linux-kernel - Re: [PATCH v1] PM-runtime: Check supplier

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Date:   Mon, 27 Jun 2022 21:00:51 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     peter.wang@...iatek.com
Cc:     Matthias Brugger <matthias.bgg@...il.com>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Avri Altman <avri.altman@....com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        wsd_upstream <wsd_upstream@...iatek.com>,
        "moderated list:ARM/Mediatek SoC..." 
        <linux-mediatek@...ts.infradead.org>, chun-hung.wu@...iatek.com,
        alice.chao@...iatek.com, cc.chou@...iatek.com,
        chaotian.jing@...iatek.com, jiajie.hao@...iatek.com,
        powen.kao@...iatek.com, qilin.tan@...iatek.com,
        lin.gui@...iatek.com, tun-yu.yu@...iatek.com
Subject: Re: [PATCH v1] PM-runtime: Check supplier_preactivated before release supplier

On Mon, Jun 13, 2022 at 2:08 PM <peter.wang@...iatek.com> wrote:
>
> From: Peter Wang <peter.wang@...iatek.com>
>
> With divice link of DL_FLAG_PM_RUNTIME, if consumer call pm_runtime_get_suppliers
> to prevent supplier enter suspend, pm_runtime_release_supplier should
> check supplier_preactivated before let supplier enter suspend.

Why?

> If the link is drop or release, bypass check supplier_preactivated.
>
> Signed-off-by: Peter Wang <peter.wang@...iatek.com>
> ---
>  drivers/base/core.c          |  2 +-
>  drivers/base/power/runtime.c | 15 ++++++++++++---
>  include/linux/pm_runtime.h   |  5 +++--
>  3 files changed, 16 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 7cd789c4985d..3b9cc559928f 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -486,7 +486,7 @@ static void device_link_release_fn(struct work_struct *work)
>         /* Ensure that all references to the link object have been dropped. */
>         device_link_synchronize_removal();
>
> -       pm_runtime_release_supplier(link, true);
> +       pm_runtime_release_supplier(link, true, true);
>
>         put_device(link->consumer);
>         put_device(link->supplier);
> diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
> index 676dc72d912d..3c4f425937a1 100644
> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -314,10 +314,19 @@ static int rpm_get_suppliers(struct device *dev)
>   * and if @check_idle is set, check if that device is idle (and so it can be
>   * suspended).
>   */
> -void pm_runtime_release_supplier(struct device_link *link, bool check_idle)
> +void pm_runtime_release_supplier(struct device_link *link, bool check_idle,
> +       bool drop)
>  {
>         struct device *supplier = link->supplier;
>
> +       /*
> +        * When consumer hold supplier, supplier cannot enter suspend.
> +        * Driect release supplier and let supplier enter suspend is not allow.
> +        * Unless the link is drop, direct relsease supplier should be okay.
> +        */
> +       if (link->supplier_preactivated && !drop)
> +               return;
> +
>         /*
>          * The additional power.usage_count check is a safety net in case
>          * the rpm_active refcount becomes saturated, in which case
> @@ -338,7 +347,7 @@ static void __rpm_put_suppliers(struct device *dev, bool try_to_suspend)
>
>         list_for_each_entry_rcu(link, &dev->links.suppliers, c_node,
>                                 device_links_read_lock_held())
> -               pm_runtime_release_supplier(link, try_to_suspend);
> +               pm_runtime_release_supplier(link, try_to_suspend, false);
>  }
>
>  static void rpm_put_suppliers(struct device *dev)
> @@ -1838,7 +1847,7 @@ void pm_runtime_drop_link(struct device_link *link)
>                 return;
>
>         pm_runtime_drop_link_count(link->consumer);
> -       pm_runtime_release_supplier(link, true);
> +       pm_runtime_release_supplier(link, true, true);
>  }
>
>  static bool pm_runtime_need_not_resume(struct device *dev)
> diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h
> index 9e4d056967c6..354ffb1eaec0 100644
> --- a/include/linux/pm_runtime.h
> +++ b/include/linux/pm_runtime.h
> @@ -88,7 +88,8 @@ extern void pm_runtime_get_suppliers(struct device *dev);
>  extern void pm_runtime_put_suppliers(struct device *dev);
>  extern void pm_runtime_new_link(struct device *dev);
>  extern void pm_runtime_drop_link(struct device_link *link);
> -extern void pm_runtime_release_supplier(struct device_link *link, bool check_idle);
> +extern void pm_runtime_release_supplier(struct device_link *link,
> +       bool check_idle, bool drop);
>
>  extern int devm_pm_runtime_enable(struct device *dev);
>
> @@ -315,7 +316,7 @@ static inline void pm_runtime_put_suppliers(struct device *dev) {}
>  static inline void pm_runtime_new_link(struct device *dev) {}
>  static inline void pm_runtime_drop_link(struct device_link *link) {}
>  static inline void pm_runtime_release_supplier(struct device_link *link,
> -                                              bool check_idle) {}
> +                                              bool check_idle, bool drop) {}
>
>  #endif /* !CONFIG_PM */
>
> --
> 2.18.0
>