From: Alan Stern <stern@rowland.harvard.edu>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Linux PM list <linux-pm@vger.kernel.org>,
Mika Westerberg <mika.westerberg@linux.intel.com>,
Aaron Lu <aaron.lu@intel.com>,
ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC][PATCH 1/3] PM / sleep: Flags to speed up suspend-resume of runtime-suspended devices
Date: Wed, 7 May 2014 11:43:39 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44L0.1405071126340.1325-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <8506078.MQGrQB8sAy@vostro.rjw.lan>
On Wed, 7 May 2014, Rafael J. Wysocki wrote:
We seem to be in agreement that this is the way you want to go...
> > All right. Then this seems to be what you want:
> >
> > For some devices, it's okay to remain in runtime suspend
> > throughout a complete system suspend/resume cycle (if the
> > device was in runtime suspend at the start of the cycle).
> > We would like to do this whenever possible, to avoid the
> > overhead of extra power-up and power-down events.
>
> Yes.
>
> > However, problems may arise because the device's descendants
> > may require it to be at full power at various points during
> > the cycle. Therefore the only way to do this safely is if the
> > device _and_ all its descendants can remain runtime suspended
> > until the resume stage of system resume.
>
> It may not be the only way, but it is *a* way to do this safely.
>
> > To this end, introduce dev->power.leave_runtime_suspended.
> > If a subsystem or driver sets this flag during the ->prepare()
> > callback, and if the flag is set in all of the device's
> > descendants, and if the device is still in runtime suspend when
> > the ->suspend() callback would normally be invoked, then the PM
> > core will not invoke the device's ->suspend(),
> > ->suspend_late(), ->suspend_irq(), ->resume_irq(),
> > ->resume_early(), or ->resume() callbacks. Instead, it will
> > invoke ->runtime_resume() during the resume stage of system
> > resume.
>
> Yes.
>
> > By setting this flag, a driver or subsystem tells the PM core
> > that the device is runtime suspended, it is in a suitable state
> > for system suspend (for example, the wakeup setting does not
> > need to be changed), and it does not need to return to full
> > power until the resume stage.
>
> Yes.
>
> > Does that correctly describe what you want to do, the potential
> > problems, and the proposed solution?
>
> Almost. Devices with power.ignore_children set are not covered by this.
I thought they were. In what respect aren't they? You mean because
they can be runtime suspended while their children remain active?
I don't think that matters here. Suppose a parent device's
leave_runtime_suspended flag is set but one of its children isn't
runtime suspended. Then that child's leave_runtime_suspended flag
won't be set, so the parent device won't meet the criterion for
skipping the normal PM callbacks.
Or do you mean that a child might expect the parent to be at full power
when the child is resumed (plus the fact that doing a runtime resume on
the child will not automatically resume the parent)? That doesn't
matter either, because the PM core will do a runtime-resume of the
parent before the child's ->runtime_resume() is called.
> > If so, then it appears the parent_needed flag is unnecessary.
>
> Well, I can agree with that. It wasn't there in my first patchset and I added
> it kind of in the hope to be able to deal with the ignore_children devices
> with the help of it.
Yeah. I contributed to that, by not understanding exactly what you
were trying to accomplish.
> OK, I guess I need to prepare a new version without the parent_needed flag for
> further discussion. :-)
Consider using the description above (or some variant of it) for the
new Changelog. IMNSHO it does a much better job of explaining the
patch than your original version. :-)
Alan Stern
next prev parent reply other threads:[~2014-05-07 15:43 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-14 23:12 [RFC][PATCH 0/3] PM: Mechanism to avoid resuming runtime-suspended devices during system suspend Rafael J. Wysocki
2014-01-14 23:13 ` [RFC][PATCH 1/3] PM / sleep: Flag to avoid executing suspend callbacks for devices Rafael J. Wysocki
2014-01-14 23:14 ` [RFC][PATCH 2/3] PM / runtime: Routine for checking device status during system suspend Rafael J. Wysocki
