// SPDX-License-Identifier: GPL-2.0
/*
 * Hardware performance events for the Alpha.
 *
 * We implement HW counts on the EV67 and subsequent CPUs only.
 *
 * (C) 2010 Michael J. Cree
 *
 * Somewhat based on the Sparc code, and to a lesser extent the PowerPC and
 * ARM code, which are copyright by their respective authors.
 */

#include <linux/perf_event.h>
#include <linux/kprobes.h>
#include <linux/kernel.h>
#include <linux/kdebug.h>
#include <linux/mutex.h>
#include <linux/init.h>

#include <asm/hwrpb.h>
#include <linux/atomic.h>
#include <asm/irq.h>
#include <asm/irq_regs.h>
#include <asm/pal.h>
#include <asm/wrperfmon.h>
#include <asm/hw_irq.h>


/* The maximum number of PMCs on any Alpha CPU whatsoever. */
#define MAX_HWEVENTS 3
#define PMC_NO_INDEX -1

/* For tracking PMCs and the hw events they monitor on each CPU. */
struct cpu_hw_events {
        int                     enabled;
        /* Number of events scheduled; also number entries valid in arrays below. */
        int                     n_events;
        /* Number events added since last hw_perf_disable(). */
        int                     n_added;
        /* Events currently scheduled. */
        struct perf_event       *event[MAX_HWEVENTS];
        /* Event type of each scheduled event. */
        unsigned long           evtype[MAX_HWEVENTS];
        /* Current index of each scheduled event; if not yet determined
         * contains PMC_NO_INDEX.
         */
        int                     current_idx[MAX_HWEVENTS];
        /* The active PMCs' config for easy use with wrperfmon(). */
        unsigned long           config;
        /* The active counters' indices for easy use with wrperfmon(). */
        unsigned long           idx_mask;
};
DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events);



/*
 * A structure to hold the description of the PMCs available on a particular
 * type of Alpha CPU.
 */
struct alpha_pmu_t {
        /* Mapping of the perf system hw event types to indigenous event types */
        const int *event_map;
        /* The number of entries in the event_map */
        int  max_events;
        /* The number of PMCs on this Alpha */
        int  num_pmcs;
        /*
         * All PMC counters reside in the IBOX register PCTR.  This is the
         * LSB of the counter.
         */
        int  pmc_count_shift[MAX_HWEVENTS];
        /*
         * The mask that isolates the PMC bits when the LSB of the counter
         * is shifted to bit 0.
         */
        unsigned long pmc_count_mask[MAX_HWEVENTS];
        /* The maximum period the PMC can count. */
        unsigned long pmc_max_period[MAX_HWEVENTS];
        /*
         * The maximum value that may be written to the counter due to
         * hardware restrictions is pmc_max_period - pmc_left.
         */
        long pmc_left[3];
         /* Subroutine for allocation of PMCs.  Enforces constraints. */
        int (*check_constraints)(struct perf_event **, unsigned long *, int);
        /* Subroutine for checking validity of a raw event for this PMU. */
        int (*raw_event_valid)(u64 config);
};

/*
 * The Alpha CPU PMU description currently in operation.  This is set during
 * the boot process to the specific CPU of the machine.
 */
static const struct alpha_pmu_t *alpha_pmu;


#define HW_OP_UNSUPPORTED -1

/*
 * The hardware description of the EV67, EV68, EV69, EV7 and EV79 PMUs
 * follow. Since they are identical we refer to them collectively as the
 * EV67 henceforth.
 */

/*
 * EV67 PMC event types
 *
 * There is no one-to-one mapping of the possible hw event types to the
 * actual codes that are used to program the PMCs hence we introduce our
 * own hw event type identifiers.
 */
enum ev67_pmc_event_type {
        EV67_CYCLES = 1,
        EV67_INSTRUCTIONS,
        EV67_BCACHEMISS,
        EV67_MBOXREPLAY,
        EV67_LAST_ET
};
#define EV67_NUM_EVENT_TYPES (EV67_LAST_ET-EV67_CYCLES)


