#undef DEBUG

/*
 * ARM performance counter support.
 *
 * Copyright (C) 2009 picoChip Designs, Ltd., Jamie Iles
 * Copyright (C) 2010 ARM Ltd., Will Deacon <will.deacon@arm.com>
 *
 * This code is based on the sparc64 perf event code, which is in turn based
 * on the x86 code.
 */
#define pr_fmt(fmt) "hw perfevents: " fmt

#include <linux/bitmap.h>
#include <linux/cpumask.h>
#include <linux/cpu_pm.h>
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/perf/arm_pmu.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/sched/clock.h>
#include <linux/spinlock.h>
#include <linux/irq.h>
#include <linux/irqdesc.h>

#include <asm/irq_regs.h>

static int
armpmu_map_cache_event(const unsigned (*cache_map)
                                      [PERF_COUNT_HW_CACHE_MAX]
                                      [PERF_COUNT_HW_CACHE_OP_MAX]
                                      [PERF_COUNT_HW_CACHE_RESULT_MAX],
                       u64 config)
{
        unsigned int cache_type, cache_op, cache_result, ret;

        cache_type = (config >>  0) & 0xff;
        if (cache_type >= PERF_COUNT_HW_CACHE_MAX)
                return -EINVAL;

        cache_op = (config >>  8) & 0xff;
        if (cache_op >= PERF_COUNT_HW_CACHE_OP_MAX)
                return -EINVAL;

        cache_result = (config >> 16) & 0xff;
        if (cache_result >= PERF_COUNT_HW_CACHE_RESULT_MAX)
                return -EINVAL;

        ret = (int)(*cache_map)[cache_type][cache_op][cache_result];

        if (ret == CACHE_OP_UNSUPPORTED)
                return -ENOENT;

        return ret;
}

static int
armpmu_map_hw_event(const unsigned (*event_map)[PERF_COUNT_HW_MAX], u64 config)
{
        int mapping;

        if (config >= PERF_COUNT_HW_MAX)
                return -EINVAL;

        mapping = (*event_map)[config];
        return mapping == HW_OP_UNSUPPORTED ? -ENOENT : mapping;
}

static int
armpmu_map_raw_event(u32 raw_event_mask, u64 config)
{
        return (int)(config & raw_event_mask);
}

int
armpmu_map_event(struct perf_event *event,
                 const unsigned (*event_map)[PERF_COUNT_HW_MAX],
                 const unsigned (*cache_map)
                                [PERF_COUNT_HW_CACHE_MAX]
                                [PERF_COUNT_HW_CACHE_OP_MAX]
                                [PERF_COUNT_HW_CACHE_RESULT_MAX],
                 u32 raw_event_mask)
{
        u64 config = event->attr.config;
        int type = event->attr.type;

        if (type == event->pmu->type)
                return armpmu_map_raw_event(raw_event_mask, config);

        switch (type) {
        case PERF_TYPE_HARDWARE:
                return armpmu_map_hw_event(event_map, config);
        case PERF_TYPE_HW_CACHE:
                return armpmu_map_cache_event(cache_map, config);
        case PERF_TYPE_RAW:
                return armpmu_map_raw_event(raw_event_mask, config);
        }

        return -ENOENT;
}

int armpmu_event_set_period(struct perf_event *event)
{
        struct arm_pmu *armpmu = to_arm_pmu(event->pmu);
        struct hw_perf_event *hwc = &event->hw;
        s64 left = local64_read(&hwc->period_left);
        s64 period = hwc->sample_period;
        int ret = 0;

        if (unlikely(left <= -period)) {
                left = period;
                local64_set(&hwc->period_left, left);
                hwc->last_period = period;
                ret = 1;
        }

        if (unlikely(left <= 0)) {
                left += period;
                local64_set(&hwc->period_left, left);
                hwc->last_period = period;
                ret = 1;
        }

