCH v2 1/2] dt-bindings: misc: adi,axi-tdd: Add device-tree binding for TDD engine
> > >
> > > [External]
> > >
> > > On Thu, Sep 28, 2023 at 12:28:03PM +0300, Eliza Balas wrote:
> > > > Add device tree documentation for the AXI TDD Core.
> > > > The generic TDD controller is in essence a waveform generator
> > > > capable of addressing RF applications which require Time Division
> > > > Duplexing, as well as controlling other modules of general
> > > > applications through its dedicated 32 channel outputs.
> > > >
> > > > The reason of creating the generic TDD controller was to reduce
> > > > the naming confusion around the existing repurposed TDD core
> > > > built for AD9361, as well as expanding its number of output
> > > > channels for systems which require more than six controlling signals.
> > > >
> > > > Signed-off-by: Eliza Balas <eliza.balas@...log.com>
> > > > ---
> > > >  .../devicetree/bindings/misc/adi,axi-tdd.yaml | 65 +++++++++++++++++++
> > > >  MAINTAINERS                                   |  7 ++
> > > >  2 files changed, 72 insertions(+)
> > > >  create mode 100644 Documentation/devicetree/bindings/misc/adi,axi-tdd.yaml
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/misc/adi,axi-tdd.yaml b/Documentation/devicetree/bindings/misc/adi,axi-
> tdd.yaml
> > > > new file mode 100644
> > > > index 000000000000..8938da801b95
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/misc/adi,axi-tdd.yaml
> > > > @@ -0,0 +1,65 @@
> > > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > > +# Copyright 2023 Analog Devices Inc.
> > > > +%YAML 1.2
> > > > +---
> > > > +$id: https://urldefense.com/v3/__http://devicetree.org/schemas/misc/adi,axi-
> > > tdd.yaml*__;Iw!!A3Ni8CS0y2Y!5Cxus2huppjhkiJZLWTpJEgA0IXdLZx4t0fS9J1yt0xgjp9g3Y1N5PbZ7pAcIkKU4WPbS_TR9yjTKw$
> > > > +$schema: https://urldefense.com/v3/__http://devicetree.org/meta-
> > >
> schemas/core.yaml*__;Iw!!A3Ni8CS0y2Y!5Cxus2huppjhkiJZLWTpJEgA0IXdLZx4t0fS9J1yt0xgjp9g3Y1N5PbZ7pAcIkKU4WPbS_RK8aQ9xw$
> > > > +
> > > > +title: Analog Devices AXI TDD Core
> > > > +
> > > > +maintainers:
> > > > +  - Eliza Balas <eliza.balas@...log.com>
> > > > +
> > > > +description: |
> > > > +  The TDD controller is a waveform generator capable of addressing RF
> > > > +  applications which require Time Division Duplexing, as well as controlling
> > > > +  other modules of general applications through its dedicated 32 channel
> > > > +  outputs. It solves the synchronization issue when transmitting and receiving
> > > > +  multiple frames of data through multiple buffers.
> > > > +  The TDD IP core is part of the Analog Devices hdl reference designs and has
> > > > +  the following features:
> > > > +    * Up to 32 independent output channels
> > > > +    * Start/stop time values per channel
> > > > +    * Enable and polarity bit values per channel
> > > > +    * 32 bit-max internal reference counter
> > > > +    * Initial startup delay before waveform generation
> > > > +    * Configurable frame length and number of frames per burst
> > > > +    * 3 sources of synchronization: external, internal and software generated
> > > > +  For more information see the wiki:
> > > > +  https://wiki.analog.com/resources/fpga/docs/axi_tdd
> > > > +
> > > > +properties:
> > > > +  compatible:
> > > > +    enum:
> > > > +      - adi,axi-tdd-2.00.a
> > >
> > > Where does this version number come from? I looked at the above link and
> > > see versions such as '2021_R2', '2019_r2', etc. I didn't dig deeper
> > > whether there's some per IP version.
> > >
> > > If you want to use version numbers, please document the versioning
> > > scheme. For example, see
> > > Documentation/devicetree/bindings/sifive/sifive-blocks-ip-versioning.txt.
> > >
> > > Rob
> >
> > The version refers to the IP version. The version of the IP is also
> > specified in its VERSION register (there is a drop down to expand the
> > register map on the wiki page) which is verified by the driver during
> > probe. "2021_R2" refers to the compatible tool version used for
> > creating the FPGAIP Core.
> 
> If you have version registers in these IPs, what benefit does version
> numbers in the compatible string bring?
> Rather than using the version numbers to validate what the DT gave you,
> which not the kernel's job IMO, why not just use the information from
> the register to determine the version?
> 
> Cheers,
> Conor.

As the description of this patch says, we want to resolve the naming confusion around the existing repurposed TDD core (https://wiki.analog.com/resources/eval/user-guides/ad-pzsdr2400tdd-eb/reference_hdl#tdd_controller)
built for AD9361 and this TDD Engine IP core (https://wiki.analog.com/resources/fpga/docs/axi_tdd) which is a similar core, with more output channels and some extra features. The version numbers in the compatible string are used to differentiate between the two IPs.

Best regards,
Eliza