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Commit be8f185d authored by Juri Lelli's avatar Juri Lelli Committed by Catalin Marinas
Browse files

arm64: add sysfs cpu_capacity attribute 



Add a sysfs cpu_capacity attribute with which it is possible to read and
write (thus over-writing default values) CPUs capacity. This might be
useful in situations where values needs changing after boot.

The new attribute shows up as:

 /sys/devices/system/cpu/cpu*/cpu_capacity

Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: default avatarJuri Lelli <juri.lelli@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 7202bde8

arch/arm64/kernel/topology.c

+64 −0
Original line number Diff line number Diff line
@@ -20,12 +20,15 @@ 
#include <linux/of.h>

#include <linux/sched.h>

#include <linux/slab.h>

#include <linux/string.h>

#include <linux/cpufreq.h>



#include <asm/cpu.h>

#include <asm/cputype.h>

#include <asm/topology.h>



static DEFINE_PER_CPU(unsigned long, cpu_scale) = SCHED_CAPACITY_SCALE;

static DEFINE_MUTEX(cpu_scale_mutex);



unsigned long arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)

{
@@ -37,6 +40,65 @@ static void set_capacity_scale(unsigned int cpu, unsigned long capacity) 
	per_cpu(cpu_scale, cpu) = capacity;

}



#ifdef CONFIG_PROC_SYSCTL

static ssize_t cpu_capacity_show(struct device *dev,

				 struct device_attribute *attr,

				 char *buf)

{

	struct cpu *cpu = container_of(dev, struct cpu, dev);



	return sprintf(buf, "%lu\n",

			arch_scale_cpu_capacity(NULL, cpu->dev.id));

}



static ssize_t cpu_capacity_store(struct device *dev,

				  struct device_attribute *attr,

				  const char *buf,

				  size_t count)

{

	struct cpu *cpu = container_of(dev, struct cpu, dev);

	int this_cpu = cpu->dev.id, i;

	unsigned long new_capacity;

	ssize_t ret;



	if (count) {

		ret = kstrtoul(buf, 0, &new_capacity);

		if (ret)

			return ret;

		if (new_capacity > SCHED_CAPACITY_SCALE)

			return -EINVAL;



		mutex_lock(&cpu_scale_mutex);

		for_each_cpu(i, &cpu_topology[this_cpu].core_sibling)

			set_capacity_scale(i, new_capacity);

		mutex_unlock(&cpu_scale_mutex);

	}



	return count;

}



static DEVICE_ATTR_RW(cpu_capacity);



static int register_cpu_capacity_sysctl(void)

{

	int i;

	struct device *cpu;



	for_each_possible_cpu(i) {

		cpu = get_cpu_device(i);

		if (!cpu) {

			pr_err("%s: too early to get CPU%d device!\n",

			       __func__, i);

			continue;

		}

		device_create_file(cpu, &dev_attr_cpu_capacity);

	}



	return 0;

}

subsys_initcall(register_cpu_capacity_sysctl);

#endif



static u32 capacity_scale;

static u32 *raw_capacity;

static bool cap_parsing_failed;
@@ -87,6 +149,7 @@ static void normalize_cpu_capacity(void) 
		return;



	pr_debug("cpu_capacity: capacity_scale=%u\n", capacity_scale);

	mutex_lock(&cpu_scale_mutex);

	for_each_possible_cpu(cpu) {

		pr_debug("cpu_capacity: cpu=%d raw_capacity=%u\n",

			 cpu, raw_capacity[cpu]);
@@ -96,6 +159,7 @@ static void normalize_cpu_capacity(void) 
		pr_debug("cpu_capacity: CPU%d cpu_capacity=%lu\n",

			cpu, arch_scale_cpu_capacity(NULL, cpu));

	}

	mutex_unlock(&cpu_scale_mutex);

}



#ifdef CONFIG_CPU_FREQ