        /*
         * Limit the maximum period to prevent the counter value
         * from overtaking the one we are about to program. In
         * effect we are reducing max_period to account for
         * interrupt latency (and we are being very conservative).
         */
        if (left > (armpmu->max_period >> 1))
                left = armpmu->max_period >> 1;

        local64_set(&hwc->prev_count, (u64)-left);

        armpmu->write_counter(event, (u64)(-left) & 0xffffffff);

        perf_event_update_userpage(event);

        return ret;
}

u64 armpmu_event_update(struct perf_event *event)
{
        struct arm_pmu *armpmu = to_arm_pmu(event->pmu);
        struct hw_perf_event *hwc = &event->hw;
        u64 delta, prev_raw_count, new_raw_count;

again:
        prev_raw_count = local64_read(&hwc->prev_count);
        new_raw_count = armpmu->read_counter(event);

        if (local64_cmpxchg(&hwc->prev_count, prev_raw_count,
                             new_raw_count) != prev_raw_count)
                goto again;

        delta = (new_raw_count - prev_raw_count) & armpmu->max_period;

        local64_add(delta, &event->count);
        local64_sub(delta, &hwc->period_left);

        return new_raw_count;
}

static void
armpmu_read(struct perf_event *event)
{
        armpmu_event_update(event);
}

static void
armpmu_stop(struct perf_event *event, int flags)
{
        struct arm_pmu *armpmu = to_arm_pmu(event->pmu);
        struct hw_perf_event *hwc = &event->hw;

        /*
         * ARM pmu always has to update the counter, so ignore
         * PERF_EF_UPDATE, see comments in armpmu_start().
         */
        if (!(hwc->state & PERF_HES_STOPPED)) {
                armpmu->disable(event);
                armpmu_event_update(event);
                hwc->state |= PERF_HES_STOPPED | PERF_HES_UPTODATE;
        }
}

static void armpmu_start(struct perf_event *event, int flags)
{
        struct arm_pmu *armpmu = to_arm_pmu(event->pmu);
        struct hw_perf_event *hwc = &event->hw;

        /*
         * ARM pmu always has to reprogram the period, so ignore
         * PERF_EF_RELOAD, see the comment below.
         */
        if (flags & PERF_EF_RELOAD)
                WARN_ON_ONCE(!(hwc->state & PERF_HES_UPTODATE));

        hwc->state = 0;
        /*
         * Set the period again. Some counters can't be stopped, so when we
         * were stopped we simply disabled the IRQ source and the counter
         * may have been left counting. If we don't do this step then we may
         * get an interrupt too soon or *way* too late if the overflow has
         * happened since disabling.
         */
        armpmu_event_set_period(event);
        armpmu->enable(event);
}

static void
armpmu_del(struct perf_event *event, int flags)
{
        struct arm_pmu *armpmu = to_arm_pmu(event->pmu);
        struct pmu_hw_events *hw_events = this_cpu_ptr(armpmu->hw_events);
        struct hw_perf_event *hwc = &event->hw;
        int idx = hwc->idx;

        armpmu_stop(event, PERF_EF_UPDATE);
        hw_events->events[idx] = NULL;
        clear_bit(idx, hw_events->used_mask);
        if (armpmu->clear_event_idx)
                armpmu->clear_event_idx(hw_events, event);

        perf_event_update_userpage(event);
}

static int
armpmu_add(struct perf_event *event, int flags)
{
        struct arm_pmu *armpmu = to_arm_pmu(event->pmu);
        struct pmu_hw_events *hw_events = this_cpu_ptr(armpmu->hw_events);
        struct hw_perf_event *hwc = &event->hw;
        int idx;

        /* An event following a process won't be stopped earlier */
        if (!cpumask_test_cpu(smp_processor_id(), &armpmu->supported_cpus))
                return -ENOENT;

        /* If we don't have a space for the counter then finish early. */
        idx = armpmu->get_event_idx(hw_events, event);
        if (idx < 0)
                return idx;

        /*
         * If there is an event in the counter we are going to use then make
         * sure it is disabled.
         */
        event->hw.idx = idx;
        armpmu->disable(event);
        hw_events->events[idx] = event;

        hwc->state = PERF_HES_STOPPED | PERF_HES_UPTODATE;
        if (flags & PERF_EF_START)
                armpmu_start(event, PERF_EF_RELOAD);

