Re: Question regarding scmi_perf_domain.c

[Sudeep Holla <sudeep.holla@arm.com>]

On Wed, Oct 11, 2023 at 12:30:35AM +0000, Peng Fan wrote:
> > Subject: Re: Question regarding scmi_perf_domain.c
> > 
> > On Tue, Oct 10, 2023 at 01:43:32PM +0000, Peng Fan wrote:
> > > > Subject: Re: Question regarding scmi_perf_domain.c
> > > >
> > > > On Tue, Oct 10, 2023 at 01:15:26PM +0000, Peng Fan wrote:
> > > > >
> > > > > Thanks for the detailed explanation, so power-domains property
> > > > > could be used both for power domain or performance domain. But if
> > > > > one device has both power domain and performance domain. Only
> > > > > power-domain property is not enough. I may understand wrong, let me
> > look into the code.
> > > > >
> > > >
> > > > I haven't tried this but something I could come up quick wit Juno
> > > > DTS as
> > > > reference:
> > > >
> > > > We can change something like this:
> > > >
> > > >       scmi_dvfs: protocol@13 {
> > > >               reg = <0x13>;
> > > > -             #clock-cells = <1>;
> > > > +             #power-domain-cells = <1>;
> > > >               mbox-names = "tx", "rx";
> > > >               mboxes = <&mailbox 1 0 &mailbox 1 1>;
> > > >               shmem = <&cpu_scp_hpri0 &cpu_scp_hpri1>;
> > > >       };
> > > >
> > > > And then in the consumer node(taking GPU as it has both perf and
> > > > power domains). The CPUs are simpler as don't have explicit power
> > > > domains, some Qcom platforms do use that. Anyways I would change
> > GPU node like this.
> > > > Hope this clarifies things for you.
> > > >
> > > >  &gpu {
> > > > -       clocks = <&scmi_dvfs 2>;
> > > > -       power-domains = <&scmi_devpd 9>;
> > > > +       power-domains = <&scmi_dvfs 2 &scmi_devpd 9>;
> > > > +       power-domain-names = "perf", "power";
> > >
> > > With one single power domain, the platform common code will
> > > automatically power on the domain before probe, with help from
> > > genpd_dev_pm_attach.
> > >
> > > But with multiple entries, device driver should handle power domains
> > > by themselves.
> > >
> > > Maybe Ulf could comment whether the genpd could update to support
> > > perf/power case just as one power domain entry before.
> > >
> > 
> > Hmm, I would rather check if the genpd can still handle automatic
> > power on of the domain before probe with one power and one perf domain.
> > IWO, one power domains and other domains in the mix. The reason why we
> > can't have single domain to support both power and perf using SCMI is
> > we don't know if the domains are 1:1 as presented by the SCMI platform
> > firmware.
> > 
> > AFAIU it was the main issue/confusion you raised initially. I am
> > surprised as how we had all these discussions and now you are circling
> > back and requesting to combine the support in single domain which
> > contradicts your initial confusion. I am seriously lost as what you are
> > looking for now ?
> 
> No, I am not requesting to combine in single domain. I still wanna perf
> domain and power domain has their own IDs. But I was not aware
> perf domain is using power-domains property, so one device has
> power domains and perf domains both, the automatic power domain
> on is broken. I was thinking we introduce a new property saying
> perf-domains property.
> 

IIUC, this should not need any extra information from the DT than what we
already have. It is just implementation could improve to deal with your ask.

-- 
Regards,
Sudeep