linux-kernel - Re: [PATCH v4 1/5] PM: domains: Allow a genpd consumer to require a synced power off

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Message-ID: <20221228184304.4lldh7dxp2pnplzc@builder.lan>
Date:   Wed, 28 Dec 2022 12:43:04 -0600
From:   Bjorn Andersson <andersson@...nel.org>
To:     Akhil P Oommen <quic_akhilpo@...cinc.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     freedreno <freedreno@...ts.freedesktop.org>,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        Rob Clark <robdclark@...il.com>,
        Ulf Hansson <ulf.hansson@...aro.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>,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH v4 1/5] PM: domains: Allow a genpd consumer to require a
 synced power off

On Wed, Dec 21, 2022 at 10:43:59PM +0530, Akhil P Oommen 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>

Reviewed-by: Bjorn Andersson <andersson@...nel.org>

@Rafael, would you be willing to share an immutable branch with this
change? Or would you be okay with me doing so from the qcom clock tree?

Regards,
Bjorn

> ---
> 
> Changes in v4:
> - Update genpd function documentation (Ulf)
> 
> Changes in v2:
> - Minor formatting fix
> 
>  drivers/base/power/domain.c | 26 ++++++++++++++++++++++++++
>  include/linux/pm_domain.h   |  5 +++++
>  2 files changed, 31 insertions(+)
> 
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 967bcf9d415e..84662d338188 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -519,6 +519,31 @@ 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.
> + *
> + * It is assumed that the users guarantee that the genpd wouldn't be detached
> + * while this routine is getting called.
> + */
> +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 +587,7 @@ 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
>