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

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Message-ID: <20220511091136.34dade9b@kernel.org>
Date:   Wed, 11 May 2022 09:11:36 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Michael Walle <michael@...le.cc>
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
Subject: Re: [PATCH v4 1/3] dt-bindings: net: adin: document phy clock

On Wed, 11 May 2022 14:58:55 +0200 Michael Walle wrote:
> > 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.

Is that true for all PHYs? I've seen "larger" devices mention holdover
or some other form of automatic fallback in the DPLL if input clock is
lost. I thought that's the case here, too:

> > > +      The phy can also automatically switch between the reference and the
> > > +      respective 125MHz clocks based on its internal state.