linux-kernel - Re: [PATCH v3 1/5] PM: domains: Allow a genpd consumer to require a synced power off

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Message-ID: <84ab14d8-8177-a921-7ae2-7d05248a190b@quicinc.com>
Date:   Wed, 21 Dec 2022 22:45:29 +0530
From:   Akhil P Oommen <quic_akhilpo@...cinc.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
CC:     freedreno <freedreno@...ts.freedesktop.org>,
        <dri-devel@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>,
        Rob Clark <robdclark@...il.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kevin Hilman <khilman@...nel.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        <linux-kernel@...r.kernel.org>, <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v3 1/5] PM: domains: Allow a genpd consumer to require a
 synced power off

On 12/21/2022 8:13 PM, Ulf Hansson wrote:
> On Tue, 20 Dec 2022 at 08:44, Akhil P Oommen <quic_akhilpo@...cinc.com> wrote:
>> From: Ulf Hansson <ulf.hansson@...aro.org>
>>
>> Some genpd providers doesn't ensure that it has turned off at hardware.
>> This is fine until the consumer really requires during some special
>> scenarios that the power domain collapse at hardware before it is
>> turned ON again.
>>
>> An example is the reset sequence of Adreno GPU which requires that the
>> 'gpucc cx gdsc' power domain should move to OFF state in hardware at
>> least once before turning in ON again to clear the internal state.
>>
>> Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
>> Signed-off-by: Akhil P Oommen <quic_akhilpo@...cinc.com>
>> ---
>>
>> (no changes since v2)
>>
>> Changes in v2:
>> - Minor formatting fix
>>
>>  drivers/base/power/domain.c | 23 +++++++++++++++++++++++
>>  include/linux/pm_domain.h   |  5 +++++
>>  2 files changed, 28 insertions(+)
>>
>> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
>> index 967bcf9d415e..53524a102321 100644
>> --- a/drivers/base/power/domain.c
>> +++ b/drivers/base/power/domain.c
>> @@ -519,6 +519,28 @@ ktime_t dev_pm_genpd_get_next_hrtimer(struct device *dev)
>>  }
>>  EXPORT_SYMBOL_GPL(dev_pm_genpd_get_next_hrtimer);
>>
>> +/*
>> + * dev_pm_genpd_synced_poweroff - Next power off should be synchronous
>> + *
>> + * @dev: A device that is attached to the genpd.
>> + *
>> + * Allows a consumer of the genpd to notify the provider that the next power off
>> + * should be synchronous.
> Nitpick; similar to other dev_pm_genpd_* function-descriptions, I
> think it's important to add the below information.
>
> "It is assumed that the users guarantee that the genpd wouldn't be
> detached while this routine is getting called."
>
> Can you please add that?
Thanks. Fixed in revision 4.

-Akhil.
>
>> + */
>> +void dev_pm_genpd_synced_poweroff(struct device *dev)
>> +{
>> +       struct generic_pm_domain *genpd;
>> +
>> +       genpd = dev_to_genpd_safe(dev);
>> +       if (!genpd)
>> +               return;
>> +
>> +       genpd_lock(genpd);
>> +       genpd->synced_poweroff = true;
>> +       genpd_unlock(genpd);
>> +}
>> +EXPORT_SYMBOL_GPL(dev_pm_genpd_synced_poweroff);
>> +
>>  static int _genpd_power_on(struct generic_pm_domain *genpd, bool timed)
>>  {
>>         unsigned int state_idx = genpd->state_idx;
>> @@ -562,6 +584,7 @@ static int _genpd_power_on(struct generic_pm_domain *genpd, bool timed)
>>
>>  out:
>>         raw_notifier_call_chain(&genpd->power_notifiers, GENPD_NOTIFY_ON, NULL);
>> +       genpd->synced_poweroff = false;
>>         return 0;
>>  err:
>>         raw_notifier_call_chain(&genpd->power_notifiers, GENPD_NOTIFY_OFF,
>> diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
>> index 1cd41bdf73cf..f776fb93eaa0 100644
>> --- a/include/linux/pm_domain.h
>> +++ b/include/linux/pm_domain.h
>> @@ -136,6 +136,7 @@ struct generic_pm_domain {
>>         unsigned int prepared_count;    /* Suspend counter of prepared devices */
>>         unsigned int performance_state; /* Aggregated max performance state */
>>         cpumask_var_t cpus;             /* A cpumask of the attached CPUs */
>> +       bool synced_poweroff;           /* A consumer needs a synced poweroff */
>>         int (*power_off)(struct generic_pm_domain *domain);
>>         int (*power_on)(struct generic_pm_domain *domain);
>>         struct raw_notifier_head power_notifiers; /* Power on/off notifiers */
>> @@ -235,6 +236,7 @@ int dev_pm_genpd_add_notifier(struct device *dev, struct notifier_block *nb);
>>  int dev_pm_genpd_remove_notifier(struct device *dev);
>>  void dev_pm_genpd_set_next_wakeup(struct device *dev, ktime_t next);
>>  ktime_t dev_pm_genpd_get_next_hrtimer(struct device *dev);
>> +void dev_pm_genpd_synced_poweroff(struct device *dev);
>>
>>  extern struct dev_power_governor simple_qos_governor;
>>  extern struct dev_power_governor pm_domain_always_on_gov;
>> @@ -300,6 +302,9 @@ static inline ktime_t dev_pm_genpd_get_next_hrtimer(struct device *dev)
>>  {
>>         return KTIME_MAX;
>>  }
>> +static inline void dev_pm_genpd_synced_poweroff(struct device *dev)
>> +{ }
>> +
>>  #define simple_qos_governor            (*(struct dev_power_governor *)(NULL))
>>  #define pm_domain_always_on_gov                (*(struct dev_power_governor *)(NULL))
>>  #endif
>> --
>> 2.7.4
>>
> Kind regards
> Uffe