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SubjectRe: [PATCH 1/2] PM / Domains: Add GENPD_FLAG_SUSPEND_ON flag
On 2020-08-13 18:04, Ulf Hansson wrote:
> On Wed, 12 Aug 2020 at 19:03, Sibi Sankar <sibis@codeaurora.org> 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@codeaurora.org> 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@codeaurora.org>
>> >> ---
>> >> 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.

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