Re: [PATCH v25 04/10] firmware: psci: Add support for PSCI auxiliary devices

From: Bartosz Golaszewski

Date: Wed Sep 16 2026 - 05:36:18 EST

On Mon, 14 Sep 2026 16:59:08 +0200, Shivendra Pratap
<shivendra.pratap@xxxxxxxxxxxxxxxx> said:
> 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 multiple
> drivers attached to a single device node.
>
> Introduce a PSCI auxiliary-device provider that binds to "arm,psci-1.0"
> and registers PSCI child devices on the auxiliary bus. As the first
> user, register cpuidle-psci-domain as an auxiliary device.
>
> Update cpuidle-psci-domain to probe as an auxiliary driver and use
> the PSCI device node for power-domain traversal.
>
> Suggested-by: Ulf Hansson <ulf.hansson@xxxxxxxxxxxxxxxx>
> Suggested-by: Lee Jones <lee@xxxxxxxxxx>
> Suggested-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>
> Signed-off-by: Shivendra Pratap <shivendra.pratap@xxxxxxxxxxxxxxxx>
> ---
> MAINTAINERS | 1 +
> drivers/cpuidle/Kconfig.arm | 1 +
> drivers/cpuidle/cpuidle-psci-domain.c | 31 +++++++++++++++-----------
> drivers/firmware/psci/Kconfig | 14 ++++++++++++
> drivers/firmware/psci/Makefile | 1 +
> drivers/firmware/psci/psci-devices.c | 41 +++++++++++++++++++++++++++++++++++
> 6 files changed, 76 insertions(+), 13 deletions(-)
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 207a6e2db70c..9c0334ee2ed2 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -21932,6 +21932,7 @@ L: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx (moderated for non-subscribers)
> S: Maintained
> F: Documentation/devicetree/bindings/arm/psci.yaml
> F: drivers/firmware/psci/
> +F: drivers/firmware/psci/psci-devices.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..f22e18b05053 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 ARM_PSCI_DEVICES
> 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..0ce6a83f6588 100644
> --- a/drivers/cpuidle/cpuidle-psci-domain.c
> +++ b/drivers/cpuidle/cpuidle-psci-domain.c
> @@ -9,10 +9,11 @@
>
> #define pr_fmt(fmt) "CPUidle PSCI: " fmt
>
> +#include <linux/auxiliary_bus.h>
> #include <linux/cpu.h>
> #include <linux/device.h>
> #include <linux/kernel.h>
> -#include <linux/platform_device.h>
> +#include <linux/module.h>
> #include <linux/pm_domain.h>
> #include <linux/pm_runtime.h>
> #include <linux/psci.h>
> @@ -122,14 +123,10 @@ 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)
> +static int psci_cpuidle_domain_probe(struct auxiliary_device *auxdev,
> + const struct auxiliary_device_id *id)
> {
> - struct device_node *np = pdev->dev.of_node;
> + struct device_node *np = auxdev->dev.of_node;
> bool use_osi = psci_has_osi_support();
> int ret = 0, pd_count = 0;
>
> @@ -177,16 +174,24 @@ static int psci_cpuidle_domain_probe(struct platform_device *pdev)
> return ret;
> }
>
> -static struct platform_driver psci_cpuidle_domain_driver = {
> - .probe = psci_cpuidle_domain_probe,
> +static const struct auxiliary_device_id psci_cpuidle_domain_id_table[] = {
> + { .name = "arm-psci.psci-cpuidle-domain" },
> + { }
> +};
> +MODULE_DEVICE_TABLE(auxiliary, psci_cpuidle_domain_id_table);
> +
> +static struct auxiliary_driver psci_cpuidle_domain_driver = {
> + .probe = psci_cpuidle_domain_probe,
> .driver = {
> - .name = "psci-cpuidle-domain",
> - .of_match_table = psci_of_match,
> + .suppress_bind_attrs = true,
> },
> + .id_table = psci_cpuidle_domain_id_table,
> };
>
> static int __init psci_idle_init_domains(void)
> {
> - return platform_driver_register(&psci_cpuidle_domain_driver);
> + return __auxiliary_driver_register(&psci_cpuidle_domain_driver,
> + THIS_MODULE,
> + "psci-cpuidle-domain");
> }
> core_initcall(psci_idle_init_domains);
> diff --git a/drivers/firmware/psci/Kconfig b/drivers/firmware/psci/Kconfig
> index 97944168b5e6..68e381f1a618 100644
> --- a/drivers/firmware/psci/Kconfig
> +++ b/drivers/firmware/psci/Kconfig
> @@ -2,6 +2,20 @@
> config ARM_PSCI_FW
> bool
>
> +config ARM_PSCI_DEVICES
> + bool "PSCI auxiliary device support"
> + depends on ARM_PSCI_FW
> + depends on OF
> + select AUXILIARY_BUS
> + default y
> + help
> + Say Y here to enable auxiliary device support for PSCI.
> +
> + This creates auxiliary devices for PSCI functionality implemented
> + outside the core PSCI firmware driver. These devices allow PSCI
> + child drivers to bind through the auxiliary bus while sharing the
> + PSCI firmware device as their parent.
> +
> config ARM_PSCI_CHECKER
> bool "ARM PSCI checker"
> depends on ARM_PSCI_FW && HOTPLUG_CPU && CPU_IDLE && !TORTURE_TEST
> diff --git a/drivers/firmware/psci/Makefile b/drivers/firmware/psci/Makefile
> index 1956b882470f..8e75a0ed6f74 100644
> --- a/drivers/firmware/psci/Makefile
> +++ b/drivers/firmware/psci/Makefile
> @@ -1,4 +1,5 @@
> # SPDX-License-Identifier: GPL-2.0
> #
> obj-$(CONFIG_ARM_PSCI_FW) += psci.o
> +obj-$(CONFIG_ARM_PSCI_DEVICES) += psci-devices.o
> obj-$(CONFIG_ARM_PSCI_CHECKER) += psci_checker.o
> diff --git a/drivers/firmware/psci/psci-devices.c b/drivers/firmware/psci/psci-devices.c
> new file mode 100644
> index 000000000000..f1eca61e3269
> --- /dev/null
> +++ b/drivers/firmware/psci/psci-devices.c
> @@ -0,0 +1,41 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
> + */
> +
> +#include <linux/auxiliary_bus.h>
> +#include <linux/init.h>

