text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * Copyright 2020 Linaro Limited
   *
   * Author: Daniel Lezcano <daniel.lezcano@linaro.org>
   *
   * The DTPM CPU is based on the energy model. It hooks the CPU in the
   * DTPM tree which in turns update the power number by propagating the
   * power number from the CPU energy model information to the parents.
   *
   * The association between the power and the performance state, allows
   * to set the power of the CPU at the OPP granularity.
   *
   * The CPU hotplug is supported and the power numbers will be updated
   * if a CPU is hot plugged / unplugged.
   */
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/cpumask.h>
  #include <linux/cpufreq.h>
  #include <linux/cpuhotplug.h>
  #include <linux/dtpm.h>
  #include <linux/energy_model.h>
  #include <linux/pm_qos.h>
  #include <linux/slab.h>
  #include <linux/units.h>
  
  struct dtpm_cpu {
  	struct dtpm dtpm;
  	struct freq_qos_request qos_req;
  	int cpu;
  };
  
  static DEFINE_PER_CPU(struct dtpm_cpu *, dtpm_per_cpu);
  
  static struct dtpm_cpu *to_dtpm_cpu(struct dtpm *dtpm)
  {
  	return container_of(dtpm, struct dtpm_cpu, dtpm);
  }
  
  static u64 set_pd_power_limit(struct dtpm *dtpm, u64 power_limit)
  {
  	struct dtpm_cpu *dtpm_cpu = to_dtpm_cpu(dtpm);
  	struct em_perf_domain *pd = em_cpu_get(dtpm_cpu->cpu);
  	struct cpumask cpus;
  	unsigned long freq;
  	u64 power;
  	int i, nr_cpus;
  
  	cpumask_and(&cpus, cpu_online_mask, to_cpumask(pd->cpus));
  	nr_cpus = cpumask_weight(&cpus);
  
  	for (i = 0; i < pd->nr_perf_states; i++) {
  
  		power = pd->table[i].power * MICROWATT_PER_MILLIWATT * nr_cpus;
  
  		if (power > power_limit)
  			break;
  	}
  
  	freq = pd->table[i - 1].frequency;
  
  	freq_qos_update_request(&dtpm_cpu->qos_req, freq);
  
  	power_limit = pd->table[i - 1].power *
  		MICROWATT_PER_MILLIWATT * nr_cpus;
  
  	return power_limit;
  }
  
  static u64 scale_pd_power_uw(struct cpumask *pd_mask, u64 power)
  {
  	unsigned long max = 0, sum_util = 0;
  	int cpu;
  
  	for_each_cpu_and(cpu, pd_mask, cpu_online_mask) {
  
  		/*
  		 * The capacity is the same for all CPUs belonging to
  		 * the same perf domain, so a single call to
  		 * arch_scale_cpu_capacity() is enough. However, we
  		 * need the CPU parameter to be initialized by the
  		 * loop, so the call ends up in this block.
  		 *
  		 * We can initialize 'max' with a cpumask_first() call
  		 * before the loop but the bits computation is not
  		 * worth given the arch_scale_cpu_capacity() just
  		 * returns a value where the resulting assembly code
  		 * will be optimized by the compiler.
  		 */
  		max = arch_scale_cpu_capacity(cpu);
  		sum_util += sched_cpu_util(cpu, max);
  	}
  
  	/*
  	 * In the improbable case where all the CPUs of the perf
  	 * domain are offline, 'max' will be zero and will lead to an
  	 * illegal operation with a zero division.
  	 */
  	return max ? (power * ((sum_util << 10) / max)) >> 10 : 0;
  }
  
  static u64 get_pd_power_uw(struct dtpm *dtpm)
  {
  	struct dtpm_cpu *dtpm_cpu = to_dtpm_cpu(dtpm);
  	struct em_perf_domain *pd;
  	struct cpumask *pd_mask;
  	unsigned long freq;
  	int i;
  
  	pd = em_cpu_get(dtpm_cpu->cpu);
  
  	pd_mask = em_span_cpus(pd);
  
  	freq = cpufreq_quick_get(dtpm_cpu->cpu);
  
  	for (i = 0; i < pd->nr_perf_states; i++) {
  
  		if (pd->table[i].frequency < freq)
  			continue;
  
  		return scale_pd_power_uw(pd_mask, pd->table[i].power *
  					 MICROWATT_PER_MILLIWATT);
  	}
  
  	return 0;
  }
  
  static int update_pd_power_uw(struct dtpm *dtpm)
  {
  	struct dtpm_cpu *dtpm_cpu = to_dtpm_cpu(dtpm);
  	struct em_perf_domain *em = em_cpu_get(dtpm_cpu->cpu);
  	struct cpumask cpus;
  	int nr_cpus;
  
  	cpumask_and(&cpus, cpu_online_mask, to_cpumask(em->cpus));
  	nr_cpus = cpumask_weight(&cpus);
  
  	dtpm->power_min = em->table[0].power;
  	dtpm->power_min *= MICROWATT_PER_MILLIWATT;
  	dtpm->power_min *= nr_cpus;
  
