From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Linux PM <linux-pm@vger.kernel.org>,
Bjorn Helgaas <bhelgaas@google.com>,
Alan Stern <stern@rowland.harvard.edu>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux ACPI <linux-acpi@vger.kernel.org>,
Linux PCI <linux-pci@vger.kernel.org>,
Linux Documentation <linux-doc@vger.kernel.org>,
Mika Westerberg <mika.westerberg@linux.intel.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Kevin Hilman <khilman@kernel.org>
Subject: Re: [PATCH v3 1/6] PM / core: Add LEAVE_SUSPENDED driver flag
Date: Fri, 17 Nov 2017 00:07:59 +0100 [thread overview]
Message-ID: <2654404.6YT5rmSnae@aspire.rjw.lan> (raw)
In-Reply-To: <CAPDyKFpzSd4zwW_awuxuim0gzyKV5s9dm66X+szsSUKRnBakbA@mail.gmail.com>
On Thursday, November 16, 2017 4:10:16 PM CET Ulf Hansson wrote:
> On 12 November 2017 at 01:37, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >
> > Define and document a new driver flag, DPM_FLAG_LEAVE_SUSPENDED, to
> > instruct the PM core and middle-layer (bus type, PM domain, etc.)
> > code that it is desirable to leave the device in runtime suspend
> > after system-wide transitions to the working state (for example,
> > the device may be slow to resume and it may be better to avoid
> > resuming it right away).
> >
> > Generally, the middle-layer code involved in the handling of the
> > device is expected to indicate to the PM core whether or not the
> > device may be left in suspend with the help of the device's
> > power.may_skip_resume status bit. That has to happen in the "noirq"
> > phase of the preceding system suspend (or analogous) transition.
> > The middle layer is then responsible for handling the device as
> > appropriate in its "noirq" resume callback which is executed
> > regardless of whether or not the device may be left suspended, but
> > the other resume callbacks (except for ->complete) will be skipped
> > automatically by the core if the device really can be left in
> > suspend.
> >
> > The additional power.must_resume status bit introduced for the
> > implementation of this mechanisn is used internally by the PM core
> > to track the requirement to resume the device (which may depend on
> > its children etc).
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > ---
> >
> > v2 -> v3: Take dev->power.usage_count when updating power.must_resume in
> > __device_suspend_noirq().
> >
> > ---
> > Documentation/driver-api/pm/devices.rst | 24 ++++++++++-
> > drivers/base/power/main.c | 66 +++++++++++++++++++++++++++++---
> > drivers/base/power/runtime.c | 9 ++--
> > include/linux/pm.h | 14 +++++-
> > include/linux/pm_runtime.h | 9 ++--
> > 5 files changed, 104 insertions(+), 18 deletions(-)
> >
> > Index: linux-pm/include/linux/pm.h
> > ===================================================================
> > --- linux-pm.orig/include/linux/pm.h
> > +++ linux-pm/include/linux/pm.h
> > @@ -559,6 +559,7 @@ struct pm_subsys_data {
> > * NEVER_SKIP: Do not skip system suspend/resume callbacks for the device.
> > * SMART_PREPARE: Check the return value of the driver's ->prepare callback.
> > * SMART_SUSPEND: No need to resume the device from runtime suspend.
> > + * LEAVE_SUSPENDED: Avoid resuming the device during system resume if possible.
> > *
> > * Setting SMART_PREPARE instructs bus types and PM domains which may want
> > * system suspend/resume callbacks to be skipped for the device to return 0 from
> > @@ -572,10 +573,14 @@ struct pm_subsys_data {
> > * necessary from the driver's perspective. It also may cause them to skip
> > * invocations of the ->suspend_late and ->suspend_noirq callbacks provided by
> > * the driver if they decide to leave the device in runtime suspend.
> > + *
> > + * Setting LEAVE_SUSPENDED informs the PM core and middle-layer code that the
> > + * driver prefers the device to be left in runtime suspend after system resume.
> > */
>
> Question: Can LEAVE_SUSPENDED and NEVER_SKIP be valid combination? I
> guess not!? Should we validate for wrong combinations?
