| Message ID | 1952050.gHGtV5tzZn@aspire.rjw.lan (mailing list archive) |
|---|---|
| State | Mainlined |
| Delegated to: | Rafael Wysocki |
| Headers | show |
On 12 January 2018 at 14:12, Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > One of the limitations of pm_runtime_force_suspend/resume() is that > if a parent driver wants to use these functions, all of its child > drivers generally have to do that too because of the parent usage > counter manipulations necessary to get the correct state of the parent > during system-wide transitions to the working state (system resume). > However, that limitation turns out to be artificial, so remove it. According to my comment on the other thread, this stands true in case the child is managed by runtime PM as well. Otherwise this looks good to me. > > Namely, pm_runtime_force_suspend() only needs to update the children > counter of its parent (if there's is a parent) when the device can > stay in suspend after the subsequent system resume transition, as > that counter is correct already otherwise. Now, if the parent's > children counter is not updated, it is not necessary to increment > the parent's usage counter in that case any more, as long as the > children counters of devices are checked along with their usage > counters in order to decide whether or not the devices may be left > in suspend after the subsequent system resume transition. > > Accordingly, modify pm_runtime_force_suspend() to only call > pm_runtime_set_suspended() for devices whose usage and children > counters are at the "no references" level (the runtime PM status > of the device needs to be updated to "suspended" anyway in case > this function is called once again for the same device during the > transition under way), drop the parent usage counter incrementation > from it and update pm_runtime_force_resume() to compensate for these > changes. > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org> > --- > drivers/base/power/runtime.c | 74 +++++++++++++++++++------------------------ > 1 file changed, 34 insertions(+), 40 deletions(-) > > Index: linux-pm/drivers/base/power/runtime.c > =================================================================== > --- linux-pm.orig/drivers/base/power/runtime.c > +++ linux-pm/drivers/base/power/runtime.c > @@ -1613,17 +1613,28 @@ void pm_runtime_drop_link(struct device > spin_unlock_irq(&dev->power.lock); > } > > +static bool pm_runtime_need_not_resume(struct device *dev) > +{ > + return atomic_read(&dev->power.usage_count) <= 1 && > + atomic_read(&dev->power.child_count) == 0; How about adding an additional patch on top taking into account the ignore_children flag and folding that into the series, kind of as you also suggested? My point is, we might as well take the opportunity to fix this right away, don't you think? [...] Kind regards Uffe
On Friday, January 12, 2018 2:59:38 PM CET Ulf Hansson wrote: > On 12 January 2018 at 14:12, Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > > > One of the limitations of pm_runtime_force_suspend/resume() is that > > if a parent driver wants to use these functions, all of its child > > drivers generally have to do that too because of the parent usage > > counter manipulations necessary to get the correct state of the parent > > during system-wide transitions to the working state (system resume). > > However, that limitation turns out to be artificial, so remove it. > > According to my comment on the other thread, this stands true in case > the child is managed by runtime PM as well. What do you mean by "managed by runtime PM"? > Otherwise this looks good to me. > > > > > Namely, pm_runtime_force_suspend() only needs to update the children > > counter of its parent (if there's is a parent) when the device can > > stay in suspend after the subsequent system resume transition, as > > that counter is correct already otherwise. Now, if the parent's > > children counter is not updated, it is not necessary to increment > > the parent's usage counter in that case any more, as long as the > > children counters of devices are checked along with their usage > > counters in order to decide whether or not the devices may be left > > in suspend after the subsequent system resume transition. > > > > Accordingly, modify pm_runtime_force_suspend() to only call > > pm_runtime_set_suspended() for devices whose usage and children > > counters are at the "no references" level (the runtime PM status > > of the device needs to be updated to "suspended" anyway in case > > this function is called once again for the same device during the > > transition under way), drop the parent usage counter incrementation > > from it and update pm_runtime_force_resume() to compensate for these > > changes. > > > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org> > > --- > > drivers/base/power/runtime.c | 74 +++++++++++++++++++------------------------ > > 1 file changed, 34 insertions(+), 40 deletions(-) > > > > Index: linux-pm/drivers/base/power/runtime.c > > =================================================================== > > --- linux-pm.orig/drivers/base/power/runtime.c > > +++ linux-pm/drivers/base/power/runtime.c > > @@ -1613,17 +1613,28 @@ void pm_runtime_drop_link(struct device > > spin_unlock_irq(&dev->power.lock); > > } > > > > +static bool pm_runtime_need_not_resume(struct device *dev) > > +{ > > + return atomic_read(&dev->power.usage_count) <= 1 && > > + atomic_read(&dev->power.child_count) == 0; > > How about adding an additional patch on top taking into account the > ignore_children flag and folding that into the series, kind of as you > also suggested? I will do that, no worries. > My point is, we might as well take the opportunity to fix this right > away, don't you think? OK, I'll send a patch on top of this series. Thanks, Rafael
