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SubjectRe: [PATCH] cpufreq: skip cpufreq resume if it's not suspended
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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
>
>

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