linux-kernel - Re: [PATCH RFT/RFC] mfd: cs42l43: setup true links with software nodes

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Message-ID: <aR29uKW7yLxws9jA@opensource.cirrus.com>
Date: Wed, 19 Nov 2025 12:53:12 +0000
From: Charles Keepax <ckeepax@...nsource.cirrus.com>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        David Rhodes <david.rhodes@...rus.com>,
        Richard Fitzgerald <rf@...nsource.cirrus.com>,
        Lee Jones <lee@...nel.org>, Mark Brown <broonie@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Maciej Strozek <mstrozek@...nsource.cirrus.com>,
        Andy Shevchenko <andy@...nel.org>, linux-sound@...r.kernel.org,
        patches@...nsource.cirrus.com, linux-kernel@...r.kernel.org,
        linux-spi@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH RFT/RFC] mfd: cs42l43: setup true links with software
 nodes

On Wed, Nov 19, 2025 at 03:58:08AM -0800, Bartosz Golaszewski wrote:
> On Wed, 19 Nov 2025 12:24:09 +0100, Charles Keepax
> <ckeepax@...nsource.cirrus.com> said:
> > On Wed, Nov 19, 2025 at 12:06:57PM +0100, Bartosz Golaszewski wrote:
> >> On Wed, Nov 19, 2025 at 11:58 AM Andy Shevchenko
> > Ok I think I see what is happening now, the swnode is created on
> > the first cell (the pinctrl). Then it moves onto the second cell,
> > but mfd_acpi_add_device() copies the firmware node into both
> > devices, the device_set_node() call at the bottom. So it inherits
> > the swnode node through that primary fwnode.
> >
> 
> You probably mean this line:
> 
>      device_set_node(&pdev->dev, acpi_fwnode_handle(adev ?: parent));

Indeed yeah that one.

> What is the actual device whose node we copy here? Would doing the following
> help?

Its the actual ACPI node for the device, the cs42l43, sorry if
that isn't what you are looking for not sure I totally follow the
question here.

> -	device_set_node(&pdev->dev, acpi_fwnode_handle(adev ?: parent));
> +	acpi_fwnode = acpi_fwnode_handle(adev ?: parent);
> +
> +	if (!is_software_node(acpi_fwnode) || !cell->swnode)
> +		device_set_node(&pdev->dev, acpi_fwnode_handle(adev ?: parent));
>  }
>  #else
>  static inline void mfd_acpi_add_device(const struct mfd_cell *cell,
> 
> > I am guessing this code has perhaps been more heavily tested on
> > device tree where it is more common to have nodes for each cell,
> > whereas ACPI is far more likely to have a single firmware node for
> > the whole device.
> >
> 
> If my logic above is right, we should not set the node here unless it's
> an actual node coming from firmware OR the cell doesn't define its own
> software node.

Will that not leave the MFD children without access to the actual ACPI
node though? (Not tested just eye-balling).

Can we tackle this the other way around? Since there is only a
single fwnode for the device, can we find a way to get away with
a single software node for the device too?

Thanks,
Charles