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Date:   Tue, 15 Dec 2020 08:08:35 -0600
From:   Rob Herring <robh@...nel.org>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Serge Semin <fancer.lancer@...il.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Johan Hovold <johan@...nel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Joao Pinto <jpinto@...opsys.com>,
        Lars Persson <larper@...s.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Vyacheslav Mitrofanov 
        <Vyacheslav.Mitrofanov@...kalelectronics.ru>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        netdev <netdev@...r.kernel.org>,
        "moderated list:ARM/STM32 ARCHITECTURE" 
        <linux-stm32@...md-mailman.stormreply.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 04/25] dt-bindings: net: dwmac: Refactor snps,*-config properties

On Tue, Dec 15, 2020 at 2:54 AM Serge Semin
<Sergey.Semin@...kalelectronics.ru> wrote:
>
> Hello Rob,
>
> On Mon, Dec 14, 2020 at 08:30:06AM -0600, Rob Herring wrote:
> > On Mon, Dec 14, 2020 at 12:15:54PM +0300, Serge Semin wrote:
> > > Currently the "snps,axi-config", "snps,mtl-rx-config" and
> > > "snps,mtl-tx-config" properties are declared as a single phandle reference
> > > to a node with corresponding parameters defined. That's not good for
> > > several reasons. First of all scattering around a device tree some
> > > particular device-specific configs with no visual relation to that device
> > > isn't suitable from maintainability point of view. That leads to a
> > > disturbed representation of the actual device tree mixing actual device
> > > nodes and some vendor-specific configs. Secondly using the same configs
> > > set for several device nodes doesn't represent well the devices structure,
> > > since the interfaces these configs describe in hardware belong to
> > > different devices and may actually differ. In the later case having the
> > > configs node separated from the corresponding device nodes gets to be
> > > even unjustified.
> > >
> > > So instead of having a separate DW *MAC configs nodes we suggest to
> > > define them as sub-nodes of the device nodes, which interfaces they
> > > actually describe. By doing so we'll make the DW *MAC nodes visually
> > > correct describing all the aspects of the IP-core configuration. Thus
> > > we'll be able to describe the configs sub-nodes bindings right in the
> > > snps,dwmac.yaml file.
> > >
> > > Note the former "snps,axi-config", "snps,mtl-rx-config" and
> > > "snps,mtl-tx-config" bindings have been marked as deprecated.
> > >
> > > Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
> > >
> > > ---
> > >
> > > Note the current DT schema tool requires the vendor-specific properties to be
> > > defined in accordance with the schema: dtschema/meta-schemas/vendor-props.yaml
> > > It means the property can be;
> > > - boolean,
> > > - string,
> > > - defined with $ref and additional constraints,
> > > - defined with allOf: [ $ref ] and additional constraints.
> > >
> > > The modification provided by this commit needs to extend that definition to
> > > make the DT schema tool correctly parse this schema. That is we need to let
> > > the vendors-specific properties to also accept the oneOf-based combined
> > > sub-schema. Like this:
> > >
> > > --- a/dtschema/meta-schemas/vendor-props.yaml
> > > +++ b/dtschema/meta-schemas/vendor-props.yaml
> > > @@ -48,15 +48,24 @@
> > >        - properties:   # A property with a type and additional constraints
> > >            $ref:
> > >              pattern: "types.yaml#[\/]{0,1}definitions\/.*"
> > > -          allOf:
> > > -            items:
> > > -              - properties:
> > > +
> > > +        if:
> > > +          not:
> > > +            required:
> > > +              - $ref
> > > +        then:
> > > +          patternProperties:
> > > +            "^(all|one)Of$":
> > > +              contains:
> > > +                properties:
> > >                    $ref:
> > >                      pattern: "types.yaml#[\/]{0,1}definitions\/.*"
> > >                  required:
> > >                    - $ref
> > > -        oneOf:
> > > +
> > > +        anyOf:
> > >            - required: [ $ref ]
> > >            - required: [ allOf ]
> > > +          - required: [ oneOf ]
> > >
> > >  ...
> > > ---
> > >  .../devicetree/bindings/net/snps,dwmac.yaml   | 380 +++++++++++++-----
> > >  1 file changed, 288 insertions(+), 92 deletions(-)
> > >
> > > diff --git a/Documentation/devicetree/bindings/net/snps,dwmac.yaml b/Documentation/devicetree/bindings/net/snps,dwmac.yaml
> > > index 0dd543c6c08e..44aa88151cba 100644
> > > --- a/Documentation/devicetree/bindings/net/snps,dwmac.yaml
> > > +++ b/Documentation/devicetree/bindings/net/snps,dwmac.yaml
> > > @@ -150,69 +150,251 @@ properties:
> > >        in a different mode than the PHY in order to function.
> > >
> > >    snps,axi-config:
> > > -    $ref: /schemas/types.yaml#definitions/phandle
> > > -    description:
> > > -      AXI BUS Mode parameters. Phandle to a node that can contain the
> > > -      following properties
> > > -        * snps,lpi_en, enable Low Power Interface
> > > -        * snps,xit_frm, unlock on WoL
> > > -        * snps,wr_osr_lmt, max write outstanding req. limit
> > > -        * snps,rd_osr_lmt, max read outstanding req. limit
> > > -        * snps,kbbe, do not cross 1KiB boundary.
> > > -        * snps,blen, this is a vector of supported burst length.
> > > -        * snps,fb, fixed-burst
> > > -        * snps,mb, mixed-burst
> > > -        * snps,rb, rebuild INCRx Burst
> > > +    description: AXI BUS Mode parameters
> > > +    oneOf:
> > > +      - deprecated: true
> > > +        $ref: /schemas/types.yaml#definitions/phandle
> > > +      - type: object
> > > +        properties:
> >
>
> > Anywhere have have the same node/property string meaning 2 different
> > things is a pain, let's not create another one.
>
> IIUC you meant that having a node and property with the same name
> isn't ok. Right? If so could you explain why not? especially seeing
> the property is expected to be set with phandle reference to that
> node. That seemed like a perfect solution to me. We wouldn't need to
> introduce a new property/node name, but just deprecate the
> corresponding name to be a property.

Right. It's also a property or node name having 2 different meanings.
I think your schema above demonstrates the problem in that it
unnecessarily complicates the schema. It's not such a problem here as
it is self contained. The worst example is 'ports'. That's a container
of graph port nodes, ethernet switch nodes or a property pointing to
DRM graphics pipelines. If there's multiple meanings, then we can't
apply a schema unconditionally. Or we can only check it matches one of
the 3 definitions.

> > Just define a new node
> > 'axi-config'. Or just put all the properties into the node directly.
> > Grouping them has little purpose.
>
> Hm, you suggest to remove the vendor prefix, right?

Yes, we don't do vendor prefixes on node names either.

> If so what about
> the rest of the changes introduced here in this patch? They concern
> "snps,mtl-tx-config" and "snps,mtl-rx-config" properties (please note
> these changes are a bit more complicated than once connected with
> "snps,axi-config"). Should I remove the vendor-prefix from them too?

Yes.

> Anyway that seems a bit questionable, because all the "snps,*-config"
> properties/nodes seems more vendor-specific than generic. Am I wrong
> in that matter?
>
> If you think they are generic, then the "{axi,mtl-rx,mtl-tx}-config"
> nodes most likely should be described in the dedicated DT schema...
>
> -Sergey
>

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