Why not? There's no real overlap between them.
>
> [...]
>
> > /**
> > * __device_suspend_noirq - Execute a "noirq suspend" callback for given device.
> > * @dev: Device to handle.
> > @@ -1127,10 +1161,28 @@ static int __device_suspend_noirq(struct
> > }
> >
> > error = dpm_run_callback(callback, dev, state, info);
> > - if (!error)
> > - dev->power.is_noirq_suspended = true;
> > - else
> > + if (error) {
> > async_error = error;
> > + goto Complete;
> > + }
> > +
> > + dev->power.is_noirq_suspended = true;
> > +
> > + if (dev_pm_test_driver_flags(dev, DPM_FLAG_LEAVE_SUSPENDED)) {
> > + /*
> > + * The only safe strategy here is to require that if the device
> > + * may not be left in suspend, resume callbacks must be invoked
> > + * for it.
> > + */
> > + dev->power.must_resume = dev->power.must_resume ||
> > + !dev->power.may_skip_resume ||
> > + atomic_read(&dev->power.usage_count);
>
> dev->power.usage_count is always > 0 at this point, meaning that
> dev->power.must_resume always becomes true. :-)
>
> You should rather use "atomic_read(&dev->power.usage_count) > 1".
Right, thanks. I tend to forget about that.
> > + } else {
> > + dev->power.must_resume = true;
> > + }
> > +
> > + if (dev->power.must_resume)
> > + dpm_superior_set_must_resume(dev);
> >
> > Complete:
> > complete_all(&dev->power.completion);
> > @@ -1487,6 +1539,9 @@ static int __device_suspend(struct devic
> > dev->power.direct_complete = false;
> > }
> >
> > + dev->power.may_skip_resume = false;
> > + dev->power.must_resume = false;
> > +
>
> First, these assignment could be bypassed if the direct_complete path
> is used. Perhaps it's more robust to reset these flags already in
> device_prepare().
In the direct-complete case may_skip_resume doesn't matter.
must_resume should be set to "false", however, so that parents of
direct-complete devices may be left in suspend (in case they don't
fall under direct-complete themselves), so good catch.
But it is sufficient to do that before the power.direct_complete check above. :-)
> Second, have you considered setting the default value of
> dev->power.may_skip_resume to true?
Yes.
> That would means the subsystem
> instead need to implement an opt-out method. I am thinking that it may
> not be an issue, since we anyway at this point, don't have drivers
> using the LEAVE_SUSPENDED flag.
Opt-out doesn't work because of the need to invoke the "noirq" callbacks.
> [...]
>
> > +However, it may be desirable to leave some devices in runtime suspend after
> > +system transitions to the working state and device drivers can use the
> > +``DPM_FLAG_LEAVE_SUSPENDED`` flag to indicate to the PM core (and middle-layer
> > +code) that this is the case. Whether or not the devices will actually be left
> > +in suspend may depend on their state before the given system suspend-resume
> > +cycle and on the type of the system transition under way. In particular,
> > +devices are not left suspended if that transition is a restore from hibernation,
> > +as device states are not guaranteed to be reflected by the information stored in
> > +the hibernation image in that case.
> > +
> > +The middle-layer code involved in the handling of the device has to indicate to
> > +the PM core if the device may be left in suspend with the help of its
> > +:c:member:`power.may_skip_resume` status bit. That has to happen in the "noirq"
> > +phase of the preceding system-wide suspend (or analogous) transition. The
>
> Does it have to be managed in the "noirq" phase? Wouldn't be perfectly
> okay do this in the suspend and suspend_late phases as well?
The wording is slightly misleading I think.
In fact technically may_skip_resume may be set earlier, but the core checks it
in the "noirq" phase only anyway.
