arch_topology: Relocate cpu_scale to topology.[h|c]

arch_topology.c provides functionality to parse and scale CPU capacity.
It also provides a corresponding sysfs interface. Some architectures
parse and scale CPU capacity differently as per their own needs. On
Intel processors, for instance, it is responsibility of the Intel
P-state driver.

Relocate the implementation of that interface to a common location in
topology.c. Architectures can use the interface and populate it using
their own mechanisms.

An alternative approach would be to compile arch_topology.c even if
not needed only to get this interface. This approach would create
duplicated and conflicting functionality and data structures.

Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Tested-by: Christian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/20250419025504.9760-2-ricardo.neri-calderon@linux.intel.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 52 insertions, 0 deletions

diff --git a/drivers/base/topology.c b/drivers/base/topology.c
index b962da263eee..8b42df05feff 100644
--- a/drivers/base/topology.c
+++ b/drivers/base/topology.c
@@ -208,3 +208,55 @@ static int __init topology_sysfs_init(void)
 }
 
 device_initcall(topology_sysfs_init);
+
+DEFINE_PER_CPU(unsigned long, cpu_scale) = SCHED_CAPACITY_SCALE;
+EXPORT_PER_CPU_SYMBOL_GPL(cpu_scale);
+
+void topology_set_cpu_scale(unsigned int cpu, unsigned long capacity)
+{
+	per_cpu(cpu_scale, cpu) = capacity;
+}
+
+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 sysfs_emit(buf, "%lu\n", topology_get_cpu_scale(cpu->dev.id));
+}
+
+static DEVICE_ATTR_RO(cpu_capacity);
+
+static int cpu_capacity_sysctl_add(unsigned int cpu)
+{
+	struct device *cpu_dev = get_cpu_device(cpu);
+
+	if (!cpu_dev)
+		return -ENOENT;
+
+	device_create_file(cpu_dev, &dev_attr_cpu_capacity);
+
+	return 0;
+}
+
+static int cpu_capacity_sysctl_remove(unsigned int cpu)
+{
+	struct device *cpu_dev = get_cpu_device(cpu);
+
+	if (!cpu_dev)
+		return -ENOENT;
+
+	device_remove_file(cpu_dev, &dev_attr_cpu_capacity);
+
+	return 0;
+}
+
+static int register_cpu_capacity_sysctl(void)
+{
+	cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "topology/cpu-capacity",
+			  cpu_capacity_sysctl_add, cpu_capacity_sysctl_remove);
+
+	return 0;
+}
+subsys_initcall(register_cpu_capacity_sysctl);