linux-kernel - Re: [PATCH 15/16] misc: lan966x_pci: Add dtso nodes in order to support SFPs

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Message-Id: <D91XV1I4CY37.20T12FMZ5QLQ5@bootlin.com>
Date: Wed, 09 Apr 2025 09:44:25 +0200
From: "Thomas Petazzoni" <thomas.petazzoni@...tlin.com>
To: "Andrew Lunn" <andrew@...n.ch>
Cc: "Herve Codina" <herve.codina@...tlin.com>, "Greg Kroah-Hartman"
 <gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>,
 "Danilo Krummrich" <dakr@...nel.org>, "Shawn Guo" <shawnguo@...nel.org>,
 "Sascha Hauer" <s.hauer@...gutronix.de>, "Pengutronix Kernel Team"
 <kernel@...gutronix.de>, "Fabio Estevam" <festevam@...il.com>, "Michael
 Turquette" <mturquette@...libre.com>, "Stephen Boyd" <sboyd@...nel.org>,
 "Andi Shyti" <andi.shyti@...nel.org>, "Wolfram Sang"
 <wsa+renesas@...g-engineering.com>, "Peter Rosin" <peda@...ntia.se>, "Derek
 Kiernan" <derek.kiernan@....com>, "Dragan Cvetic" <dragan.cvetic@....com>,
 "Arnd Bergmann" <arnd@...db.de>, "Rob Herring" <robh@...nel.org>, "Saravana
 Kannan" <saravanak@...gle.com>, "Bjorn Helgaas" <bhelgaas@...gle.com>,
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 Shevchenko" <andriy.shevchenko@...ux.intel.com>, "Daniel Scally"
 <djrscally@...il.com>, "Heikki Krogerus" <heikki.krogerus@...ux.intel.com>,
 "Sakari Ailus" <sakari.ailus@...ux.intel.com>, "Wolfram Sang"
 <wsa@...nel.org>, "Geert Uytterhoeven" <geert+renesas@...der.be>,
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 <linux-i2c@...r.kernel.org>, <devicetree@...r.kernel.org>,
 <linux-pci@...r.kernel.org>, <linux-spi@...r.kernel.org>,
 <linux-acpi@...r.kernel.org>, "Allan Nielsen"
 <allan.nielsen@...rochip.com>, "Horatiu Vultur"
 <horatiu.vultur@...rochip.com>, "Steen Hegelund"
 <steen.hegelund@...rochip.com>, "Luca Ceresoli" <luca.ceresoli@...tlin.com>
Subject: Re: [PATCH 15/16] misc: lan966x_pci: Add dtso nodes in order to
 support SFPs

On Tue Apr 8, 2025 at 5:38 PM CEST, Andrew Lunn wrote:

> "HW blocks inside an SoC." That would be the SoC .dtsi file. Anything
> outside of the SoC is in the .dts file. OEM vendors take the SoC,
> build a board around it, and name there .dts file after the board,
> describing how the board components are connected to the SoC.
>
> So..
>
> So by PCI endpoint, you mean the PCIe chip? So it sounds like there
> should be a .dtsi file describing the chip.
>
> Everything outside of the chip, like the SFP cages, are up to the
> vendor building the board. I would say that should be described in a
> .dtso file, which describes how the board components are connected to
> the PCIe chip? And that .dtso file should be named after the board,
> since there are going to many of them, from different OEM vendors.

Indeed, that makes sense. So if I get correctly your suggestion,
instead of having a .dtso that describes everything, it should be
split between:

 - A .dtsi that describes what's inside the LAN996x when used in PCI
   endpoint mode

 - A .dtso that includes the above .dtsi, and that describes what on
   the PCI board around the LAN966x.

Correct?

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com