Re: [PATCH v3 5/7] drivers: firmware: psci: Add hierarchical domain idle states converter

[Maulik Shah]

On 2/4/2020 8:51 PM, Sudeep Holla wrote:
> On Tue, Feb 04, 2020 at 10:22:42AM +0530, Maulik Shah wrote:
> > On 2/3/2020 10:38 PM, Sudeep Holla wrote:
> > > On Mon, Feb 03, 2020 at 07:05:38PM +0530, Maulik Shah wrote:
> > > > From: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> > > >
> > > > If the hierarchical CPU topology is used, but the OS initiated mode isn't
> > > > supported, we need to rely solely on the regular cpuidle framework to
> > > > manage the idle state selection, rather than using genpd and its
> > > > governor.
> > > >
> > > > For this reason, introduce a new PSCI DT helper function,
> > > > psci_dt_pm_domains_parse_states(), which parses and converts the
> > > > hierarchically described domain idle states from DT, into regular flattened
> > > > cpuidle states. The converted states are added to the existing cpuidle
> > > > driver's array of idle states, which make them available for cpuidle.
> > > And what's the main motivation for this if OSI is not supported in the
> > > firmware ?
> > Hi Sudeep,
> >
> > Main motivation is to do last-man activities before the CPU cluster can
> > enter a deep idle state.
> Details on those last-man activities will help the discussion. Basically
> I am wondering what they are and why they need to done in OSPM ?

Hi Sudeep,

there are cases like,

Last cpu going to deepest idle mode need to lower various resoruce 
requirements (for eg DDR freq).

This is done by calling rpmh_flush which send SLEEP values for various 
shared resources.

> > > > Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> > > > [applied to new path, resolved conflicts]
> > > > Signed-off-by: Maulik Shah <mkshah@xxxxxxxxxxxxxx>
> > > > ---
> > > >    drivers/cpuidle/cpuidle-psci-domain.c | 137 +++++++++++++++++++++++++++++-----
> > > >    drivers/cpuidle/cpuidle-psci.c        |  41 +++++-----
> > > >    drivers/cpuidle/cpuidle-psci.h        |  11 +++
> > > >    3 files changed, 153 insertions(+), 36 deletions(-)
> > > >
> > > > diff --git a/drivers/cpuidle/cpuidle-psci-domain.c b/drivers/cpuidle/cpuidle-psci-domain.c
> > > > index 423f03b..3c417f7 100644
> > > > --- a/drivers/cpuidle/cpuidle-psci-domain.c
> > > > +++ b/drivers/cpuidle/cpuidle-psci-domain.c
> > > > @@ -26,13 +26,17 @@ struct psci_pd_provider {
> > > >    };
> > > >
> > > >    static LIST_HEAD(psci_pd_providers);
> > > > -static bool osi_mode_enabled __initdata;
> > > > +static bool osi_mode_enabled;
> > > >
> > > >    static int psci_pd_power_off(struct generic_pm_domain *pd)
> > > >    {
> > > >    	struct genpd_power_state *state = &pd->states[pd->state_idx];
> > > >    	u32 *pd_state;
> > > >
> > > > +	/* If we have failed to enable OSI mode, then abort power off. */
> > > > +	if ((psci_has_osi_support()) && !osi_mode_enabled)
> > > > +		return -EBUSY;
> > > > +
> > > Why is this needed ? IIUC we don't create genpd domains if OSI is not
> > > enabled.
> > we do create genpd domains, for cpu domains, we just abort power off here
> > since idle states are converted into regular flattened mode.
> OK, IIRC the OSI patches from Ulf didn't add the genpd or rather removed
> them in case of any failure to enable OSI. Has that been changed ? If so,
> why ?
>
> > however genpd poweroff will be used by parent domain (rsc in this case)
> > which is kept in hireachy in DTSI with cluster domain to do last man
> > activities.
> I am bit confused here. Either we do OSI or PC and what you are describing
> sounds like a mix-n-match to me and I am totally against it.

we still do PC based on sc7180. there is no OSI.

can you please check v4 series, i have cleaned this change by remove 
converter part.

Thanks,

Maulik

> --
> Regards,
> Sudeep

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