linux-kernel - Re: [PATCH v2 05/26] bus: simple-pm-bus: Populate child nodes at probe

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Message-ID: <aBy_aBkC7NpicXho@smile.fi.intel.com>
Date: Thu, 8 May 2025 17:27:52 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Herve Codina <herve.codina@...tlin.com>
Cc: Andrew Lunn <andrew@...n.ch>,
	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>,
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	Wolfram Sang <wsa@...nel.org>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	linux-kernel@...r.kernel.org, imx@...ts.linux.dev,
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	Allan Nielsen <allan.nielsen@...rochip.com>,
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	Luca Ceresoli <luca.ceresoli@...tlin.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v2 05/26] bus: simple-pm-bus: Populate child nodes at
 probe

On Wed, May 07, 2025 at 09:12:47AM +0200, Herve Codina wrote:
> The simple-pm-bus drivers handles several simple bus. When it is used

bus --> busses ?

> with busses other than a compatible "simple-pm-bus", it don't populate
> its child devices during its probe.
> 
> This confuses fw_devlink and results in wrong or missing devlinks.
> 
> Once a driver is bound to a device and the probe() has been called,
> device_links_driver_bound() is called.
> 
> This function performs operation based on the following assumption:
>     If a child firmware node of the bound device is not added as a
>     device, it will never be added.
> 
> Among operations done on fw_devlinks of those "never be added" devices,
> device_links_driver_bound() changes their supplier.
> 
> With devices attached to a simple-bus compatible device, this change
> leads to wrong devlinks where supplier of devices points to the device
> parent (i.e. simple-bus compatible device) instead of the device itself
> (i.e. simple-bus child).
> 
> When the device attached to the simple-bus is removed, because devlinks
> are not correct, its consumers are not removed first.
> 
> In order to have correct devlinks created, make the simple-pm-bus driver
> compliant with the devlink assumption and create its child devices
> during its probe.

...

>  	if (match && match->data) {
>  		if (of_property_match_string(np, "compatible", match->compatible) == 0)

Side note, there is an fwnode_is_device_compatible() API for such cases. And IIRC
there is also OF variant of it.

> -			return 0;
> +			goto populate;
>  		else
>  			return -ENODEV;
>  	}

...

> +	if (pdev->dev.of_node)

Why do you need this check? AFAICS it dups the one the call has already in it.

> +		of_platform_depopulate(&pdev->dev);

-- 
With Best Regards,
Andy Shevchenko