Thanks,
Rafael
next prev parent reply other threads:[~2017-11-16 23:08 UTC|newest]
Thread overview: 135+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-16 1:12 [PATCH 0/12] PM / sleep: Driver flags for system suspend/resume Rafael J. Wysocki
2017-10-16 1:29 ` [PATCH 01/12] PM / core: Add NEVER_SKIP and SMART_PREPARE driver flags Rafael J. Wysocki
2017-10-16 5:34 ` Lukas Wunner
2017-10-16 22:03 ` Rafael J. Wysocki
2017-10-16 6:28 ` Greg Kroah-Hartman
2017-10-16 22:05 ` Rafael J. Wysocki
2017-10-17 7:15 ` Greg Kroah-Hartman
2017-10-17 15:26 ` Rafael J. Wysocki
2017-10-18 6:56 ` Greg Kroah-Hartman
2017-10-16 6:31 ` Greg Kroah-Hartman
2017-10-16 22:07 ` Rafael J. Wysocki
2017-10-17 13:26 ` Greg Kroah-Hartman
2017-10-16 20:16 ` Alan Stern
2017-10-16 22:11 ` Rafael J. Wysocki
2017-10-18 23:17 ` [Update][PATCH v2 " Rafael J. Wysocki
2017-10-19 7:33 ` Greg Kroah-Hartman
2017-10-20 11:11 ` Rafael J. Wysocki
2017-10-20 11:35 ` Greg Kroah-Hartman
2017-10-20 11:28 ` Rafael J. Wysocki
2017-10-23 16:37 ` Ulf Hansson
2017-10-23 20:41 ` Rafael J. Wysocki
2017-10-16 1:29 ` [PATCH 02/12] PCI / PM: Use the NEVER_SKIP driver flag Rafael J. Wysocki
2017-10-23 16:40 ` Ulf Hansson
2017-10-16 1:29 ` [PATCH 03/12] PM: i2c-designware-platdrv: Use DPM_FLAG_SMART_PREPARE Rafael J. Wysocki
2017-10-23 16:57 ` Ulf Hansson
2017-10-16 1:29 ` [PATCH 04/12] PM / core: Add SMART_SUSPEND driver flag Rafael J. Wysocki
2017-10-23 19:01 ` Ulf Hansson
2017-10-24 5:22 ` Ulf Hansson
2017-10-24 8:55 ` Rafael J. Wysocki
2017-10-16 1:29 ` [PATCH 05/12] PCI / PM: Drop unnecessary invocations of pcibios_pm_ops callbacks Rafael J. Wysocki
2017-10-23 19:06 ` Ulf Hansson
2017-10-16 1:29 ` [PATCH 06/12] PCI / PM: Take SMART_SUSPEND driver flag into account Rafael J. Wysocki
2017-10-16 1:29 ` [PATCH 07/12] ACPI / LPSS: Consolidate runtime PM and system sleep handling Rafael J. Wysocki
2017-10-23 19:09 ` Ulf Hansson
2017-10-16 1:30 ` [PATCH 08/12] ACPI / PM: Take SMART_SUSPEND driver flag into account Rafael J. Wysocki
2017-10-16 1:30 ` [PATCH 09/12] PM / mfd: intel-lpss: Use DPM_FLAG_SMART_SUSPEND Rafael J. Wysocki
2017-10-31 15:09 ` Lee Jones
2017-10-31 16:28 ` Rafael J. Wysocki
2017-11-01 9:28 ` Lee Jones
2017-11-01 20:26 ` Rafael J. Wysocki
2017-11-08 11:08 ` Lee Jones
2017-10-16 1:30 ` [PATCH 10/12] PM / core: Add LEAVE_SUSPENDED driver flag Rafael J. Wysocki
2017-10-23 19:38 ` Ulf Hansson
2017-10-16 1:31 ` [PATCH 11/12] PM: i2c-designware-platdrv: Optimize power management Rafael J. Wysocki
2017-10-26 20:41 ` Wolfram Sang
2017-10-26 21:14 ` Rafael J. Wysocki
2017-10-16 1:32 ` [PATCH 12/12] PM / core: Add AVOID_RPM driver flag Rafael J. Wysocki
2017-10-17 15:33 ` Andy Shevchenko
2017-10-17 15:59 ` Rafael J. Wysocki
