| Message ID | 5769060.47kJca3s00@aspire.rjw.lan (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
On 28 October 2017 at 00:22, Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > Define and document a SMART_SUSPEND flag to instruct bus types and PM > domains that the system suspend callbacks provided by the driver can > cope with runtime-suspended devices, so from the driver's perspective > it should be safe to leave devices in runtime suspend during system > suspend. > > Setting that flag may also cause middle-layer code (bus types, > PM domains etc.) to skip invocations of the ->suspend_late and > ->suspend_noirq callbacks provided by the driver if the device > is in runtime suspend at the beginning of the "late" phase of > the system-wide suspend transition, in which case the driver's > system-wide resume callbacks may be invoked back-to-back with > its ->runtime_suspend callback, so the driver has to be able to > cope with that too. > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> If not too late: Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org> > --- > > -> v2: Drop the changes in main.c, as the logic implemented by them > previously is now going to be implemented in the PCI bus type > and the ACPI PM domain directly. > > --- > Documentation/driver-api/pm/devices.rst | 20 ++++++++++++++++++++ > drivers/base/power/main.c | 3 +++ > include/linux/pm.h | 8 ++++++++ > 3 files changed, 31 insertions(+) > > 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 > @@ -766,6 +766,26 @@ the state of devices (possibly except fo > from their ``->prepare`` and ``->suspend`` callbacks (or equivalent) *before* > invoking device drivers' ``->suspend`` callbacks (or equivalent). > > +Some bus types and PM domains have a policy to resume all devices from runtime > +suspend upfront in their ``->suspend`` callbacks, but that may not be really > +necessary if the driver of the device can cope with runtime-suspended devices. > +The driver can indicate that by setting ``DPM_FLAG_SMART_SUSPEND`` in > +:c:member:`power.driver_flags` at the probe time, by passing it to the > +:c:func:`dev_pm_set_driver_flags` helper. That also may cause middle-layer code > +(bus types, PM domains etc.) to skip the ``->suspend_late`` and > +``->suspend_noirq`` callbacks provided by the driver if the device remains in > +runtime suspend at the beginning of the ``suspend_late`` phase of system-wide > +suspend (or in the ``poweroff_late`` phase of hibernation), when runtime PM > +has been disabled for it, under the assumption that its state should not change > +after that point until the system-wide transition is over. If that happens, the > +driver's system-wide resume callbacks, if present, may still be invoked during > +the subsequent system-wide resume transition and the device's runtime power > +management status may be set to "active" before enabling runtime PM for it, > +so the driver must be prepared to cope with the invocation of its system-wide > +resume callbacks back-to-back with its ``->runtime_suspend`` one (without the > +intervening ``->runtime_resume`` and so on) and the final state of the device > +must reflect the "active" status for runtime PM in that case. > + > 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 > Index: linux-pm/drivers/base/power/main.c > =================================================================== > --- linux-pm.orig/drivers/base/power/main.c > +++ linux-pm/drivers/base/power/main.c > @@ -1652,6 +1652,9 @@ 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)); > + > /* > * If a device's parent goes into runtime suspend at the wrong time, > * it won't be possible to resume the device. To prevent this we > Index: linux-pm/include/linux/pm.h > =================================================================== > --- linux-pm.orig/include/linux/pm.h > +++ linux-pm/include/linux/pm.h > @@ -558,6 +558,7 @@ 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. > * > * 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 > @@ -565,9 +566,16 @@ struct pm_subsys_data { > * other words, the system suspend/resume callbacks can only be skipped for the > * device if its driver doesn't object against that). This flag has no effect > * if NEVER_SKIP is set. > + * > + * Setting SMART_SUSPEND instructs bus types and PM domains which may want to > + * runtime resume the device upfront during system suspend that doing so is not > + * 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. > */ > #define DPM_FLAG_NEVER_SKIP BIT(0) > #define DPM_FLAG_SMART_PREPARE BIT(1) > +#define DPM_FLAG_SMART_SUSPEND BIT(2) > > struct dev_pm_info { > pm_message_t power_state; >
