netdev - Re: [PATCH v4 1/3] dt-bindings: net: adin: document phy clock

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Date:   Wed, 11 May 2022 14:58:55 +0200
From:   Michael Walle <michael@...le.cc>
To:     kuba@...nel.org
Cc:     alexandru.ardelean@...log.com, alvaro.karsz@...id-run.com,
        davem@...emloft.net, edumazet@...gle.com, josua@...id-run.com,
        krzysztof.kozlowski+dt@...aro.org, michael.hennerich@...log.com,
        netdev@...r.kernel.org, pabeni@...hat.com, robh+dt@...nel.org,
        Michael Walle <michael@...le.cc>
Subject: Re: [PATCH v4 1/3] dt-bindings: net: adin: document phy clock

> On Mon,  9 May 2022 17:36:33 +0300 Josua Mayer wrote:
> > +  adi,phy-output-clock:
> > +    description: Select clock output on GP_CLK pin. Three clocks are available:
> > +      A 25MHz reference, a free-running 125MHz and a recovered 125MHz.
> > +      The phy can also automatically switch between the reference and the
> > +      respective 125MHz clocks based on its internal state.
> > +    $ref: /schemas/types.yaml#/definitions/string
> > +    enum:
> > +      - 25mhz-reference
> > +      - 125mhz-free-running
> > +      - 125mhz-recovered
> > +      - adaptive-free-running
> > +      - adaptive-recovered
> 
> I'm still not convinced that exposing the free running vs recovered
> distinction from the start is a good idea. Intuitively it'd seem that
> it's better to use the recovered clock to feed the wire side of the MAC,
> this patch set uses the free running. So I'd personally strip the last 
> part off and add it later if needed.

FWIW, the recovered clock only works if there is a link. AFAIR on the
AR8031 you can have the free-running one enabled even if there is no
link, which might sometimes be useful.

-michael