![Lingutla Chandrasekhar](/assets/img/avatar_default.png)
If user updates any cpu's cpu_capacity, then the new value is going to be applied to all its online sibling cpus. But this need not to be correct always, as sibling cpus (in ARM, same micro architecture cpus) would have different cpu_capacity with different performance characteristics. So, updating the user supplied cpu_capacity to all cpu siblings is not correct. And another problem is, current code assumes that 'all cpus in a cluster or with same package_id (core_siblings), would have same cpu_capacity'. But with commit '5bdd2b3f0f8 ("arm64: topology: add support to remove cpu topology sibling masks")', when a cpu hotplugged out, the cpu information gets cleared in its sibling cpus. So, user supplied cpu_capacity would be applied to only online sibling cpus at the time. After that, if any cpu hotplugged in, it would have different cpu_capacity than its siblings, which breaks the above assumption. So, instead of mucking around the core sibling mask for user supplied value, use device-tree to set cpu capacity. And make the cpu_capacity node as read-only to know the asymmetry between cpus in the system. While at it, remove cpu_scale_mutex usage, which used for sysfs write protection. Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Tested-by: Quentin Perret <quentin.perret@arm.com> Reviewed-by: Quentin Perret <quentin.perret@arm.com> Acked-by: Sudeep Holla <sudeep.holla@arm.com> Signed-off-by: Lingutla Chandrasekhar <clingutla@codeaurora.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
247 lines
5.7 KiB
C
247 lines
5.7 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Arch specific cpu topology information
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*
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* Copyright (C) 2016, ARM Ltd.
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* Written by: Juri Lelli, ARM Ltd.
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*/
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#include <linux/acpi.h>
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#include <linux/cpu.h>
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#include <linux/cpufreq.h>
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#include <linux/device.h>
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#include <linux/of.h>
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#include <linux/slab.h>
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#include <linux/string.h>
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#include <linux/sched/topology.h>
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#include <linux/cpuset.h>
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DEFINE_PER_CPU(unsigned long, freq_scale) = SCHED_CAPACITY_SCALE;
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void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
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unsigned long max_freq)
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{
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unsigned long scale;
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int i;
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scale = (cur_freq << SCHED_CAPACITY_SHIFT) / max_freq;
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for_each_cpu(i, cpus)
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per_cpu(freq_scale, i) = scale;
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}
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DEFINE_PER_CPU(unsigned long, cpu_scale) = SCHED_CAPACITY_SCALE;
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void topology_set_cpu_scale(unsigned int cpu, unsigned long capacity)
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{
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per_cpu(cpu_scale, cpu) = capacity;
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}
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static ssize_t cpu_capacity_show(struct device *dev,
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struct device_attribute *attr,
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char *buf)
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{
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struct cpu *cpu = container_of(dev, struct cpu, dev);
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return sprintf(buf, "%lu\n", topology_get_cpu_scale(NULL, cpu->dev.id));
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}
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static void update_topology_flags_workfn(struct work_struct *work);
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static DECLARE_WORK(update_topology_flags_work, update_topology_flags_workfn);
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static DEVICE_ATTR_RO(cpu_capacity);
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static int register_cpu_capacity_sysctl(void)
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{
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int i;
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struct device *cpu;
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for_each_possible_cpu(i) {
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cpu = get_cpu_device(i);
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if (!cpu) {
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pr_err("%s: too early to get CPU%d device!\n",
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__func__, i);
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continue;
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}
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device_create_file(cpu, &dev_attr_cpu_capacity);
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}
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return 0;
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}
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subsys_initcall(register_cpu_capacity_sysctl);
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static int update_topology;
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int topology_update_cpu_topology(void)
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{
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return update_topology;
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}
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/*
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* Updating the sched_domains can't be done directly from cpufreq callbacks
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* due to locking, so queue the work for later.