/* Mapping of the hw event types to the perf tool interface */
static const int ev67_perfmon_event_map[] = {
        [PERF_COUNT_HW_CPU_CYCLES]       = EV67_CYCLES,
        [PERF_COUNT_HW_INSTRUCTIONS]     = EV67_INSTRUCTIONS,
        [PERF_COUNT_HW_CACHE_REFERENCES] = HW_OP_UNSUPPORTED,
        [PERF_COUNT_HW_CACHE_MISSES]     = EV67_BCACHEMISS,
};

struct ev67_mapping_t {
        int config;
        int idx;
};

/*
 * The mapping used for one event only - these must be in same order as enum
 * ev67_pmc_event_type definition.
 */
static const struct ev67_mapping_t ev67_mapping[] = {
        {EV67_PCTR_INSTR_CYCLES, 1},     /* EV67_CYCLES, */
        {EV67_PCTR_INSTR_CYCLES, 0},     /* EV67_INSTRUCTIONS */
        {EV67_PCTR_INSTR_BCACHEMISS, 1}, /* EV67_BCACHEMISS */
        {EV67_PCTR_CYCLES_MBOX, 1}       /* EV67_MBOXREPLAY */
};


/*
 * Check that a group of events can be simultaneously scheduled on to the
 * EV67 PMU.  Also allocate counter indices and config.
 */
static int ev67_check_constraints(struct perf_event **event,
                                unsigned long *evtype, int n_ev)
{
        int idx0;
        unsigned long config;

        idx0 = ev67_mapping[evtype[0]-1].idx;
        config = ev67_mapping[evtype[0]-1].config;
        if (n_ev == 1)
                goto success;

        BUG_ON(n_ev != 2);

        if (evtype[0] == EV67_MBOXREPLAY || evtype[1] == EV67_MBOXREPLAY) {
                /* MBOX replay traps must be on PMC 1 */
                idx0 = (evtype[0] == EV67_MBOXREPLAY) ? 1 : 0;
                /* Only cycles can accompany MBOX replay traps */
                if (evtype[idx0] == EV67_CYCLES) {
                        config = EV67_PCTR_CYCLES_MBOX;
                        goto success;
                }
        }

        if (evtype[0] == EV67_BCACHEMISS || evtype[1] == EV67_BCACHEMISS) {
                /* Bcache misses must be on PMC 1 */
                idx0 = (evtype[0] == EV67_BCACHEMISS) ? 1 : 0;
                /* Only instructions can accompany Bcache misses */
                if (evtype[idx0] == EV67_INSTRUCTIONS) {
                        config = EV67_PCTR_INSTR_BCACHEMISS;
                        goto success;
                }
        }

        if (evtype[0] == EV67_INSTRUCTIONS || evtype[1] == EV67_INSTRUCTIONS) {
                /* Instructions must be on PMC 0 */
                idx0 = (evtype[0] == EV67_INSTRUCTIONS) ? 0 : 1;
                /* By this point only cycles can accompany instructions */
                if (evtype[idx0^1] == EV67_CYCLES) {
                        config = EV67_PCTR_INSTR_CYCLES;
                        goto success;
                }
        }

        /* Otherwise, darn it, there is a conflict.  */
        return -1;

success:
        event[0]->hw.idx = idx0;
        event[0]->hw.config_base = config;
        if (n_ev == 2) {
                event[1]->hw.idx = idx0 ^ 1;
                event[1]->hw.config_base = config;
        }
        return 0;
}


static int ev67_raw_event_valid(u64 config)
{
        return config >= EV67_CYCLES && config < EV67_LAST_ET;
};


static const struct alpha_pmu_t ev67_pmu = {
        .event_map = ev67_perfmon_event_map,
        .max_events = ARRAY_SIZE(ev67_perfmon_event_map),
        .num_pmcs = 2,
        .pmc_count_shift = {EV67_PCTR_0_COUNT_SHIFT, EV67_PCTR_1_COUNT_SHIFT, 0},
        .pmc_count_mask = {EV67_PCTR_0_COUNT_MASK,  EV67_PCTR_1_COUNT_MASK,  0},
        .pmc_max_period = {(1UL<<20) - 1, (1UL<<20) - 1, 0},
        .pmc_left = {16, 4, 0},
        .check_constraints = ev67_check_constraints,
        .raw_event_valid = ev67_raw_event_valid,
};