Index: linux-pm/drivers/base/power/runtime.c =================================================================== --- linux-pm.orig/drivers/base/power/runtime.c +++ linux-pm/drivers/base/power/runtime.c @@ -1613,17 +1613,28 @@ void pm_runtime_drop_link(struct device spin_unlock_irq(&dev->power.lock); } +static bool pm_runtime_need_not_resume(struct device *dev) +{ + return atomic_read(&dev->power.usage_count) <= 1 && + atomic_read(&dev->power.child_count) == 0; +} + /** * pm_runtime_force_suspend - Force a device into suspend state if needed. * @dev: Device to suspend. * * Disable runtime PM so we safely can check the device's runtime PM status and - * if it is active, invoke it's .runtime_suspend callback to bring it into - * suspend state. Keep runtime PM disabled to preserve the state unless we - * encounter errors. + * if it is active, invoke its ->runtime_suspend callback to suspend it and + * change its runtime PM status field to RPM_SUSPENDED. Also, if the device's + * usage and children counters don't indicate that the device was in use before + * the system-wide transition under way, decrement its parent's children counter + * (if there is a parent). Keep runtime PM disabled to preserve the state + * unless we encounter errors. * * Typically this function may be invoked from a system suspend callback to make - * sure the device is put into low power state. + * sure the device is put into low power state and it should only be used during + * system-wide PM transitions to sleep states. It assumes that the analogous + * pm_runtime_force_resume() will be used to resume the device. */ int pm_runtime_force_suspend(struct device *dev) { @@ -1646,17 +1657,18 @@ int pm_runtime_force_suspend(struct devi goto err; /* - * Increase the runtime PM usage count for the device's parent, in case - * when we find the device being used when system suspend was invoked. - * This informs pm_runtime_force_resume() to resume the parent - * immediately, which is needed to be able to resume its children, - * when not deferring the resume to be managed via runtime PM. + * If the device can stay in suspend after the system-wide transition + * to the working state that will follow, drop the children counter of + * its parent, but set its status to RPM_SUSPENDED anyway in case this + * function will be called again for it in the meantime. */ - if (dev->parent && atomic_read(&dev->power.usage_count) > 1) - pm_runtime_get_noresume(dev->parent); + if (pm_runtime_need_not_resume(dev)) + pm_runtime_set_suspended(dev); + else + __update_runtime_status(dev, RPM_SUSPENDED); - pm_runtime_set_suspended(dev); return 0; + err: pm_runtime_enable(dev); return ret; @@ -1669,13 +1681,9 @@ EXPORT_SYMBOL_GPL(pm_runtime_force_suspe * * Prior invoking this function we expect the user to have brought the device * into low power state by a call to pm_runtime_force_suspend(). Here we reverse - * those actions and brings the device into full power, if it is expected to be - * used on system resume. To distinguish that, we check whether the runtime PM - * usage count is greater than 1 (the PM core increases the usage count in the - * system PM prepare phase), as that indicates a real user (such as a subsystem, - * driver, userspace, etc.) is using it. If that is the case, the device is - * expected to be used on system resume as well, so then we resume it. In the - * other case, we defer the resume to be managed via runtime PM. + * those actions and bring the device into full power, if it is expected to be + * used on system resume. In the other case, we defer the resume to be managed + * via runtime PM. * * Typically this function may be invoked from a system resume callback. */ @@ -1684,32 +1692,18 @@ int pm_runtime_force_resume(struct devic int (*callback)(struct device *); int ret = 0; - callback = RPM_GET_CALLBACK(dev, runtime_resume); - - if (!callback) { - ret = -ENOSYS; - goto out; - } - - if (!pm_runtime_status_suspended(dev)) + if (!pm_runtime_status_suspended(dev) || pm_runtime_need_not_resume(dev)) goto out; /* - * Decrease the parent's runtime PM usage count, if we increased it - * during system suspend in pm_runtime_force_suspend(). - */ - if (atomic_read(&dev->power.usage_count) > 1) { - if (dev->parent) - pm_runtime_put_noidle(dev->parent); - } else { - goto out; - } + * The value of the parent's children counter is correct already, so + * just update the status of the device. + */ + __update_runtime_status(dev, RPM_ACTIVE); - ret = pm_runtime_set_active(dev); - if (ret) - goto out; + callback = RPM_GET_CALLBACK(dev, runtime_resume); - ret = callback(dev); + ret = callback ? callback(dev) : -ENOSYS; if (ret) { pm_runtime_set_suspended(dev); goto out;