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*/
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static void update_topology_flags_workfn(struct work_struct *work)
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{
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update_topology = 1;
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rebuild_sched_domains();
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pr_debug("sched_domain hierarchy rebuilt, flags updated\n");
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update_topology = 0;
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}
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static u32 capacity_scale;
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static u32 *raw_capacity;
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static int free_raw_capacity(void)
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{
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kfree(raw_capacity);
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raw_capacity = NULL;
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return 0;
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}
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void topology_normalize_cpu_scale(void)
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{
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u64 capacity;
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int cpu;
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if (!raw_capacity)
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return;
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pr_debug("cpu_capacity: capacity_scale=%u\n", capacity_scale);
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for_each_possible_cpu(cpu) {
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pr_debug("cpu_capacity: cpu=%d raw_capacity=%u\n",
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cpu, raw_capacity[cpu]);
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capacity = (raw_capacity[cpu] << SCHED_CAPACITY_SHIFT)
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/ capacity_scale;
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topology_set_cpu_scale(cpu, capacity);
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pr_debug("cpu_capacity: CPU%d cpu_capacity=%lu\n",
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cpu, topology_get_cpu_scale(NULL, cpu));
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}
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}
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bool __init topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu)
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{
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static bool cap_parsing_failed;
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int ret;
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u32 cpu_capacity;
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if (cap_parsing_failed)
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return false;
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ret = of_property_read_u32(cpu_node, "capacity-dmips-mhz",
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&cpu_capacity);
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if (!ret) {
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if (!raw_capacity) {
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raw_capacity = kcalloc(num_possible_cpus(),
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sizeof(*raw_capacity),
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GFP_KERNEL);
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if (!raw_capacity) {
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pr_err("cpu_capacity: failed to allocate memory for raw capacities\n");
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cap_parsing_failed = true;
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return false;
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}
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}
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capacity_scale = max(cpu_capacity, capacity_scale);
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raw_capacity[cpu] = cpu_capacity;
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pr_debug("cpu_capacity: %pOF cpu_capacity=%u (raw)\n",
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cpu_node, raw_capacity[cpu]);
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} else {
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if (raw_capacity) {
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pr_err("cpu_capacity: missing %pOF raw capacity\n",
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cpu_node);
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pr_err("cpu_capacity: partial information: fallback to 1024 for all CPUs\n");
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}
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cap_parsing_failed = true;
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free_raw_capacity();
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}
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return !ret;
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}
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#ifdef CONFIG_CPU_FREQ
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static cpumask_var_t cpus_to_visit;
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static void parsing_done_workfn(struct work_struct *work);
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static DECLARE_WORK(parsing_done_work, parsing_done_workfn);
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static int
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init_cpu_capacity_callback(struct notifier_block *nb,
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unsigned long val,
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void *data)
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{
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struct cpufreq_policy *policy = data;
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int cpu;
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if (!raw_capacity)
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return 0;
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if (val != CPUFREQ_NOTIFY)
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return 0;
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pr_debug("cpu_capacity: init cpu capacity for CPUs [%*pbl] (to_visit=%*pbl)\n",
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cpumask_pr_args(policy->related_cpus),
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cpumask_pr_args(cpus_to_visit));
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cpumask_andnot(cpus_to_visit, cpus_to_visit, policy->related_cpus);
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for_each_cpu(cpu, policy->related_cpus) {
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raw_capacity[cpu] = topology_get_cpu_scale(NULL, cpu) *
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policy->cpuinfo.max_freq / 1000UL;
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capacity_scale = max(raw_capacity[cpu], capacity_scale);
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}
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if (cpumask_empty(cpus_to_visit)) {
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topology_normalize_cpu_scale();
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schedule_work(&update_topology_flags_work);
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free_raw_capacity();
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pr_debug("cpu_capacity: parsing done\n");
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schedule_work(&parsing_done_work);
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}
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return 0;
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}
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static struct notifier_block init_cpu_capacity_notifier = {
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.notifier_call = init_cpu_capacity_callback,
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};
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static int __init register_cpufreq_notifier(void)
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{
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int ret;
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/*
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* on ACPI-based systems we need to use the default cpu capacity
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* until we have the necessary code to parse the cpu capacity, so
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* skip registering cpufreq notifier.
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*/
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if (!acpi_disabled || !raw_capacity)
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return -EINVAL;
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if (!alloc_cpumask_var(&cpus_to_visit, GFP_KERNEL)) {
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pr_err("cpu_capacity: failed to allocate memory for cpus_to_visit\n");
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return -ENOMEM;
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}
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cpumask_copy(cpus_to_visit, cpu_possible_mask);
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ret = cpufreq_register_notifier(&init_cpu_capacity_notifier,
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CPUFREQ_POLICY_NOTIFIER);
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if (ret)
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free_cpumask_var(cpus_to_visit);
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return ret;
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}
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core_initcall(register_cpufreq_notifier);
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static void parsing_done_workfn(struct work_struct *work)
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{
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cpufreq_unregister_notifier(&init_cpu_capacity_notifier,
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CPUFREQ_POLICY_NOTIFIER);
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free_cpumask_var(cpus_to_visit);
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}
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#else
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core_initcall(free_raw_capacity);
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#endif
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