Messages in this thread | | | From | Ulf Hansson <> | Date | Thu, 21 Oct 2021 21:56:12 +0200 | Subject | Re: [PATCH 2/2] PM: sleep: Fix runtime PM based cpuidle support |
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On Thu, 21 Oct 2021 at 21:02, Rafael J. Wysocki <rafael@kernel.org> wrote: > > On Thu, Oct 21, 2021 at 8:12 PM Ulf Hansson <ulf.hansson@linaro.org> wrote: > > > > On Thu, 21 Oct 2021 at 18:33, Rafael J. Wysocki <rafael@kernel.org> wrote: > > > > > > On Thu, Oct 21, 2021 at 6:17 PM Ulf Hansson <ulf.hansson@linaro.org> wrote: > > [cut] > > > > So in theory you could check the pm_runtime_put_sync_suspend() return > > > value and fall back to something like WFI if that's an error code. > > > > I have already tried that, but it simply got too complicated. The main > > issue was that runtime PM could become disabled for the device in the > > middle of executing the ->enter() callback. > > So IIUC the problem is that you cannot resume after suspending in that case. > > IOW, you need to guarantee that if the suspend is successful, the > resume also will take place, but if the suspend fails, you basically > don't care.
Exactly.
> > > For example, if pm_runtime_get_sync() fails, I still need to make sure > > the reference counting in genpd becomes correct - and I can't do that > > using dev_pm_genpd_resume(). That's because it's not designed to be > > called in this "unknown" suspend phase, but should be called after the > > noirq phase and be properly balanced with dev_pm_genpd_suspend(). > > > > In other words, the error path didn't work out for me. > > It should be sufficient to call wake_up_all_idle_cpus() in the suspend > path before dpm_suspend_late(), because system suspend acquires a > PM-runtime reference on every device. IOW, it won't let any devices > runtime-suspend, so if your power domain devices are resumed in that > path, they will never suspend again in it and the > pm_runtime_put_sync_suspend() in __psci_enter_domain_idle_state() > becomes a reference counter management call which works regardless of > whether or not PM runtime is disabled.
That sounds like a great idea, this should work too! Then the question is, how to make that call to wake_up_all_idle_cpus() to become optional - or only invoked for the cpuidle drivers that need it.
In any case, I will try this out, thanks for the suggestion!
Kind regards Uffe
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