linux-kernel - Re: [RFC PATCH v5 4/4] PM: domains: Add and set generic sync state callback

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Date:   Tue, 4 Jul 2023 15:54:28 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Abel Vesa <abel.vesa@...aro.org>
Cc:     "Rafael J . Wysocki" <rafael@...nel.org>,
        Kevin Hilman <khilman@...nel.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Saravana Kannan <saravanak@...gle.com>,
        Bjorn Andersson <andersson@...nel.org>,
        linux-pm@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm@...r.kernel.org,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Subject: Re: [RFC PATCH v5 4/4] PM: domains: Add and set generic sync state callback

On Wed, 21 Jun 2023 at 16:40, Abel Vesa <abel.vesa@...aro.org> wrote:
>
> For every provider that doesn't register a sync_state callback,
> register a generic one. This new generic sync_state callback queues up a
> power off request.
>
> Signed-off-by: Abel Vesa <abel.vesa@...aro.org>
> ---
>  drivers/base/power/domain.c | 23 +++++++++++++++++++++++
>  include/linux/pm_domain.h   |  3 +++
>  2 files changed, 26 insertions(+)
>
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 5967ade160e2..ec16db0599ac 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -654,6 +654,27 @@ static void genpd_queue_power_off_work(struct generic_pm_domain *genpd)
>         queue_work(pm_wq, &genpd->power_off_work);
>  }
>
> +/**
> + * pm_genpd_power_off_unused_sync_state - Power off all domains for provider.
> + * @dev: Provider's device.
> + *
> + * Request power off for all unused domains of the provider.
> + * This should be used exclusively as sync state callback for genpd providers.
> + */
> +void pm_genpd_power_off_unused_sync_state(struct device *dev)
> +{
> +       struct generic_pm_domain *genpd;
> +
> +       mutex_lock(&gpd_list_lock);
> +
> +       list_for_each_entry(genpd, &gpd_list, gpd_list_node)
> +               if (genpd->provider && genpd->provider->dev == dev)

Not all genpds have the ->provider assigned. Moreover, the
of_genpd_mutex is protecting the list of providers, we should use that
instead.

> +                       genpd_queue_power_off_work(genpd);
> +
> +       mutex_unlock(&gpd_list_lock);
> +}
> +EXPORT_SYMBOL_GPL(pm_genpd_power_off_unused_sync_state);

Why does this need to be exported? Is there a provider that assigns
it's own sync state callback that needs to call this? If that is the
case, I would prefer to see a user of this API as a part of the series
too.

> +
>  /**
>   * genpd_keep_on - Tells if the domain should skip the power 'off' request
>   * @genpd: PM domain to be checked.
> @@ -2329,6 +2350,8 @@ static int genpd_add_provider(struct device_node *np, genpd_xlate_t xlate,
>         cp->xlate = xlate;
>         fwnode_dev_initialized(&np->fwnode, true);
>
> +       dev_set_drv_sync_state(np->fwnode.dev, pm_genpd_power_off_unused_sync_state);
> +
>         mutex_lock(&of_genpd_mutex);
>         list_add(&cp->link, &of_genpd_providers);
>         mutex_unlock(&of_genpd_mutex);
> diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
> index 3eb32c4b6d4f..78164244b89f 100644
> --- a/include/linux/pm_domain.h
> +++ b/include/linux/pm_domain.h
> @@ -279,6 +279,9 @@ static inline int pm_genpd_remove(struct generic_pm_domain *genpd)
>         return -EOPNOTSUPP;
>  }
>
> +static inline void pm_genpd_power_off_unused_sync_state(struct device *dev)
> +{ }
> +
>  static inline int dev_pm_genpd_set_performance_state(struct device *dev,
>                                                      unsigned int state)
>  {

Kind regards
Uffe