On Thu, 15 May 2014 13:11:15 +0200 "Rafael J. Wysocki" <r...@rjwysocki.net> wrote:
> On Wednesday, May 14, 2014 03:24:21 PM Jacob Pan wrote: > > On Tue, 13 May 2014 03:10:19 +0200 > > "Rafael J. Wysocki" <r...@rjwysocki.net> wrote: > > > > > From: Rafael J. Wysocki <rafael.j.wyso...@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 complete stage of system resume. > > > > > > To this end, introduce a new device PM flag, power.direct_complete > > > and modify the PM core to use that flag as follows. > > > > > > If the ->prepare() callback of a device returns a positive number, > > > the PM core will regard that as an indication that it may leave > > > the device runtime-suspended. It will then check if the system > > > power transition in progress is a suspend (and not hibernation in > > > particular) and if the device is, indeed, runtime-suspended. In > > > that case, the PM core will set the device's > > > power.direct_complete flag. Otherwise it will clear > > > power.direct_complete for the device and it also will later clear > > > it for the device's parent (if there's one). > > > > > > Next, the PM core will not invoke the ->suspend() > > > ->suspend_late(), ->suspend_irq(), ->resume_irq(), > > > ->resume_early(), or ->resume() callbacks for all devices having > > > power.direct_complete set. It will invoke their ->complete() > > > callbacks, however, and those callbacks are then responsible for > > > resuming the devices as appropriate, if necessary. > > > > > > Changelog partly based on an Alan Stern's description of the idea > > > (http://marc.info/?l=linux-pm&m=139940466625569&w=2). > > > > > > Signed-off-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com> > > > --- > > > drivers/base/power/main.c | 45 > > > ++++++++++++++++++++++++++++----------------- > > > include/linux/pm.h | 1 + 2 files changed, 29 > > > insertions(+), 17 deletions(-) > > > > > > Index: linux-pm/include/linux/pm.h > > > =================================================================== > > > --- linux-pm.orig/include/linux/pm.h > > > +++ linux-pm/include/linux/pm.h > > > @@ -546,6 +546,7 @@ struct dev_pm_info { > > > bool is_late_suspended:1; > > > bool ignore_children:1; > > > bool early_init:1; /* > > > Owned by the PM core */ > > > + bool direct_complete:1; /* > > > Owned by the PM core */ spinlock_t lock; > > > #ifdef CONFIG_PM_SLEEP > > > struct list_head entry; > > > Index: linux-pm/drivers/base/power/main.c > > > =================================================================== > > > --- linux-pm.orig/drivers/base/power/main.c > > > +++ linux-pm/drivers/base/power/main.c > > > @@ -479,7 +479,7 @@ static int device_resume_noirq(struct de > > > TRACE_DEVICE(dev); > > > TRACE_RESUME(0); > > > > > > - if (dev->power.syscore) > > > + if (dev->power.syscore || dev->power.direct_complete) > > > goto Out; > > > > > > if (!dev->power.is_noirq_suspended) > > > @@ -605,7 +605,7 @@ static int device_resume_early(struct de > > > TRACE_DEVICE(dev); > > > TRACE_RESUME(0); > > > > > > - if (dev->power.syscore) > > > + if (dev->power.syscore || dev->power.direct_complete) > > > goto Out; > > > > > > if (!dev->power.is_late_suspended) > > > @@ -732,7 +732,7 @@ static int device_resume(struct device * > > > TRACE_DEVICE(dev); > > > TRACE_RESUME(0); > > > > > > - if (dev->power.syscore) > > > + if (dev->power.syscore || dev->power.direct_complete) > > > goto Complete; > > > > > > dpm_wait(dev->parent, async); > > > @@ -1007,7 +1007,7 @@ static int __device_suspend_noirq(struct > > > goto Complete; > > > } > > > > > > - if (dev->power.syscore) > > > + if (dev->power.syscore || dev->power.direct_complete) > > > goto Complete; > > > > > > dpm_wait_for_children(dev, async); > > > @@ -1146,7 +1146,7 @@ static int __device_suspend_late(struct > > > goto Complete; > > > } > > > > > > - if (dev->power.syscore) > > > + if (dev->power.syscore || dev->power.direct_complete) > > > goto Complete; > > > > > > dpm_wait_for_children(dev, async); > > > @@ -1312,7 +1312,7 @@ static int __device_suspend(struct devic > > > > > > dpm_wait_for_children(dev, async); > > > > > > - if (async_error || dev->power.syscore) > > > + if (async_error || dev->power.syscore || > > > dev->power.direct_complete) goto Complete; > > > > > > dpm_watchdog_set(&wd, dev); > > > @@ -1365,10 +1365,19 @@ static int __device_suspend(struct devic > > > > > > End: > > > if (!error) { > > > + struct device *parent = dev->parent; > > > + > > > dev->power.is_suspended = true; > > > - if (dev->power.wakeup_path > > > - && dev->parent > > > && !dev->parent->power.ignore_children) > > > - dev->parent->power.wakeup_path = true; > > > + if (parent) { > > > + spin_lock_irq(&parent->power.lock); > > > + > > > + dev->parent->power.direct_complete = > > > false; > > should we respect ignore_children flag here? not all parent devices > > create children with proper .prepare() function. this allows parents > > override children. > > I am looking at USB, a USB device could have logical children such > > as ep_xx, they don't go through the same subsystem .prepare(). > > Well, I'm not sure about that. Let me consider that for a while. OK. let me be more clear about the situation i see in USB. Correct me if I am wrong, a USB device will always has at least one endpoint/ep_00 as a kid for control pipe, it is a logical device. So when device_prepare() is called, its call back is NULL which makes .direct_complete = 0. Since children device suspend is called before parents, the parents .direct_complete flag will always get cleared. What i am trying to achieve here is to see if we avoid resuming built-in (hardwired connect_type) non-hub USB devices based on this new patchset. E.g. we don't want to resume/suspend USB camera every time in system suspend/resume cycle if they are already rpm suspended. We can save ~100ms resume time for the devices we have tested. > > Alan, what do you think? > > > > > > + if (dev->power.wakeup_path > > > + > > > && !dev->parent->power.ignore_children) > > > + dev->parent->power.wakeup_path = > > > true; + > > > + spin_unlock_irq(&parent->power.lock); > > > + } > > > } > > > > > > device_unlock(dev); > > > @@ -1470,7 +1479,7 @@ static int device_prepare(struct device > > > { > > > int (*callback)(struct device *) = NULL; > > > char *info = NULL; > > > - int error = 0; > > > + int ret = 0; > > > > > > if (dev->power.syscore) > > > return 0; > > > @@ -1518,17 +1527,19 @@ static int device_prepare(struct device > > > callback = dev->driver->pm->prepare; > > > } > > > > > > - if (callback) { > > > - error = callback(dev); > > > - suspend_report_result(callback, error); > > > - } > > > + if (callback) > > > + ret = callback(dev); > > > > > > device_unlock(dev); > > > > > > - if (error) > > > + if (ret < 0) { > > > + suspend_report_result(callback, ret); > > > pm_runtime_put(dev); > > > - > > > - return error; > > > + return ret; > > > + } > > > + dev->power.direct_complete = ret > 0 && state.event == > > > PM_EVENT_SUSPEND > > > + && > > > pm_runtime_suspended(dev); > > > + return 0; > > > } > > > > > > /** > > > > > > -- > > Rafael > [Jacob Pan] -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