On Mon, Nov 6, 2017 at 9:09 AM, Ulf Hansson <ulf.hansson@linaro.org> wrote: > On 28 October 2017 at 00:22, Rafael J. Wysocki <rjw@rjwysocki.net> wrote: >> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> >> >> Define and document a SMART_SUSPEND flag to instruct bus types and PM >> domains that the system suspend callbacks provided by the driver can >> cope with runtime-suspended devices, so from the driver's perspective >> it should be safe to leave devices in runtime suspend during system >> suspend. >> >> Setting that flag may also cause middle-layer code (bus types, >> PM domains etc.) to skip invocations of the ->suspend_late and >> ->suspend_noirq callbacks provided by the driver if the device >> is in runtime suspend at the beginning of the "late" phase of >> the system-wide suspend transition, in which case the driver's >> system-wide resume callbacks may be invoked back-to-back with >> its ->runtime_suspend callback, so the driver has to be able to >> cope with that too. >> >> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> >> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > If not too late: > > Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org> Not too late, thanks! I'll be sending the next batch of this shortly. :-)
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 @@ -766,6 +766,26 @@ the state of devices (possibly except fo from their ``->prepare`` and ``->suspend`` callbacks (or equivalent) *before* invoking device drivers' ``->suspend`` callbacks (or equivalent). +Some bus types and PM domains have a policy to resume all devices from runtime +suspend upfront in their ``->suspend`` callbacks, but that may not be really +necessary if the driver of the device can cope with runtime-suspended devices. +The driver can indicate that by setting ``DPM_FLAG_SMART_SUSPEND`` in +:c:member:`power.driver_flags` at the probe time, by passing it to the +:c:func:`dev_pm_set_driver_flags` helper. That also may cause middle-layer code +(bus types, PM domains etc.) to skip the ``->suspend_late`` and +``->suspend_noirq`` callbacks provided by the driver if the device remains in +runtime suspend at the beginning of the ``suspend_late`` phase of system-wide +suspend (or in the ``poweroff_late`` phase of hibernation), when runtime PM +has been disabled for it, under the assumption that its state should not change +after that point until the system-wide transition is over. If that happens, the +driver's system-wide resume callbacks, if present, may still be invoked during +the subsequent system-wide resume transition and the device's runtime power +management status may be set to "active" before enabling runtime PM for it, +so the driver must be prepared to cope with the invocation of its system-wide +resume callbacks back-to-back with its ``->runtime_suspend`` one (without the +intervening ``->runtime_resume`` and so on) and the final state of the device +must reflect the "active" status for runtime PM in that case. + 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 Index: linux-pm/drivers/base/power/main.c =================================================================== --- linux-pm.orig/drivers/base/power/main.c +++ linux-pm/drivers/base/power/main.c @@ -1652,6 +1652,9 @@ 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)); + /* * If a device's parent goes into runtime suspend at the wrong time, * it won't be possible to resume the device. To prevent this we Index: linux-pm/include/linux/pm.h =================================================================== --- linux-pm.orig/include/linux/pm.h +++ linux-pm/include/linux/pm.h @@ -558,6 +558,7 @@ 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. * * 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 @@ -565,9 +566,16 @@ struct pm_subsys_data { * other words, the system suspend/resume callbacks can only be skipped for the * device if its driver doesn't object against that). This flag has no effect * if NEVER_SKIP is set. + * + * Setting SMART_SUSPEND instructs bus types and PM domains which may want to + * runtime resume the device upfront during system suspend that doing so is not + * 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. */ #define DPM_FLAG_NEVER_SKIP BIT(0) #define DPM_FLAG_SMART_PREPARE BIT(1) +#define DPM_FLAG_SMART_SUSPEND BIT(2) struct dev_pm_info { pm_message_t power_state;