/*
 * Meta performance counter support.
 *  Copyright (C) 2012 Imagination Technologies Ltd
 *
 * This code is based on the sh pmu code:
 *  Copyright (C) 2009 Paul Mundt
 *
 * and on the arm pmu code:
 *  Copyright (C) 2009 picoChip Designs, Ltd., James Iles
 *  Copyright (C) 2010 ARM Ltd., Will Deacon <will.deacon@arm.com>
 *
 * 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/atomic.h>
#include <linux/export.h>
#include <linux/init.h>
#include <linux/irqchip/metag.h>
#include <linux/perf_event.h>
#include <linux/slab.h>

#include <asm/core_reg.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/processor.h>

#include "perf_event.h"

static int _hw_perf_event_init(struct perf_event *);
static void _hw_perf_event_destroy(struct perf_event *);

/* Determines which core type we are */
static struct metag_pmu *metag_pmu __read_mostly;

/* Processor specific data */
static DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events);

/* PMU admin */
const char *perf_pmu_name(void)
{
        if (!metag_pmu)
                return NULL;

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

int perf_num_counters(void)
{
        if (metag_pmu)
                return metag_pmu->max_events;

        return 0;
}
EXPORT_SYMBOL_GPL(perf_num_counters);

static inline int metag_pmu_initialised(void)
{
        return !!metag_pmu;
}

static void release_pmu_hardware(void)
{
        int irq;
        unsigned int version = (metag_pmu->version &
                        (METAC_ID_MINOR_BITS | METAC_ID_REV_BITS)) >>
                        METAC_ID_REV_S;

        /* Early cores don't have overflow interrupts */
        if (version < 0x0104)
                return;

        irq = internal_irq_map(17);
        if (irq >= 0)
                free_irq(irq, (void *)1);

        irq = internal_irq_map(16);
        if (irq >= 0)
                free_irq(irq, (void *)0);
}

static int reserve_pmu_hardware(void)
{
        int err = 0, irq[2];
        unsigned int version = (metag_pmu->version &
                        (METAC_ID_MINOR_BITS | METAC_ID_REV_BITS)) >>
                        METAC_ID_REV_S;

        /* Early cores don't have overflow interrupts */
        if (version < 0x0104)
                goto out;

        /*
         * Bit 16 on HWSTATMETA is the interrupt for performance counter 0;
         * similarly, 17 is the interrupt for performance counter 1.
         * We can't (yet) interrupt on the cycle counter, because it's a
         * register, however it holds a 32-bit value as opposed to 24-bit.
         */
        irq[0] = internal_irq_map(16);
        if (irq[0] < 0) {
                pr_err("unable to map internal IRQ %d\n", 16);
                goto out;
        }
        err = request_irq(irq[0], metag_pmu->handle_irq, IRQF_NOBALANCING,
                        "metagpmu0", (void *)0);
        if (err) {
                pr_err("unable to request IRQ%d for metag PMU counters\n",
                                irq[0]);
                goto out;
        }

        irq[1] = internal_irq_map(17);
        if (irq[1] < 0) {
                pr_err("unable to map internal IRQ %d\n", 17);
                goto out_irq1;
        }
        err = request_irq(irq[1], metag_pmu->handle_irq, IRQF_NOBALANCING,
                        "metagpmu1", (void *)1);
        if (err) {
                pr_err("unable to request IRQ%d for metag PMU counters\n",
                                irq[1]);
                goto out_irq1;
        }

        return 0;

out_irq1:
        free_irq(irq[0], (void *)0);
out:
        return err;
}

/* PMU operations */
static void metag_pmu_enable(struct pmu *pmu)
{
}

static void metag_pmu_disable(struct pmu *pmu)
{
}

static int metag_pmu_event_init(struct perf_event *event)
{
        int err = 0;
        atomic_t *active_events = &metag_pmu->active_events;

        if (!metag_pmu_initialised()) {
                err = -ENODEV;
                goto out;
        }