        /* Propagate our changes to the userspace mapping. */
        perf_event_update_userpage(event);

        return 0;
}

static int
validate_event(struct pmu *pmu, struct pmu_hw_events *hw_events,
                               struct perf_event *event)
{
        struct arm_pmu *armpmu;

        if (is_software_event(event))
                return 1;

        /*
         * Reject groups spanning multiple HW PMUs (e.g. CPU + CCI). The
         * core perf code won't check that the pmu->ctx == leader->ctx
         * until after pmu->event_init(event).
         */
        if (event->pmu != pmu)
                return 0;

        if (event->state < PERF_EVENT_STATE_OFF)
                return 1;

        if (event->state == PERF_EVENT_STATE_OFF && !event->attr.enable_on_exec)
                return 1;

        armpmu = to_arm_pmu(event->pmu);
        return armpmu->get_event_idx(hw_events, event) >= 0;
}

static int
validate_group(struct perf_event *event)
{
        struct perf_event *sibling, *leader = event->group_leader;
        struct pmu_hw_events fake_pmu;

        /*
         * Initialise the fake PMU. We only need to populate the
         * used_mask for the purposes of validation.
         */
        memset(&fake_pmu.used_mask, 0, sizeof(fake_pmu.used_mask));

        if (!validate_event(event->pmu, &fake_pmu, leader))
                return -EINVAL;

        list_for_each_entry(sibling, &leader->sibling_list, group_entry) {
                if (!validate_event(event->pmu, &fake_pmu, sibling))
                        return -EINVAL;
        }

        if (!validate_event(event->pmu, &fake_pmu, event))
                return -EINVAL;

        return 0;
}

static struct arm_pmu_platdata *armpmu_get_platdata(struct arm_pmu *armpmu)
{
        struct platform_device *pdev = armpmu->plat_device;

        return pdev ? dev_get_platdata(&pdev->dev) : NULL;
}

static irqreturn_t armpmu_dispatch_irq(int irq, void *dev)
{
        struct arm_pmu *armpmu;
        struct arm_pmu_platdata *plat;
        int ret;
        u64 start_clock, finish_clock;

        /*
         * we request the IRQ with a (possibly percpu) struct arm_pmu**, but
         * the handlers expect a struct arm_pmu*. The percpu_irq framework will
         * do any necessary shifting, we just need to perform the first
         * dereference.
         */
        armpmu = *(void **)dev;

        plat = armpmu_get_platdata(armpmu);

        start_clock = sched_clock();
        if (plat && plat->handle_irq)
                ret = plat->handle_irq(irq, armpmu, armpmu->handle_irq);
        else
                ret = armpmu->handle_irq(irq, armpmu);
        finish_clock = sched_clock();

        perf_sample_event_took(finish_clock - start_clock);
        return ret;
}

static int
event_requires_mode_exclusion(struct perf_event_attr *attr)
{
        return attr->exclude_idle || attr->exclude_user ||
               attr->exclude_kernel || attr->exclude_hv;
}

static int
__hw_perf_event_init(struct perf_event *event)
{
        struct arm_pmu *armpmu = to_arm_pmu(event->pmu);
        struct hw_perf_event *hwc = &event->hw;
        int mapping;

        mapping = armpmu->map_event(event);

        if (mapping < 0) {
                pr_debug("event %x:%llx not supported\n", event->attr.type,
                         event->attr.config);
                return mapping;
        }

        /*
         * We don't assign an index until we actually place the event onto
         * hardware. Use -1 to signify that we haven't decided where to put it
         * yet. For SMP systems, each core has it's own PMU so we can't do any
         * clever allocation or constraints checking at this point.
         */
        hwc->idx                = -1;
        hwc->config_base        = 0;
        hwc->config             = 0;
        hwc->event_base         = 0;

