| Message ID | 13167729.Euq9qh5SXX@aspire.rjw.lan (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
On 18 November 2017 at 15:31, 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> Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org> Kind regards Uffe > --- > > v3 -> v4: Fix the dev->power.usage_count check added in v3, clarify > documentation, add comment to explain why the runtime PM status > is changed in device_resume_noirq() and make the description of > the NEVER_SKIP flag more precise. > > v2 -> v3: Take dev->power.usage_count when updating power.must_resume in > __device_suspend_noirq(). > > --- > Documentation/driver-api/pm/devices.rst | 27 ++++++++++- > drivers/base/power/main.c | 73 +++++++++++++++++++++++++++++--- > include/linux/pm.h | 16 +++++-- > 3 files changed, 105 insertions(+), 11 deletions(-) > > Index: linux-pm/include/linux/pm.h > =================================================================== > --- linux-pm.orig/include/linux/pm.h > +++ linux-pm/include/linux/pm.h > @@ -556,9 +556,10 @@ struct pm_subsys_data { > * These flags can be set by device drivers at the probe time. They need not be > * cleared by the drivers as the driver core will take care of that. > * > - * NEVER_SKIP: Do not skip system suspend/resume callbacks for the device. > + * NEVER_SKIP: Do not skip all 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 suspend after system resume. > */ > -#define DPM_FLAG_NEVER_SKIP BIT(0) > -#define DPM_FLAG_SMART_PREPARE BIT(1) > -#define DPM_FLAG_SMART_SUSPEND BIT(2) > +#define DPM_FLAG_NEVER_SKIP BIT(0) > +#define DPM_FLAG_SMART_PREPARE BIT(1) > +#define DPM_FLAG_SMART_SUSPEND BIT(2) > +#define DPM_FLAG_LEAVE_SUSPENDED BIT(3) > > struct dev_pm_info { > pm_message_t power_state; > @@ -597,6 +602,8 @@ struct dev_pm_info { > bool wakeup_path:1; > bool syscore:1; > bool no_pm_callbacks:1; /* Owned by the PM core */ > + unsigned int must_resume:1; /* Owned by the PM core */ > + unsigned int may_skip_resume:1; /* Set by subsystems */ > #else > unsigned int should_wakeup:1; > #endif > @@ -765,6 +772,7 @@ extern int pm_generic_poweroff_late(stru > extern int pm_generic_poweroff(struct device *dev); > extern void pm_generic_complete(struct device *dev); > > +extern bool dev_pm_may_skip_resume(struct device *dev); > extern bool dev_pm_smart_suspend_and_suspended(struct device *dev); > > #else /* !CONFIG_PM_SLEEP */ > Index: linux-pm/drivers/base/power/main.c > =================================================================== > --- linux-pm.orig/drivers/base/power/main.c > +++ linux-pm/drivers/base/power/main.c > @@ -528,6 +528,18 @@ static void dpm_watchdog_clear(struct dp > /*------------------------- Resume routines -------------------------*/ > > /** > + * dev_pm_may_skip_resume - System-wide device resume optimization check. > + * @dev: Target device. > + * > + * Checks whether or not the device may be left in suspend after a system-wide > + * transition to the working state. > + */ > +bool dev_pm_may_skip_resume(struct device *dev) > +{ > + return !dev->power.must_resume && pm_transition.event != PM_EVENT_RESTORE; > +} > + > +/** > * device_resume_noirq - Execute a "noirq resume" callback for given device. > * @dev: Device to handle. > * @state: PM transition of the system being carried out. > @@ -575,6 +587,19 @@ static int device_resume_noirq(struct de > error = dpm_run_callback(callback, dev, state, info); > dev->power.is_noirq_suspended = false; > > + if (dev_pm_may_skip_resume(dev)) { > + /* > + * The device is going to be left in suspend, but it might not > + * have been in runtime suspend before the system suspended, so > + * its runtime PM status needs to be updated to avoid confusing > + * the runtime PM framework when runtime PM is enabled for the > + * device again. > + */ > + pm_runtime_set_suspended(dev); > + dev->power.is_late_suspended = false; > + dev->power.is_suspended = false; > + } > + > Out: > complete_all(&dev->power.completion); > TRACE_RESUME(error); > @@ -1076,6 +1101,22 @@ static pm_message_t resume_event(pm_mess > return PMSG_ON; > } > > +static void dpm_superior_set_must_resume(struct device *dev) > +{ > + struct device_link *link; > + int idx; > + > + if (dev->parent) > + dev->parent->power.must_resume = true; > + > + idx = device_links_read_lock(); > + > + list_for_each_entry_rcu(link, &dev->links.suppliers, c_node) > + link->supplier->power.must_resume = true; > + > + device_links_read_unlock(idx); > +} > + > /** > * __device_suspend_noirq - Execute a "noirq suspend" callback for given device. > * @dev: Device to handle. > @@ -1127,10 +1168,28 @@ 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) > 1; > + } 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 +1546,9 @@ static int __device_suspend(struct devic > dev->power.direct_complete = false; > } > > + dev->power.may_skip_resume = false; > + dev->power.must_resume = false; > + > dpm_watchdog_set(&wd, dev); > device_lock(dev); > > @@ -1652,8 +1714,9 @@ static int device_prepare(struct device > if (dev->power.syscore) > return 0; > > - WARN_ON(dev_pm_test_driver_flags(dev, DPM_FLAG_SMART_SUSPEND) && > - !pm_runtime_enabled(dev)); > + WARN_ON(!pm_runtime_enabled(dev) && > + dev_pm_test_driver_flags(dev, DPM_FLAG_SMART_SUSPEND | > + DPM_FLAG_LEAVE_SUSPENDED)); > > /* > * If a device's parent goes into runtime suspend at the wrong time, > Index: linux-pm/Documentation/driver-api/pm/devices.rst > =================================================================== > --- linux-pm.orig/Documentation/driver-api/pm/devices.rst > +++ linux-pm/Documentation/driver-api/pm/devices.rst > @@ -788,6 +788,29 @@ must reflect the "active" status for run > > During system-wide resume from a sleep state it's easiest to put devices into > the full-power state, as explained in :file:`Documentation/power/runtime_pm.txt`. > -Refer to that document for more information regarding this particular issue as > +[Refer to that document for more information regarding this particular issue as > well as for information on the device runtime power management framework in > -general. > +general.] > + > +However, it often is desirable to leave devices in suspend after system > +transitions to the working state, especially if those devices had been in > +runtime suspend before the preceding system-wide suspend (or analogous) > +transition. Device drivers can use the ``DPM_FLAG_LEAVE_SUSPENDED`` flag to > +indicate to the PM core (and middle-layer code) that they prefer the specific > +devices handled by them to be left suspended and they have no problems with > +skipping their system-wide resume callbacks for this reason. 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 is expected to > +indicate to the PM core if the device may be left in suspend by setting its > +:c:member:`power.may_skip_resume` status bit which is checked by the PM core > +during the "noirq" phase of the preceding system-wide 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 is left suspended, but the other resume callbacks > +(except for ``->complete``) will be skipped automatically by the PM core if the > +device really can be left in suspend. >
On Mon, Nov 20, 2017 at 1:25 PM, Ulf Hansson <ulf.hansson@linaro.org> wrote: > On 18 November 2017 at 15:31, 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> > > Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org> Thanks!
Index: linux-pm/include/linux/pm.h =================================================================== --- linux-pm.orig/include/linux/pm.h +++ linux-pm/include/linux/pm.h @@ -556,9 +556,10 @@ struct pm_subsys_data { * These flags can be set by device drivers at the probe time. They need not be * cleared by the drivers as the driver core will take care of that. * - * NEVER_SKIP: Do not skip system suspend/resume callbacks for the device. + * NEVER_SKIP: Do not skip all 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 suspend after system resume. */ -#define DPM_FLAG_NEVER_SKIP BIT(0) -#define DPM_FLAG_SMART_PREPARE BIT(1) -#define DPM_FLAG_SMART_SUSPEND BIT(2) +#define DPM_FLAG_NEVER_SKIP BIT(0) +#define DPM_FLAG_SMART_PREPARE BIT(1) +#define DPM_FLAG_SMART_SUSPEND BIT(2) +#define DPM_FLAG_LEAVE_SUSPENDED BIT(3) struct dev_pm_info { pm_message_t power_state; @@ -597,6 +602,8 @@ struct dev_pm_info { bool wakeup_path:1; bool syscore:1; bool no_pm_callbacks:1; /* Owned by the PM core */ + unsigned int must_resume:1; /* Owned by the PM core */ + unsigned int may_skip_resume:1; /* Set by subsystems */ #else unsigned int should_wakeup:1; #endif @@ -765,6 +772,7 @@ extern int pm_generic_poweroff_late(stru extern int pm_generic_poweroff(struct device *dev); extern void pm_generic_complete(struct device *dev); +extern bool dev_pm_may_skip_resume(struct device *dev); extern bool dev_pm_smart_suspend_and_suspended(struct device *dev); #else /* !CONFIG_PM_SLEEP */ Index: linux-pm/drivers/base/power/main.c =================================================================== --- linux-pm.orig/drivers/base/power/main.c +++ linux-pm/drivers/base/power/main.c @@ -528,6 +528,18 @@ static void dpm_watchdog_clear(struct dp /*------------------------- Resume routines -------------------------*/ /** + * dev_pm_may_skip_resume - System-wide device resume optimization check. + * @dev: Target device. + * + * Checks whether or not the device may be left in suspend after a system-wide + * transition to the working state. + */ +bool dev_pm_may_skip_resume(struct device *dev) +{ + return !dev->power.must_resume && pm_transition.event != PM_EVENT_RESTORE; +} + +/** * device_resume_noirq - Execute a "noirq resume" callback for given device. * @dev: Device to handle. * @state: PM transition of the system being carried out. @@ -575,6 +587,19 @@ static int device_resume_noirq(struct de error = dpm_run_callback(callback, dev, state, info); dev->power.is_noirq_suspended = false; + if (dev_pm_may_skip_resume(dev)) { + /* + * The device is going to be left in suspend, but it might not + * have been in runtime suspend before the system suspended, so + * its runtime PM status needs to be updated to avoid confusing + * the runtime PM framework when runtime PM is enabled for the + * device again. + */ + pm_runtime_set_suspended(dev); + dev->power.is_late_suspended = false; + dev->power.is_suspended = false; + } + Out: complete_all(&dev->power.completion); TRACE_RESUME(error); @@ -1076,6 +1101,22 @@ static pm_message_t resume_event(pm_mess return PMSG_ON; } +static void dpm_superior_set_must_resume(struct device *dev) +{ + struct device_link *link; + int idx; + + if (dev->parent) + dev->parent->power.must_resume = true; + + idx = device_links_read_lock(); + + list_for_each_entry_rcu(link, &dev->links.suppliers, c_node) + link->supplier->power.must_resume = true; + + device_links_read_unlock(idx); +} + /** * __device_suspend_noirq - Execute a "noirq suspend" callback for given device. * @dev: Device to handle. @@ -1127,10 +1168,28 @@ 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) > 1; + } 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 +1546,9 @@ static int __device_suspend(struct devic dev->power.direct_complete = false; } + dev->power.may_skip_resume = false; + dev->power.must_resume = false; + dpm_watchdog_set(&wd, dev); device_lock(dev); @@ -1652,8 +1714,9 @@ static int device_prepare(struct device if (dev->power.syscore) return 0; - WARN_ON(dev_pm_test_driver_flags(dev, DPM_FLAG_SMART_SUSPEND) && - !pm_runtime_enabled(dev)); + WARN_ON(!pm_runtime_enabled(dev) && + dev_pm_test_driver_flags(dev, DPM_FLAG_SMART_SUSPEND | + DPM_FLAG_LEAVE_SUSPENDED)); /* * If a device's parent goes into runtime suspend at the wrong time, Index: linux-pm/Documentation/driver-api/pm/devices.rst =================================================================== --- linux-pm.orig/Documentation/driver-api/pm/devices.rst +++ linux-pm/Documentation/driver-api/pm/devices.rst @@ -788,6 +788,29 @@ must reflect the "active" status for run During system-wide resume from a sleep state it's easiest to put devices into the full-power state, as explained in :file:`Documentation/power/runtime_pm.txt`. -Refer to that document for more information regarding this particular issue as +[Refer to that document for more information regarding this particular issue as well as for information on the device runtime power management framework in -general. +general.] + +However, it often is desirable to leave devices in suspend after system +transitions to the working state, especially if those devices had been in +runtime suspend before the preceding system-wide suspend (or analogous) +transition. Device drivers can use the ``DPM_FLAG_LEAVE_SUSPENDED`` flag to +indicate to the PM core (and middle-layer code) that they prefer the specific +devices handled by them to be left suspended and they have no problems with +skipping their system-wide resume callbacks for this reason. 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 is expected to +indicate to the PM core if the device may be left in suspend by setting its +:c:member:`power.may_skip_resume` status bit which is checked by the PM core +during the "noirq" phase of the preceding system-wide 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 is left suspended, but the other resume callbacks +(except for ``->complete``) will be skipped automatically by the PM core if the +device really can be left in suspend.