/*
 * Helper routines to ensure that we read/write only the correct PMC bits
 * when calling the wrperfmon PALcall.
 */
static inline void alpha_write_pmc(int idx, unsigned long val)
{
        val &= alpha_pmu->pmc_count_mask[idx];
        val <<= alpha_pmu->pmc_count_shift[idx];
        val |= (1<<idx);
        wrperfmon(PERFMON_CMD_WRITE, val);
}

static inline unsigned long alpha_read_pmc(int idx)
{
        unsigned long val;

        val = wrperfmon(PERFMON_CMD_READ, 0);
        val >>= alpha_pmu->pmc_count_shift[idx];
        val &= alpha_pmu->pmc_count_mask[idx];
        return val;
}

/* Set a new period to sample over */
static int alpha_perf_event_set_period(struct perf_event *event,
                                struct hw_perf_event *hwc, int idx)
{
        long left = local64_read(&hwc->period_left);
        long 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;
        }

        /*
         * Hardware restrictions require that the counters must not be
         * written with values that are too close to the maximum period.
         */
        if (unlikely(left < alpha_pmu->pmc_left[idx]))
                left = alpha_pmu->pmc_left[idx];

        if (left > (long)alpha_pmu->pmc_max_period[idx])
                left = alpha_pmu->pmc_max_period[idx];

        local64_set(&hwc->prev_count, (unsigned long)(-left));

        alpha_write_pmc(idx, (unsigned long)(-left));

        perf_event_update_userpage(event);

        return ret;
}


/*
 * Calculates the count (the 'delta') since the last time the PMC was read.
 *
 * As the PMCs' full period can easily be exceeded within the perf system
 * sampling period we cannot use any high order bits as a guard bit in the
 * PMCs to detect overflow as is done by other architectures.  The code here
 * calculates the delta on the basis that there is no overflow when ovf is
 * zero.  The value passed via ovf by the interrupt handler corrects for
 * overflow.
 *
 * This can be racey on rare occasions -- a call to this routine can occur
 * with an overflowed counter just before the PMI service routine is called.
 * The check for delta negative hopefully always rectifies this situation.
 */
static unsigned long alpha_perf_event_update(struct perf_event *event,
                                        struct hw_perf_event *hwc, int idx, long ovf)
{
        long prev_raw_count, new_raw_count;
        long delta;

again:
        prev_raw_count = local64_read(&hwc->prev_count);
        new_raw_count = alpha_read_pmc(idx);

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

        delta = (new_raw_count - (prev_raw_count & alpha_pmu->pmc_count_mask[idx])) + ovf;

        /* It is possible on very rare occasions that the PMC has overflowed
         * but the interrupt is yet to come.  Detect and fix this situation.
         */
        if (unlikely(delta < 0)) {
                delta += alpha_pmu->pmc_max_period[idx] + 1;
        }

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

        return new_raw_count;
}


/*
 * Collect all HW events into the array event[].
 */
static int collect_events(struct perf_event *group, int max_count,
                          struct perf_event *event[], unsigned long *evtype,
                          int *current_idx)
{
        struct perf_event *pe;
        int n = 0;

        if (!is_software_event(group)) {
                if (n >= max_count)
                        return -1;
                event[n] = group;
                evtype[n] = group->hw.event_base;
                current_idx[n++] = PMC_NO_INDEX;
        }
        for_each_sibling_event(pe, group) {
                if (!is_software_event(pe) && pe->state != PERF_EVENT_STATE_OFF) {
                        if (n >= max_count)
                                return -1;
                        event[n] = pe;
                        evtype[n] = pe->hw.event_base;
                        current_idx[n++] = PMC_NO_INDEX;
                }
        }
        return n;
}



