linux-kernel - Re: [PATCH] PM / Runtime: Only force-resume device if it has been force-suspended

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Date:	Thu, 03 Mar 2016 12:35:53 -0800
From:	Kevin Hilman <khilman@...libre.com>
To:	Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>
Cc:	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH] PM / Runtime: Only force-resume device if it has been force-suspended

Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com> writes:

> The pm_runtime_force_suspend() and pm_runtime_force_resume() helpers are
> designed to help driver being RPM-centric by offering an easy way to
> manager runtime PM state during system suspend and resume. The first

s/manager/manage/

> function will force the device into runtime suspend at system suspend
> time, while the second one will perform the reverse operation at system
> resume time.
>
> However, the pm_runtime_force_resume() really forces resume, regarding

s/regarding/regardless/

> of whether the device was running or already suspended before the call
> to pm_runtime_force_suspend(). This results in devices being runtime
> resumed at system resume time when they shouldn't.

Agreed.

> Fix this by recording whether the device has been forcefully suspended
> in pm_runtime_force_suspend() and condition resume in
> pm_runtime_force_resume() to that state.
>
> All current users of pm_runtime_force_resume() call the function
> uncontionally in their system resume handler (some actually set it as
> the resume handler), all after calling pm_runtime_force_suspend() at
> system suspend time. The change in behaviour should thus be safe.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>

Reviewed-by: Kevin Hilman <khilman@...libre.com>

I agree this is the right approach, but Ulf should ack this too since
he's looked into all the strange corner case involved and may know of
something I've missed.

Kevin