        if (has_branch_stack(event))
                return -EOPNOTSUPP;

        event->destroy = _hw_perf_event_destroy;

        if (!atomic_inc_not_zero(active_events)) {
                mutex_lock(&metag_pmu->reserve_mutex);
                if (atomic_read(active_events) == 0)
                        err = reserve_pmu_hardware();

                if (!err)
                        atomic_inc(active_events);

                mutex_unlock(&metag_pmu->reserve_mutex);
        }

        /* Hardware and caches counters */
        switch (event->attr.type) {
        case PERF_TYPE_HARDWARE:
        case PERF_TYPE_HW_CACHE:
        case PERF_TYPE_RAW:
                err = _hw_perf_event_init(event);
                break;

        default:
                return -ENOENT;
        }

        if (err)
                event->destroy(event);

out:
        return err;
}

void metag_pmu_event_update(struct perf_event *event,
                struct hw_perf_event *hwc, int idx)
{
        u64 prev_raw_count, new_raw_count;
        s64 delta;

        /*
         * If this counter is chained, it may be that the previous counter
         * value has been changed beneath us.
         *
         * To get around this, we read and exchange the new raw count, then
         * add the delta (new - prev) to the generic counter atomically.
         *
         * Without interrupts, this is the simplest approach.
         */
again:
        prev_raw_count = local64_read(&hwc->prev_count);
        new_raw_count = metag_pmu->read(idx);

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

        /*
         * Calculate the delta and add it to the counter.
         */
        delta = (new_raw_count - prev_raw_count) & MAX_PERIOD;

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

int metag_pmu_event_set_period(struct perf_event *event,
                struct hw_perf_event *hwc, int idx)
{
        s64 left = local64_read(&hwc->period_left);
        s64 period = hwc->sample_period;
        int ret = 0;

        /* The period may have been changed */
        if (unlikely(period != hwc->last_period))
                left += period - hwc->last_period;

        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;
        }

        if (left > (s64)metag_pmu->max_period)
                left = metag_pmu->max_period;

        if (metag_pmu->write) {
                local64_set(&hwc->prev_count, -(s32)left);
                metag_pmu->write(idx, -left & MAX_PERIOD);
        }

        perf_event_update_userpage(event);

        return ret;
}

static void metag_pmu_start(struct perf_event *event, int flags)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        struct hw_perf_event *hwc = &event->hw;
        int idx = hwc->idx;

        if (WARN_ON_ONCE(idx == -1))
                return;

        /*
         * We always have to reprogram the period, so ignore PERF_EF_RELOAD.
         */
        if (flags & PERF_EF_RELOAD)
                WARN_ON_ONCE(!(hwc->state & PERF_HES_UPTODATE));

        hwc->state = 0;

        /*
         * Reset the period.
         * Some counters can't be stopped (i.e. are core global), so when the
         * counter was 'stopped' we merely disabled the IRQ. If we don't reset
         * the period, then we'll either: a) get an overflow too soon;
         * or b) too late if the overflow happened since disabling.
         * Obviously, this has little bearing on cores without the overflow
         * interrupt, as the performance counter resets to zero on write
         * anyway.
         */
        if (metag_pmu->max_period)
                metag_pmu_event_set_period(event, hwc, hwc->idx);
        cpuc->events[idx] = event;
        metag_pmu->enable(hwc, idx);
}

static void metag_pmu_stop(struct perf_event *event, int flags)
{
        struct hw_perf_event *hwc = &event->hw;

        /*
         * We should always update the counter on stop; see comment above
         * why.
         */
        if (!(hwc->state & PERF_HES_STOPPED)) {
                metag_pmu_event_update(event, hwc, hwc->idx);
                metag_pmu->disable(hwc, hwc->idx);
                hwc->state |= PERF_HES_STOPPED | PERF_HES_UPTODATE;
        }
}

static int metag_pmu_add(struct perf_event *event, int flags)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        struct hw_perf_event *hwc = &event->hw;
        int idx = 0, ret = 0;

        perf_pmu_disable(event->pmu);

