[PATCH v2 2/2] cpuidle: psci: Allow PM domain to be initialized even if no OSI mode

[Ulf Hansson]

On Tue, 1 Sep 2020 at 15:32, Sudeep Holla <sudeep.holla at arm.com> wrote:
>
> On Tue, Sep 01, 2020 at 02:12:26PM +0200, Ulf Hansson wrote:
> > If the PSCI OSI mode isn't supported or fails to be enabled, the PM domain
> > topology with the genpd providers isn't initialized. This is perfectly fine
> > from cpuidle-psci point of view.
> >
> > However, since the PM domain topology in the DTS files is a description of
> > the HW, no matter of whether the PSCI OSI mode is supported or not, other
> > consumers besides the CPUs may rely on it.
> >
> > Therefore, let's always allow the initialization of the PM domain topology
> > to succeed, independently of whether the PSCI OSI mode is supported.
> > Consequentially we need to track if we succeed to enable the OSI mode, as
> > to know when a domain idlestate can be selected.
> >
> > Note that, CPU devices are still not being attached to the PM domain
> > topology, unless the PSCI OSI mode is supported.
> >
> > Signed-off-by: Ulf Hansson <ulf.hansson at linaro.org>
> > ---
> >
> > Changes in v2:
> >       - Assign the genpd ->power_off() callback, only when the PSCI OSI mode
> >       has been successfully enabled.
> >
> > ---
> >  drivers/cpuidle/cpuidle-psci-domain.c | 57 ++++++++++++++-------------
> >  1 file changed, 29 insertions(+), 28 deletions(-)
> >
> > diff --git a/drivers/cpuidle/cpuidle-psci-domain.c b/drivers/cpuidle/cpuidle-psci-domain.c
> > index b6ab0415f450..256e7e35b5af 100644
> > --- a/drivers/cpuidle/cpuidle-psci-domain.c
> > +++ b/drivers/cpuidle/cpuidle-psci-domain.c
> > @@ -105,7 +105,7 @@ static void psci_pd_free_states(struct genpd_power_state *states,
> >       kfree(states);
> >  }
> >
> > -static int psci_pd_init(struct device_node *np)
> > +static int psci_pd_init(struct device_node *np, bool use_osi)
> >  {
> >       struct generic_pm_domain *pd;
> >       struct psci_pd_provider *pd_provider;
> > @@ -135,11 +135,14 @@ static int psci_pd_init(struct device_node *np)
> >
> >       pd->free_states = psci_pd_free_states;
> >       pd->name = kbasename(pd->name);
> > -     pd->power_off = psci_pd_power_off;
> >       pd->states = states;
> >       pd->state_count = state_count;
> >       pd->flags |= GENPD_FLAG_IRQ_SAFE | GENPD_FLAG_CPU_DOMAIN;
> >
> > +     /* Use the ->power_off() callback when OSI is enabled. */
>
> IIUC, you did mention that we need to attach PD even when the OSI fails
> as this could be shared domain. With the below conditional assignment
> of power_off, I understand that if OSI fails and we have domains attached,
> then it will be always ON ?

>From a genpd point of view, the corresponding PM domain can be powered
off (as long as all attached consumers allow that as well, of course).

Hmm, maybe we should add a GENPD_FLAG_ALWAYS_ON, to really enforce
that it stays on?

>
>
> Other than that, this patch looks good.
>
> Acked-by: Sudeep Holla <sudeep.holla at arm.com>

Thanks!

Kind regards
Uffe