/*
 * Performance event support framework for SuperH hardware counters.
 *
 *  Copyright (C) 2009  Paul Mundt
 *
 * Heavily based on the x86 and PowerPC implementations.
 *
 * x86:
 *  Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
 *  Copyright (C) 2008-2009 Red Hat, Inc., Ingo Molnar
 *  Copyright (C) 2009 Jaswinder Singh Rajput
 *  Copyright (C) 2009 Advanced Micro Devices, Inc., Robert Richter
 *  Copyright (C) 2008-2009 Red Hat, Inc., Peter Zijlstra
 *  Copyright (C) 2009 Intel Corporation, <markus.t.metzger@intel.com>
 *
 * ppc:
 *  Copyright 2008-2009 Paul Mackerras, IBM Corporation.
 *
 * 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/kernel.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/irq.h>
#include <linux/perf_event.h>
#include <linux/export.h>
#include <asm/processor.h>

struct cpu_hw_events {
        struct perf_event       *events[MAX_HWEVENTS];
        unsigned long           used_mask[BITS_TO_LONGS(MAX_HWEVENTS)];
        unsigned long           active_mask[BITS_TO_LONGS(MAX_HWEVENTS)];
};

DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events);

static struct sh_pmu *sh_pmu __read_mostly;

/* Number of perf_events counting hardware events */
static atomic_t num_events;
/* Used to avoid races in calling reserve/release_pmc_hardware */
static DEFINE_MUTEX(pmc_reserve_mutex);

/*
 * Stub these out for now, do something more profound later.
 */
int reserve_pmc_hardware(void)
{
        return 0;
}

void release_pmc_hardware(void)
{
}

static inline int sh_pmu_initialized(void)
{
        return !!sh_pmu;
}

const char *perf_pmu_name(void)
{
        if (!sh_pmu)
                return NULL;

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

int perf_num_counters(void)
{
        if (!sh_pmu)
                return 0;

        return sh_pmu->num_events;
}
EXPORT_SYMBOL_GPL(perf_num_counters);

/*
 * Release the PMU if this is the last perf_event.
 */
static void hw_perf_event_destroy(struct perf_event *event)
{
        if (!atomic_add_unless(&num_events, -1, 1)) {
                mutex_lock(&pmc_reserve_mutex);
                if (atomic_dec_return(&num_events) == 0)
                        release_pmc_hardware();
                mutex_unlock(&pmc_reserve_mutex);
        }
}

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

        if (!sh_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 = (*sh_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 config = -1;
        int err;

        if (!sh_pmu_initialized())
                return -ENODEV;

        /*
         * See if we need to reserve the counter.
         *
         * If no events are currently in use, then we have to take a
         * mutex to ensure that we don't race with another task doing
         * reserve_pmc_hardware or release_pmc_hardware.
         */
        err = 0;
        if (!atomic_inc_not_zero(&num_events)) {
                mutex_lock(&pmc_reserve_mutex);
                if (atomic_read(&num_events) == 0 &&
                    reserve_pmc_hardware())
                        err = -EBUSY;
                else
                        atomic_inc(&num_events);
                mutex_unlock(&pmc_reserve_mutex);
        }

        if (err)
                return err;

        event->destroy = hw_perf_event_destroy;

        switch (attr->type) {
        case PERF_TYPE_RAW:
                config = attr->config & sh_pmu->raw_event_mask;
                break;
        case PERF_TYPE_HW_CACHE:
                err = hw_perf_cache_event(attr->config, &config);
                if (err)
                        return err;
                break;
        case PERF_TYPE_HARDWARE:
                if (attr->config >= sh_pmu->max_events)
                        return -EINVAL;

                config = sh_pmu->event_map(attr->config);
                break;
        }

        if (config == -1)
                return -EINVAL;

        hwc->config |= config;

        return 0;
}

static void sh_perf_event_update(struct perf_event *event,
                                   struct hw_perf_event *hwc, int idx)
{
        u64 prev_raw_count, new_raw_count;
        s64 delta;
        int shift = 0;

        /*
         * Depending on the counter configuration, they may or may not
         * be chained, in which case the previous counter value can be
         * updated underneath us if the lower-half overflows.
         *
         * Our tactic to handle this is to first atomically read and
         * exchange a new raw count - then add that new-prev delta
         * count to the generic counter atomically.
         *
         * As there is no interrupt associated with the overflow events,
         * this is the simplest approach for maintaining consistency.
         */
again:
        prev_raw_count = local64_read(&hwc->prev_count);
        new_raw_count = sh_pmu->read(idx);

