linux/kernel/power/energy_model.c
Lukasz Luba fb9d62b27a PM: EM: postpone creating the debugfs dir till fs_initcall
The debugfs directory '/sys/kernel/debug/energy_model' is needed before
the Energy Model registration can happen. With the recent change in
debugfs subsystem it's not allowed to create this directory at early
stage (core_initcall). Thus creating this directory would fail.

Postpone the creation of the EM debug dir to later stage: fs_initcall.

It should be safe since all clients: CPUFreq drivers, Devfreq drivers
will be initialized in later stages.

The custom debug log below prints the time of creation the EM debug dir
at fs_initcall and successful registration of EMs at later stages.

[    1.505717] energy_model: creating rootdir
[    3.698307] cpu cpu0: EM: created perf domain
[    3.709022] cpu cpu1: EM: created perf domain

Fixes: 56348560d4 ("debugfs: do not attempt to create a new file before the filesystem is initalized")
Reported-by: Ionela Voinescu <ionela.voinescu@arm.com>
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2021-03-23 19:53:48 +01:00

375 lines
9.1 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Energy Model of devices
*
* Copyright (c) 2018-2020, Arm ltd.
* Written by: Quentin Perret, Arm ltd.
* Improvements provided by: Lukasz Luba, Arm ltd.
*/
#define pr_fmt(fmt) "energy_model: " fmt
#include <linux/cpu.h>
#include <linux/cpumask.h>
#include <linux/debugfs.h>
#include <linux/energy_model.h>
#include <linux/sched/topology.h>
#include <linux/slab.h>
/*
* Mutex serializing the registrations of performance domains and letting
* callbacks defined by drivers sleep.
*/
static DEFINE_MUTEX(em_pd_mutex);
static bool _is_cpu_device(struct device *dev)
{
return (dev->bus == &cpu_subsys);
}
#ifdef CONFIG_DEBUG_FS
static struct dentry *rootdir;
static void em_debug_create_ps(struct em_perf_state *ps, struct dentry *pd)
{
struct dentry *d;
char name[24];
snprintf(name, sizeof(name), "ps:%lu", ps->frequency);
/* Create per-ps directory */
d = debugfs_create_dir(name, pd);
debugfs_create_ulong("frequency", 0444, d, &ps->frequency);
debugfs_create_ulong("power", 0444, d, &ps->power);
debugfs_create_ulong("cost", 0444, d, &ps->cost);
}
static int em_debug_cpus_show(struct seq_file *s, void *unused)
{
seq_printf(s, "%*pbl\n", cpumask_pr_args(to_cpumask(s->private)));
return 0;
}
DEFINE_SHOW_ATTRIBUTE(em_debug_cpus);
static int em_debug_units_show(struct seq_file *s, void *unused)
{
struct em_perf_domain *pd = s->private;
char *units = pd->milliwatts ? "milliWatts" : "bogoWatts";
seq_printf(s, "%s\n", units);
return 0;
}
DEFINE_SHOW_ATTRIBUTE(em_debug_units);
static void em_debug_create_pd(struct device *dev)
{
struct dentry *d;
int i;
/* Create the directory of the performance domain */
d = debugfs_create_dir(dev_name(dev), rootdir);
if (_is_cpu_device(dev))
debugfs_create_file("cpus", 0444, d, dev->em_pd->cpus,
&em_debug_cpus_fops);
debugfs_create_file("units", 0444, d, dev->em_pd, &em_debug_units_fops);
/* Create a sub-directory for each performance state */
for (i = 0; i < dev->em_pd->nr_perf_states; i++)
em_debug_create_ps(&dev->em_pd->table[i], d);
}
static void em_debug_remove_pd(struct device *dev)
{
struct dentry *debug_dir;
debug_dir = debugfs_lookup(dev_name(dev), rootdir);
debugfs_remove_recursive(debug_dir);
