From: Kevin Hilman <khilman@linaro.org>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Alan Stern <stern@rowland.harvard.edu>,
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: Flag to speed up suspend-resume of runtime-suspended devices
Date: Mon, 12 May 2014 09:33:26 -0700 [thread overview]
Message-ID: <7hha4vkld5.fsf@paris.lan> (raw)
In-Reply-To: <2529433.Aygp7Yxy87@vostro.rjw.lan> (Rafael J. Wysocki's message of "Sat, 10 May 2014 03:38:27 +0200")
"Rafael J. Wysocki" <rjw@rjwysocki.net> writes:
> On Friday, May 09, 2014 03:48:21 PM Kevin Hilman wrote:
>> "Rafael J. Wysocki" <rjw@rjwysocki.net> writes:
>>
>> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>> >
>> > Currently, some subsystems (e.g. PCI and the ACPI PM domain) have to
>> > resume all runtime-suspended devices during system suspend, mostly
>> > because those devices may need to be reprogrammed due to different
>> > wakeup settings for system sleep and for runtime PM.
>> >
>> > For some devices, though, it's OK 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.
>> >
>> > 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
>> > most straightforward way to do this safely is if the device and all its
>> > descendants can remain runtime suspended until the resume stage of system
>> > resume.
>> >
>> > 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 at the beginning of the ->suspend()
>> > callback, that callback is allowed to return 0 without clearing
>> > power.leave_runtime_suspended and without changing the state of the
>> > device, unless the current state of the device is not appropriate for
>> > the upcoming system sleep state (for example, the device is supposed to
>> > wake up the system from that state and its current wakeup settings are
>> > not suitable for that). Then, the PM core will not invoke the device's
>> > ->suspend_late(), ->suspend_irq(), ->resume_irq(), ->resume_early(), or
>> > ->resume() callbacks.
>>
>> Up to here, this sounds great.
>>
>> > Instead, it will invoke ->runtime_resume() during the device resume
>> > stage of system resume.
>>
>> But this part I'm not fully following...
>
> You're not looking at the most recent one. :-)
Sorry about that, I haven't been able to keep up with the versions.
> Please look here: https://patchwork.kernel.org/patch/4139181/
OK.
>> > By leaving this flag set after ->suspend(), 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.
>>
>> But taking this "leave runtime suspended" idea the next logical step,
>> why would/should a device need to return to full power at the ->resume()
>> stage? especially when it wasn't at full power when ->suspend()
>> happened?
>
> Good question and I've been thinking about that for a while.
>
> Generally, the main reason for resuming is that on some platforms devices are
> automatically powered up by firmware and in those cases it's better to
> resume them (to make the runtime PM status reflect the physical state) and
> suspend again later.
>
> Generally speaking, subsystems that need to do that know what they are and
> that's what I was talking about in the most recent reply to Alan:
>
> http://marc.info/?l=linux-pm&m=139967477806094&w=4
>
> Currently, I think, there are two options on the table really.
>
> 1. Do more or less what https://patchwork.kernel.org/patch/4139181/ does
> with a modification to check that ->suspend() doesn't "cheat" (by setting
> the flag that had been unset before it was called). The subsystem's
> ->resume() would then decide what to do with the device (resume it or
> leave it suspended).
>
> 2. Do what Alan was suggesting, that is set the flag in ->prepare() and
> make the PM core skip *all* of the system suspend/resume callbacks
> for devices with that flag set and let the ->complete() callback
> decide what to do with the device.
>
> I'm leaning a bit towards 2, but still considering 1 too.
If it matters, I have a slight preference for 2 also, though as long as
the subsytem/device gets to decide whether to resume, I think I'm OK
with either approach.
Kevin
next prev parent reply other threads:[~2014-05-12 16:33 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
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 [this message]
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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