  	dtpm->power_max = em->table[em->nr_perf_states - 1].power;
  	dtpm->power_max *= MICROWATT_PER_MILLIWATT;
  	dtpm->power_max *= nr_cpus;
  
  	return 0;
  }
  
  static void pd_release(struct dtpm *dtpm)
  {
  	struct dtpm_cpu *dtpm_cpu = to_dtpm_cpu(dtpm);
  
  	if (freq_qos_request_active(&dtpm_cpu->qos_req))
  		freq_qos_remove_request(&dtpm_cpu->qos_req);
  
  	kfree(dtpm_cpu);
  }
  
  static struct dtpm_ops dtpm_ops = {
  	.set_power_uw	 = set_pd_power_limit,
  	.get_power_uw	 = get_pd_power_uw,
  	.update_power_uw = update_pd_power_uw,
  	.release	 = pd_release,
  };
  
  static int cpuhp_dtpm_cpu_offline(unsigned int cpu)
  {
  	struct em_perf_domain *pd;
  	struct dtpm_cpu *dtpm_cpu;
  
  	pd = em_cpu_get(cpu);
  	if (!pd)
  		return -EINVAL;
  
  	dtpm_cpu = per_cpu(dtpm_per_cpu, cpu);
  
  	return dtpm_update_power(&dtpm_cpu->dtpm);
  }
  
  static int cpuhp_dtpm_cpu_online(unsigned int cpu)
  {
  	struct dtpm_cpu *dtpm_cpu;
  	struct cpufreq_policy *policy;
  	struct em_perf_domain *pd;
  	char name[CPUFREQ_NAME_LEN];
  	int ret = -ENOMEM;
  
  	policy = cpufreq_cpu_get(cpu);
  	if (!policy)
  		return 0;
  
  	pd = em_cpu_get(cpu);
  	if (!pd)
  		return -EINVAL;
  
  	dtpm_cpu = per_cpu(dtpm_per_cpu, cpu);
  	if (dtpm_cpu)
  		return dtpm_update_power(&dtpm_cpu->dtpm);
  
  	dtpm_cpu = kzalloc(sizeof(*dtpm_cpu), GFP_KERNEL);
  	if (!dtpm_cpu)
  		return -ENOMEM;
  
  	dtpm_init(&dtpm_cpu->dtpm, &dtpm_ops);
  	dtpm_cpu->cpu = cpu;
  
  	for_each_cpu(cpu, policy->related_cpus)
  		per_cpu(dtpm_per_cpu, cpu) = dtpm_cpu;
  
  	snprintf(name, sizeof(name), "cpu%d-cpufreq", dtpm_cpu->cpu);
  
  	ret = dtpm_register(name, &dtpm_cpu->dtpm, NULL);
  	if (ret)
  		goto out_kfree_dtpm_cpu;
  
  	ret = freq_qos_add_request(&policy->constraints,
  				   &dtpm_cpu->qos_req, FREQ_QOS_MAX,
  				   pd->table[pd->nr_perf_states - 1].frequency);
  	if (ret)
  		goto out_dtpm_unregister;
  
  	return 0;
  
  out_dtpm_unregister:
  	dtpm_unregister(&dtpm_cpu->dtpm);
  	dtpm_cpu = NULL;
  
  out_kfree_dtpm_cpu:
  	for_each_cpu(cpu, policy->related_cpus)
  		per_cpu(dtpm_per_cpu, cpu) = NULL;
  	kfree(dtpm_cpu);
  
  	return ret;
  }
  
  static int __init dtpm_cpu_init(void)
  {
  	int ret;
  
  	/*
  	 * The callbacks at CPU hotplug time are calling
  	 * dtpm_update_power() which in turns calls update_pd_power().
  	 *
  	 * The function update_pd_power() uses the online mask to
  	 * figure out the power consumption limits.
  	 *
  	 * At CPUHP_AP_ONLINE_DYN, the CPU is present in the CPU
  	 * online mask when the cpuhp_dtpm_cpu_online function is
  	 * called, but the CPU is still in the online mask for the
  	 * tear down callback. So the power can not be updated when
  	 * the CPU is unplugged.
  	 *
  	 * At CPUHP_AP_DTPM_CPU_DEAD, the situation is the opposite as
  	 * above. The CPU online mask is not up to date when the CPU
  	 * is plugged in.
  	 *
  	 * For this reason, we need to call the online and offline
  	 * callbacks at different moments when the CPU online mask is
  	 * consistent with the power numbers we want to update.
  	 */
  	ret = cpuhp_setup_state(CPUHP_AP_DTPM_CPU_DEAD, "dtpm_cpu:offline",
  				NULL, cpuhp_dtpm_cpu_offline);
  	if (ret < 0)
  		return ret;
  
  	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "dtpm_cpu:online",
  				cpuhp_dtpm_cpu_online, NULL);
  	if (ret < 0)
  		return ret;
  
  	return 0;
  }
  
  DTPM_DECLARE(dtpm_cpu, dtpm_cpu_init);
  