linux-kernel - Re: [PATCH] PM / sleep: Let devices force direct

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Message-ID: <7hioc2hkrj.fsf@deeprootsystems.com>
Date:	Fri, 08 May 2015 13:33:36 -0700
From:	Kevin Hilman <khilman@...nel.org>
To:	Tomeu Vizoso <tomeu.vizoso@...labora.com>
Cc:	linux-kernel@...r.kernel.org,
	Alan Stern <stern@...land.harvard.edu>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-pm@...r.kernel.org
Subject: Re: [PATCH] PM / sleep: Let devices force direct_complete

Tomeu Vizoso <tomeu.vizoso@...labora.com> writes:

> Introduce a new per-device flag power.force_direct_complete that will
> instruct the PM core to let that device remain in runtime suspend when
> the system goes into a sleep power state, regardless of the PM state of
> any of its descendants.
>
> This is needed because otherwise it would be needed to get dozens of
> drivers to implement the prepare() callback and be runtime PM active
> even if they don't have a 1-to-1 relationship with a piece of HW.
>
> This only applies to devices that aren't wakeup-capable, as those would
> need to setup their IRQs as wakeup-capable in their prepare() callbacks.
>
> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@...labora.com>
> ---
>
> Hi,
>
> I'm sending this as a standalone patch as suggested by Alan.
>
> Thanks,
>
> Tomeu
>
> ---
>  Documentation/power/runtime_pm.txt | 10 ++++++++++
>  drivers/base/power/main.c          | 14 ++++++++++----
>  include/linux/pm.h                 |  1 +
>  3 files changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt
> index 44fe1d2..3b0c68d 100644
> --- a/Documentation/power/runtime_pm.txt
> +++ b/Documentation/power/runtime_pm.txt
> @@ -665,6 +665,16 @@ as appropriate.  This only applies to system suspend transitions that are not
>  related to hibernation (see Documentation/power/devices.txt for more
>  information).
>  
> +For devices that know that can remain runtime suspended when the system

s/that know that/that know they/ ?

> +transitions to a sleep state regardless of the PM state of their descendants,
> +the flag power.force_direct_complete can be set on their device structures.
> +This can be useful when a real device has several virtual devices as
> +descendants and it would be very cumbersome to make sure that they return a
> +positive value in their .prepare() callback and have runtime PM enabled. Usage
> +of power.force_direct_complete is only allowed to devices that aren't
> +wakeup-capable, as they would need to set their IRQs as wakeups in their
> +.prepare() callbacks before the system transitions to a sleep state.

Kevin
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