2014-01-16 13:32 ` Mika Westerberg
2014-01-16 16:07 ` [Update][RFC][PATCH " Rafael J. Wysocki
2014-01-14 23:16 ` [RFC][PATCH 3/3] ACPI / PM: Avoid resuming devices in ACPI PM domain " Rafael J. Wysocki
2014-01-15 13:57 ` [Update][RFC][PATCH " Rafael J. Wysocki
2014-02-16 23:49 ` [RFC][PATCH 0/3] PM: Mechanism to avoid resuming runtime-suspended devices " Rafael J. Wysocki
2014-02-16 23:50 ` [PATCH 1/3] PM / sleep: New flag to speed up suspend-resume of suspended devices Rafael J. Wysocki
2014-02-18 12:59 ` Ulf Hansson
2014-02-18 13:25 ` Rafael J. Wysocki
2014-02-19 17:01 ` Alan Stern
2014-02-20 1:23 ` Rafael J. Wysocki
2014-02-20 1:42 ` Rafael J. Wysocki
2014-02-20 17:03 ` Alan Stern
2014-02-24 0:00 ` Rafael J. Wysocki
2014-02-24 19:36 ` Alan Stern
2014-02-25 0:07 ` Rafael J. Wysocki
2014-02-25 17:08 ` Alan Stern
2014-02-25 23:56 ` Rafael J. Wysocki
2014-02-26 16:49 ` Alan Stern
2014-02-26 21:44 ` Rafael J. Wysocki
2014-02-26 22:17 ` Alan Stern
2014-02-26 23:13 ` Rafael J. Wysocki
2014-02-27 15:02 ` Alan Stern
2014-04-24 22:36 ` [RFC][PATCH 0/3] PM: Mechanism to avoid resuming runtime-suspended devices during system suspend, v2 Rafael J. Wysocki
2014-04-24 22:37 ` [RFC][PATCH 1/3] PM / sleep: Flags to speed up suspend-resume of runtime-suspended devices Rafael J. Wysocki
2014-05-01 21:39 ` Alan Stern
2014-05-01 23:15 ` Rafael J. Wysocki
2014-05-01 23:36 ` Rafael J. Wysocki
2014-05-02 0:04 ` Rafael J. Wysocki
2014-05-02 15:41 ` Rafael J. Wysocki
2014-05-02 18:44 ` Alan Stern
2014-05-05 0:09 ` Rafael J. Wysocki
2014-05-05 15:46 ` Alan Stern
2014-05-06 1:31 ` Rafael J. Wysocki
2014-05-06 19:31 ` Alan Stern
2014-05-07 0:36 ` Rafael J. Wysocki
2014-05-07 15:43 ` Alan Stern [this message]
2014-05-07 23:27 ` [RFC][PATCH 0/3] (was: Re: [RFC][PATCH 1/3] PM / sleep: Flags to speed up suspend-resume of runtime-suspended devices) Rafael J. Wysocki
2014-05-07 23:29 ` [RFC][PATCH 1/3] PM / sleep: Flag to speed up suspend-resume of runtime-suspended devices Rafael J. Wysocki
2014-05-08 7:49 ` Ulf Hansson
2014-05-08 10:53 ` Rafael J. Wysocki
2014-05-08 10:59 ` Ulf Hansson
2014-05-08 11:44 ` Rafael J. Wysocki
2014-05-08 12:25 ` Ulf Hansson
2014-05-08 20:02 ` Rafael J. Wysocki
2014-05-08 14:36 ` Alan Stern
2014-05-08 14:57 ` Alan Stern
2014-05-08 20:17 ` Rafael J. Wysocki
2014-05-08 21:03 ` Rafael J. Wysocki
2014-05-08 21:20 ` Alan Stern
2014-05-08 21:42 ` Rafael J. Wysocki
2014-05-08 21:50 ` Rafael J. Wysocki
2014-05-08 22:28 ` [RFC][PATCH 0/3] (was: Re: PM / sleep: Flag to speed up suspend-resume of runtime-suspended devices) Rafael J. Wysocki
2014-05-08 22:41 ` [RFC][PATCH 1/3] PM / sleep: Flag to speed up suspend-resume of runtime-suspended devices Rafael J. Wysocki
2014-05-09 7:23 ` Ulf Hansson
2014-05-09 11:33 ` Rafael J. Wysocki
2014-05-08 22:41 ` [RFC][PATCH 2/3] PM / runtime: Routine for checking device status during system suspend Rafael J. Wysocki
2014-05-08 22:42 ` [RFC][PATCH 3/3] ACPI / PM: Avoid resuming devices in ACPI PM domain " Rafael J. Wysocki
2014-05-09 1:52 ` [RFC][PATCH 1/3] PM / sleep: Flag to speed up suspend-resume of runtime-suspended devices Alan Stern
2014-05-09 22:49 ` Rafael J. Wysocki
2014-05-11 16:46 ` Alan Stern
2014-05-13 0:51 ` Rafael J. Wysocki
2014-05-08 21:08 ` Alan Stern
2014-05-09 22:48 ` Kevin Hilman
2014-05-10 1:38 ` Rafael J. Wysocki
2014-05-12 16:33 ` Kevin Hilman
2014-05-07 23:31 ` [Resend][PATCH 2/3] PM / runtime: Routine for checking device status during system suspend Rafael J. Wysocki
2014-05-07 23:33 ` [RFC][PATCH 3/3] ACPI / PM: Avoid resuming devices in ACPI PM domain " Rafael J. Wysocki
2014-05-08 14:59 ` Alan Stern
2014-05-08 19:40 ` Rafael J. Wysocki
2014-05-02 16:12 ` [RFC][PATCH 1/3] PM / sleep: Flags to speed up suspend-resume of runtime-suspended devices Alan Stern
2014-04-24 22:39 ` [RFC][PATCH 2/3][Resend] PM / runtime: Routine for checking device status during system suspend Rafael J. Wysocki
2014-04-25 11:28 ` Ulf Hansson
2014-04-24 22:40 ` [RFC][PATCH 3/3] ACPI / PM: Avoid resuming devices in ACPI PM domain " Rafael J. Wysocki
2014-02-16 23:51 ` [PATCH 2/3][Resend] PM / runtime: Routine for checking device status " Rafael J. Wysocki
2014-02-16 23:52 ` [PATCH 3/3] ACPI / PM: Avoid resuming devices in ACPI PM domain " Rafael J. Wysocki
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