Re: [PATCH 2/7] irqchip/irq-qcom-mpm: Register MPM under CPU cluster power domain

[Konrad Dybcio]

On 7/22/26 12:18 AM, Dmitry Baryshkov wrote:
> On Wed, Jul 15, 2026 at 12:45:48PM +0200, Konrad Dybcio wrote:
>> On 7/15/26 12:34 PM, Stephan Gerhold wrote:
>>> On Wed, Jul 15, 2026 at 11:46:58AM +0200, Konrad Dybcio wrote:
>>>> On 7/13/26 12:25 PM, Sneh Mankad wrote:
>>>>> MPM irqchip needs to notify RPM (Resource Power Manager) processor to read
>>>>> the latest wake up capable interrupts when the CPU cluster is entering the
>>>>> deepest idle state. This is done by sending IPC interrupt to RPM and is
>>>>> implemented as .power_off() callback by registering MPM as parent power
>>>>> domain to CPU cluster.
>>>>
>>>> [...]
>>>>
>>>>> If MPM has not registered with CPU cluster power domain, utilize the CPU PM
>>>>> notifications to manage RPM communication when the last CPU goes to power
>>>>> collapse.
>>>>
>>>> I have mixed feelings about this case. The RPMH RSC driver keeps that as a
>>>> fallback for platforms which don't have PSCI OSI mode specifically.
>>>>
>>>> On the other hand, there are platforms (early arm64 - pre-msm8996 and almost
>>>> all of the arm32 platforms) that don't define any CPU power domains, so
>>>> perhaps it's necessary after all..
>>>>
>>>
>>> I don't think this fallback is relevant for the non-PSCI QC platforms,
>>> for the following reasons:
>>>
>>>  - They don't define the MPM.
>>>  - They don't support cluster idle upstream, so they don't need to
>>>    define the MPM. They can't reach the idle state where it would become
>>>    relevant.
>>>  - The setup for cluster idle without PSCI is essentially equivalent to
>>>    OSI, except that the SPM/SAW driver needs to program the idle state
>>>    to enter. There is one SPM/SAW for every idle domain (e.g. on
>>>    MSM8939: 2x4 CPU, 2x Cluster, 1x System). You can just model the
>>>    SPM/SAW instances as power domains to get the same setup as PSCI OSI
>>>    (I had a draft for this at some point). So if someone ever implements
>>>    this, we should be able to use the same approach as for PSCI OSI.
> 
> For the regerence, MPM existed since MSM8960. I think it was never
> _that_ important to implement support for it in the upstream.

For a long time time, MSM8960 didn't have much more than basic
UART, USB and always-on, always-max-power peripherals. So..

Konrad