Messages in this thread | | | From | Tomeu Vizoso <> | Date | Thu, 16 Jul 2015 10:47:51 +0200 | Subject | Re: [PATCH v4 2/3] PM / sleep: Go direct_complete if driver has no callbacks |
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On 16 July 2015 at 02:41, Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > On Wednesday, July 15, 2015 02:47:50 PM Alan Stern wrote: >> On Wed, 15 Jul 2015, Tomeu Vizoso wrote: >> >> > If a suitable prepare callback cannot be found for a given device and >> > its driver has no PM callbacks at all, assume that it can go direct to >> > complete when the system goes to sleep. >> > >> > The reason for this is that there's lots of devices in a system that do >> > no PM at all and there's no reason for them to prevent their ancestors >> > to do direct_complete if they can support it. >> > >> > Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com> >> > --- >> > >> > drivers/base/power/main.c | 17 +++++++++++++++++ >> > 1 file changed, 17 insertions(+) >> > >> > diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c >> > index 1710c26ba097..edda3f233c7c 100644 >> > --- a/drivers/base/power/main.c >> > +++ b/drivers/base/power/main.c >> > @@ -1540,6 +1540,21 @@ int dpm_suspend(pm_message_t state) >> > return error; >> > } >> > >> > +static bool driver_has_no_pm_callbacks(struct device_driver *drv) >> > +{ >> > + if (!drv->pm) >> > + return true; >> > + >> > + return !drv->pm->prepare && >> > + !drv->pm->suspend && >> > + !drv->pm->suspend_late && >> > + !drv->pm->suspend_noirq && >> > + !drv->pm->resume_noirq && >> > + !drv->pm->resume_early && >> > + !drv->pm->resume && >> > + !drv->pm->complete; >> > +} >> >> This isn't exactly what I meant. We also need to check the dev_pm_ops >> fields in dev->pm_domain, dev->type, dev->class, and dev->bus. Only if >> _all_ of these callbacks are missing should we use direct_complete. > > Also checking that on every suspend is kind of wasteful, because those things > do not change very often.
Do you have any suggestion on when would be a good time to do that check? device_pm_sleep_init() and device_pm_add() are unfortunately too early.
Alternatively we could check once on the first suspend and cache it, but I'm not sure that complexity would be worth it.
Thanks,
Tomeu
> Thanks, > Rafael > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.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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