ARM: 8622/3: 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

Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
index aa63287d9a1054e51fa9b9d7294a582758f24a10..ebf47d91b8041f2cacf83cf3eb5a3497a6f721c5 100644 (file)
--- a/arch/arm/kernel/topology.c
+++ b/arch/arm/kernel/topology.c
@@ -22,7 +22,9 @@
 #include <linux/of.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
+#include <linux/string.h>
 
+#include <asm/cpu.h>
 #include <asm/cputype.h>
 #include <asm/topology.h>
 
@@ -42,6 +44,7 @@
  * updated during this sequence.
  */
 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)
 {
@@ -53,6 +56,65 @@ 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
+
 #ifdef CONFIG_OF
 struct cpu_efficiency {
        const char *compatible;
@@ -132,6 +194,7 @@ 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) {
                capacity = (raw_capacity[cpu] << SCHED_CAPACITY_SHIFT)
                        / capacity_scale;
@@ -139,6 +202,7 @@ 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