/*
 * arch/arm64/kernel/topology.c
 *
 * Copyright (C) 2011,2013,2014 Linaro Limited.
 *
 * Based on the arm32 version written by Vincent Guittot in turn based on
 * arch/sh/kernel/topology.c
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 */

#include <linux/acpi.h>
#include <linux/arch_topology.h>
#include <linux/cacheinfo.h>
#include <linux/cpufreq.h>
#include <linux/cpu_smt.h>
#include <linux/init.h>
#include <linux/percpu.h>
#include <linux/sched/isolation.h>
#include <linux/xarray.h>

#include <asm/cpu.h>
#include <asm/cputype.h>
#include <asm/topology.h>

#ifdef CONFIG_ARM64_AMU_EXTN
#define read_corecnt()  read_sysreg_s(SYS_AMEVCNTR0_CORE_EL0)
#define read_constcnt() read_sysreg_s(SYS_AMEVCNTR0_CONST_EL0)
#else
#define read_corecnt()  (0UL)
#define read_constcnt() (0UL)
#endif

#undef pr_fmt
#define pr_fmt(fmt) "AMU: " fmt

/*
 * Ensure that amu_scale_freq_tick() will return SCHED_CAPACITY_SCALE until
 * the CPU capacity and its associated frequency have been correctly
 * initialized.
 */
static DEFINE_PER_CPU_READ_MOSTLY(unsigned long, arch_max_freq_scale) =  1UL << (2 * SCHED_CAPACITY_SHIFT);
static cpumask_var_t amu_fie_cpus;

struct amu_cntr_sample {
        u64             arch_const_cycles_prev;
        u64             arch_core_cycles_prev;
        unsigned long   last_scale_update;
};

static DEFINE_PER_CPU_SHARED_ALIGNED(struct amu_cntr_sample, cpu_amu_samples);

void update_freq_counters_refs(void)
{
        struct amu_cntr_sample *amu_sample = this_cpu_ptr(&cpu_amu_samples);

        amu_sample->arch_core_cycles_prev = read_corecnt();
        amu_sample->arch_const_cycles_prev = read_constcnt();
}

static inline bool freq_counters_valid(int cpu)
{
        struct amu_cntr_sample *amu_sample = per_cpu_ptr(&cpu_amu_samples, cpu);

        if ((cpu >= nr_cpu_ids) || !cpumask_test_cpu(cpu, cpu_present_mask))
                return false;

        if (!cpu_has_amu_feat(cpu)) {
                pr_debug("CPU%d: counters are not supported.\n", cpu);
                return false;
        }

        if (unlikely(!amu_sample->arch_const_cycles_prev ||
                     !amu_sample->arch_core_cycles_prev)) {
                pr_debug("CPU%d: cycle counters are not enabled.\n", cpu);
                return false;
        }

        return true;
}

void freq_inv_set_max_ratio(int cpu, u64 max_rate)
{
        u64 ratio, ref_rate = arch_timer_get_rate();

        if (unlikely(!max_rate || !ref_rate)) {
                WARN_ONCE(1, "CPU%d: invalid maximum or reference frequency.\n",
                         cpu);
                return;
        }

        /*
         * Pre-compute the fixed ratio between the frequency of the constant
         * reference counter and the maximum frequency of the CPU.
         *
         *                          ref_rate
         * arch_max_freq_scale =   ---------- * SCHED_CAPACITY_SCALE²
         *                          max_rate
         *
         * We use a factor of 2 * SCHED_CAPACITY_SHIFT -> SCHED_CAPACITY_SCALE²
         * in order to ensure a good resolution for arch_max_freq_scale for
         * very low reference frequencies (down to the KHz range which should
         * be unlikely).
         */
        ratio = ref_rate << (2 * SCHED_CAPACITY_SHIFT);
        ratio = div64_u64(ratio, max_rate);
        if (!ratio) {
                WARN_ONCE(1, "Reference frequency too low.\n");
                return;
        }