/*
 * Check that a group of events can be simultaneously scheduled on to the PMU.
 */
static int alpha_check_constraints(struct perf_event **events,
                                   unsigned long *evtypes, int n_ev)
{

        /* No HW events is possible from hw_perf_group_sched_in(). */
        if (n_ev == 0)
                return 0;

        if (n_ev > alpha_pmu->num_pmcs)
                return -1;

        return alpha_pmu->check_constraints(events, evtypes, n_ev);
}


/*
 * If new events have been scheduled then update cpuc with the new
 * configuration.  This may involve shifting cycle counts from one PMC to
 * another.
 */
static void maybe_change_configuration(struct cpu_hw_events *cpuc)
{
        int j;

        if (cpuc->n_added == 0)
                return;

        /* Find counters that are moving to another PMC and update */
        for (j = 0; j < cpuc->n_events; j++) {
                struct perf_event *pe = cpuc->event[j];

                if (cpuc->current_idx[j] != PMC_NO_INDEX &&
                        cpuc->current_idx[j] != pe->hw.idx) {
                        alpha_perf_event_update(pe, &pe->hw, cpuc->current_idx[j], 0);
                        cpuc->current_idx[j] = PMC_NO_INDEX;
                }
        }

        /* Assign to counters all unassigned events. */
        cpuc->idx_mask = 0;
        for (j = 0; j < cpuc->n_events; j++) {
                struct perf_event *pe = cpuc->event[j];
                struct hw_perf_event *hwc = &pe->hw;
                int idx = hwc->idx;

                if (cpuc->current_idx[j] == PMC_NO_INDEX) {
                        alpha_perf_event_set_period(pe, hwc, idx);
                        cpuc->current_idx[j] = idx;
                }

                if (!(hwc->state & PERF_HES_STOPPED))
                        cpuc->idx_mask |= (1<<cpuc->current_idx[j]);
        }
        cpuc->config = cpuc->event[0]->hw.config_base;
}



/* Schedule perf HW event on to PMU.
 *  - this function is called from outside this module via the pmu struct
 *    returned from perf event initialisation.
 */
static int alpha_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 n0;
        int ret;
        unsigned long irq_flags;

        /*
         * The Sparc code has the IRQ disable first followed by the perf
         * disable, however this can lead to an overflowed counter with the
         * PMI disabled on rare occasions.  The alpha_perf_event_update()
         * routine should detect this situation by noting a negative delta,
         * nevertheless we disable the PMCs first to enable a potential
         * final PMI to occur before we disable interrupts.
         */
        perf_pmu_disable(event->pmu);
        local_irq_save(irq_flags);

        /* Default to error to be returned */
        ret = -EAGAIN;

        /* Insert event on to PMU and if successful modify ret to valid return */
        n0 = cpuc->n_events;
        if (n0 < alpha_pmu->num_pmcs) {
                cpuc->event[n0] = event;
                cpuc->evtype[n0] = event->hw.event_base;
                cpuc->current_idx[n0] = PMC_NO_INDEX;

                if (!alpha_check_constraints(cpuc->event, cpuc->evtype, n0+1)) {
                        cpuc->n_events++;
                        cpuc->n_added++;
                        ret = 0;
                }
        }

        hwc->state = PERF_HES_UPTODATE;
        if (!(flags & PERF_EF_START))
                hwc->state |= PERF_HES_STOPPED;

        local_irq_restore(irq_flags);
        perf_pmu_enable(event->pmu);

        return ret;
}



/* Disable performance monitoring unit
 *  - this function is called from outside this module via the pmu struct
 *    returned from perf event initialisation.
 */
static void alpha_pmu_del(struct perf_event *event, int flags)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
        struct hw_perf_event *hwc = &event->hw;
        unsigned long irq_flags;
        int j;

        perf_pmu_disable(event->pmu);
        local_irq_save(irq_flags);

        for (j = 0; j < cpuc->n_events; j++) {
                if (event == cpuc->event[j]) {
                        int idx = cpuc->current_idx[j];

