Re: [PATCH v24 04/12] mfd: psci-mfd: Add PSCI MFD driver for cpuidle-psci-domain cell

[Lee Jones <lee@kernel.org>]

On Mon, 03 Aug 2026, Shivendra Pratap wrote:

> PSCI has multiple kernel consumers, such as cpuidle-psci-domain.
> Currently, both the PSCI core driver and cpuidle-psci-domain bind
> directly to the same PSCI node "arm,psci-1.0". Additional consumers, if
> introduced, would also need to bind in the same way, leading to several
> drivers attached to a single device node.
> 
> Introduce a PSCI MFD driver that binds to "arm,psci-1.0" and registers
> PSCI child cells. As the first user, register cpuidle-psci-domain as a
> child cell.
> 
> Update cpuidle-psci-domain to probe as an MFD child and use the parent
> PSCI node for power-domain traversal.
> 
> Suggested-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
> Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
> Signed-off-by: Shivendra Pratap <shivendra.pratap@oss.qualcomm.com>
> ---
>  MAINTAINERS                           |  1 +
>  drivers/cpuidle/Kconfig.arm           |  1 +
>  drivers/cpuidle/cpuidle-psci-domain.c |  9 +-------
>  drivers/mfd/Kconfig                   | 12 ++++++++++
>  drivers/mfd/Makefile                  |  2 ++
>  drivers/mfd/psci-mfd.c                | 43 +++++++++++++++++++++++++++++++++++

We don't usually allow the use of the term MFD in devices.

What does this do?  Is it a mux?  psci-mux?

If not, think about what it is and call it that instead.

>  6 files changed, 60 insertions(+), 8 deletions(-)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index fe67f7bfa44c..0b6e4f89f319 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -21671,6 +21671,7 @@ L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
>  S:	Maintained
>  F:	Documentation/devicetree/bindings/arm/psci.yaml
>  F:	drivers/firmware/psci/
> +F:	drivers/mfd/psci-mfd.c
>  F:	include/linux/psci.h
>  F:	include/uapi/linux/psci.h
>  
> diff --git a/drivers/cpuidle/Kconfig.arm b/drivers/cpuidle/Kconfig.arm
> index b88b01aa5829..c5ecca0d7397 100644
> --- a/drivers/cpuidle/Kconfig.arm
> +++ b/drivers/cpuidle/Kconfig.arm
> @@ -36,6 +36,7 @@ config ARM_PSCI_CPUIDLE_DOMAIN
>  	bool "PSCI CPU idle Domain"
>  	depends on ARM_PSCI_CPUIDLE
>  	depends on PM_GENERIC_DOMAINS_OF
> +	depends on MFD_PSCI
>  	select DT_IDLE_GENPD
>  	default y
>  	help
> diff --git a/drivers/cpuidle/cpuidle-psci-domain.c b/drivers/cpuidle/cpuidle-psci-domain.c
> index b9e4ad7d43a3..a2d01810f295 100644
> --- a/drivers/cpuidle/cpuidle-psci-domain.c
> +++ b/drivers/cpuidle/cpuidle-psci-domain.c
> @@ -17,7 +17,6 @@
>  #include <linux/pm_runtime.h>
>  #include <linux/psci.h>
>  #include <linux/slab.h>
> -#include <linux/string.h>
>  
>  #include "cpuidle-psci.h"
>  #include "dt_idle_genpd.h"
> @@ -122,14 +121,9 @@ static void psci_pd_remove(void)
>  	}
>  }
>  
> -static const struct of_device_id psci_of_match[] = {
> -	{ .compatible = "arm,psci-1.0" },
> -	{}
> -};
> -
>  static int psci_cpuidle_domain_probe(struct platform_device *pdev)
>  {
> -	struct device_node *np = pdev->dev.of_node;
> +	struct device_node *np = pdev->dev.parent->of_node;

dev_of_node(pdev->dev.parent);