}
static int __init em_debug_init(void)
{
/* Create /sys/kernel/debug/energy_model directory */
rootdir = debugfs_create_dir("energy_model", NULL);
return 0;
}
fs_initcall(em_debug_init);
#else /* CONFIG_DEBUG_FS */
static void em_debug_create_pd(struct device *dev) {}
static void em_debug_remove_pd(struct device *dev) {}
#endif
static int em_create_perf_table(struct device *dev, struct em_perf_domain *pd,
int nr_states, struct em_data_callback *cb)
{
unsigned long opp_eff, prev_opp_eff = ULONG_MAX;
unsigned long power, freq, prev_freq = 0;
struct em_perf_state *table;
int i, ret;
u64 fmax;
table = kcalloc(nr_states, sizeof(*table), GFP_KERNEL);
if (!table)
return -ENOMEM;
/* Build the list of performance states for this performance domain */
for (i = 0, freq = 0; i < nr_states; i++, freq++) {
/*
* active_power() is a driver callback which ceils 'freq' to
* lowest performance state of 'dev' above 'freq' and updates
* 'power' and 'freq' accordingly.
*/
ret = cb->active_power(&power, &freq, dev);
if (ret) {
dev_err(dev, "EM: invalid perf. state: %d\n",
ret);
goto free_ps_table;
}
/*
* We expect the driver callback to increase the frequency for
* higher performance states.
*/
if (freq <= prev_freq) {
dev_err(dev, "EM: non-increasing freq: %lu\n",
freq);
goto free_ps_table;
}
/*
* The power returned by active_state() is expected to be
* positive and to fit into 16 bits.
*/
if (!power || power > EM_MAX_POWER) {
dev_err(dev, "EM: invalid power: %lu\n",
power);
goto free_ps_table;
}
table[i].power = power;
table[i].frequency = prev_freq = freq;
/*
* The hertz/watts efficiency ratio should decrease as the
* frequency grows on sane platforms. But this isn't always
* true in practice so warn the user if a higher OPP is more
* power efficient than a lower one.
*/
opp_eff = freq / power;
if (opp_eff >= prev_opp_eff)
dev_dbg(dev, "EM: hertz/watts ratio non-monotonically decreasing: em_perf_state %d >= em_perf_state%d\n",
i, i - 1);
prev_opp_eff = opp_eff;
}
/* Compute the cost of each performance state. */
fmax = (u64) table[nr_states - 1].frequency;
for (i = 0; i < nr_states; i++) {
table[i].cost = div64_u64(fmax * table[i].power,
table[i].frequency);
}
pd->table = table;
pd->nr_perf_states = nr_states;
return 0;
free_ps_table:
kfree(table);
return -EINVAL;
}
static int em_create_pd(struct device *dev, int nr_states,
struct em_data_callback *cb, cpumask_t *cpus)
{
struct em_perf_domain *pd;
struct device *cpu_dev;
int cpu, ret;
if (_is_cpu_device(dev)) {
pd = kzalloc(sizeof(*pd) + cpumask_size(), GFP_KERNEL);
if (!pd)
return -ENOMEM;
cpumask_copy(em_span_cpus(pd), cpus);
} else {
pd = kzalloc(sizeof(*pd), GFP_KERNEL);
if (!pd)
return -ENOMEM;
}
ret = em_create_perf_table(dev, pd, nr_states, cb);
if (ret) {
kfree(pd);
return ret;
}
if (_is_cpu_device(dev))
for_each_cpu(cpu, cpus) {
cpu_dev = get_cpu_device(cpu);
cpu_dev->em_pd = pd;
}
dev->em_pd = pd;
return 0;
}
/**
* em_pd_get() - Return the performance domain for a device
* @dev : Device to find the performance domain for
*
* Returns the performance domain to which @dev belongs, or NULL if it doesn't
* exist.
*/
struct em_perf_domain *em_pd_get(struct device *dev)
{
if (IS_ERR_OR_NULL(dev))
return NULL;
return dev->em_pd;
}
EXPORT_SYMBOL_GPL(em_pd_get);
/**
* em_cpu_get() - Return the performance domain for a CPU
