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Message-ID: <2072799.Uj3u7nOOPY@vostro.rjw.lan> Date: Thu, 08 May 2014 22:02:14 +0200 From: "Rafael J. Wysocki" <rjw@...ysocki.net> To: Ulf Hansson <ulf.hansson@...aro.org> Cc: Alan Stern <stern@...land.harvard.edu>, Linux PM list <linux-pm@...r.kernel.org>, Mika Westerberg <mika.westerberg@...ux.intel.com>, Aaron Lu <aaron.lu@...el.com>, ACPI Devel Maling List <linux-acpi@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [RFC][PATCH 1/3] PM / sleep: Flag to speed up suspend-resume of runtime-suspended devices On Thursday, May 08, 2014 02:25:06 PM Ulf Hansson wrote: > On 8 May 2014 13:44, Rafael J. Wysocki <rjw@...ysocki.net> wrote: > > On Thursday, May 08, 2014 12:59:20 PM Ulf Hansson wrote: > >> On 8 May 2014 12:53, Rafael J. Wysocki <rjw@...ysocki.net> wrote: > >> > On Thursday, May 08, 2014 09:49:36 AM Ulf Hansson wrote: > >> >> On 8 May 2014 01:29, Rafael J. Wysocki <rjw@...ysocki.net> wrote: > >> >> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.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 resume stage of system > >> >> > resume. > >> >> > > >> >> > To this end, introduce dev->power.leave_runtime_suspended. > >> >> > If a subsystem or driver sets this flag during the ->prepare() callback, > >> >> > and if the flag is set in all of the device's descendants, and if the > >> >> > device is still in runtime suspend at the beginning of the ->suspend() > >> >> > callback, that callback is allowed to return 0 without clearing > >> >> > power.leave_runtime_suspended and without changing the state of the > >> >> > device, unless the current state of the device is not appropriate for > >> >> > the upcoming system sleep state (for example, the device is supposed to > >> >> > wake up the system from that state and its current wakeup settings are > >> >> > not suitable for that). Then, the PM core will not invoke the device's > >> >> > ->suspend_late(), ->suspend_irq(), ->resume_irq(), ->resume_early(), or > >> >> > ->resume() callbacks. Instead, it will invoke ->runtime_resume() during > >> >> > the device resume stage of system resume. > >> >> > > >> >> > By leaving this flag set after ->suspend(), a driver or subsystem tells > >> >> > the PM core that the device is runtime suspended, it is in a suitable > >> >> > state for system suspend (for example, the wakeup setting does not > >> >> > need to be changed), and it does not need to return to full > >> >> > power until the resume stage. > >> >> > > >> >> > Changelog 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.wysocki@...el.com> > >> >> > --- > >> >> > drivers/base/power/main.c | 31 ++++++++++++++++++++++++------- > >> >> > drivers/base/power/runtime.c | 10 ++++++++++ > >> >> > include/linux/pm.h | 3 +++ > >> >> > include/linux/pm_runtime.h | 16 ++++++++++++++++ > >> >> > kernel/power/Kconfig | 4 ++++ > >> >> > 5 files changed, 57 insertions(+), 7 deletions(-) > >> >> > > >> >> > Index: linux-pm/kernel/power/Kconfig > >> >> > =================================================================== > >> >> > --- linux-pm.orig/kernel/power/Kconfig > >> >> > +++ linux-pm/kernel/power/Kconfig > >> >> > @@ -147,6 +147,10 @@ config PM > >> >> > def_bool y > >> >> > depends on PM_SLEEP || PM_RUNTIME > >> >> > > >> >> > +config PM_BOTH > >> >> > + def_bool y > >> >> > + depends on PM_SLEEP && PM_RUNTIME > >> >> > + > >> >> > >> >> Should we not depend on PM_RUNTIME only? Thus we don't need the new > >> >> Kconfig, > >> > > >> > Well, OK. I guess we can tolerate one useless statement in rpm_resume() > >> > in case CONFIG_PM_SLEEP is unset. > >> > > >> >> and then we could rename the new APIs to pm_runtime_* instead. > >> > > >> > That would just make the name longer - for what value? > >> > >> Only "__set_leave_runtime_suspended" will be a bit longer. > >> > >> The idea I had was to clearly indicate, these functions is a part of > >> PM_RUNTIME API. > >> > >> Compare what you have: > >> __set_leave_runtime_suspended > >> pm_set_leave_runtime_suspended > >> pm_leave_runtime_suspended > >> > >> To what I suggest: > >> __pm_runtime_set_leave_suspended > >> pm_runtime_set_leave_suspended > >> pm_runtime_leave_suspended > > > > And why exactly do you think these are any better? > > Because that's how all (almost all) other functions in the runtime PM > API are specified - I believe it makes sense to keep them aligned. > > Anyway, if you insist in keeping your functions names, it's not that > of a big deal for me. > > Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org> > > > > > The flag is not called leave_suspended surely? > > To me that doesn't matter, the flag has nothing to do with the > function names in an API. Well, the point is that pm_runtime_leave_suspended suggests that the runtime PM framework is supposed to leave the device suspended, while this isn't the case. This essentially is a system suspend flag that depends on runtime PM being available. Thanks! -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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