        /*
         * Check whether we need to exclude the counter from certain modes.
         */
        if ((!armpmu->set_event_filter ||
             armpmu->set_event_filter(hwc, &event->attr)) &&
             event_requires_mode_exclusion(&event->attr)) {
                pr_debug("ARM performance counters do not support "
                         "mode exclusion\n");
                return -EOPNOTSUPP;
        }

        /*
         * Store the event encoding into the config_base field.
         */
        hwc->config_base            |= (unsigned long)mapping;

        if (!is_sampling_event(event)) {
                /*
                 * For non-sampling runs, limit the sample_period to half
                 * of the counter width. That way, the new counter value
                 * is far less likely to overtake the previous one unless
                 * you have some serious IRQ latency issues.
                 */
                hwc->sample_period  = armpmu->max_period >> 1;
                hwc->last_period    = hwc->sample_period;
                local64_set(&hwc->period_left, hwc->sample_period);
        }

        if (event->group_leader != event) {
                if (validate_group(event) != 0)
                        return -EINVAL;
        }

        return 0;
}

static int armpmu_event_init(struct perf_event *event)
{
        struct arm_pmu *armpmu = to_arm_pmu(event->pmu);

        /*
         * Reject CPU-affine events for CPUs that are of a different class to
         * that which this PMU handles. Process-following events (where
         * event->cpu == -1) can be migrated between CPUs, and thus we have to
         * reject them later (in armpmu_add) if they're scheduled on a
         * different class of CPU.
         */
        if (event->cpu != -1 &&
                !cpumask_test_cpu(event->cpu, &armpmu->supported_cpus))
                return -ENOENT;

        /* does not support taken branch sampling */
        if (has_branch_stack(event))
                return -EOPNOTSUPP;

        if (armpmu->map_event(event) == -ENOENT)
                return -ENOENT;

        return __hw_perf_event_init(event);
}

static void armpmu_enable(struct pmu *pmu)
{
        struct arm_pmu *armpmu = to_arm_pmu(pmu);
        struct pmu_hw_events *hw_events = this_cpu_ptr(armpmu->hw_events);
        int enabled = bitmap_weight(hw_events->used_mask, armpmu->num_events);

        /* For task-bound events we may be called on other CPUs */
        if (!cpumask_test_cpu(smp_processor_id(), &armpmu->supported_cpus))
                return;

        if (enabled)
                armpmu->start(armpmu);
}

static void armpmu_disable(struct pmu *pmu)
{
        struct arm_pmu *armpmu = to_arm_pmu(pmu);

        /* For task-bound events we may be called on other CPUs */
        if (!cpumask_test_cpu(smp_processor_id(), &armpmu->supported_cpus))
                return;

        armpmu->stop(armpmu);
}

/*
 * In heterogeneous systems, events are specific to a particular
 * microarchitecture, and aren't suitable for another. Thus, only match CPUs of
 * the same microarchitecture.
 */
static int armpmu_filter_match(struct perf_event *event)
{
        struct arm_pmu *armpmu = to_arm_pmu(event->pmu);
        unsigned int cpu = smp_processor_id();
        return cpumask_test_cpu(cpu, &armpmu->supported_cpus);
}

static ssize_t armpmu_cpumask_show(struct device *dev,
                                   struct device_attribute *attr, char *buf)
{
        struct arm_pmu *armpmu = to_arm_pmu(dev_get_drvdata(dev));
        return cpumap_print_to_pagebuf(true, buf, &armpmu->supported_cpus);
}

static DEVICE_ATTR(cpus, S_IRUGO, armpmu_cpumask_show, NULL);

static struct attribute *armpmu_common_attrs[] = {
        &dev_attr_cpus.attr,
        NULL,
};

static struct attribute_group armpmu_common_attr_group = {
        .attrs = armpmu_common_attrs,
};

/* Set at runtime when we know what CPU type we are. */
static struct arm_pmu *__oprofile_cpu_pmu;

