Messages in this thread Patch in this message | | | From | Ikjoon Jang <> | Date | Tue, 12 Nov 2019 13:10:44 +0800 | Subject | Re: [RFC PATCH RESEND] cpuidle: undelaying cpuidle in dpm_{suspend|resume}() |
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On Fri, Nov 8, 2019 at 7:22 PM Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > > On Wednesday, October 30, 2019 3:21:05 AM CET Ikjoon Jang wrote: > > cpuidle is paused only during dpm_suspend_noirq() ~ dpm_resume_noirq(). > > But some device drivers need random sized IOs in dpm_{suspend|resume}() > > stage (e.g. re-downloading firmware in resume). > > And with such a device, cpuidle's latencies could be critical to > > response time of system suspend/resume. > > > > To minimize those latencies, we could apply pm_qos to such device drivers, > > but simply undelaying cpuidle from dpm_suspend_noirq() to dpm suspend() > > seems no harm. > > While the patch is generally acceptable, the changelog is not. > > First, what does "undelying" mean?
You're right, that should be fixed, actually I used 'undelaying' from commit: 8651f97bd951d (PM / cpuidle: System resume hang fix with cpuidle), when the first time cpuidle_{pause|resume} is introduced:
"Since we are dealing with drivers it seems best to call this function during dpm_suspend(). Delaying the call till dpm_suspend_noirq() does no harm, as long as it is before cpu_hotplug_begin() to avoid race conditions with cpu hotpulg operations."
Delaying does no harm, but I think that there had been no specific reason of this delay from the beginning. Undelaying does no harm too.
> > Second, you seem to be talking about the cases in which exit latencies of > idle states are not small relative to the system suspend/resume time, so > without any specific examples this is not really convincing. > > Also, potentially, there is another reason to make this change, which is > that on some systems i2c (or similar) controllers may be requisite for > idle state entry and exit, so it may make sense in general to prevent > cpuidle from being used over the entire suspend and resume of the > system. However, without any example of a system in which that matters > it still is not convincing enough IMO. >
Currently I've got only one specific device for examples. Maybe this patch needs more generalized examples for applying to all other machines.
Thanks!
> > Signed-off-by: Ikjoon Jang <ikjn@chromium.org> > > --- > > drivers/base/power/main.c | 6 ++---- > > 1 file changed, 2 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c > > index 134a8af51511..5928dd2139e8 100644 > > --- a/drivers/base/power/main.c > > +++ b/drivers/base/power/main.c > > @@ -773,8 +773,6 @@ void dpm_resume_noirq(pm_message_t state) > > > > resume_device_irqs(); > > device_wakeup_disarm_wake_irqs(); > > - > > - cpuidle_resume(); > > } > > > > static pm_callback_t dpm_subsys_resume_early_cb(struct device *dev, > > @@ -1069,6 +1067,7 @@ void dpm_resume(pm_message_t state) > > > > cpufreq_resume(); > > devfreq_resume(); > > + cpuidle_resume(); > > trace_suspend_resume(TPS("dpm_resume"), state.event, false); > > } > > > > @@ -1411,8 +1410,6 @@ int dpm_suspend_noirq(pm_message_t state) > > { > > int ret; > > > > - cpuidle_pause(); > > - > > device_wakeup_arm_wake_irqs(); > > suspend_device_irqs(); > > > > @@ -1830,6 +1827,7 @@ int dpm_suspend(pm_message_t state) > > trace_suspend_resume(TPS("dpm_suspend"), state.event, true); > > might_sleep(); > > > > + cpuidle_pause(); > > devfreq_suspend(); > > cpufreq_suspend(); > > > > > > > >
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