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Date: Fri, 7 Jul 2017 17:01:28 +0100
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
linux@....linux.org.uk,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Russell King <rmk+kernel@...linux.org.uk>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Juri Lelli <juri.lelli@....com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Peter Zijlstra <peterz@...radead.org>,
Morten Rasmussen <morten.rasmussen@....com>,
"Rafael J . Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant
load-tracking support
On 06/07/17 11:40, Viresh Kumar wrote:
> On 06-07-17, 10:49, Dietmar Eggemann wrote:
[...]
>> In case arch_set_freq_scale() is not defined (and because of the
>> pr_debug() drivers/cpufreq/cpufreq.c is not compiled with -DDEBUG)
>
> The line within () needs to be improved to convey a clear message.
Probably not needed anymore. See below.
[...]
>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>> index 9bf97a366029..a04c5886a5ce 100644
>> --- a/drivers/cpufreq/cpufreq.c
>> +++ b/drivers/cpufreq/cpufreq.c
>> @@ -347,6 +347,28 @@ static void __cpufreq_notify_transition(struct cpufreq_policy *policy,
>> }
>> }
>>
>> +/*********************************************************************
>> + * FREQUENCY INVARIANT CPU CAPACITY SUPPORT *
>> + *********************************************************************/
>> +
>> +#ifndef arch_set_freq_scale
>> +static void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
>> + unsigned long max_freq)
>> +{}
>> +#endif
>> +
>> +static void cpufreq_set_freq_scale(struct cpufreq_policy *policy,
>> + struct cpufreq_freqs *freqs)
>> +{
>> + unsigned long cur_freq = freqs ? freqs->new : policy->cur;
>> + unsigned long max_freq = policy->cpuinfo.max_freq;
>> +
>> + pr_debug("cpus %*pbl cur/cur max freq %lu/%lu kHz\n",
>> + cpumask_pr_args(policy->related_cpus), cur_freq, max_freq);
>> +
>> + arch_set_freq_scale(policy->related_cpus, cur_freq, max_freq);
>
> I am not sure why all these are required to be sent here and will come back to
> it later on after going through other patches.
See below.
>> +}
>> +
>> /**
>> * cpufreq_notify_transition - call notifier chain and adjust_jiffies
>> * on frequency transition.
>> @@ -405,6 +427,8 @@ void cpufreq_freq_transition_begin(struct cpufreq_policy *policy,
>>
>> spin_unlock(&policy->transition_lock);
>>
>> + cpufreq_set_freq_scale(policy, freqs);
>> +
>
> Why do this before even changing the frequency ? We may fail while changing it.
>
> IMHO, you should call this routine whenever we update policy->cur and that
> happens regularly in __cpufreq_notify_transition() and few other places..
See below.
>> cpufreq_notify_transition(policy, freqs, CPUFREQ_PRECHANGE);
>> }
>> EXPORT_SYMBOL_GPL(cpufreq_freq_transition_begin);
>> @@ -2203,6 +2227,8 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
>> blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
>> CPUFREQ_NOTIFY, new_policy);
>>
>> + cpufreq_set_freq_scale(new_policy, NULL);
>
> Why added it here ? To get it initialized ? If yes, then we should do that in
> cpufreq_online() where we first initialize policy->cur.
I agree. This can go away. Initialization is not really needed here. We initialize
the scale values to SCHED_CAPACITY_SCALE at boot-time.
> Apart from this, you also need to update this in the schedutil governor (if you
> haven't done that in this series later) as that also updates policy->cur in the
> fast path.
So what about I call arch_set_freq_scale() in __cpufreq_notify_transition() in the
CPUFREQ_POSTCHANGE case for slow-switching and in cpufreq_driver_fast_switch() for
fast-switching?
Like this: (only slow-path slightly tested):
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 9bf97a366029..77c4d5e7a598 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -301,6 +301,12 @@ static void adjust_jiffies(unsigned long val, struct cpufreq_freqs *ci)
#endif
}
+#ifndef arch_set_freq_scale
+static void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
+ unsigned long max_freq)
+{}
+#endif
+
static void __cpufreq_notify_transition(struct cpufreq_policy *policy,
struct cpufreq_freqs *freqs, unsigned int state)
{
@@ -343,6 +349,8 @@ static void __cpufreq_notify_transition(struct cpufreq_policy *policy,
CPUFREQ_POSTCHANGE, freqs);
if (likely(policy) && likely(policy->cpu == freqs->cpu))
policy->cur = freqs->new;
+ arch_set_freq_scale(policy->related_cpus, policy->cur,
+ policy->cpuinfo.max_freq);
break;
}
}
@@ -1824,9 +1832,18 @@ EXPORT_SYMBOL(cpufreq_unregister_notifier);
unsigned int cpufreq_driver_fast_switch(struct cpufreq_policy *policy,
unsigned int target_freq)
{
+ unsigned int ret;
+
target_freq = clamp_val(target_freq, policy->min, policy->max);
- return cpufreq_driver->fast_switch(policy, target_freq);
+ ret = cpufreq_driver->fast_switch(policy, target_freq);
+
+ if (ret != CPUFREQ_ENTRY_INVALID) {
+ arch_set_freq_scale(policy->related_cpus, target_freq,
+ policy->cpuinfo.max_freq);
+ }
+
+ return ret;
}
EXPORT_SYMBOL_GPL(cpufreq_driver_fast_switch);
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