                        /* Shift remaining entries down into the existing
                         * slot.
                         */
                        while (++j < cpuc->n_events) {
                                cpuc->event[j - 1] = cpuc->event[j];
                                cpuc->evtype[j - 1] = cpuc->evtype[j];
                                cpuc->current_idx[j - 1] =
                                        cpuc->current_idx[j];
                        }

                        /* Absorb the final count and turn off the event. */
                        alpha_perf_event_update(event, hwc, idx, 0);
                        perf_event_update_userpage(event);

                        cpuc->idx_mask &= ~(1UL<<idx);
                        cpuc->n_events--;
                        break;
                }
        }

        local_irq_restore(irq_flags);
        perf_pmu_enable(event->pmu);
}


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

        alpha_perf_event_update(event, hwc, hwc->idx, 0);
}


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

        if (!(hwc->state & PERF_HES_STOPPED)) {
                cpuc->idx_mask &= ~(1UL<<hwc->idx);
                hwc->state |= PERF_HES_STOPPED;
        }

        if ((flags & PERF_EF_UPDATE) && !(hwc->state & PERF_HES_UPTODATE)) {
                alpha_perf_event_update(event, hwc, hwc->idx, 0);
                hwc->state |= PERF_HES_UPTODATE;
        }

        if (cpuc->enabled)
                wrperfmon(PERFMON_CMD_DISABLE, (1UL<<hwc->idx));
}


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

        if (WARN_ON_ONCE(!(hwc->state & PERF_HES_STOPPED)))
                return;

        if (flags & PERF_EF_RELOAD) {
                WARN_ON_ONCE(!(hwc->state & PERF_HES_UPTODATE));
                alpha_perf_event_set_period(event, hwc, hwc->idx);
        }

        hwc->state = 0;

        cpuc->idx_mask |= 1UL<<hwc->idx;
        if (cpuc->enabled)
                wrperfmon(PERFMON_CMD_ENABLE, (1UL<<hwc->idx));
}


/*
 * Check that CPU performance counters are supported.
 * - currently support EV67 and later CPUs.
 * - actually some later revisions of the EV6 have the same PMC model as the
 *     EV67 but we don't do suffiently deep CPU detection to detect them.
 *     Bad luck to the very few people who might have one, I guess.
 */
static int supported_cpu(void)
{
        struct percpu_struct *cpu;
        unsigned long cputype;

        /* Get cpu type from HW */
        cpu = (struct percpu_struct *)((char *)hwrpb + hwrpb->processor_offset);
        cputype = cpu->type & 0xffffffff;
        /* Include all of EV67, EV68, EV7, EV79 and EV69 as supported. */
        return (cputype >= EV67_CPU) && (cputype <= EV69_CPU);
}



static void hw_perf_event_destroy(struct perf_event *event)
{
        /* Nothing to be done! */
        return;
}



static int __hw_perf_event_init(struct perf_event *event)
{
        struct perf_event_attr *attr = &event->attr;
        struct hw_perf_event *hwc = &event->hw;
        struct perf_event *evts[MAX_HWEVENTS];
        unsigned long evtypes[MAX_HWEVENTS];
        int idx_rubbish_bin[MAX_HWEVENTS];
        int ev;
        int n;

