netdev - Re: [PATCH v8 net-next 01/10] dt-bindings: net: dsa: dt bindings for microchip lan937x

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Date:   Wed, 2 Mar 2022 17:11:43 +0530
From:   Prasanna Vengateshan <prasanna.vengateshan@...rochip.com>
To:     Florian Fainelli <f.fainelli@...il.com>, <robh+dt@...nel.org>
CC:     <UNGLinuxDriver@...rochip.com>, <woojung.huh@...rochip.com>,
        <hkallweit1@...il.com>, <linux@...linux.org.uk>,
        <davem@...emloft.net>, <kuba@...nel.org>,
        <linux-kernel@...r.kernel.org>, <vivien.didelot@...il.com>,
        <devicetree@...r.kernel.org>, Rob Herring <robh@...nel.org>,
        <andrew@...n.ch>, <netdev@...r.kernel.org>, <olteanv@...il.com>
Subject: Re: [PATCH v8 net-next 01/10] dt-bindings: net: dsa: dt bindings
 for microchip lan937x

Hi Rob and Florian,

On Fri, 2022-02-11 at 19:56 -0800, Florian Fainelli wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the
> content is safe
> 
> On 2/9/2022 3:58 AM, Prasanna Vengateshan wrote:
> > On Mon, 2022-02-07 at 18:53 -0800, Florian Fainelli wrote:
> > > EXTERNAL EMAIL: Do not click links or open attachments unless you know the
> > > content is safe
> > > 
> > > On 2/7/2022 9:21 AM, Prasanna Vengateshan wrote:
> > > > Documentation in .yaml format and updates to the MAINTAINERS
> > > > Also 'make dt_binding_check' is passed.
> > > > 
> > > > RGMII internal delay values for the mac is retrieved from
> > > > rx-internal-delay-ps & tx-internal-delay-ps as per the feedback from
> > > > v3 patch series.
> > > > https://lore.kernel.org/netdev/20210802121550.gqgbipqdvp5x76ii@skbuf/
> > > > 
> > > > It supports only the delay value of 0ns and 2ns.
> > > > 
> > > > Signed-off-by: Prasanna Vengateshan <prasanna.vengateshan@...rochip.com>
> > > > Reviewed-by: Rob Herring <robh@...nel.org>
> > > > ---
> > > >    .../bindings/net/dsa/microchip,lan937x.yaml   | 179 ++++++++++++++++++
> > > >    MAINTAINERS                                   |   1 +
> > > >    2 files changed, 180 insertions(+)
> > > >    create mode 100644
> > > > Documentation/devicetree/bindings/net/dsa/microchip,lan937x.yaml
> > > > 
> > > > +    maxItems: 1
> > > > +
> > > > +  mdio:
> > > > +    $ref: /schemas/net/mdio.yaml#
> > > > +    unevaluatedProperties: false
> > > 
> > > This should be moved to dsa.yaml since this is about describing the
> > > switch's internal MDIO bus controller. This is applicable to any switch,
> > > really.
> > 
> > Thanks for your review and feedback. Do you mean that 'mdio' to be added in
> > dsa.yaml instead adding here?
> 
> Yes indeed, since this is a common property of all DSA switches, it can
> be defined or not depending on whether the switch does have an internal
> MDIO bus controller or not.
> 
> > 
> > > 
> > > > +
> > > > +patternProperties:
> > > > +  "^(ethernet-)?ports$":
> > > > +    patternProperties:
> > > > +      "^(ethernet-)?port@[0-7]+$":
> > > > +        allOf:
> > > > +          - if:
> > > > +              properties:
> > > > +                phy-mode:
> > > > +                  contains:
> > > > +                    enum:
> > > > +                      - rgmii
> > > > +                      - rgmii-rxid
> > > > +                      - rgmii-txid
> > > > +                      - rgmii-id
> > > > +            then:
> > > > +              properties:
> > > > +                rx-internal-delay-ps:
> > > > +                  $ref: "#/$defs/internal-delay-ps"
> > > > +                tx-internal-delay-ps:
> > > > +                  $ref: "#/$defs/internal-delay-ps"
> > > 
> > > Likewise, this should actually be changed in ethernet-controller.yaml
> > 
> > There is *-internal-delay-ps property defined for mac in ethernet-
> > controller.yaml. Should that be changed like above?
> 
> It seems to me that these properties override whatever 'phy-mode'
> property is defined, but in premise you are right that this is largely
> applicable to RGMII only. I seem to recall that the QCA8K driver had
> some sort of similar delay being applied even in SGMII mode but I am not
> sure if we got to the bottom of this.
> 
> Please make sure that this does not create regressions for other DTS in
> the tree before going with that change in ethernet-controller.yaml.
> 

I just tried changing rx-internal-delay-ps & tx-internal-delay-ps on conditional
basis like above in the ethernet-controller.yaml and it passed 'make
dt_binding_check' as well. 

It would be like below if existing *-internal-delay-ps are removed from
ethernet-controller.yaml.

allOf:
  - if:
      properties:
        phy-mode:
          contains:
            enum:
              - rgmii
              - rgmii-rxid
              - rgmii-txid
              - rgmii-id
            then:
              properties:
                rx-internal-delay-ps:
                  description:
                    RGMII Receive Clock Delay defined in pico seconds.This is 
                    used for controllers that have configurable RX internal 
                    delays. If this property is present then the MAC applies 
                    the RX delay.
                tx-internal-delay-ps:
                  description:
                    RGMII Transmit Clock Delay defined in pico seconds.This is
                    used for controllers that have configurable TX internal
                    delays. If this property is present then the MAC applies
                    the TX delay.   

After the above changes, these two properties descriptions are different compare
to other properties. So i just wanted to know whether i am following the right
approach or are there any other proposal available? Thanks.

Prasanna V