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

On Mon, Aug 3, 2026 at 11:45 AM Shivendra Pratap
<[email protected]> 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.

I don't think PSCI should be modeled as an MFD device with childrens.

Instead, this looks rather like a better fit for the auxiliary
bus/driver. Please consider using that instead.

Kind regards
Uffe

>
> Update cpuidle-psci-domain to probe as an MFD child and use the parent
> PSCI node for power-domain traversal.
>
> Suggested-by: Bartosz Golaszewski <[email protected]>
> Reviewed-by: Bartosz Golaszewski <[email protected]>
> Signed-off-by: Shivendra Pratap <[email protected]>
> ---
>  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 +++++++++++++++++++++++++++++++++++
>  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:      [email protected] (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;
>         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"
> +       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. Child drivers are probed only if enabled in the
> +         kernel configuration. 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",
> +       },
> +};
> +
> +static int psci_mfd_probe(struct platform_device *pdev)
> +{
> +       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);
> +}
> +
> +core_initcall(psci_mfd_init);
> +
> +MODULE_LICENSE("GPL");
>
> --
> 2.34.1
>