[PATCH v2 03/10] drivers base/arch_topology: frequency-invariant load-tracking support

[Dietmar Eggemann <dietmar.eggemann@arm.com>]

Implements an arch-specific frequency-scaling function
topology_get_freq_scale() which provides the following frequency
scaling factor:

  current_freq(cpu) << SCHED_CAPACITY_SHIFT / max_supported_freq(cpu)

One possible consumer of this is the Per-Entity Load Tracking (PELT)
mechanism of the task scheduler.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
---
 drivers/base/arch_topology.c  | 20 ++++++++++++++++++++
 include/linux/arch_topology.h |  7 +++++++
 2 files changed, 27 insertions(+)

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index f4832c662762..63fb3f945d21 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -22,6 +22,26 @@
 #include <linux/string.h>
 #include <linux/sched/topology.h>
 
+static DEFINE_PER_CPU(unsigned long, freq_scale) = SCHED_CAPACITY_SCALE;
+
+unsigned long topology_get_freq_scale(struct sched_domain *sd, int cpu)
+{
+	return per_cpu(freq_scale, cpu);
+}
+
+void topology_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
+			     unsigned long max_freq)
+{
+	unsigned long scale;
+	int i;
+
+	scale = (cur_freq << SCHED_CAPACITY_SHIFT) / max_freq;
+
+	for_each_cpu(i, cpus)
+		per_cpu(freq_scale, i) = scale;
+}
+
+
 static DEFINE_MUTEX(cpu_scale_mutex);
 static DEFINE_PER_CPU(unsigned long, cpu_scale) = SCHED_CAPACITY_SCALE;
 
diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
index 9af3c174c03a..168104d2d2cf 100644
--- a/include/linux/arch_topology.h
+++ b/include/linux/arch_topology.h
@@ -4,6 +4,8 @@
 #ifndef _LINUX_ARCH_TOPOLOGY_H_
 #define _LINUX_ARCH_TOPOLOGY_H_
 
+#include <linux/cpumask.h>
+
 void topology_normalize_cpu_scale(void);
 
 struct device_node;
@@ -14,4 +16,9 @@ unsigned long topology_get_cpu_scale(struct sched_domain *sd, int cpu);
 
 void topology_set_cpu_scale(unsigned int cpu, unsigned long capacity);
 
+unsigned long topology_get_freq_scale(struct sched_domain *sd, int cpu);
+
+void topology_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
+			     unsigned long max_freq);
+
 #endif /* _LINUX_ARCH_TOPOLOGY_H_ */
-- 
2.11.0