2017-10-17 16:25 ` Andy Shevchenko
2017-10-16 7:08 ` [PATCH 0/12] PM / sleep: Driver flags for system suspend/resume Greg Kroah-Hartman
2017-10-16 21:50 ` Rafael J. Wysocki
2017-10-17 8:36 ` Ulf Hansson
2017-10-17 15:25 ` Rafael J. Wysocki
2017-10-17 19:41 ` Ulf Hansson
2017-10-17 20:12 ` Alan Stern
2017-10-17 23:07 ` Rafael J. Wysocki
2017-10-18 0:39 ` Rafael J. Wysocki
2017-10-18 10:24 ` Rafael J. Wysocki
2017-10-18 12:34 ` Ulf Hansson
2017-10-18 21:54 ` Rafael J. Wysocki
2017-10-18 11:57 ` Ulf Hansson
2017-10-18 13:00 ` Rafael J. Wysocki
2017-10-18 14:11 ` Ulf Hansson
2017-10-18 19:45 ` Grygorii Strashko
2017-10-18 21:48 ` Rafael J. Wysocki
2017-10-19 8:33 ` Ulf Hansson
2017-10-19 17:21 ` Grygorii Strashko
2017-10-19 18:04 ` Ulf Hansson
2017-10-19 18:11 ` Ulf Hansson
2017-10-19 21:31 ` Grygorii Strashko
2017-10-20 6:05 ` Ulf Hansson
2017-10-18 22:12 ` Rafael J. Wysocki
2017-10-19 12:21 ` Ulf Hansson
2017-10-19 18:01 ` Ulf Hansson
2017-10-20 1:19 ` Rafael J. Wysocki
2017-10-20 5:57 ` Ulf Hansson
2017-10-20 20:46 ` Bjorn Helgaas
2017-10-21 1:04 ` Rafael J. Wysocki
2017-10-27 22:11 ` [PATCH v2 0/6] PM / sleep: Driver flags for system suspend/resume (part 1) Rafael J. Wysocki
2017-10-27 22:17 ` [PATCH v2 1/6] PM / core: Add NEVER_SKIP and SMART_PREPARE driver flags Rafael J. Wysocki
2017-11-06 8:07 ` Ulf Hansson
2017-10-27 22:19 ` [PATCH v2 2/6] PCI / PM: Use the NEVER_SKIP driver flag Rafael J. Wysocki
2017-10-27 22:22 ` [PATCH v2 3/6] PM / core: Add SMART_SUSPEND " Rafael J. Wysocki
2017-11-06 8:09 ` Ulf Hansson
2017-11-06 11:23 ` Rafael J. Wysocki
2017-10-27 22:23 ` [PATCH v2 4/6] PCI / PM: Drop unnecessary invocations of pcibios_pm_ops callbacks Rafael J. Wysocki
2017-10-27 22:27 ` [PATCH v2 5/6] PCI / PM: Take SMART_SUSPEND driver flag into account Rafael J. Wysocki
2017-10-31 22:48 ` Bjorn Helgaas
2017-10-27 22:30 ` [PATCH v2 6/6] ACPI " Rafael J. Wysocki
2017-11-08 0:41 ` [PATCH v2 0/6] PM / sleep: Driver flags for system suspend/resume (part 2) Rafael J. Wysocki
2017-11-08 13:25 ` [PATCH v2 1/6] PM / core: Add LEAVE_SUSPENDED driver flag Rafael J. Wysocki
2017-11-10 9:09 ` Ulf Hansson
2017-11-10 23:45 ` Rafael J. Wysocki
2017-11-11 0:41 ` Rafael J. Wysocki
2017-11-11 1:36 ` Rafael J. Wysocki
2017-11-14 16:07 ` Ulf Hansson
2017-11-15 1:48 ` Rafael J. Wysocki
2017-11-16 10:18 ` Ulf Hansson
2017-11-08 13:28 ` [PATCH v2 2/6] PCI / PM: Support for " Rafael J. Wysocki
2017-11-08 20:38 ` Bjorn Helgaas
2017-11-08 21:09 ` Rafael J. Wysocki
2017-11-08 13:34 ` [PATCH v2 3/6] ACPI / PM: Support for LEAVE_SUSPENDED driver flag in ACPI PM domain Rafael J. Wysocki
2017-11-08 13:37 ` [PATCH v2 4/6] PM / core: Add helpers for subsystem callback selection Rafael J. Wysocki