        /* check whether we're counting instructions */
        if (hwc->config == 0x100) {
                if (__test_and_set_bit(METAG_INST_COUNTER,
                                cpuc->used_mask)) {
                        ret = -EAGAIN;
                        goto out;
                }
                idx = METAG_INST_COUNTER;
        } else {
                /* Check whether we have a spare counter */
                idx = find_first_zero_bit(cpuc->used_mask,
                                atomic_read(&metag_pmu->active_events));
                if (idx >= METAG_INST_COUNTER) {
                        ret = -EAGAIN;
                        goto out;
                }

                __set_bit(idx, cpuc->used_mask);
        }
        hwc->idx = idx;

        /* Make sure the counter is disabled */
        metag_pmu->disable(hwc, idx);

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

        perf_event_update_userpage(event);
out:
        perf_pmu_enable(event->pmu);
        return ret;
}

static void metag_pmu_del(struct perf_event *event, int flags)
{
        struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
        struct hw_perf_event *hwc = &event->hw;
        int idx = hwc->idx;

        WARN_ON(idx < 0);
        metag_pmu_stop(event, PERF_EF_UPDATE);
        cpuc->events[idx] = NULL;
        __clear_bit(idx, cpuc->used_mask);

        perf_event_update_userpage(event);
}

static void metag_pmu_read(struct perf_event *event)
{
        struct hw_perf_event *hwc = &event->hw;

        /* Don't read disabled counters! */
        if (hwc->idx < 0)
                return;

        metag_pmu_event_update(event, hwc, hwc->idx);
}

static struct pmu pmu = {
        .pmu_enable     = metag_pmu_enable,
        .pmu_disable    = metag_pmu_disable,

        .event_init     = metag_pmu_event_init,

        .add            = metag_pmu_add,
        .del            = metag_pmu_del,
        .start          = metag_pmu_start,
        .stop           = metag_pmu_stop,
        .read           = metag_pmu_read,
};

/* Core counter specific functions */
static const int metag_general_events[] = {
        [PERF_COUNT_HW_CPU_CYCLES] = 0x03,
        [PERF_COUNT_HW_INSTRUCTIONS] = 0x100,
        [PERF_COUNT_HW_CACHE_REFERENCES] = -1,
        [PERF_COUNT_HW_CACHE_MISSES] = -1,
        [PERF_COUNT_HW_BRANCH_INSTRUCTIONS] = -1,
        [PERF_COUNT_HW_BRANCH_MISSES] = -1,
        [PERF_COUNT_HW_BUS_CYCLES] = -1,
        [PERF_COUNT_HW_STALLED_CYCLES_FRONTEND] = -1,
        [PERF_COUNT_HW_STALLED_CYCLES_BACKEND] = -1,
        [PERF_COUNT_HW_REF_CPU_CYCLES] = -1,
};