        WRITE_ONCE(per_cpu(arch_max_freq_scale, cpu), (unsigned long)ratio);
}

static void amu_scale_freq_tick(void)
{
        struct amu_cntr_sample *amu_sample = this_cpu_ptr(&cpu_amu_samples);
        u64 prev_core_cnt, prev_const_cnt;
        u64 core_cnt, const_cnt, scale;

        prev_const_cnt = amu_sample->arch_const_cycles_prev;
        prev_core_cnt = amu_sample->arch_core_cycles_prev;

        update_freq_counters_refs();

        const_cnt = amu_sample->arch_const_cycles_prev;
        core_cnt = amu_sample->arch_core_cycles_prev;

        /*
         * This should not happen unless the AMUs have been reset and the
         * counter values have not been restored - unlikely
         */
        if (unlikely(core_cnt <= prev_core_cnt ||
                     const_cnt <= prev_const_cnt))
                return;

        /*
         *          /\core    arch_max_freq_scale
         * scale =  ------- * --------------------
         *          /\const   SCHED_CAPACITY_SCALE
         *
         * See validate_cpu_freq_invariance_counters() for details on
         * arch_max_freq_scale and the use of SCHED_CAPACITY_SHIFT.
         */
        scale = core_cnt - prev_core_cnt;
        scale *= this_cpu_read(arch_max_freq_scale);
        scale = div64_u64(scale >> SCHED_CAPACITY_SHIFT,
                          const_cnt - prev_const_cnt);

        scale = min_t(unsigned long, scale, SCHED_CAPACITY_SCALE);
        this_cpu_write(arch_freq_scale, (unsigned long)scale);

        amu_sample->last_scale_update = jiffies;
}

static struct scale_freq_data amu_sfd = {
        .source = SCALE_FREQ_SOURCE_ARCH,
        .set_freq_scale = amu_scale_freq_tick,
};

static __always_inline bool amu_fie_cpu_supported(unsigned int cpu)
{
        return cpumask_available(amu_fie_cpus) &&
                cpumask_test_cpu(cpu, amu_fie_cpus);
}

void arch_cpu_idle_enter(void)
{
        unsigned int cpu = smp_processor_id();

        if (!amu_fie_cpu_supported(cpu))
                return;

        /* Kick in AMU update but only if one has not happened already */
        if (housekeeping_cpu(cpu, HK_TYPE_TICK) &&
            time_is_before_jiffies(per_cpu(cpu_amu_samples.last_scale_update, cpu)))
                amu_scale_freq_tick();
}

#define AMU_SAMPLE_EXP_MS       20

int arch_freq_get_on_cpu(int cpu)
{
        struct amu_cntr_sample *amu_sample;
        unsigned int start_cpu = cpu;
        unsigned long last_update;
        unsigned int freq = 0;
        u64 scale;

        if (!amu_fie_cpu_supported(cpu) || !arch_scale_freq_ref(cpu))
                return -EOPNOTSUPP;

        while (1) {

                amu_sample = per_cpu_ptr(&cpu_amu_samples, cpu);

                last_update = amu_sample->last_scale_update;

                /*
                 * For those CPUs that are in full dynticks mode, or those that have
                 * not seen tick for a while, try an alternative source for the counters
                 * (and thus freq scale), if available, for given policy: this boils
                 * down to identifying an active cpu within the same freq domain, if any.
                 */
                if (!housekeeping_cpu(cpu, HK_TYPE_TICK) ||
                    time_is_before_jiffies(last_update + msecs_to_jiffies(AMU_SAMPLE_EXP_MS))) {
                        struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
                        int ref_cpu;

                        if (!policy)
                                return -EINVAL;

                        if (!cpumask_intersects(policy->related_cpus,
                                                housekeeping_cpumask(HK_TYPE_TICK))) {
                                cpufreq_cpu_put(policy);
                                return -EOPNOTSUPP;
                        }