/*
 * Despite the names, these two functions are CPU-specific and are used
 * by the OProfile/perf code.
 */
const char *perf_pmu_name(void)
{
        if (!__oprofile_cpu_pmu)
                return NULL;

        return __oprofile_cpu_pmu->name;
}
EXPORT_SYMBOL_GPL(perf_pmu_name);

int perf_num_counters(void)
{
        int max_events = 0;

        if (__oprofile_cpu_pmu != NULL)
                max_events = __oprofile_cpu_pmu->num_events;

        return max_events;
}
EXPORT_SYMBOL_GPL(perf_num_counters);

void armpmu_free_irq(struct arm_pmu *armpmu, int cpu)
{
        struct pmu_hw_events __percpu *hw_events = armpmu->hw_events;
        int irq = per_cpu(hw_events->irq, cpu);

        if (!cpumask_test_and_clear_cpu(cpu, &armpmu->active_irqs))
                return;

        if (irq_is_percpu(irq)) {
                free_percpu_irq(irq, &hw_events->percpu_pmu);
                cpumask_clear(&armpmu->active_irqs);
                return;
        }

        free_irq(irq, per_cpu_ptr(&hw_events->percpu_pmu, cpu));
}

void armpmu_free_irqs(struct arm_pmu *armpmu)
{
        int cpu;

        for_each_cpu(cpu, &armpmu->supported_cpus)
                armpmu_free_irq(armpmu, cpu);
}

int armpmu_request_irq(struct arm_pmu *armpmu, int cpu)
{
        int err = 0;
        struct pmu_hw_events __percpu *hw_events = armpmu->hw_events;
        const irq_handler_t handler = armpmu_dispatch_irq;
        int irq = per_cpu(hw_events->irq, cpu);
        if (!irq)
                return 0;

        if (irq_is_percpu(irq) && cpumask_empty(&armpmu->active_irqs)) {
                err = request_percpu_irq(irq, handler, "arm-pmu",
                                         &hw_events->percpu_pmu);
        } else if (irq_is_percpu(irq)) {
                int other_cpu = cpumask_first(&armpmu->active_irqs);
                int other_irq = per_cpu(hw_events->irq, other_cpu);

                if (irq != other_irq) {
                        pr_warn("mismatched PPIs detected.\n");
                        err = -EINVAL;
                        goto err_out;
                }
        } else {
                struct arm_pmu_platdata *platdata = armpmu_get_platdata(armpmu);
                unsigned long irq_flags;

                err = irq_force_affinity(irq, cpumask_of(cpu));

                if (err && num_possible_cpus() > 1) {
                        pr_warn("unable to set irq affinity (irq=%d, cpu=%u)\n",
                                irq, cpu);
                        goto err_out;
                }

                if (platdata && platdata->irq_flags) {
                        irq_flags = platdata->irq_flags;
                } else {
                        irq_flags = IRQF_PERCPU |
                                    IRQF_NOBALANCING |
                                    IRQF_NO_THREAD;
                }

                err = request_irq(irq, handler, irq_flags, "arm-pmu",
                                  per_cpu_ptr(&hw_events->percpu_pmu, cpu));
        }

        if (err)
                goto err_out;

        cpumask_set_cpu(cpu, &armpmu->active_irqs);
        return 0;

err_out:
        pr_err("unable to request IRQ%d for ARM PMU counters\n", irq);
        return err;
}

int armpmu_request_irqs(struct arm_pmu *armpmu)
{
        int cpu, err;

        for_each_cpu(cpu, &armpmu->supported_cpus) {
                err = armpmu_request_irq(armpmu, cpu);
                if (err)
                        break;
        }

        return err;
}

static int armpmu_get_cpu_irq(struct arm_pmu *pmu, int cpu)
{
        struct pmu_hw_events __percpu *hw_events = pmu->hw_events;
        return per_cpu(hw_events->irq, cpu);
}

