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

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

On 8/13/2026 6:08 PM, Lee Jones wrote:
> 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.

will rename it.

> 
>>   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);

Ack.

> 
>>   	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>"

Ack. Will make it more relevant.

> 
>> +       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.

Ack.

> 
>> +static int psci_mfd_probe(struct platform_device *pdev)
> 
> No to _mfd_.

Ack.


>> +{
>> +	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.

Ack.

> 
>> +core_initcall(psci_mfd_init);
> 
> This is usually a hack.  Why can't you use -EPROBE_DEFER?

Ack.

thanks,
Shivendra