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

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Message-ID: <072a773c-2e42-1b82-9fe7-63c9a3dc9c7d@solid-run.com>
Date:   Sun, 15 May 2022 10:16:47 +0300
From:   Josua Mayer <josua@...id-run.com>
To:     Jakub Kicinski <kuba@...nel.org>, Michael Walle <michael@...le.cc>
Cc:     alexandru.ardelean@...log.com, alvaro.karsz@...id-run.com,
        davem@...emloft.net, edumazet@...gle.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

\o/

I am not sure I can follow your conversation here ...

Am 13.05.22 um 01:44 schrieb Jakub Kicinski:
> On Thu, 12 May 2022 23:20:18 +0200 Michael Walle wrote:
>>> It's pure speculation on my side. I don't even know if PHYs use
>>> the recovered clock to clock its output towards the MAC or that's
>>> a different clock domain.
>>>
>>> My concern is that people will start to use DT to configure SyncE which
>>> is entirely a runtime-controllable thing, and doesn't belong.
Okay.
However phy drivers do not seem to implement runtime control of those 
clock output pins currently, so they are configured once in DT.
>>> Hence
>>> my preference to hide the recovered vs free-running detail if we can
>>> pick one that makes most sense for now.
I am not a fan of hiding information. The clock configuration register 
clearly supports this distinction.

Is this a political stance to say users may not "accidentally" enable 
SyncE by patching DT?
If so we should print a warning message when someone selects it?
>>
>> I see. That makes sense, but then wouldn't it make more sense to pick
>> the (simple) free-running one? As for SyncE you'd need the recovered
>> clock.
> 
> Sounds good.

Yep, it seems recovered clock is only for SyncE - and only if there is a 
master clock on the network. Sadly however documentation is sparse and I 
do not know if the adi phys would fall back to using their internal 
clock, or just refuse to operate at all.