259 lines
6.6 KiB
C
259 lines
6.6 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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* Energy Model of CPUs
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*
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* Copyright (c) 2018, Arm ltd.
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* Written by: Quentin Perret, Arm ltd.
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*/
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#define pr_fmt(fmt) "energy_model: " fmt
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#include <linux/cpu.h>
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#include <linux/cpumask.h>
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#include <linux/debugfs.h>
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#include <linux/energy_model.h>
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#include <linux/sched/topology.h>
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#include <linux/slab.h>
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/* Mapping of each CPU to the performance domain to which it belongs. */
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static DEFINE_PER_CPU(struct em_perf_domain *, em_data);
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/*
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* Mutex serializing the registrations of performance domains and letting
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* callbacks defined by drivers sleep.
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*/
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static DEFINE_MUTEX(em_pd_mutex);
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#ifdef CONFIG_DEBUG_FS
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static struct dentry *rootdir;
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static void em_debug_create_cs(struct em_cap_state *cs, struct dentry *pd)
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{
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struct dentry *d;
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char name[24];
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snprintf(name, sizeof(name), "cs:%lu", cs->frequency);
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/* Create per-cs directory */
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d = debugfs_create_dir(name, pd);
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debugfs_create_ulong("frequency", 0444, d, &cs->frequency);
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debugfs_create_ulong("power", 0444, d, &cs->power);
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debugfs_create_ulong("cost", 0444, d, &cs->cost);
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}
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static int em_debug_cpus_show(struct seq_file *s, void *unused)
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{
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seq_printf(s, "%*pbl\n", cpumask_pr_args(to_cpumask(s->private)));
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return 0;
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}
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DEFINE_SHOW_ATTRIBUTE(em_debug_cpus);
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static void em_debug_create_pd(struct em_perf_domain *pd, int cpu)
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{
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struct dentry *d;
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char name[8];
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int i;
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snprintf(name, sizeof(name), "pd%d", cpu);
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/* Create the directory of the performance domain */
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d = debugfs_create_dir(name, rootdir);
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debugfs_create_file("cpus", 0444, d, pd->cpus, &em_debug_cpus_fops);
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/* Create a sub-directory for each capacity state */
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for (i = 0; i < pd->nr_cap_states; i++)
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em_debug_create_cs(&pd->table[i], d);
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}
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static int __init em_debug_init(void)
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{
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/* Create /sys/kernel/debug/energy_model directory */
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rootdir = debugfs_create_dir("energy_model", NULL);
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return 0;
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}
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core_initcall(em_debug_init);
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#else /* CONFIG_DEBUG_FS */
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static void em_debug_create_pd(struct em_perf_domain *pd, int cpu) {}
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#endif
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static struct em_perf_domain *em_create_pd(cpumask_t *span, int nr_states,
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struct em_data_callback *cb)
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{
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unsigned long opp_eff, prev_opp_eff = ULONG_MAX;
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unsigned long power, freq, prev_freq = 0;
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int i, ret, cpu = cpumask_first(span);
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struct em_cap_state *table;
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struct em_perf_domain *pd;
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u64 fmax;
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if (!cb->active_power)
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return NULL;
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pd = kzalloc(sizeof(*pd) + cpumask_size(), GFP_KERNEL);
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if (!pd)
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return NULL;
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table = kcalloc(nr_states, sizeof(*table), GFP_KERNEL);
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if (!table)
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goto free_pd;
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/* Build the list of capacity states for this performance domain */
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for (i = 0, freq = 0; i < nr_states; i++, freq++) {
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/*
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* active_power() is a driver callback which ceils 'freq' to
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* lowest capacity state of 'cpu' above 'freq' and updates
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* 'power' and 'freq' accordingly.
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*/
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ret = cb->active_power(&power, &freq, cpu);
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if (ret) {
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pr_err("pd%d: invalid cap. state: %d\n", cpu, ret);
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goto free_cs_table;
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}
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/*
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* We expect the driver callback to increase the frequency for
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* higher capacity states.
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*/
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if (freq <= prev_freq) {
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pr_err("pd%d: non-increasing freq: %lu\n", cpu, freq);
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goto free_cs_table;
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}
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/*
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* The power returned by active_state() is expected to be
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* positive, in milli-watts and to fit into 16 bits.