        /* We only support a limited range of HARDWARE event types with one
         * only programmable via a RAW event type.
         */
        if (attr->type == PERF_TYPE_HARDWARE) {
                if (attr->config >= alpha_pmu->max_events)
                        return -EINVAL;
                ev = alpha_pmu->event_map[attr->config];
        } else if (attr->type == PERF_TYPE_HW_CACHE) {
                return -EOPNOTSUPP;
        } else if (attr->type == PERF_TYPE_RAW) {
                if (!alpha_pmu->raw_event_valid(attr->config))
                        return -EINVAL;
                ev = attr->config;
        } else {
                return -EOPNOTSUPP;
        }

        if (ev < 0) {
                return ev;
        }

        /*
         * We place the event type in event_base here and leave calculation
         * of the codes to programme the PMU for alpha_pmu_enable() because
         * it is only then we will know what HW events are actually
         * scheduled on to the PMU.  At that point the code to programme the
         * PMU is put into config_base and the PMC to use is placed into
         * idx.  We initialise idx (below) to PMC_NO_INDEX to indicate that
         * it is yet to be determined.
         */
        hwc->event_base = ev;

        /* Collect events in a group together suitable for calling
         * alpha_check_constraints() to verify that the group as a whole can
         * be scheduled on to the PMU.
         */
        n = 0;
        if (event->group_leader != event) {
                n = collect_events(event->group_leader,
                                alpha_pmu->num_pmcs - 1,
                                evts, evtypes, idx_rubbish_bin);
                if (n < 0)
                        return -EINVAL;
        }
        evtypes[n] = hwc->event_base;
        evts[n] = event;

        if (alpha_check_constraints(evts, evtypes, n + 1))
                return -EINVAL;

        /* Indicate that PMU config and idx are yet to be determined. */
        hwc->config_base = 0;
        hwc->idx = PMC_NO_INDEX;

        event->destroy = hw_perf_event_destroy;

        /*
         * Most architectures reserve the PMU for their use at this point.
         * As there is no existing mechanism to arbitrate usage and there
         * appears to be no other user of the Alpha PMU we just assume
         * that we can just use it, hence a NO-OP here.
         *
         * Maybe an alpha_reserve_pmu() routine should be implemented but is
         * anything else ever going to use it?
         */

        if (!hwc->sample_period) {
                hwc->sample_period = alpha_pmu->pmc_max_period[0];
                hwc->last_period = hwc->sample_period;
                local64_set(&hwc->period_left, hwc->sample_period);
        }

        return 0;
}

/*
 * Main entry point to initialise a HW performance event.
 */
static int alpha_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_HARDWARE:
        case PERF_TYPE_HW_CACHE:
                break;

        default:
                return -ENOENT;
        }

        if (!alpha_pmu)
                return -ENODEV;

        /* Do the real initialisation work. */
        err = __hw_perf_event_init(event);

        return err;
}

/*
 * Main entry point - enable HW performance counters.
 */
static void alpha_pmu_enable(struct pmu *pmu)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);

        if (cpuc->enabled)
                return;

        cpuc->enabled = 1;
        barrier();

        if (cpuc->n_events > 0) {
                /* Update cpuc with information from any new scheduled events. */
                maybe_change_configuration(cpuc);

                /* Start counting the desired events. */
                wrperfmon(PERFMON_CMD_LOGGING_OPTIONS, EV67_PCTR_MODE_AGGREGATE);
                wrperfmon(PERFMON_CMD_DESIRED_EVENTS, cpuc->config);
                wrperfmon(PERFMON_CMD_ENABLE, cpuc->idx_mask);
        }
}


/*
 * Main entry point - disable HW performance counters.
 */

static void alpha_pmu_disable(struct pmu *pmu)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);

        if (!cpuc->enabled)
                return;

        cpuc->enabled = 0;
        cpuc->n_added = 0;

        wrperfmon(PERFMON_CMD_DISABLE, cpuc->idx_mask);
}

static struct pmu pmu = {
        .pmu_enable     = alpha_pmu_enable,
        .pmu_disable    = alpha_pmu_disable,
        .event_init     = alpha_pmu_event_init,
        .add            = alpha_pmu_add,
        .del            = alpha_pmu_del,
        .start          = alpha_pmu_start,
        .stop           = alpha_pmu_stop,
        .read           = alpha_pmu_read,
        .capabilities   = PERF_PMU_CAP_NO_EXCLUDE,
};