>  	bool use_osi = psci_has_osi_support();
>  	int ret = 0, pd_count = 0;
>  
> @@ -181,7 +175,6 @@ static struct platform_driver psci_cpuidle_domain_driver = {
>  	.probe  = psci_cpuidle_domain_probe,
>  	.driver = {
>  		.name = "psci-cpuidle-domain",
> -		.of_match_table = psci_of_match,
>  	},
>  };
>  
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index e4fd4572472f..d18655d76172 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -2374,6 +2374,18 @@ config MFD_KHADAS_MCU
>  	  additional drivers must be enabled in order to use the functionality
>  	  of the device.
>  
> +config MFD_PSCI
> +	bool "PSCI MFD for psci child cells"

"PSCI mux for registering PSCI component devices" ?

> +	depends on ARM_PSCI_FW
> +	depends on OF
> +	select MFD_CORE
> +	default y
> +	help
> +	  PSCI MFD registers PSCI child cells and exposes them as
> +	  platform devices.

This is what all DT related MFD devices do.

> +       Child drivers are probed only if enabled in the
> +	  kernel configuration.

Nothing new here either.  This is the norm.

"PSCI Mux is a Linux specific device splitter designed to register
 multiple PSCI related components via a single Device Tree compatible.
 Without it, devices would each bind to a single node ... <which causes
 problems with x, y and z>"

> +       Select this option whenever a supported PSCI
> +	  child driver is selected.
> +
>  config MFD_ACER_A500_EC
>  	tristate "Support for Acer Iconia Tab A500 Embedded Controller"
>  	depends on I2C
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index 72d3944b0ad8..f3edfad702ff 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -24,6 +24,8 @@ obj-$(CONFIG_MFD_EXYNOS_LPASS)	+= exynos-lpass.o
>  obj-$(CONFIG_MFD_GATEWORKS_GSC)	+= gateworks-gsc.o
>  obj-$(CONFIG_MFD_MACSMC)	+= macsmc.o
>  
> +obj-$(CONFIG_MFD_PSCI)		+= psci-mfd.o
> +
>  obj-$(CONFIG_MFD_TI_LP873X)	+= lp873x.o
>  obj-$(CONFIG_MFD_TI_LP87565)	+= lp87565.o
>  obj-$(CONFIG_MFD_TI_AM335X_TSCADC)	+= ti_am335x_tscadc.o
> diff --git a/drivers/mfd/psci-mfd.c b/drivers/mfd/psci-mfd.c
> new file mode 100644
> index 000000000000..7affd6bb09dd
> --- /dev/null
> +++ b/drivers/mfd/psci-mfd.c
> @@ -0,0 +1,43 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
> + */
> +
> +#include <linux/mfd/core.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +
> +static const struct mfd_cell psci_cells[] = {
> +	{
> +		.name = "psci-cpuidle-domain",
> +	},
> +};

MFD_CELL_NAME() ?

MFD drivers have to support more than one device from the get-go.
Please add your other device here in this patch.

> +static int psci_mfd_probe(struct platform_device *pdev)

No to _mfd_.

> +{
> +	return devm_mfd_add_devices(&pdev->dev, PLATFORM_DEVID_AUTO, psci_cells,
> +				   ARRAY_SIZE(psci_cells), NULL, 0, NULL);
> +}
> +
> +static const struct of_device_id psci_mfd_of_match[] = {
> +	{ .compatible = "arm,psci-1.0" },
> +	{ }
> +};
> +
> +static struct platform_driver psci_mfd_driver = {
> +	.probe = psci_mfd_probe,
> +	.driver = {
> +		.name = "psci-mfd",
> +		.of_match_table = psci_mfd_of_match,
> +	},
> +};
> +
> +static int __init psci_mfd_init(void)
> +{
> +	return platform_driver_register(&psci_mfd_driver);
> +}
> +

Remove this line.

> +core_initcall(psci_mfd_init);

This is usually a hack.  Why can't you use -EPROBE_DEFER?

> +
> +MODULE_LICENSE("GPL");
> 
> -- 
> 2.34.1
> 

-- 
Lee Jones