/*
 * PMU hardware loses all context when a CPU goes offline.
 * When a CPU is hotplugged back in, since some hardware registers are
 * UNKNOWN at reset, the PMU must be explicitly reset to avoid reading
 * junk values out of them.
 */
static int arm_perf_starting_cpu(unsigned int cpu, struct hlist_node *node)
{
        struct arm_pmu *pmu = hlist_entry_safe(node, struct arm_pmu, node);
        int irq;

        if (!cpumask_test_cpu(cpu, &pmu->supported_cpus))
                return 0;
        if (pmu->reset)
                pmu->reset(pmu);

        irq = armpmu_get_cpu_irq(pmu, cpu);
        if (irq) {
                if (irq_is_percpu(irq)) {
                        enable_percpu_irq(irq, IRQ_TYPE_NONE);
                        return 0;
                }
        }

        return 0;
}

static int arm_perf_teardown_cpu(unsigned int cpu, struct hlist_node *node)
{
        struct arm_pmu *pmu = hlist_entry_safe(node, struct arm_pmu, node);
        int irq;

        if (!cpumask_test_cpu(cpu, &pmu->supported_cpus))
                return 0;

        irq = armpmu_get_cpu_irq(pmu, cpu);
        if (irq && irq_is_percpu(irq))
                disable_percpu_irq(irq);

        return 0;
}

#ifdef CONFIG_CPU_PM
static void cpu_pm_pmu_setup(struct arm_pmu *armpmu, unsigned long cmd)
{
        struct pmu_hw_events *hw_events = this_cpu_ptr(armpmu->hw_events);
        struct perf_event *event;
        int idx;

        for (idx = 0; idx < armpmu->num_events; idx++) {
                /*
                 * If the counter is not used skip it, there is no
                 * need of stopping/restarting it.
                 */
                if (!test_bit(idx, hw_events->used_mask))
                        continue;

                event = hw_events->events[idx];

                switch (cmd) {
                case CPU_PM_ENTER:
                        /*
                         * Stop and update the counter
                         */
                        armpmu_stop(event, PERF_EF_UPDATE);
                        break;
                case CPU_PM_EXIT:
                case CPU_PM_ENTER_FAILED:
                         /*
                          * Restore and enable the counter.
                          * armpmu_start() indirectly calls
                          *
                          * perf_event_update_userpage()
                          *
                          * that requires RCU read locking to be functional,
                          * wrap the call within RCU_NONIDLE to make the
                          * RCU subsystem aware this cpu is not idle from
                          * an RCU perspective for the armpmu_start() call
                          * duration.
                          */
                        RCU_NONIDLE(armpmu_start(event, PERF_EF_RELOAD));
                        break;
                default:
                        break;
                }
        }
}

static int cpu_pm_pmu_notify(struct notifier_block *b, unsigned long cmd,
                             void *v)
{
        struct arm_pmu *armpmu = container_of(b, struct arm_pmu, cpu_pm_nb);
        struct pmu_hw_events *hw_events = this_cpu_ptr(armpmu->hw_events);
        int enabled = bitmap_weight(hw_events->used_mask, armpmu->num_events);

        if (!cpumask_test_cpu(smp_processor_id(), &armpmu->supported_cpus))
                return NOTIFY_DONE;

        /*
         * Always reset the PMU registers on power-up even if
         * there are no events running.
         */
        if (cmd == CPU_PM_EXIT && armpmu->reset)
                armpmu->reset(armpmu);

        if (!enabled)
                return NOTIFY_OK;

        switch (cmd) {
        case CPU_PM_ENTER:
                armpmu->stop(armpmu);
                cpu_pm_pmu_setup(armpmu, cmd);
                break;
        case CPU_PM_EXIT:
                cpu_pm_pmu_setup(armpmu, cmd);
        case CPU_PM_ENTER_FAILED:
                armpmu->start(armpmu);
                break;
        default:
                return NOTIFY_DONE;
        }

        return NOTIFY_OK;
}

static int cpu_pm_pmu_register(struct arm_pmu *cpu_pmu)
{
        cpu_pmu->cpu_pm_nb.notifier_call = cpu_pm_pmu_notify;
        return cpu_pm_register_notifier(&cpu_pmu->cpu_pm_nb);
}

static void cpu_pm_pmu_unregister(struct arm_pmu *cpu_pmu)
{
        cpu_pm_unregister_notifier(&cpu_pmu->cpu_pm_nb);
}
#else
static inline int cpu_pm_pmu_register(struct arm_pmu *cpu_pmu) { return 0; }
static inline void cpu_pm_pmu_unregister(struct arm_pmu *cpu_pmu) { }
#endif