static const int metag_pmu_cache_events[C(MAX)][C(OP_MAX)][C(RESULT_MAX)] = {
        [C(L1D)] = {
                [C(OP_READ)] = {
                        [C(RESULT_ACCESS)] = 0x08,
                        [C(RESULT_MISS)] = CACHE_OP_UNSUPPORTED,
                },
                [C(OP_WRITE)] = {
                        [C(RESULT_ACCESS)] = CACHE_OP_UNSUPPORTED,
                        [C(RESULT_MISS)] = CACHE_OP_UNSUPPORTED,
                },
                [C(OP_PREFETCH)] = {
                        [C(RESULT_ACCESS)] = CACHE_OP_UNSUPPORTED,
                        [C(RESULT_MISS)] = CACHE_OP_UNSUPPORTED,
                },
        },
        [C(L1I)] = {
                [C(OP_READ)] = {
                        [C(RESULT_ACCESS)] = 0x09,
                        [C(RESULT_MISS)] = 0x0a,
                },
                [C(OP_WRITE)] = {
                        [C(RESULT_ACCESS)] = CACHE_OP_UNSUPPORTED,
                        [C(RESULT_MISS)] = CACHE_OP_UNSUPPORTED,
                },
                [C(OP_PREFETCH)] = {
                        [C(RESULT_ACCESS)] = CACHE_OP_UNSUPPORTED,
                        [C(RESULT_MISS)] = CACHE_OP_UNSUPPORTED,
                },
        },
        [C(LL)] = {
                [C(OP_READ)] = {
                        [C(RESULT_ACCESS)] = CACHE_OP_UNSUPPORTED,
                        [C(RESULT_MISS)] = CACHE_OP_UNSUPPORTED,
                },
                [C(OP_WRITE)] = {
                        [C(RESULT_ACCESS)] = CACHE_OP_UNSUPPORTED,
                        [C(RESULT_MISS)] = CACHE_OP_UNSUPPORTED,
                },
                [C(OP_PREFETCH)] = {
                        [C(RESULT_ACCESS)] = CACHE_OP_UNSUPPORTED,
                        [C(RESULT_MISS)] = CACHE_OP_UNSUPPORTED,
                },
        },
        [C(DTLB)] = {
                [C(OP_READ)] = {
                        [C(RESULT_ACCESS)] = 0xd0,
                        [C(RESULT_MISS)] = 0xd2,
                },
                [C(OP_WRITE)] = {
                        [C(RESULT_ACCESS)] = 0xd4,
                        [C(RESULT_MISS)] = 0xd5,
                },
                [C(OP_PREFETCH)] = {
                        [C(RESULT_ACCESS)] = CACHE_OP_UNSUPPORTED,
                        [C(RESULT_MISS)] = CACHE_OP_UNSUPPORTED,
                },
        },
        [C(ITLB)] = {
                [C(OP_READ)] = {
                        [C(RESULT_ACCESS)] = 0xd1,
                        [C(RESULT_MISS)] = 0xd3,
                },
                [C(OP_WRITE)] = {
                        [C(RESULT_ACCESS)] = CACHE_OP_UNSUPPORTED,
                        [C(RESULT_MISS)] = CACHE_OP_UNSUPPORTED,
                },
                [C(OP_PREFETCH)] = {
                        [C(RESULT_ACCESS)] = CACHE_OP_UNSUPPORTED,
                        [C(RESULT_MISS)] = CACHE_OP_UNSUPPORTED,
                },
        },
        [C(BPU)] = {
                [C(OP_READ)] = {
                        [C(RESULT_ACCESS)] = CACHE_OP_UNSUPPORTED,
                        [C(RESULT_MISS)] = CACHE_OP_UNSUPPORTED,
                },
                [C(OP_WRITE)] = {
                        [C(RESULT_ACCESS)] = CACHE_OP_UNSUPPORTED,
                        [C(RESULT_MISS)] = CACHE_OP_UNSUPPORTED,
                },
                [C(OP_PREFETCH)] = {
                        [C(RESULT_ACCESS)] = CACHE_OP_UNSUPPORTED,
                        [C(RESULT_MISS)] = CACHE_OP_UNSUPPORTED,
                },
        },
        [C(NODE)] = {
                [C(OP_READ)] = {
                        [C(RESULT_ACCESS)] = CACHE_OP_UNSUPPORTED,
                        [C(RESULT_MISS)] = CACHE_OP_UNSUPPORTED,
                },
                [C(OP_WRITE)] = {
                        [C(RESULT_ACCESS)] = CACHE_OP_UNSUPPORTED,
                        [C(RESULT_MISS)] = CACHE_OP_UNSUPPORTED,
                },
                [C(OP_PREFETCH)] = {
                        [C(RESULT_ACCESS)] = CACHE_OP_UNSUPPORTED,
                        [C(RESULT_MISS)] = CACHE_OP_UNSUPPORTED,
                },
        },
};


static void _hw_perf_event_destroy(struct perf_event *event)
{
        atomic_t *active_events = &metag_pmu->active_events;
        struct mutex *pmu_mutex = &metag_pmu->reserve_mutex;

        if (atomic_dec_and_mutex_lock(active_events, pmu_mutex)) {
                release_pmu_hardware();
                mutex_unlock(pmu_mutex);
        }
}

static int _hw_perf_cache_event(int config, int *evp)
{
        unsigned long type, op, result;
        int ev;

        if (!metag_pmu->cache_events)
                return -EINVAL;

