linux-kernel - Re: [PATCH v2 net-next 01/14] dt-bindings: ptp: add NETC Timer PTP clock

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Message-ID: <ec01c2f1-7ab8-4830-846d-aa772e6cc853@kernel.org>
Date: Thu, 17 Jul 2025 12:04:12 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Wei Fang <wei.fang@....com>
Cc: "robh@...nel.org" <robh@...nel.org>,
 "krzk+dt@...nel.org" <krzk+dt@...nel.org>,
 "conor+dt@...nel.org" <conor+dt@...nel.org>,
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 Claudiu Manoil <claudiu.manoil@....com>,
 Vladimir Oltean <vladimir.oltean@....com>, Clark Wang
 <xiaoning.wang@....com>, "andrew+netdev@...n.ch" <andrew+netdev@...n.ch>,
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 <pabeni@...hat.com>, "vadim.fedorenko@...ux.dev"
 <vadim.fedorenko@...ux.dev>, Frank Li <frank.li@....com>,
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Subject: Re: [PATCH v2 net-next 01/14] dt-bindings: ptp: add NETC Timer PTP
 clock

On 17/07/2025 10:30, Wei Fang wrote:
>> On Wed, Jul 16, 2025 at 03:30:58PM +0800, Wei Fang wrote:
>>> +properties:
>>> +  compatible:
>>> +    enum:
>>> +      - pci1131,ee02
>>> +
>>> +  reg:
>>> +    maxItems: 1
>>> +
>>> +  clocks:
>>> +    maxItems: 1
>>> +    description:
>>> +      The reference clock of NETC Timer, if not present, indicates that
>>> +      the system clock of NETC IP is selected as the reference clock.
>>
>> If not present...
>>
>>> +
>>> +  clock-names:
>>
>> ... this also is not present...
>>
>>> +    description:
>>> +      NETC Timer has three reference clock sources, set
>> TMR_CTRL[CK_SEL]
>>> +      by parsing clock name to select one of them as the reference clock.
>>> +      The "system" means that the system clock of NETC IP is used as the
>>> +      reference clock.
>>> +      The "ccm_timer" means another clock from CCM as the reference
>> clock.
>>> +      The "ext_1588" means the reference clock comes from external IO
>> pins.
>>> +    enum:
>>> +      - system
>>
>> So what does system mean?
>>
> 
> "system" is the system clock of the NETC subsystem, we can explicitly specify
> this clock as the PTP reference clock of the Timer in the DT node. Or do not
> add clock properties to the DT node, it implicitly indicates that the reference
> clock of the Timer is the "system" clock.
> 

Eh, no. If absence of clock input means you are using specific clock
input it is contradictory to the first. You cannot use some clock input
if you claim that it can be missing.

You define here clock inputs. This is what this property is about.

Best regards,
Krzysztof