Re: [PATCH 2/2] cpuidle: psci: Enable s2idle when using OSI with the PM domain topology

["Rafael J. Wysocki" <rafael@kernel.org>]

On Thu, Oct 1, 2020 at 12:18 PM Sudeep Holla <sudeep.holla@arm.com> wrote:
>
> On Tue, Sep 01, 2020 at 10:27:07AM +0200, Ulf Hansson wrote:
> > To select domain idle states for cpuidle-psci, the PM domains via genpd are
> > being managed by using runtime PM. This works fine for the regular idle
> > path, but it doesn't when doing s2idle.
> >
> > More precisely, the domain idle states becomes temporarily disabled, which
> > is because the PM core disables runtime PM for devices during system
> > suspend.
>
> When you refer system suspend above, you mean both S2R and S2I ?
>
> > Even if genpd tries to power off the PM domain in the
> > suspend_noirq phase, that doesn't help to properly select a domain idle
> > state, as this needs to be done on per CPU basis.
> >
>
> And what prevents doing per CPU basis ?
>
> > Let's address the issue by enabling the syscore flag for the attached CPU
> > devices. This prevents genpd from trying to power off the corresponding PM
> > domains in the suspend_noirq phase. Moreover, let's assign a specific
> > ->enter_s2idle() callback for the corresponding domain idle state and let
> > it invoke pm_genpd_syscore_poweroff|poweron(), rather than using runtime
> > PM.
> >
>
> The syscore_suspend is not executed for S2I and using syscore APIs here
> is bit confusing IMO.

Right.

> If Rafael is fine,

No, I'm not.

Cheers!

> I have no objections.
>
> > Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> > ---
> >  drivers/cpuidle/cpuidle-psci-domain.c |  2 ++
> >  drivers/cpuidle/cpuidle-psci.c        | 30 +++++++++++++++++++++++----
> >  2 files changed, 28 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/cpuidle/cpuidle-psci-domain.c b/drivers/cpuidle/cpuidle-psci-domain.c
> > index b6e9649ab0da..65437ba5fa78 100644
> > --- a/drivers/cpuidle/cpuidle-psci-domain.c
> > +++ b/drivers/cpuidle/cpuidle-psci-domain.c
> > @@ -324,6 +324,8 @@ struct device *psci_dt_attach_cpu(int cpu)
> >       if (cpu_online(cpu))
> >               pm_runtime_get_sync(dev);
> >
> > +     dev_pm_syscore_device(dev, true);
> > +
> >       return dev;
> >  }
> >
> > diff --git a/drivers/cpuidle/cpuidle-psci.c b/drivers/cpuidle/cpuidle-psci.c
> > index 74463841805f..6322d55a0a7d 100644
> > --- a/drivers/cpuidle/cpuidle-psci.c
> > +++ b/drivers/cpuidle/cpuidle-psci.c
> > @@ -19,6 +19,7 @@
> >  #include <linux/of_device.h>
> >  #include <linux/platform_device.h>
> >  #include <linux/psci.h>
> > +#include <linux/pm_domain.h>
> >  #include <linux/pm_runtime.h>
> >  #include <linux/slab.h>
> >  #include <linux/string.h>
> > @@ -52,8 +53,9 @@ static inline int psci_enter_state(int idx, u32 state)
> >       return CPU_PM_CPU_IDLE_ENTER_PARAM(psci_cpu_suspend_enter, idx, state);
> >  }
> >
> > -static int psci_enter_domain_idle_state(struct cpuidle_device *dev,
> > -                                     struct cpuidle_driver *drv, int idx)
> > +static int __psci_enter_domain_idle_state(struct cpuidle_device *dev,
> > +                                       struct cpuidle_driver *drv, int idx,
> > +                                       bool s2idle)
> >  {
> >       struct psci_cpuidle_data *data = this_cpu_ptr(&psci_cpuidle_data);
> >       u32 *states = data->psci_states;
> > @@ -66,7 +68,10 @@ static int psci_enter_domain_idle_state(struct cpuidle_device *dev,
> >               return -1;
> >
> >       /* Do runtime PM to manage a hierarchical CPU toplogy. */
> > -     pm_runtime_put_sync_suspend(pd_dev);
> > +     if (s2idle)
> > +             pm_genpd_syscore_poweroff(pd_dev);
> > +     else
> > +             pm_runtime_put_sync_suspend(pd_dev);
>
> Since CPU genpd is special and handled so in core, can this be moved to core ?
> I mean pm_runtime_put_sync_suspend handle that based genpd_is_cpu_domain.
>
> --
> Regards,
> Sudeep

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