static int cpu_pmu_init(struct arm_pmu *cpu_pmu)
{
        int err;

        err = cpuhp_state_add_instance(CPUHP_AP_PERF_ARM_STARTING,
                                       &cpu_pmu->node);
        if (err)
                goto out;

        err = cpu_pm_pmu_register(cpu_pmu);
        if (err)
                goto out_unregister;

        return 0;

out_unregister:
        cpuhp_state_remove_instance_nocalls(CPUHP_AP_PERF_ARM_STARTING,
                                            &cpu_pmu->node);
out:
        return err;
}

static void cpu_pmu_destroy(struct arm_pmu *cpu_pmu)
{
        cpu_pm_pmu_unregister(cpu_pmu);
        cpuhp_state_remove_instance_nocalls(CPUHP_AP_PERF_ARM_STARTING,
                                            &cpu_pmu->node);
}

struct arm_pmu *armpmu_alloc(void)
{
        struct arm_pmu *pmu;
        int cpu;

        pmu = kzalloc(sizeof(*pmu), GFP_KERNEL);
        if (!pmu) {
                pr_info("failed to allocate PMU device!\n");
                goto out;
        }

        pmu->hw_events = alloc_percpu(struct pmu_hw_events);
        if (!pmu->hw_events) {
                pr_info("failed to allocate per-cpu PMU data.\n");
                goto out_free_pmu;
        }

        pmu->pmu = (struct pmu) {
                .pmu_enable     = armpmu_enable,
                .pmu_disable    = armpmu_disable,
                .event_init     = armpmu_event_init,
                .add            = armpmu_add,
                .del            = armpmu_del,
                .start          = armpmu_start,
                .stop           = armpmu_stop,
                .read           = armpmu_read,
                .filter_match   = armpmu_filter_match,
                .attr_groups    = pmu->attr_groups,
                /*
                 * This is a CPU PMU potentially in a heterogeneous
                 * configuration (e.g. big.LITTLE). This is not an uncore PMU,
                 * and we have taken ctx sharing into account (e.g. with our
                 * pmu::filter_match callback and pmu::event_init group
                 * validation).
                 */
                .capabilities   = PERF_PMU_CAP_HETEROGENEOUS_CPUS,
        };

        pmu->attr_groups[ARMPMU_ATTR_GROUP_COMMON] =
                &armpmu_common_attr_group;

        for_each_possible_cpu(cpu) {
                struct pmu_hw_events *events;

                events = per_cpu_ptr(pmu->hw_events, cpu);
                raw_spin_lock_init(&events->pmu_lock);
                events->percpu_pmu = pmu;
        }

        return pmu;

out_free_pmu:
        kfree(pmu);
out:
        return NULL;
}

void armpmu_free(struct arm_pmu *pmu)
{
        free_percpu(pmu->hw_events);
        kfree(pmu);
}

int armpmu_register(struct arm_pmu *pmu)
{
        int ret;

        ret = cpu_pmu_init(pmu);
        if (ret)
                return ret;

        ret = perf_pmu_register(&pmu->pmu, pmu->name, -1);
        if (ret)
                goto out_destroy;

        if (!__oprofile_cpu_pmu)
                __oprofile_cpu_pmu = pmu;

        pr_info("enabled with %s PMU driver, %d counters available\n",
                pmu->name, pmu->num_events);

        return 0;

out_destroy:
        cpu_pmu_destroy(pmu);
        return ret;
}

static int arm_pmu_hp_init(void)
{
        int ret;

        ret = cpuhp_setup_state_multi(CPUHP_AP_PERF_ARM_STARTING,
                                      "perf/arm/pmu:starting",
                                      arm_perf_starting_cpu,
                                      arm_perf_teardown_cpu);
        if (ret)
                pr_err("CPU hotplug notifier for ARM PMU could not be registered: %d\n",
                       ret);
        return ret;
}
subsys_initcall(arm_pmu_hp_init);