linux-kernel - Re: [PATCH net-next v12 07/14] dpll: zl3073x: Add clock

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Message-ID: <cpgoccukn5tuespqse5fep4gzzaeggth2dkzqh6l5jjchumfyc@5kjorwx57med>
Date: Wed, 2 Jul 2025 14:01:27 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Ivan Vecera <ivecera@...hat.com>
Cc: netdev@...r.kernel.org, Vadim Fedorenko <vadim.fedorenko@...ux.dev>, 
	Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Prathosh Satish <Prathosh.Satish@...rochip.com>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Jonathan Corbet <corbet@....net>, Jason Gunthorpe <jgg@...pe.ca>, 
	Shannon Nelson <shannon.nelson@....com>, Dave Jiang <dave.jiang@...el.com>, 
	Jonathan Cameron <Jonathan.Cameron@...wei.com>, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-doc@...r.kernel.org, Michal Schmidt <mschmidt@...hat.com>, 
	Petr Oros <poros@...hat.com>
Subject: Re: [PATCH net-next v12 07/14] dpll: zl3073x: Add clock_id field

Wed, Jul 02, 2025 at 01:43:38PM +0200, ivecera@...hat.com wrote:
>
>On 02. 07. 25 12:31 odp., Jiri Pirko wrote:
>> Sun, Jun 29, 2025 at 09:10:42PM +0200, ivecera@...hat.com wrote:
>> > Add .clock_id to zl3073x_dev structure that will be used by later
>> > commits introducing DPLL feature. The clock ID is required for DPLL
>> > device registration.
>> > 
>> > To generate this ID, use chip ID read during device initialization.
>> > In case where multiple zl3073x based chips are present, the chip ID
>> > is shifted and lower bits are filled by an unique value - using
>> > the I2C device address for I2C connections and the chip-select value
>> > for SPI connections.
>> 
>> You say that multiple chips may have the same chip ID? How is that
>> possible? Isn't it supposed to be unique?
>> I understand clock ID to be invariant regardless where you plug your
>> device. When you construct it from i2c address, sounds wrong.
>
>The chip id is not like serial number but it is like device id under
>PCI. So if you will have multiple chips with this chip id you have to
>distinguish somehow between them, this is the reason why I2C address
>is added into the final value.
>
>Anyway this device does not have any attribute that corresponds to
>clock id (as per our previous discussion) and it will be better to NOT
>require clock id from DPLL core side.

Yes, better not to require it comparing to having it wrong.

>
>Ivan
>
>