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

[Dmitry Baryshkov]

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.

> Yeah I said 'necessary' because of the arm32 platforms. This would probably
> be the preferable way forward.
> 
> > I'm not aware of non-OSI PSCI platforms with MPM either, so I'm not sure
> > when this fallback would be used.
> 
> I think it's generally only SC7180 and there's definitely no MPM there.

Yes, it looks like there were no other non-OSI platforms. It was either
normal OSI PSCI or the old SPM idle.

> 
> > We probably do need some fallback for the old sm6375/agatii DTBs though.
> 
> The sleep logic doesn't really matter without the platforms hitting a
> specific power state anyway, so I'm not sure we actually have to (i.e.
> the regressed path can't be exercised today anyway)
> 
> Konrad

-- 
With best wishes
Dmitry