Re: [PATCH 1/2] PM / Domains: Add GENPD_FLAG_SUSPEND_ON flag

[Sibi Sankar]

On 2020-08-13 18:04, Ulf Hansson wrote:
> On Wed, 12 Aug 2020 at 19:03, Sibi Sankar <sibis@xxxxxxxxxxxxxx> wrote:
> > Uffe,
> > Thanks for taking time to review the
> > series!
> >
> > On 2020-08-12 15:15, Ulf Hansson wrote:
> > > On Tue, 11 Aug 2020 at 21:03, Sibi Sankar <sibis@xxxxxxxxxxxxxx> wrote:
> > >>
> > >> This is for power domains which needs to stay powered on for suspend
> > >> but can be powered on/off as part of runtime PM. This flag is aimed at
> > >> power domains coupled to remote processors which enter suspend states
> > >> independent to that of the application processor. Such power domains
> > >> are turned off only on remote processor crash/shutdown.
> > >
> > > As Kevin also requested, please elaborate more on the use case.
> > >
> > > Why exactly must the PM domain stay powered on during system suspend?
> > > Is there a wakeup configured that needs to be managed - or is there a
> > > co-processor/FW behaviour that needs to be obeyed to?
> >
> > Yes this is a co-processor behavior that
> > needs to be obeyed. Specifically application
> > processor notifies the Always on Subsystem
> > (AOSS) that a particular co-processor is up
> > using the power domains exposed by AOSS QMP
> > driver. AOSS uses this information to wait
> > for the co-processors to suspend before
> > starting its sleep sequence. The application
> > processor powers off these power domains only
> > if the co-processor has crashed or powered
> > off.
>
> Thanks for clarifying!
>
> Although, can you please elaborate a bit more on the actual use case?
> What are the typical co-processor and what drivers are involved in
> managing it?

The co-processors using the power domains
exposed by qcom_aoss driver are modem,
audio dsp, compute dsp managed using
qcom_q6v5_mss and qcom_q6v5_pas driver.

> As you may know, runtime PM becomes disabled during system suspend of
> a device. Which means, if the driver tries to power off the
> coprocessor (via calling pm_runtime_put() for example), somewhere in
> the system suspend phase of the corresponding device, its attached PM
> domain stays powered on when managed by genpd.

The drivers aren't really expected
do anything during suspend/resume
pretty much because the co-processors
enter low-power modes independent to
that of the application processor. On
co-processor crash the remoteproc core
does a pm_stay_awake followed by a
pm_relax after crash recovery.

> Then in the suspend_noirq phase, genpd tries to power off the PM
> domain, unless there are wakeups to consider.
>
> Taking the above into account, wouldn't that mean that you potentially
> may end up keeping the PM domain powered on, even if it actually can
> be powered off in the suspend_noirq phase by genpd?
>
> Kind regards
> Uffe
>
> > >
> > >>
> > >> Signed-off-by: Sibi Sankar <sibis@xxxxxxxxxxxxxx>
> > >> ---
> > >>  drivers/base/power/domain.c | 3 ++-
> > >>  include/linux/pm_domain.h   | 5 +++++
> > >>  2 files changed, 7 insertions(+), 1 deletion(-)
> > >>
> > >> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> > >> index 2cb5e04cf86cd..ba78ac4a450d4 100644
> > >> --- a/drivers/base/power/domain.c
> > >> +++ b/drivers/base/power/domain.c
> > >> @@ -129,6 +129,7 @@ static const struct genpd_lock_ops genpd_spin_ops
> > >> = {
> > >>  #define genpd_is_active_wakeup(genpd)  (genpd->flags &
> > >> GENPD_FLAG_ACTIVE_WAKEUP)
> > >>  #define genpd_is_cpu_domain(genpd)     (genpd->flags &
> > >> GENPD_FLAG_CPU_DOMAIN)
> > >>  #define genpd_is_rpm_always_on(genpd)  (genpd->flags &
> > >> GENPD_FLAG_RPM_ALWAYS_ON)
> > >> +#define genpd_is_suspend_on(genpd)     (genpd->flags &
> > >> GENPD_FLAG_SUSPEND_ON)
> > >>
> > >>  static inline bool irq_safe_dev_in_no_sleep_domain(struct device
> > >> *dev,
> > >>                 const struct generic_pm_domain *genpd)
> > >> @@ -949,7 +950,7 @@ static void genpd_sync_power_off(struct
> > >> generic_pm_domain *genpd, bool use_lock,
> > >>  {
> > >>         struct gpd_link *link;
> > >>
> > >> -       if (!genpd_status_on(genpd) || genpd_is_always_on(genpd))
> > >> +       if (!genpd_status_on(genpd) || genpd_is_always_on(genpd) ||
> > >> genpd_is_suspend_on(genpd))
> > >>                 return;
> > >>
> > >>         if (genpd->suspended_count != genpd->device_count
> > >> diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
> > >> index ee11502a575b0..3002a2d68936a 100644
> > >> --- a/include/linux/pm_domain.h
> > >> +++ b/include/linux/pm_domain.h
> > >> @@ -55,6 +55,10 @@
> > >>   *
> > >>   * GENPD_FLAG_RPM_ALWAYS_ON:   Instructs genpd to always keep the PM
> > >> domain
> > >>   *                             powered on except for system suspend.
> > >> + *
> > >> + * GENPD_FLAG_SUSPEND_ON:      Instructs genpd to keep the PM domain
> > >> powered
> > >> + *                             on during suspend and runtime PM
> > >> controlled
> > >> + *                             otherwise.
> > >>   */
> > >>  #define GENPD_FLAG_PM_CLK       (1U << 0)
> > >>  #define GENPD_FLAG_IRQ_SAFE     (1U << 1)
> > >> @@ -62,6 +66,7 @@
> > >>  #define GENPD_FLAG_ACTIVE_WAKEUP (1U << 3)
> > >>  #define GENPD_FLAG_CPU_DOMAIN   (1U << 4)
> > >>  #define GENPD_FLAG_RPM_ALWAYS_ON (1U << 5)
> > >> +#define GENPD_FLAG_SUSPEND_ON   (1U << 6)
> > >>
> > >>  enum gpd_status {
> > >>         GPD_STATE_ACTIVE = 0,   /* PM domain is active */
> > >> --
> > >> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
> > >> Forum,
> > >> a Linux Foundation Collaborative Project
> > >>
> >
> > --
> > Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> > a Linux Foundation Collaborative Project.

--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project.