2017-11-08 13:38 ` [PATCH v2 5/6] PM / core: Direct handling of DPM_FLAG_LEAVE_SUSPENDED Rafael J. Wysocki
2017-11-08 13:39 ` [PATCH v2 6/6] PM / core: DPM_FLAG_SMART_SUSPEND optimization Rafael J. Wysocki
2017-11-12 0:34 ` [PATCH v3 0/6] PM / sleep: Driver flags for system suspend/resume (part 2) Rafael J. Wysocki
2017-11-12 0:37 ` [PATCH v3 1/6] PM / core: Add LEAVE_SUSPENDED driver flag Rafael J. Wysocki
2017-11-16 15:10 ` Ulf Hansson
2017-11-16 23:07 ` Rafael J. Wysocki [this message]
2017-11-17 6:11 ` Ulf Hansson
2017-11-17 13:18 ` Rafael J. Wysocki
2017-11-17 13:49 ` Ulf Hansson
2017-11-17 14:31 ` Rafael J. Wysocki
2017-11-17 15:57 ` Ulf Hansson
2017-11-17 12:45 ` Rafael J. Wysocki
2017-11-12 0:40 ` [PATCH v3 2/6] PCI / PM: Support for " Rafael J. Wysocki
2017-11-12 0:40 ` [PATCH v3 3/6] ACPI / PM: Support for LEAVE_SUSPENDED driver flag in ACPI PM domain Rafael J. Wysocki
2017-11-12 0:42 ` [PATCH v3 4/6] PM / core: Add helpers for subsystem callback selection Rafael J. Wysocki
2017-11-15 7:43 ` Ulf Hansson
2017-11-15 17:55 ` Rafael J. Wysocki
2017-11-12 0:43 ` [PATCH v3 5/6] PM / core: Direct handling of DPM_FLAG_LEAVE_SUSPENDED Rafael J. Wysocki
2017-11-12 0:44 ` [PATCH v3 6/6] PM / core: DPM_FLAG_SMART_SUSPEND optimization Rafael J. Wysocki
2017-11-18 14:27 ` [PATCH v4 0/6] PM / sleep: Driver flags for system suspend/resume (part 2) Rafael J. Wysocki
2017-11-18 14:31 ` [PATCH v4 1/6] PM / core: Add LEAVE_SUSPENDED driver flag Rafael J. Wysocki
2017-11-20 12:25 ` Ulf Hansson
2017-11-21 0:16 ` Rafael J. Wysocki
2017-11-18 14:33 ` [PATCH v4 2/6] PCI / PM: Support for " Rafael J. Wysocki
2017-11-18 14:35 ` [PATCH v4 3/6] ACPI / PM: Support for LEAVE_SUSPENDED driver flag in ACPI PM domain Rafael J. Wysocki
2017-11-18 14:37 ` [PATCH v4 4/6] PM / core: Add helpers for subsystem callback selection Rafael J. Wysocki
2017-11-18 14:41 ` [PATCH v4 5/6] PM / core: Direct handling of DPM_FLAG_LEAVE_SUSPENDED Rafael J. Wysocki
2017-11-20 13:42 ` Ulf Hansson
2017-11-22 1:10 ` Rafael J. Wysocki
2017-11-22 1:28 ` Rafael J. Wysocki
2017-11-18 14:44 ` [PATCH v4 6/6] PM / core: DPM_FLAG_SMART_SUSPEND optimization Rafael J. Wysocki
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=2654404.6YT5rmSnae@aspire.rjw.lan \
--to=rjw@rjwysocki.net \
--cc=andriy.shevchenko@linux.intel.com \
--cc=bhelgaas@google.com \
--cc=gregkh@linuxfoundation.org \
--cc=khilman@kernel.org \
--cc=linux-acpi@vger.kernel.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pci@vger.kernel.org \
--cc=linux-pm@vger.kernel.org \
--cc=mika.westerberg@linux.intel.com \
--cc=stern@rowland.harvard.edu \
--cc=ulf.hansson@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).