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ARM: 8622/3: add sysfs cpu_capacity attribute

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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

Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Juri Lelli 2016-11-06 01:34:31 +01:00 • committed by Russell King
parent 06073ee267
commit 7e5930aaef
1 changed files with 64 additions and 0 deletions
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64
arch/arm/kernel/topology.c
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@ -22,7 +22,9 @@
#include <linux/of.h> #include <linux/of.h>
#include <linux/sched.h> #include <linux/sched.h>
#include <linux/slab.h> #include <linux/slab.h>
#include <linux/string.h>
#include <asm/cpu.h>
#include <asm/cputype.h> #include <asm/cputype.h>
#include <asm/topology.h> #include <asm/topology.h>
@ -42,6 +44,7 @@
* updated during this sequence. * updated during this sequence.
*/ */
static DEFINE_PER_CPU(unsigned long, cpu_scale) = SCHED_CAPACITY_SCALE; 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) unsigned long arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
{ {
@ -53,6 +56,65 @@ static void set_capacity_scale(unsigned int cpu, unsigned long capacity)
per_cpu(cpu_scale, cpu) = 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
#ifdef CONFIG_OF #ifdef CONFIG_OF
struct cpu_efficiency { struct cpu_efficiency {
const char *compatible; const char *compatible;
@ -132,6 +194,7 @@ static void normalize_cpu_capacity(void)
return; return;
pr_debug("cpu_capacity: capacity_scale=%u\n", capacity_scale); pr_debug("cpu_capacity: capacity_scale=%u\n", capacity_scale);
mutex_lock(&cpu_scale_mutex);
for_each_possible_cpu(cpu) { for_each_possible_cpu(cpu) {
capacity = (raw_capacity[cpu] << SCHED_CAPACITY_SHIFT) capacity = (raw_capacity[cpu] << SCHED_CAPACITY_SHIFT)
/ capacity_scale; / capacity_scale;
@ -139,6 +202,7 @@ static void normalize_cpu_capacity(void)
pr_debug("cpu_capacity: CPU%d cpu_capacity=%lu\n", pr_debug("cpu_capacity: CPU%d cpu_capacity=%lu\n",
cpu, arch_scale_cpu_capacity(NULL, cpu)); cpu, arch_scale_cpu_capacity(NULL, cpu));
} }
mutex_unlock(&cpu_scale_mutex);
} }
#ifdef CONFIG_CPU_FREQ #ifdef CONFIG_CPU_FREQ