cpufreq/schedutil: use a fixed reference frequency

cpuinfo_max_freq can change at runtime because of boost as example. This
implies that the value could not the same that has been used when
computing the capacity of a CPU.

a new arch_scale_freq_ref() is available to return the fixed and coherent
frequency reference that can be used when computing a frequency based on an
utilization. Use it when available.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>

1 files changed, 27 insertions, 2 deletions

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 4492608b7d7f..9996ef429e2b 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -114,6 +114,31 @@ static void sugov_deferred_update(struct sugov_policy *sg_policy)
 	}
 }
 
+#ifdef arch_scale_freq_ref
+/**
+ * arch_scale_freq_ref_policy - get the reference frequency of a given CPU that
+ * has been used to correlate frequency and compute capacity.
+ * @cpu: the CPU in question.
+ *
+ * Return: the reference CPU frequency.
+ */
+static __always_inline
+unsigned long  arch_scale_freq_ref_policy(struct cpufreq_policy *policy)
+{
+	return arch_scale_freq_ref(policy->cpu);
+}
+#else
+static __always_inline
+unsigned long  arch_scale_freq_ref_policy(struct cpufreq_policy *policy)
+{
+	if (arch_scale_freq_invariant())
+		return policy->cpuinfo.max_freq;
+
+
+	return policy->cur;
+}
+#endif
+
 /**
  * get_next_freq - Compute a new frequency for a given cpufreq policy.
  * @sg_policy: schedutil policy object to compute the new frequency for.
@@ -139,11 +164,11 @@ static void sugov_deferred_update(struct sugov_policy *sg_policy)
 static unsigned int get_next_freq(struct sugov_policy *sg_policy,
 				  unsigned long util, unsigned long max)
 {
+	unsigned int freq;
 	struct cpufreq_policy *policy = sg_policy->policy;
-	unsigned int freq = arch_scale_freq_invariant() ?
-				policy->cpuinfo.max_freq : policy->cur;
 
 	util = map_util_perf(util);
+	freq = arch_scale_freq_ref_policy(policy);
 	freq = map_util_freq(util, freq, max);
 
 	if (freq == sg_policy->cached_raw_freq && !sg_policy->need_freq_update)