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

[Bartosz Golaszewski]

On Thu, 27 Aug 2026 14:59:06 +0200, Lee Jones <lee at kernel.org> said:
> On Wed, 26 Aug 2026, Bartosz Golaszewski wrote:
>
>> On Fri, 21 Aug 2026 14:59:49 +0200, Ulf Hansson
>> <ulf.hansson at oss.qualcomm.com> said:
>> > On Mon, Aug 3, 2026 at 11:45 AM Shivendra Pratap
>> > <shivendra.pratap at oss.qualcomm.com> 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.
>> >
>>
>> Hi Uffe!
>>
>> Since I was the one to suggest MFD - would you mind providing more arguments
>> in favor of your preferred option?
>>
>> My reasoning for MFD was that it is indeed a device that provides multiple
>> functionalities, of which cpuidle is not really he main one even though it's
>> currently the only driver binding to this node.
>>
>> In any case, we'd need a "core" driver binding to the psci node and with
>> multiple auxiliary devices with their own drivers, we'd end up reimplementing
>> MFD.
>
> Ulf could be correct.
>
> MFD is usually reserved for real devices, whereas the aux is a little
> more loose.  Please consider it as an option.
>

My point is: if you start registering auxiliary devices from a "core" platform
driver based on real child OF nodes then you're basically re-implementing MFD.

At that point you're better off just using the existing MFD infrastructure.

Thanks,
Bartosz