From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3E466C433EF for ; Thu, 21 Oct 2021 13:45:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 20B04610CB for ; Thu, 21 Oct 2021 13:45:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231207AbhJUNrl (ORCPT ); Thu, 21 Oct 2021 09:47:41 -0400 Received: from mail-oi1-f175.google.com ([209.85.167.175]:46914 "EHLO mail-oi1-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229878AbhJUNrh (ORCPT ); Thu, 21 Oct 2021 09:47:37 -0400 Received: by mail-oi1-f175.google.com with SMTP id o204so859950oih.13; Thu, 21 Oct 2021 06:45:21 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=iNaX23h9O9c/G7pG000WHJ6bQPKz9HGo1gSBNA+fGwU=; b=EDMUrcw+9C+9De1m4kE+bw2lFCcVElirqN0o/iiCpvVI6P3rHx+Io9scnDEGOok2g3 xfD+IQS8qsVypz4BRBxd638C6vwFQlHOb3cPvPs9Gz33kIt2DdlGHgN8C1JRtn2fETZa Bgk4aiaIPnEk61RuzptN0kiMG6/blPkuaSj46Vr7WkiNCjQ3Ne/jlbpohUH09pRLGTXl +WIkx2YRpFbfP7nf4dr15/IEdyB4l+IXxmt1G6+pamv7sQmKUt+955bCPH/9pc1BNuqh OcQuSR8FSK+FCz6UV0xtUIJWD5bqjv5NzeQZubuPOfpWnEtX/HSddmk3975dza4jw11e nDXA== X-Gm-Message-State: AOAM531AQFss24xO2MOjP3hXNdNSr7HsDJx4KYPFYo7ZOfTG3BNMF2/S /cNNLD5WGCCjLUu8GYQb1MJybY1rQqOCRKEWqCg= X-Google-Smtp-Source: ABdhPJyLF7e+JYzSioZz7r+D8rOUV+UL5jI7976DBV1QPmjULgnEQRgcXaFYRnZW9ADxBdhlG6Q+0Y7ElK1kivOTf+A= X-Received: by 2002:aca:5c5:: with SMTP id 188mr4421325oif.154.1634823920741; Thu, 21 Oct 2021 06:45:20 -0700 (PDT) MIME-Version: 1.0 References: <20210929144451.113334-1-ulf.hansson@linaro.org> <20210929144451.113334-3-ulf.hansson@linaro.org> In-Reply-To: From: "Rafael J. Wysocki" Date: Thu, 21 Oct 2021 15:45:09 +0200 Message-ID: Subject: Re: [PATCH 2/2] PM: sleep: Fix runtime PM based cpuidle support To: Ulf Hansson Cc: "Rafael J. Wysocki" , Daniel Lezcano , Linux PM , Maulik Shah , Peter Zijlstra , Vincent Guittot , Len Brown , Bjorn Andersson , Linux ARM , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 21, 2021 at 1:49 PM Ulf Hansson wrote: > > On Wed, 20 Oct 2021 at 20:18, Rafael J. Wysocki wrote: > > > > On Wed, Sep 29, 2021 at 4:44 PM Ulf Hansson wrote: > > > > > > In the cpuidle-psci case, runtime PM in combination with the generic PM > > > domain (genpd), may be used when entering/exiting an idlestate. More > > > precisely, genpd relies on runtime PM to be enabled for the attached device > > > (in this case it belongs to a CPU), to properly manage the reference > > > counting of its PM domain. > > > > > > This works fine most of the time, but during system suspend in the > > > dpm_suspend_late() phase, the PM core disables runtime PM for all devices. > > > Beyond this point and until runtime PM becomes re-enabled in the > > > dpm_resume_early() phase, calls to pm_runtime_get|put*() will fail. > > > > > > To make sure the reference counting in genpd becomes correct, we need to > > > prevent cpuidle-psci from using runtime PM when it has been disabled for > > > the device. Therefore, let's move the call to cpuidle_pause() from > > > dpm_suspend_noirq() to dpm_suspend_late() - and cpuidle_resume() from > > > dpm_resume_noirq() into dpm_resume_early(). > > > > > > Diagnosed-by: Maulik Shah > > > Suggested-by: Maulik Shah > > > Signed-off-by: Ulf Hansson > > > --- > > > 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 cbea78e79f3d..1c753b651272 100644 > > > --- a/drivers/base/power/main.c > > > +++ b/drivers/base/power/main.c > > > @@ -747,8 +747,6 @@ void dpm_resume_noirq(pm_message_t state) > > > > > > resume_device_irqs(); > > > device_wakeup_disarm_wake_irqs(); > > > - > > > - cpuidle_resume(); > > > } > > > > > > /** > > > @@ -870,6 +868,7 @@ void dpm_resume_early(pm_message_t state) > > > } > > > mutex_unlock(&dpm_list_mtx); > > > async_synchronize_full(); > > > + cpuidle_resume(); > > > dpm_show_time(starttime, state, 0, "early"); > > > trace_suspend_resume(TPS("dpm_resume_early"), state.event, false); > > > } > > > @@ -1336,8 +1335,6 @@ int dpm_suspend_noirq(pm_message_t state) > > > { > > > int ret; > > > > > > - cpuidle_pause(); > > > - > > > device_wakeup_arm_wake_irqs(); > > > suspend_device_irqs(); > > > > > > @@ -1467,6 +1464,7 @@ int dpm_suspend_late(pm_message_t state) > > > int error = 0; > > > > > > trace_suspend_resume(TPS("dpm_suspend_late"), state.event, true); > > > + cpuidle_pause(); > > > mutex_lock(&dpm_list_mtx); > > > pm_transition = state; > > > async_error = 0; > > > -- > > > > Well, this is somewhat heavy-handed and it affects even the systems > > that don't really need to pause cpuidle at all in the suspend path. > > Yes, I agree. > > Although, I am not really changing the behaviour in regards to this. > cpuidle_pause() is already being called in dpm_suspend_noirq(), for > everybody today. Yes, it is, but pausing it earlier will cause more energy to be spent, potentially. That said, there are not too many users of suspend_late callbacks in the tree, so it may not matter too much. > > > > Also, IIUC you don't need to pause cpuidle completely, but make it > > temporarily avoid idle states potentially affected by this issue. An > > additional CPUIDLE_STATE_DISABLED_ flag could be used for that I > > suppose and it could be set via cpuidle_suspend() called from the core > > next to cpufreq_suspend(). > > cpuidle_suspend() would then need to go and fetch the cpuidle driver > instance, which in some cases is one driver per CPU. Doesn't that get > rather messy? Per-CPU variables are used for that, so it is quite straightforward. > Additionally, since find_deepest_state() is being called for > cpuidle_enter_s2idle() too, we would need to treat the new > CPUIDLE_STATE_DISABLED_ flag in a special way, right? No, it already checks "disabled". > Is this really what we want? > > > > > The other guys who rely on the cpuidle pausing today could be switched > > over to this new mechanism later and it would be possible to get rid > > of the pausing from the system suspend path completely. > > Avoiding to pause cpuidle when it's not needed makes perfect sense. > Although, it looks to me that we could also implement that on top of > $subject patch. Yes, it could. > Unless you insist on the CPUIDLE_STATE_DISABLED_ way, I would probably > explore an option to let a cpuidle driver to set a global cpuidle flag > during ->probe(). Depending if this flag is set, we can simply skip > calling cpuidle_pause() during system suspend. > > What do you think? Well, which driver in particular is in question here?