                        for_each_cpu_wrap(ref_cpu, policy->cpus, cpu + 1) {
                                if (ref_cpu == start_cpu) {
                                        /* Prevent verifying same CPU twice */
                                        ref_cpu = nr_cpu_ids;
                                        break;
                                }
                                if (!idle_cpu(ref_cpu))
                                        break;
                        }

                        cpufreq_cpu_put(policy);

                        if (ref_cpu >= nr_cpu_ids)
                                /* No alternative to pull info from */
                                return -EAGAIN;

                        cpu = ref_cpu;
                } else {
                        break;
                }
        }
        /*
         * Reversed computation to the one used to determine
         * the arch_freq_scale value
         * (see amu_scale_freq_tick for details)
         */
        scale = arch_scale_freq_capacity(cpu);
        freq = scale * arch_scale_freq_ref(cpu);
        freq >>= SCHED_CAPACITY_SHIFT;
        return freq;
}

static void amu_fie_setup(const struct cpumask *cpus)
{
        int cpu;

        /* We are already set since the last insmod of cpufreq driver */
        if (cpumask_available(amu_fie_cpus) &&
            unlikely(cpumask_subset(cpus, amu_fie_cpus)))
                return;

        for_each_cpu(cpu, cpus)
                if (!freq_counters_valid(cpu))
                        return;

        if (!cpumask_available(amu_fie_cpus) &&
            !zalloc_cpumask_var(&amu_fie_cpus, GFP_KERNEL)) {
                WARN_ONCE(1, "Failed to allocate FIE cpumask for CPUs[%*pbl]\n",
                          cpumask_pr_args(cpus));
                return;
        }

        cpumask_or(amu_fie_cpus, amu_fie_cpus, cpus);

        topology_set_scale_freq_source(&amu_sfd, cpus);

        pr_debug("CPUs[%*pbl]: counters will be used for FIE.",
                 cpumask_pr_args(cpus));
}

static int init_amu_fie_callback(struct notifier_block *nb, unsigned long val,
                                 void *data)
{
        struct cpufreq_policy *policy = data;

        if (val == CPUFREQ_CREATE_POLICY)
                amu_fie_setup(policy->cpus);

        /*
         * We don't need to handle CPUFREQ_REMOVE_POLICY event as the AMU
         * counters don't have any dependency on cpufreq driver once we have
         * initialized AMU support and enabled invariance. The AMU counters will
         * keep on working just fine in the absence of the cpufreq driver, and
         * for the CPUs for which there are no counters available, the last set
         * value of arch_freq_scale will remain valid as that is the frequency
         * those CPUs are running at.
         */

        return 0;
}

static struct notifier_block init_amu_fie_notifier = {
        .notifier_call = init_amu_fie_callback,
};

static int cpuhp_topology_online(unsigned int cpu)
{
        struct cpufreq_policy *policy = cpufreq_cpu_policy(cpu);

        /* Those are cheap checks */

        /*
         * Skip this CPU if:
         *  - it has no cpufreq policy assigned yet,
         *  - no policy exists that spans CPUs with AMU counters, or
         *  - it was already handled.
         */
        if (unlikely(!policy) || !cpumask_available(amu_fie_cpus) ||
            cpumask_test_cpu(cpu, amu_fie_cpus))
                return 0;

        /*
         * Only proceed if all already-online CPUs in this policy
         * support AMU counters.
         */
        if (unlikely(!cpumask_subset(policy->cpus, amu_fie_cpus)))
                return 0;

        /*
         * If the new online CPU cannot pass this check, all the CPUs related to
         * the same policy should be clear from amu_fie_cpus mask, otherwise they
         * may use different source of the freq scale.
         */
        if (!freq_counters_valid(cpu)) {
                topology_clear_scale_freq_source(SCALE_FREQ_SOURCE_ARCH,
                                                 policy->related_cpus);
                cpumask_andnot(amu_fie_cpus, amu_fie_cpus, policy->related_cpus);
                return 0;
        }

        cpumask_set_cpu(cpu, amu_fie_cpus);

        topology_set_scale_freq_source(&amu_sfd, cpumask_of(cpu));

        pr_debug("CPU[%u]: counter will be used for FIE.", cpu);

        return 0;
}

static int __init init_amu_fie(void)
{
        int ret;

        ret = cpufreq_register_notifier(&init_amu_fie_notifier,
                                        CPUFREQ_POLICY_NOTIFIER);
        if (ret)
                return ret;

        ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
                                        "arm64/topology:online",
                                        cpuhp_topology_online,
                                        NULL);
        if (ret < 0) {
                cpufreq_unregister_notifier(&init_amu_fie_notifier,
                                            CPUFREQ_POLICY_NOTIFIER);
                return ret;
        }

        return 0;
}
core_initcall(init_amu_fie);

#ifdef CONFIG_ACPI_CPPC_LIB
#include <acpi/cppc_acpi.h>

static void cpu_read_corecnt(void *val)
{
        /*
         * A value of 0 can be returned if the current CPU does not support AMUs
         * or if the counter is disabled for this CPU. A return value of 0 at
         * counter read is properly handled as an error case by the users of the
         * counter.
         */
        *(u64 *)val = read_corecnt();
}

static void cpu_read_constcnt(void *val)
{
        /*
         * Return 0 if the current CPU is affected by erratum 2457168. A value
         * of 0 is also returned if the current CPU does not support AMUs or if
         * the counter is disabled. A return value of 0 at counter read is
         * properly handled as an error case by the users of the counter.
         */
        *(u64 *)val = this_cpu_has_cap(ARM64_WORKAROUND_2457168) ?
                      0UL : read_constcnt();
}

static inline
int counters_read_on_cpu(int cpu, smp_call_func_t func, u64 *val)
{
        /*
         * Abort call on counterless CPU.
         */
        if (!cpu_has_amu_feat(cpu))
                return -EOPNOTSUPP;

        if (irqs_disabled()) {
                /*
                 * When IRQs are disabled (tick path: sched_tick ->
                 * topology_scale_freq_tick or cppc_scale_freq_tick), only local
                 * CPU counter reads are allowed. Remote CPU counter read would
                 * require smp_call_function_single() which is unsafe with IRQs
                 * disabled.
                 */
                if (WARN_ON_ONCE(cpu != smp_processor_id()))
                        return -EPERM;
                func(val);
        } else {
                smp_call_function_single(cpu, func, val, 1);
        }

        return 0;
}

/*
 * Refer to drivers/acpi/cppc_acpi.c for the description of the functions
 * below.
 */
bool cpc_ffh_supported(void)
{
        int cpu = get_cpu_with_amu_feat();

        /*
         * FFH is considered supported if there is at least one present CPU that
         * supports AMUs. Using FFH to read core and reference counters for CPUs
         * that do not support AMUs, have counters disabled or that are affected
         * by errata, will result in a return value of 0.
         *
         * This is done to allow any enabled and valid counters to be read
         * through FFH, knowing that potentially returning 0 as counter value is
         * properly handled by the users of these counters.
         */
        if ((cpu >= nr_cpu_ids) || !cpumask_test_cpu(cpu, cpu_present_mask))
                return false;

        return true;
}

int cpc_read_ffh(int cpu, struct cpc_reg *reg, u64 *val)
{
        int ret = -EOPNOTSUPP;

        switch ((u64)reg->address) {
        case 0x0:
                ret = counters_read_on_cpu(cpu, cpu_read_corecnt, val);
                break;
        case 0x1:
                ret = counters_read_on_cpu(cpu, cpu_read_constcnt, val);
                break;
        }

        if (!ret) {
                *val &= GENMASK_ULL(reg->bit_offset + reg->bit_width - 1,
                                    reg->bit_offset);
                *val >>= reg->bit_offset;
        }

        return ret;
}

int cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val)
{
        return -EOPNOTSUPP;
}
#endif /* CONFIG_ACPI_CPPC_LIB */