* @cpu : CPU to find the performance domain for
*
* Returns the performance domain to which @cpu belongs, or NULL if it doesn't
* exist.
*/
struct em_perf_domain *em_cpu_get(int cpu)
{
struct device *cpu_dev;
cpu_dev = get_cpu_device(cpu);
if (!cpu_dev)
return NULL;
return em_pd_get(cpu_dev);
}
EXPORT_SYMBOL_GPL(em_cpu_get);
/**
* em_dev_register_perf_domain() - Register the Energy Model (EM) for a device
* @dev : Device for which the EM is to register
* @nr_states : Number of performance states to register
* @cb : Callback functions providing the data of the Energy Model
* @cpus : Pointer to cpumask_t, which in case of a CPU device is
* obligatory. It can be taken from i.e. 'policy->cpus'. For other
* type of devices this should be set to NULL.
* @milliwatts : Flag indicating that the power values are in milliWatts or
* in some other scale. It must be set properly.
*
* Create Energy Model tables for a performance domain using the callbacks
* defined in cb.
*
* The @milliwatts is important to set with correct value. Some kernel
* sub-systems might rely on this flag and check if all devices in the EM are
* using the same scale.
*
* If multiple clients register the same performance domain, all but the first
* registration will be ignored.
*
* Return 0 on success
*/
int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
struct em_data_callback *cb, cpumask_t *cpus,
bool milliwatts)
{
unsigned long cap, prev_cap = 0;
int cpu, ret;
if (!dev || !nr_states || !cb)
return -EINVAL;
/*
* Use a mutex to serialize the registration of performance domains and
* let the driver-defined callback functions sleep.
*/
mutex_lock(&em_pd_mutex);
if (dev->em_pd) {
ret = -EEXIST;
goto unlock;
}
if (_is_cpu_device(dev)) {
if (!cpus) {
dev_err(dev, "EM: invalid CPU mask\n");
ret = -EINVAL;
goto unlock;
}
for_each_cpu(cpu, cpus) {
if (em_cpu_get(cpu)) {
dev_err(dev, "EM: exists for CPU%d\n", cpu);
ret = -EEXIST;
goto unlock;
}
/*
* All CPUs of a domain must have the same
* micro-architecture since they all share the same
* table.
*/
cap = arch_scale_cpu_capacity(cpu);
if (prev_cap && prev_cap != cap) {
dev_err(dev, "EM: CPUs of %*pbl must have the same capacity\n",
cpumask_pr_args(cpus));
ret = -EINVAL;
goto unlock;
}
prev_cap = cap;
}
}
ret = em_create_pd(dev, nr_states, cb, cpus);
if (ret)
goto unlock;
dev->em_pd->milliwatts = milliwatts;
em_debug_create_pd(dev);
dev_info(dev, "EM: created perf domain\n");
unlock:
mutex_unlock(&em_pd_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(em_dev_register_perf_domain);
/**
* em_dev_unregister_perf_domain() - Unregister Energy Model (EM) for a device
* @dev : Device for which the EM is registered
*
* Unregister the EM for the specified @dev (but not a CPU device).
*/
void em_dev_unregister_perf_domain(struct device *dev)
{
if (IS_ERR_OR_NULL(dev) || !dev->em_pd)
return;
if (_is_cpu_device(dev))
return;
/*
* The mutex separates all register/unregister requests and protects
* from potential clean-up/setup issues in the debugfs directories.
* The debugfs directory name is the same as device's name.
*/
mutex_lock(&em_pd_mutex);
em_debug_remove_pd(dev);
kfree(dev->em_pd->table);
kfree(dev->em_pd);
dev->em_pd = NULL;
mutex_unlock(&em_pd_mutex);
}
EXPORT_SYMBOL_GPL(em_dev_unregister_perf_domain);