From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bo Yan Subject: Re: [PATCH] cpufreq: skip cpufreq resume if it's not suspended Date: Wed, 24 Jan 2018 12:53:14 -0800 Message-ID: <913f1715-bdd0-1c03-ad76-38be9d3d2298@nvidia.com> References: <1516744675-21233-1-git-send-email-byan@nvidia.com> <1744712.rO4QOLozun@aspire.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8BIT Return-path: In-Reply-To: <1744712.rO4QOLozun@aspire.rjw.lan> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: "Rafael J. Wysocki" Cc: viresh.kumar@linaro.org, sgurrappadi@nvidia.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-pm@vger.kernel.org On 01/23/2018 06:02 PM, Rafael J. Wysocki wrote: > On Tuesday, January 23, 2018 10:57:55 PM CET Bo Yan wrote: >> drivers/cpufreq/cpufreq.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c >> index 41d148af7748..95b1c4afe14e 100644 >> --- a/drivers/cpufreq/cpufreq.c >> +++ b/drivers/cpufreq/cpufreq.c >> @@ -1680,6 +1680,10 @@ void cpufreq_resume(void) >> if (!cpufreq_driver) >> return; >> >> + if (unlikely(!cpufreq_suspended)) { >> + pr_warn("%s: resume after failing suspend\n", __func__); >> + return; >> + } >> cpufreq_suspended = false; >> >> if (!has_target() && !cpufreq_driver->resume) >> > Good catch, but rather than doing this it would be better to avoid > calling cpufreq_resume() at all if cpufreq_suspend() has not been called. Yes, I thought about that, but there is no good way to skip over it without introducing another flag. cpufreq_resume is called by dpm_resume, cpufreq_suspend is called by dpm_suspend. In the failure case, dpm_resume is called, but dpm_suspend is not. So on a higher level it's already unbalanced. One possibility is to rely on the pm_transition flag. So something like: diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c index dc259d20c967..8469e6fc2b2c 100644 --- a/drivers/base/power/main.c +++ b/drivers/base/power/main.c @@ -842,6 +842,7 @@ static void async_resume(void *data, async_cookie_t cookie)  void dpm_resume(pm_message_t state)  {         struct device *dev; +       bool suspended = (pm_transition.event != PM_EVENT_ON);         ktime_t starttime = ktime_get();         trace_suspend_resume(TPS("dpm_resume"), state.event, true); @@ -885,7 +886,8 @@ void dpm_resume(pm_message_t state)         async_synchronize_full();         dpm_show_time(starttime, state, NULL); -       cpufreq_resume(); +       if (likely(suspended)) +               cpufreq_resume();         trace_suspend_resume(TPS("dpm_resume"), state.event, false);  } This relies on the fact that the pm_transition will stay as PMSG_ON if dpm_prepare failed, in which case dpm_suspend will be skipped over, pm_transition will remain as 0 until dpm_resume. dpm_suspend changes pm_transition to whatever state it receives, which is never PMSG_ON. pm_transition is not changing to PMSG_ON before dpm_resume. This is my understanding. does this make sense? > > Thanks, > Rafael > >