I think you need module.h not init.h.

> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +
> +static int arm_psci_probe(struct platform_device *pdev)
> +{
> + struct auxiliary_device *auxdev;
> +
> + auxdev = __devm_auxiliary_device_create(&pdev->dev, "arm-psci",
> + "psci-cpuidle-domain", NULL, 0);
> + if (!auxdev)
> + return -ENOMEM;
> +
> + return 0;
> +}

I would prefer you to move the code between the patches a bit. This patch
should already be introducing the full, future-proof infrastructure for
registering multiple auxiliary devices, so maybe add a static table with device
info? Then in patch 10/10 you'd just extend it for reboot modes.

I'd also not add any ifdef guards here and lesses the build-time dependencies.
You can register the device alright, it just won't get probed if the reboot-mode
support is not there.

Bart

> +
> +static const struct of_device_id arm_psci_of_match[] = {
> + { .compatible = "arm,psci-1.0" },
> + { }
> +};
> +
> +static struct platform_driver arm_psci_driver = {
> + .probe = arm_psci_probe,
> + .driver = {
> + .name = "arm-psci",
> + .of_match_table = arm_psci_of_match,
> + .suppress_bind_attrs = true,
> + },
> +};
> +
> +static int __init arm_psci_init(void)
> +{
> + return platform_driver_register(&arm_psci_driver);
> +}
> +core_initcall(arm_psci_init);
>
> --
> 2.34.1
>
>