        /* Unpack config */
        type = config & 0xff;
        op = (config >> 8) & 0xff;
        result = (config >> 16) & 0xff;

        if (type >= PERF_COUNT_HW_CACHE_MAX ||
                        op >= PERF_COUNT_HW_CACHE_OP_MAX ||
                        result >= PERF_COUNT_HW_CACHE_RESULT_MAX)
                return -EINVAL;

        ev = (*metag_pmu->cache_events)[type][op][result];
        if (ev == 0)
                return -EOPNOTSUPP;
        if (ev == -1)
                return -EINVAL;
        *evp = ev;
        return 0;
}

static int _hw_perf_event_init(struct perf_event *event)
{
        struct perf_event_attr *attr = &event->attr;
        struct hw_perf_event *hwc = &event->hw;
        int mapping = 0, err;

        switch (attr->type) {
        case PERF_TYPE_HARDWARE:
                if (attr->config >= PERF_COUNT_HW_MAX)
                        return -EINVAL;

                mapping = metag_pmu->event_map(attr->config);
                break;

        case PERF_TYPE_HW_CACHE:
                err = _hw_perf_cache_event(attr->config, &mapping);
                if (err)
                        return err;
                break;

        case PERF_TYPE_RAW:
                mapping = attr->config;
                break;
        }

        /* Return early if the event is unsupported */
        if (mapping == -1)
                return -EINVAL;

        /*
         * Early cores have "limited" counters - they have no overflow
         * interrupts - and so are unable to do sampling without extra work
         * and timer assistance.
         */
        if (metag_pmu->max_period == 0) {
                if (hwc->sample_period)
                        return -EINVAL;
        }

        /*
         * Don't assign an index until the event is placed into the hardware.
         * -1 signifies that we're still deciding where to put it. On SMP
         * systems each core has its own set of counters, so we can't do any
         * constraint checking yet.
         */
        hwc->idx = -1;

        /* Store the event encoding */
        hwc->config |= (unsigned long)mapping;

        /*
         * For non-sampling runs, limit the sample_period to half of the
         * counter width. This way, the new counter value should be less
         * likely to overtake the previous one (unless there are IRQ latency
         * issues...)
         */
        if (metag_pmu->max_period) {
                if (!hwc->sample_period) {
                        hwc->sample_period = metag_pmu->max_period >> 1;
                        hwc->last_period = hwc->sample_period;
                        local64_set(&hwc->period_left, hwc->sample_period);
                }
        }

        return 0;
}

static void metag_pmu_enable_counter(struct hw_perf_event *event, int idx)
{
        struct cpu_hw_events *events = &__get_cpu_var(cpu_hw_events);
        unsigned int config = event->config;
        unsigned int tmp = config & 0xf0;
        unsigned long flags;

        raw_spin_lock_irqsave(&events->pmu_lock, flags);

        /*
         * Check if we're enabling the instruction counter (index of
         * MAX_HWEVENTS - 1)
         */
        if (METAG_INST_COUNTER == idx) {
                WARN_ONCE((config != 0x100),
                        "invalid configuration (%d) for counter (%d)\n",
                        config, idx);
                local64_set(&event->prev_count, __core_reg_get(TXTACTCYC));
                goto unlock;
        }

        /* Check for a core internal or performance channel event. */
        if (tmp) {
                void *perf_addr;

                /*
                 * Anything other than a cycle count will write the low-
                 * nibble to the correct counter register.
                 */
                switch (tmp) {
                case 0xd0:
                        perf_addr = (void *)PERF_ICORE(idx);
                        break;

                case 0xf0:
                        perf_addr = (void *)PERF_CHAN(idx);
                        break;

                default:
                        perf_addr = NULL;
                        break;
                }

                if (perf_addr)
                        metag_out32((config & 0x0f), perf_addr);

