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Message-ID: <CAPDyKFrui-Vr1rvE01w+n4ttWeUk4cmr2jqgqk0BWe98eQtkcg@mail.gmail.com>
Date: Thu, 18 Sep 2025 16:57:34 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Peng Fan <peng.fan@....com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>, Pavel Machek <pavel@...nel.org>,
Peter Chen <peter.chen@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>,
Pengutronix Kernel Team <kernel@...gutronix.de>, Fabio Estevam <festevam@...il.com>,
Thinh Nguyen <Thinh.Nguyen@...opsys.com>, Vincent Guittot <vincent.guittot@...aro.org>,
Xu Yang <xu.yang_2@....com>, linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-usb@...r.kernel.org, imx@...ts.linux.dev, arm-scmi@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 1/4] pmdomain: core: Introduce device_set/get_out_band_wakeup()
On Tue, 2 Sept 2025 at 05:33, Peng Fan <peng.fan@....com> wrote:
>
> For some cases, a device could still wakeup the system even if its power
> domain is in off state, because the device's wakeup hardware logic is
> in an always-on domain.
>
> To support this case, introduce device_set/get_out_band_wakeup() to
> allow device drivers to control the behaviour in genpd for a device
> that is attached to it.
Would you mind trying to extend/clarify this commit-msg a bit more, to
make the benefit more clear.
For example, today we may be wasting energy, by unnecessarily keeping
PM domains powered-on during system-wide suspend, when a device has
been enabled for system-wakeup...
In regards to terminology, I would appreciate if we could use
"system-wakeup" and "out-band system-wakeup logic" and "system-wide
suspend".
>
> Signed-off-by: Peng Fan <peng.fan@....com>
> ---
> drivers/pmdomain/core.c | 6 ++++--
> include/linux/pm.h | 1 +
> include/linux/pm_wakeup.h | 17 +++++++++++++++++
Please split this into two separate patches.
> 3 files changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pmdomain/core.c b/drivers/pmdomain/core.c
> index 0006ab3d078972cc72a6dd22a2144fb31443e3da..8e37758cea88a9ee051ad9fb13bdd3feb4f8745e 100644
> --- a/drivers/pmdomain/core.c
> +++ b/drivers/pmdomain/core.c
> @@ -1549,7 +1549,8 @@ static int genpd_finish_suspend(struct device *dev,
> if (ret)
> return ret;
>
> - if (device_awake_path(dev) && genpd_is_active_wakeup(genpd))
> + if (device_awake_path(dev) && genpd_is_active_wakeup(genpd) &&
> + !device_get_out_band_wakeup(dev))
> return 0;
>
> if (genpd->dev_ops.stop && genpd->dev_ops.start &&
> @@ -1604,7 +1605,8 @@ static int genpd_finish_resume(struct device *dev,
> if (IS_ERR(genpd))
> return -EINVAL;
>
> - if (device_awake_path(dev) && genpd_is_active_wakeup(genpd))
> + if (device_awake_path(dev) && genpd_is_active_wakeup(genpd) &&
> + !device_get_out_band_wakeup(dev))
> return resume_noirq(dev);
>
> genpd_lock(genpd);
> diff --git a/include/linux/pm.h b/include/linux/pm.h
> index cc7b2dc28574c24ece2f651352d4d23ecaf15f31..5b28a4f2e87e2aa34acc709e146ce729acace344 100644
> --- a/include/linux/pm.h
> +++ b/include/linux/pm.h
> @@ -684,6 +684,7 @@ struct dev_pm_info {
> bool smart_suspend:1; /* Owned by the PM core */
> bool must_resume:1; /* Owned by the PM core */
> bool may_skip_resume:1; /* Set by subsystems */
> + bool out_band_wakeup:1;
> bool strict_midlayer:1;
> #else
> bool should_wakeup:1;
> diff --git a/include/linux/pm_wakeup.h b/include/linux/pm_wakeup.h
> index c838b4a30f876ef5a66972d16f461cfba9ff2814..c461c7edef6f7927d696b7d18b59a6a1147f53a3 100644
> --- a/include/linux/pm_wakeup.h
> +++ b/include/linux/pm_wakeup.h
> @@ -94,6 +94,16 @@ static inline void device_set_wakeup_path(struct device *dev)
> dev->power.wakeup_path = true;
> }
>
> +static inline void device_set_out_band_wakeup(struct device *dev, bool capable)
> +{
> + dev->power.out_band_wakeup = capable;
I suggest we drop the bool as in-parameter and just do:
dev->power.out_band_wakeup = true;
Moreover, I think we should clear the flag in device_prepare(), next
to where dev->power.wakeup_path is cleared.
This makes the behavior better aligned for users of these flags.
> +}
> +
> +static inline bool device_get_out_band_wakeup(struct device *dev)
Nitpick: I would rename this into device_out_band_wakeup(). At least
the "get" part is a confusing in my opinion, as indicates there is
reference taken too.
> +{
> + return dev->power.out_band_wakeup;
> +}
> +
> /* drivers/base/power/wakeup.c */
> extern struct wakeup_source *wakeup_source_register(struct device *dev,
> const char *name);
> @@ -162,6 +172,13 @@ static inline bool device_wakeup_path(struct device *dev)
>
> static inline void device_set_wakeup_path(struct device *dev) {}
>
> +static inline void device_set_out_band_wakeup(struct device *dev, bool capable) {}
> +
> +static inline bool device_get_out_band_wakeup(struct device *dev)
> +{
> + return false;
> +}
> +
> static inline void __pm_stay_awake(struct wakeup_source *ws) {}
>
> static inline void pm_stay_awake(struct device *dev) {}
>
> --
> 2.37.1
>
Otherwise, from an overall functionality point of view, this makes sense to me!
Kind regards
Uffe
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