linux-kernel - [PATCH 1/3] sched: Document arch_scale_*

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Message-Id: <20200731192016.7484-2-valentin.schneider@arm.com>
Date:   Fri, 31 Jul 2020 20:20:14 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Cc:     mingo@...nel.org, peterz@...radead.org, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, morten.rasmussen@....com,
        Quentin Perret <qperret@...gle.com>,
        Jonathan Corbet <corbet@....net>
Subject: [PATCH 1/3] sched: Document arch_scale_*_capacity()

Rather that hide their purpose in some dark, damp corner of Documentation/,
add some documentation to the default implementations.

Signed-off-by: Valentin Schneider <valentin.schneider@....com>
---
 include/linux/sched/topology.h | 10 ++++++++++
 kernel/sched/sched.h           | 10 ++++++++++
 2 files changed, 20 insertions(+)

diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
index 764222d637b7..820511289857 100644
--- a/include/linux/sched/topology.h
+++ b/include/linux/sched/topology.h
@@ -217,6 +217,16 @@ static inline bool cpus_share_cache(int this_cpu, int that_cpu)
 #endif	/* !CONFIG_SMP */
 
 #ifndef arch_scale_cpu_capacity
+/**
+ * arch_scale_cpu_capacity - get the capacity scale factor of a given CPU.
+ * @cpu: the CPU in question.
+ *
+ * Return: the CPU scale factor normalized against SCHED_CAPACITY_SCALE, i.e.
+ *
+ *             max_perf(cpu)
+ *      ----------------------------- * SCHED_CAPACITY_SCALE
+ *      max(max_perf(c) : c \in CPUs)
+ */
 static __always_inline
 unsigned long arch_scale_cpu_capacity(int cpu)
 {
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 296efd30d8c9..3fd283892761 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2049,6 +2049,16 @@ void arch_scale_freq_tick(void)
 #endif
 
 #ifndef arch_scale_freq_capacity
+/**
+ * arch_scale_freq_capacity - get the frequency scale factor of a given CPU.
+ * @cpu: the CPU in question.
+ *
+ * Return: the frequency scale factor normalized against SCHED_CAPACITY_SCALE, i.e.
+ *
+ *     f_curr
+ *     ------ * SCHED_CAPACITY_SCALE
+ *     f_max
+ */
 static __always_inline
 unsigned long arch_scale_freq_capacity(int cpu)
 {
-- 
2.27.0