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From: Ulf Hansson <email@example.com> To: "Rafael J. Wysocki" <firstname.lastname@example.org> Cc: Daniel Lezcano <email@example.com>, Linux PM <firstname.lastname@example.org>, Maulik Shah <email@example.com>, Peter Zijlstra <firstname.lastname@example.org>, Vincent Guittot <email@example.com>, Len Brown <firstname.lastname@example.org>, Bjorn Andersson <email@example.com>, Linux ARM <firstname.lastname@example.org>, Linux Kernel Mailing List <email@example.com> Subject: Re: [PATCH 2/2] PM: sleep: Fix runtime PM based cpuidle support Date: Fri, 22 Oct 2021 12:18:12 +0200 [thread overview] Message-ID: <CAPDyKFooeseEXW-O8DCAd5Jku1n0iNXfHFt_HVjcfMYFvw4a2g@mail.gmail.com> (raw) In-Reply-To: <CAPDyKFpjy5sZo6ayqPx07Jzs4J2yePy=cZk=k6VjhWB7zGeedg@mail.gmail.com> On Thu, 21 Oct 2021 at 21:56, Ulf Hansson <firstname.lastname@example.org> wrote: > > On Thu, 21 Oct 2021 at 21:02, Rafael J. Wysocki <email@example.com> wrote: > > > > On Thu, Oct 21, 2021 at 8:12 PM Ulf Hansson <firstname.lastname@example.org> wrote: > > > > > > On Thu, 21 Oct 2021 at 18:33, Rafael J. Wysocki <email@example.com> wrote: > > > > > > > > On Thu, Oct 21, 2021 at 6:17 PM Ulf Hansson <firstname.lastname@example.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! I now recall that I have already tried this, but unfortunately it doesn't work. The problem is that the dev->power.syscore flag is set for the device, which makes device_prepare() to bail out early and skip calling pm_runtime_get_noresume(). Kind regards Uffe
next prev parent reply other threads:[~2021-10-22 10:19 UTC|newest] Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-09-29 14:44 [PATCH 0/2] cpuidle: Fix runtime PM based cpuidle for s2idle Ulf Hansson 2021-09-29 14:44 ` [PATCH 1/2] cpuidle: Avoid calls to cpuidle_resume|pause() " Ulf Hansson 2021-10-06 10:22 ` Maulik Shah 2021-10-06 13:10 ` Ulf Hansson 2021-10-09 15:42 ` Rafael J. Wysocki 2021-10-09 15:39 ` Rafael J. Wysocki 2021-10-11 10:04 ` Ulf Hansson 2021-09-29 14:44 ` [PATCH 2/2] PM: sleep: Fix runtime PM based cpuidle support Ulf Hansson 2021-10-06 10:28 ` Maulik Shah 2021-10-20 18:18 ` Rafael J. Wysocki 2021-10-21 11:48 ` Ulf Hansson 2021-10-21 13:45 ` Rafael J. Wysocki 2021-10-21 14:04 ` Ulf Hansson 2021-10-21 15:09 ` Rafael J. Wysocki 2021-10-21 15:45 ` Rafael J. Wysocki 2021-10-21 16:28 ` Ulf Hansson 2021-10-21 16:41 ` Rafael J. Wysocki 2021-10-21 17:05 ` Rafael J. Wysocki 2021-10-21 18:49 ` Ulf Hansson 2021-10-21 18:36 ` Ulf Hansson 2021-10-21 16:16 ` Ulf Hansson 2021-10-21 16:33 ` Rafael J. Wysocki 2021-10-21 18:11 ` Ulf Hansson 2021-10-21 19:02 ` Rafael J. Wysocki 2021-10-21 19:56 ` Ulf Hansson 2021-10-22 9:15 ` Maulik Shah 2021-10-22 10:18 ` Ulf Hansson [this message] 2021-10-22 12:02 ` Rafael J. Wysocki 2021-10-22 12:56 ` Ulf Hansson 2021-10-22 13:08 ` Rafael J. Wysocki
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