/*
 * Main entry point - don't know when this is called but it
 * obviously dumps debug info.
 */
void perf_event_print_debug(void)
{
        unsigned long flags;
        unsigned long pcr;
        int pcr0, pcr1;
        int cpu;

        if (!supported_cpu())
                return;

        local_irq_save(flags);

        cpu = smp_processor_id();

        pcr = wrperfmon(PERFMON_CMD_READ, 0);
        pcr0 = (pcr >> alpha_pmu->pmc_count_shift[0]) & alpha_pmu->pmc_count_mask[0];
        pcr1 = (pcr >> alpha_pmu->pmc_count_shift[1]) & alpha_pmu->pmc_count_mask[1];

        pr_info("CPU#%d: PCTR0[%06x] PCTR1[%06x]\n", cpu, pcr0, pcr1);

        local_irq_restore(flags);
}


/*
 * Performance Monitoring Interrupt Service Routine called when a PMC
 * overflows.  The PMC that overflowed is passed in la_ptr.
 */
static void alpha_perf_event_irq_handler(unsigned long la_ptr,
                                        struct pt_regs *regs)
{
        struct cpu_hw_events *cpuc;
        struct perf_sample_data data;
        struct perf_event *event;
        struct hw_perf_event *hwc;
        int idx, j;

        __this_cpu_inc(irq_pmi_count);
        cpuc = this_cpu_ptr(&cpu_hw_events);

        /* Completely counting through the PMC's period to trigger a new PMC
         * overflow interrupt while in this interrupt routine is utterly
         * disastrous!  The EV6 and EV67 counters are sufficiently large to
         * prevent this but to be really sure disable the PMCs.
         */
        wrperfmon(PERFMON_CMD_DISABLE, cpuc->idx_mask);

        /* la_ptr is the counter that overflowed. */
        if (unlikely(la_ptr >= alpha_pmu->num_pmcs)) {
                /* This should never occur! */
                irq_err_count++;
                pr_warn("PMI: silly index %ld\n", la_ptr);
                wrperfmon(PERFMON_CMD_ENABLE, cpuc->idx_mask);
                return;
        }

        idx = la_ptr;

        for (j = 0; j < cpuc->n_events; j++) {
                if (cpuc->current_idx[j] == idx)
                        break;
        }

        if (unlikely(j == cpuc->n_events)) {
                /* This can occur if the event is disabled right on a PMC overflow. */
                wrperfmon(PERFMON_CMD_ENABLE, cpuc->idx_mask);
                return;
        }

        event = cpuc->event[j];

        if (unlikely(!event)) {
                /* This should never occur! */
                irq_err_count++;
                pr_warn("PMI: No event at index %d!\n", idx);
                wrperfmon(PERFMON_CMD_ENABLE, cpuc->idx_mask);
                return;
        }

        hwc = &event->hw;
        alpha_perf_event_update(event, hwc, idx, alpha_pmu->pmc_max_period[idx]+1);
        perf_sample_data_init(&data, 0, hwc->last_period);

        if (alpha_perf_event_set_period(event, hwc, idx)) {
                if (perf_event_overflow(event, &data, regs)) {
                        /* Interrupts coming too quickly; "throttle" the
                         * counter, i.e., disable it for a little while.
                         */
                        alpha_pmu_stop(event, 0);
                }
        }
        wrperfmon(PERFMON_CMD_ENABLE, cpuc->idx_mask);

        return;
}



/*
 * Init call to initialise performance events at kernel startup.
 */
int __init init_hw_perf_events(void)
{
        pr_info("Performance events: ");

        if (!supported_cpu()) {
                pr_cont("No support for your CPU.\n");
                return 0;
        }

        pr_cont("Supported CPU type!\n");

        /* Override performance counter IRQ vector */

        perf_irq = alpha_perf_event_irq_handler;

        /* And set up PMU specification */
        alpha_pmu = &ev67_pmu;

        perf_pmu_register(&pmu, "cpu", PERF_TYPE_RAW);

        return 0;
}
early_initcall(init_hw_perf_events);