                /*
                 * Now we use the high nibble as the performance event to
                 * to count.
                 */
                config = tmp >> 4;
        }

        tmp = ((config & 0xf) << 28) |
                        ((1 << 24) << hard_processor_id());
        if (metag_pmu->max_period)
                /*
                 * Cores supporting overflow interrupts may have had the counter
                 * set to a specific value that needs preserving.
                 */
                tmp |= metag_in32(PERF_COUNT(idx)) & 0x00ffffff;
        else
                /*
                 * Older cores reset the counter on write, so prev_count needs
                 * resetting too so we can calculate a correct delta.
                 */
                local64_set(&event->prev_count, 0);

        metag_out32(tmp, PERF_COUNT(idx));
unlock:
        raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static void metag_pmu_disable_counter(struct hw_perf_event *event, int idx)
{
        struct cpu_hw_events *events = &__get_cpu_var(cpu_hw_events);
        unsigned int tmp = 0;
        unsigned long flags;

        /*
         * The cycle counter can't be disabled per se, as it's a hardware
         * thread register which is always counting. We merely return if this
         * is the counter we're attempting to disable.
         */
        if (METAG_INST_COUNTER == idx)
                return;

        /*
         * The counter value _should_ have been read prior to disabling,
         * as if we're running on an early core then the value gets reset to
         * 0, and any read after that would be useless. On the newer cores,
         * however, it's better to read-modify-update this for purposes of
         * the overflow interrupt.
         * Here we remove the thread id AND the event nibble (there are at
         * least two events that count events that are core global and ignore
         * the thread id mask). This only works because we don't mix thread
         * performance counts, and event 0x00 requires a thread id mask!
         */
        raw_spin_lock_irqsave(&events->pmu_lock, flags);

        tmp = metag_in32(PERF_COUNT(idx));
        tmp &= 0x00ffffff;
        metag_out32(tmp, PERF_COUNT(idx));

        raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static u64 metag_pmu_read_counter(int idx)
{
        u32 tmp = 0;

        if (METAG_INST_COUNTER == idx) {
                tmp = __core_reg_get(TXTACTCYC);
                goto out;
        }

        tmp = metag_in32(PERF_COUNT(idx)) & 0x00ffffff;
out:
        return tmp;
}

static void metag_pmu_write_counter(int idx, u32 val)
{
        struct cpu_hw_events *events = &__get_cpu_var(cpu_hw_events);
        u32 tmp = 0;
        unsigned long flags;

        /*
         * This _shouldn't_ happen, but if it does, then we can just
         * ignore the write, as the register is read-only and clear-on-write.
         */
        if (METAG_INST_COUNTER == idx)
                return;

        /*
         * We'll keep the thread mask and event id, and just update the
         * counter itself. Also , we should bound the value to 24-bits.
         */
        raw_spin_lock_irqsave(&events->pmu_lock, flags);

        val &= 0x00ffffff;
        tmp = metag_in32(PERF_COUNT(idx)) & 0xff000000;
        val |= tmp;
        metag_out32(val, PERF_COUNT(idx));

        raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}

static int metag_pmu_event_map(int idx)
{
        return metag_general_events[idx];
}

static irqreturn_t metag_pmu_counter_overflow(int irq, void *dev)
{
        int idx = (int)dev;
        struct cpu_hw_events *cpuhw = &__get_cpu_var(cpu_hw_events);
        struct perf_event *event = cpuhw->events[idx];
        struct hw_perf_event *hwc = &event->hw;
        struct pt_regs *regs = get_irq_regs();
        struct perf_sample_data sampledata;
        unsigned long flags;
        u32 counter = 0;

        /*
         * We need to stop the core temporarily from generating another
         * interrupt while we disable this counter. However, we don't want
         * to flag the counter as free
         */
        __global_lock2(flags);
        counter = metag_in32(PERF_COUNT(idx));
        metag_out32((counter & 0x00ffffff), PERF_COUNT(idx));
        __global_unlock2(flags);

        /* Update the counts and reset the sample period */
        metag_pmu_event_update(event, hwc, idx);
        perf_sample_data_init(&sampledata, 0, hwc->last_period);
        metag_pmu_event_set_period(event, hwc, idx);

        /*
         * Enable the counter again once core overflow processing has
         * completed. Note the counter value may have been modified while it was
         * inactive to set it up ready for the next interrupt.
         */
        if (!perf_event_overflow(event, &sampledata, regs)) {
                __global_lock2(flags);
                counter = (counter & 0xff000000) |
                          (metag_in32(PERF_COUNT(idx)) & 0x00ffffff);
                metag_out32(counter, PERF_COUNT(idx));
                __global_unlock2(flags);
        }

        return IRQ_HANDLED;
}

static struct metag_pmu _metag_pmu = {
        .handle_irq     = metag_pmu_counter_overflow,
        .enable         = metag_pmu_enable_counter,
        .disable        = metag_pmu_disable_counter,
        .read           = metag_pmu_read_counter,
        .write          = metag_pmu_write_counter,
        .event_map      = metag_pmu_event_map,
        .cache_events   = &metag_pmu_cache_events,
        .max_period     = MAX_PERIOD,
        .max_events     = MAX_HWEVENTS,
};

/* PMU CPU hotplug notifier */
static int metag_pmu_cpu_notify(struct notifier_block *b, unsigned long action,
                                void *hcpu)
{
        unsigned int cpu = (unsigned int)hcpu;
        struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);

        if ((action & ~CPU_TASKS_FROZEN) != CPU_STARTING)
                return NOTIFY_DONE;

        memset(cpuc, 0, sizeof(struct cpu_hw_events));
        raw_spin_lock_init(&cpuc->pmu_lock);

        return NOTIFY_OK;
}

static struct notifier_block metag_pmu_notifier = {
        .notifier_call = metag_pmu_cpu_notify,
};

/* PMU Initialisation */
static int __init init_hw_perf_events(void)
{
        int ret = 0, cpu;
        u32 version = *(u32 *)METAC_ID;
        int major = (version & METAC_ID_MAJOR_BITS) >> METAC_ID_MAJOR_S;
        int min_rev = (version & (METAC_ID_MINOR_BITS | METAC_ID_REV_BITS))
                        >> METAC_ID_REV_S;

        /* Not a Meta 2 core, then not supported */
        if (0x02 > major) {
                pr_info("no hardware counter support available\n");
                goto out;
        } else if (0x02 == major) {
                metag_pmu = &_metag_pmu;

                if (min_rev < 0x0104) {
                        /*
                         * A core without overflow interrupts, and clear-on-
                         * write counters.
                         */
                        metag_pmu->handle_irq = NULL;
                        metag_pmu->write = NULL;
                        metag_pmu->max_period = 0;
                }

                metag_pmu->name = "meta2";
                metag_pmu->version = version;
                metag_pmu->pmu = pmu;
        }

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

        /* Initialise the active events and reservation mutex */
        atomic_set(&metag_pmu->active_events, 0);
        mutex_init(&metag_pmu->reserve_mutex);

        /* Clear the counters */
        metag_out32(0, PERF_COUNT(0));
        metag_out32(0, PERF_COUNT(1));

        for_each_possible_cpu(cpu) {
                struct cpu_hw_events *cpuc = &per_cpu(cpu_hw_events, cpu);

                memset(cpuc, 0, sizeof(struct cpu_hw_events));
                raw_spin_lock_init(&cpuc->pmu_lock);
        }

        register_cpu_notifier(&metag_pmu_notifier);
        ret = perf_pmu_register(&pmu, metag_pmu->name, PERF_TYPE_RAW);
out:
        return ret;
}
early_initcall(init_hw_perf_events);