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

        /*
         * Now we have the new raw value and have updated the prev
         * timestamp already. We can now calculate the elapsed delta
         * (counter-)time and add that to the generic counter.
         *
         * Careful, not all hw sign-extends above the physical width
         * of the count.
         */
        delta = (new_raw_count << shift) - (prev_raw_count << shift);
        delta >>= shift;

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

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

        if (!(event->hw.state & PERF_HES_STOPPED)) {
                sh_pmu->disable(hwc, idx);
                cpuc->events[idx] = NULL;
                event->hw.state |= PERF_HES_STOPPED;
        }

        if ((flags & PERF_EF_UPDATE) && !(event->hw.state & PERF_HES_UPTODATE)) {
                sh_perf_event_update(event, &event->hw, idx);
                event->hw.state |= PERF_HES_UPTODATE;
        }
}

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

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

        if (flags & PERF_EF_RELOAD)
                WARN_ON_ONCE(!(event->hw.state & PERF_HES_UPTODATE));

        cpuc->events[idx] = event;
        event->hw.state = 0;
        sh_pmu->enable(hwc, idx);
}

static void sh_pmu_del(struct perf_event *event, int flags)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);

        sh_pmu_stop(event, PERF_EF_UPDATE);
        __clear_bit(event->hw.idx, cpuc->used_mask);

        perf_event_update_userpage(event);
}

static int sh_pmu_add(struct perf_event *event, int flags)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
        struct hw_perf_event *hwc = &event->hw;
        int idx = hwc->idx;
        int ret = -EAGAIN;

        perf_pmu_disable(event->pmu);

        if (__test_and_set_bit(idx, cpuc->used_mask)) {
                idx = find_first_zero_bit(cpuc->used_mask, sh_pmu->num_events);
                if (idx == sh_pmu->num_events)
                        goto out;

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

        sh_pmu->disable(hwc, idx);

        event->hw.state = PERF_HES_UPTODATE | PERF_HES_STOPPED;
        if (flags & PERF_EF_START)
                sh_pmu_start(event, PERF_EF_RELOAD);

        perf_event_update_userpage(event);
        ret = 0;
out:
        perf_pmu_enable(event->pmu);
        return ret;
}

static void sh_pmu_read(struct perf_event *event)
{
        sh_perf_event_update(event, &event->hw, event->hw.idx);
}

static int sh_pmu_event_init(struct perf_event *event)
{
        int err;

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

        switch (event->attr.type) {
        case PERF_TYPE_RAW:
        case PERF_TYPE_HW_CACHE:
        case PERF_TYPE_HARDWARE:
                err = __hw_perf_event_init(event);
                break;

        default:
                return -ENOENT;
        }

        if (unlikely(err)) {
                if (event->destroy)
                        event->destroy(event);
        }

        return err;
}

static void sh_pmu_enable(struct pmu *pmu)
{
        if (!sh_pmu_initialized())
                return;

        sh_pmu->enable_all();
}

static void sh_pmu_disable(struct pmu *pmu)
{
        if (!sh_pmu_initialized())
                return;

        sh_pmu->disable_all();
}

static struct pmu pmu = {
        .pmu_enable     = sh_pmu_enable,
        .pmu_disable    = sh_pmu_disable,
        .event_init     = sh_pmu_event_init,
        .add            = sh_pmu_add,
        .del            = sh_pmu_del,
        .start          = sh_pmu_start,
        .stop           = sh_pmu_stop,
        .read           = sh_pmu_read,
};

static int sh_pmu_prepare_cpu(unsigned int cpu)
{
        struct cpu_hw_events *cpuhw = &per_cpu(cpu_hw_events, cpu);

        memset(cpuhw, 0, sizeof(struct cpu_hw_events));
        return 0;
}

int register_sh_pmu(struct sh_pmu *_pmu)
{
        if (sh_pmu)
                return -EBUSY;
        sh_pmu = _pmu;

        pr_info("Performance Events: %s support registered\n", _pmu->name);

        /*
         * All of the on-chip counters are "limited", in that they have
         * no interrupts, and are therefore unable to do sampling without
         * further work and timer assistance.
         */
        pmu.capabilities |= PERF_PMU_CAP_NO_INTERRUPT;

        WARN_ON(_pmu->num_events > MAX_HWEVENTS);

        perf_pmu_register(&pmu, "cpu", PERF_TYPE_RAW);
        cpuhp_setup_state(CPUHP_PERF_SUPERH, "PERF_SUPERH", sh_pmu_prepare_cpu,
                          NULL);
        return 0;
}