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Subject[PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support
Date
A frequency-invariant load-tracking solution based on cpufreq transition
notifier will not work for future fast frequency switching policies.
That is why a different solution is presented with this patch.

Let cpufreq call the function arch_set_freq_scale() to pass the current
frequency, the max supported frequency and the cpumask of the related
cpus to a consumer (an arch) which defines arch_set_freq_scale().

The consumer has to associate arch_set_freq_scale with the name of its
own implementation foo_set_freq_scale() to overwrite the empty standard
definition in drivers/cpufreq/cpufreq.c.
An arch could do this in one of its arch-specific header files
(e.g. arch/$ARCH/include/asm/topology.h) which gets included in
drivers/cpufreq/cpufreq.c.

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
function cpufreq_set_freq_scale() gets compiled out.

Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
---
drivers/cpufreq/cpufreq.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)

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);
+}
+
/**
* 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);
+
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);
+
policy->min = new_policy->min;
policy->max = new_policy->max;

--
2.11.0
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