Revert "arch_topology: Make cpu_capacity sysfs node as read-only"

This reverts commit 5d777b18.

[ionela.voinescu@arm.com: modify capacity of current CPU only]

drivers/base/arch_topology.c

@@ -7,6 +7,7 @@
  */
 
 #include <linux/acpi.h>
+#include <linux/arch_topology.h>
 #include <linux/cpu.h>
 #include <linux/cpufreq.h>
 #include <linux/device.h>
@@ -148,6 +149,7 @@ void topology_set_freq_scale(const struct cpumask *cpus, unsigned long cur_freq,
 		per_cpu(arch_freq_scale, i) = scale;
 }
 
+static DEFINE_MUTEX(cpu_scale_mutex);
 DEFINE_PER_CPU(unsigned long, cpu_scale) = SCHED_CAPACITY_SCALE;
 
 void topology_set_cpu_scale(unsigned int cpu, unsigned long capacity)
@@ -178,7 +180,35 @@ static ssize_t cpu_capacity_show(struct device *dev,
 static void update_topology_flags_workfn(struct work_struct *work);
 static DECLARE_WORK(update_topology_flags_work, update_topology_flags_workfn);
 
-static DEVICE_ATTR_RO(cpu_capacity);
+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;
+	unsigned long new_capacity;
+	ssize_t ret;
+
+	if (!count)
+		return 0;
+
+	ret = kstrtoul(buf, 0, &new_capacity);
+	if (ret)
+		return ret;
+	if (new_capacity > SCHED_CAPACITY_SCALE)
+		return -EINVAL;
+
+	mutex_lock(&cpu_scale_mutex);
+	topology_set_cpu_scale(this_cpu, new_capacity);
+	mutex_unlock(&cpu_scale_mutex);
+
+	schedule_work(&update_topology_flags_work);
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(cpu_capacity);
 
 static int register_cpu_capacity_sysctl(void)
 {
@@ -245,6 +275,7 @@ void topology_normalize_cpu_scale(void)
 	}
 
 	pr_debug("cpu_capacity: capacity_scale=%llu\n", capacity_scale);
+	mutex_lock(&cpu_scale_mutex);
 	for_each_possible_cpu(cpu) {
 		capacity = raw_capacity[cpu] * per_cpu(freq_factor, cpu);
 		capacity = div64_u64(capacity << SCHED_CAPACITY_SHIFT,
@@ -253,6 +284,7 @@ void topology_normalize_cpu_scale(void)
 		pr_debug("cpu_capacity: CPU%d cpu_capacity=%lu\n",
 			cpu, topology_get_cpu_scale(cpu));
 	}
+	mutex_unlock(&cpu_scale_mutex);
 }
 
 bool __init topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu)