linux-kernel - Re: [PATCH 1/2] PM / Domains: Add GENPD_FLAG_SUSPEND

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Date:   Wed, 12 Aug 2020 22:32:54 +0530
From:   Sibi Sankar <sibis@...eaurora.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Andy Gross <agross@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Doug Anderson <dianders@...omium.org>,
        linux-kernel-owner@...r.kernel.org,
        Kevin Hilman <khilman@...nel.org>
Subject: Re: [PATCH 1/2] PM / Domains: Add GENPD_FLAG_SUSPEND_ON flag

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@...eaurora.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.

> 
> Kind regards
> Uffe
> 
>> 
>> Signed-off-by: Sibi Sankar <sibis@...eaurora.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.