linux-kernel - Re: [PATCH 1/2] dt-bindings: net: phy: Support external PHY xtal

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Message-ID: <e2108f4c-3d0d-ca64-5ad4-ec0de6ea4bf5@gmail.com>
Date:   Wed, 31 May 2023 11:05:20 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Detlev Casanova <detlev.casanova@...labora.com>,
        Andrew Lunn <andrew@...n.ch>
Cc:     linux-kernel@...r.kernel.org,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: net: phy: Support external PHY xtal

On 5/31/23 11:00, Detlev Casanova wrote:
> On Wednesday, May 31, 2023 11:16:46 A.M. EDT Andrew Lunn wrote:
>> On Wed, May 31, 2023 at 11:03:39AM -0400, Detlev Casanova wrote:
>>> Ethernet PHYs can have external an clock that needs to be activated before
>>> probing the PHY.
>>>
>>> Signed-off-by: Detlev Casanova <detlev.casanova@...labora.com>
>>> ---
>>>
>>>   .../devicetree/bindings/net/ethernet-phy.yaml          | 10 ++++++++++
>>>   1 file changed, 10 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/net/ethernet-phy.yaml
>>> b/Documentation/devicetree/bindings/net/ethernet-phy.yaml index
>>> 4f574532ee13..e83a33c2aa59 100644
>>> --- a/Documentation/devicetree/bindings/net/ethernet-phy.yaml
>>> +++ b/Documentation/devicetree/bindings/net/ethernet-phy.yaml
>>>
>>> @@ -93,6 +93,16 @@ properties:
>>>         the turn around line low at end of the control phase of the
>>>         MDIO transaction.
>>>
>>> +  clock-names:
>>> +    items:
>>> +      - const: xtal
>>
>> I don't think xtal is the best of names here. It generally is used as
>> an abbreviation for crystal. And the commit message is about there not
>> being a crystal, but an actual clock.
>>
>> How is this clock named on the datasheet?
> 
> In the case of the PHY I used (RTL8211F), it is EXT_CLK. But this must be
> generic to any (ethernet) PHY, so using ext_clk to match it would not be
> good either.
> 
> Now this is about having an external clock, so the ext_clk name makes sense in
> this case.
> 
> I'm not pushing one name or another, let's use what you feel is more natural.

You can look up clocks by positional index, maybe this is a case where 
there are just too many names that PHY vendors will use that we should 
not be using one specific name in particular, but just define the order 
in which clocks should be specified.
-- 
Florian