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*/
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if (!power || power > EM_CPU_MAX_POWER) {
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pr_err("pd%d: invalid power: %lu\n", cpu, power);
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goto free_cs_table;
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}
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table[i].power = power;
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table[i].frequency = prev_freq = freq;
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/*
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* The hertz/watts efficiency ratio should decrease as the
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* frequency grows on sane platforms. But this isn't always
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* true in practice so warn the user if a higher OPP is more
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* power efficient than a lower one.
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*/
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opp_eff = freq / power;
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if (opp_eff >= prev_opp_eff)
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pr_warn("pd%d: hertz/watts ratio non-monotonically decreasing: em_cap_state %d >= em_cap_state%d\n",
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cpu, i, i - 1);
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prev_opp_eff = opp_eff;
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}
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/* Compute the cost of each capacity_state. */
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fmax = (u64) table[nr_states - 1].frequency;
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for (i = 0; i < nr_states; i++) {
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table[i].cost = div64_u64(fmax * table[i].power,
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table[i].frequency);
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}
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pd->table = table;
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pd->nr_cap_states = nr_states;
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cpumask_copy(to_cpumask(pd->cpus), span);
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em_debug_create_pd(pd, cpu);
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return pd;
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free_cs_table:
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kfree(table);
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free_pd:
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kfree(pd);
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return NULL;
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}
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/**
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* em_cpu_get() - Return the performance domain for a CPU
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* @cpu : CPU to find the performance domain for
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*
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* Return: the performance domain to which 'cpu' belongs, or NULL if it doesn't
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* exist.
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*/
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struct em_perf_domain *em_cpu_get(int cpu)
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{
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return READ_ONCE(per_cpu(em_data, cpu));
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}
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EXPORT_SYMBOL_GPL(em_cpu_get);
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/**
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* em_register_perf_domain() - Register the Energy Model of a performance domain
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* @span : Mask of CPUs in the performance domain
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* @nr_states : Number of capacity states to register
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* @cb : Callback functions providing the data of the Energy Model
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*
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* Create Energy Model tables for a performance domain using the callbacks
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* defined in cb.
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*
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* If multiple clients register the same performance domain, all but the first
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* registration will be ignored.
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*
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* Return 0 on success
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*/
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int em_register_perf_domain(cpumask_t *span, unsigned int nr_states,
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struct em_data_callback *cb)
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{
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unsigned long cap, prev_cap = 0;
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struct em_perf_domain *pd;
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int cpu, ret = 0;
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if (!span || !nr_states || !cb)
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return -EINVAL;
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/*
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* Use a mutex to serialize the registration of performance domains and
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* let the driver-defined callback functions sleep.
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*/
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mutex_lock(&em_pd_mutex);
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for_each_cpu(cpu, span) {
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/* Make sure we don't register again an existing domain. */
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if (READ_ONCE(per_cpu(em_data, cpu))) {
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ret = -EEXIST;
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goto unlock;
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}
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/*
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* All CPUs of a domain must have the same micro-architecture
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* since they all share the same table.
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*/
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cap = arch_scale_cpu_capacity(cpu);
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if (prev_cap && prev_cap != cap) {
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pr_err("CPUs of %*pbl must have the same capacity\n",
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cpumask_pr_args(span));
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ret = -EINVAL;
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goto unlock;
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}
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prev_cap = cap;
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}
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/* Create the performance domain and add it to the Energy Model. */
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pd = em_create_pd(span, nr_states, cb);
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if (!pd) {
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ret = -EINVAL;
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goto unlock;
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}
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for_each_cpu(cpu, span) {
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/*
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* The per-cpu array can be read concurrently from em_cpu_get().
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* The barrier enforces the ordering needed to make sure readers
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* can only access well formed em_perf_domain structs.
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*/
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smp_store_release(per_cpu_ptr(&em_data, cpu), pd);
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}
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pr_debug("Created perf domain %*pbl\n", cpumask_pr_args(span));
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unlock:
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mutex_unlock(&em_pd_mutex);
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return ret;
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}
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EXPORT_SYMBOL_GPL(em_register_perf_domain);
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