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

[Shivendra Pratap <shivendra.pratap@oss.qualcomm.com>]

On 9/16/2026 2:59 PM, Bartosz Golaszewski wrote:
> On Mon, 14 Sep 2026 16:59:08 +0200, Shivendra Pratap
> <shivendra.pratap@oss.qualcomm.com> 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@oss.qualcomm.com>
>> Suggested-by: Lee Jones <lee@kernel.org>
>> Suggested-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 | 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@lists.infradead.org (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.

Ack.


> 
>> +#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.

Ack. will update it.

> 
> 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.

Ack.

thanks,
Shivendra