/*
 * Copyright 2014 Tilera Corporation. All Rights Reserved.
 *
 *   This program is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU General Public License
 *   as published by the Free Software Foundation, version 2.
 *
 *   This program is distributed in the hope that it will be useful, but
 *   WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 *   NON INFRINGEMENT.  See the GNU General Public License for
 *   more details.
 *
 *
 * Perf_events support for Tile processor.
 *
 * This code is based upon the x86 perf event
 * code, which is:
 *
 *  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>
 *  Copyright (C) 2009 Google, Inc., Stephane Eranian
 */

#include <linux/kprobes.h>
#include <linux/kernel.h>
#include <linux/kdebug.h>
#include <linux/mutex.h>
#include <linux/bitmap.h>
#include <linux/irq.h>
#include <linux/interrupt.h>
#include <linux/perf_event.h>
#include <linux/atomic.h>
#include <asm/traps.h>
#include <asm/stack.h>
#include <asm/pmc.h>
#include <hv/hypervisor.h>

#define TILE_MAX_COUNTERS       4

#define PERF_COUNT_0_IDX        0
#define PERF_COUNT_1_IDX        1
#define AUX_PERF_COUNT_0_IDX    2
#define AUX_PERF_COUNT_1_IDX    3

struct cpu_hw_events {
        int                     n_events;
        struct perf_event       *events[TILE_MAX_COUNTERS]; /* counter order */
        struct perf_event       *event_list[TILE_MAX_COUNTERS]; /* enabled
                                                                order */
        int                     assign[TILE_MAX_COUNTERS];
        unsigned long           active_mask[BITS_TO_LONGS(TILE_MAX_COUNTERS)];
        unsigned long           used_mask;
};

/* TILE arch specific performance monitor unit */
struct tile_pmu {
        const char      *name;
        int             version;
        const int       *hw_events;     /* generic hw events table */
        /* generic hw cache events table */
        const int       (*cache_events)[PERF_COUNT_HW_CACHE_MAX]
                                       [PERF_COUNT_HW_CACHE_OP_MAX]
                                       [PERF_COUNT_HW_CACHE_RESULT_MAX];
        int             (*map_hw_event)(u64);    /*method used to map
                                                  hw events */
        int             (*map_cache_event)(u64); /*method used to map
                                                  cache events */

        u64             max_period;             /* max sampling period */
        u64             cntval_mask;            /* counter width mask */
        int             cntval_bits;            /* counter width */
        int             max_events;             /* max generic hw events
                                                in map */
        int             num_counters;           /* number base + aux counters */
        int             num_base_counters;      /* number base counters */
};

DEFINE_PER_CPU(u64, perf_irqs);
static DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events);

#define TILE_OP_UNSUPP          (-1)

#ifndef __tilegx__
/* TILEPro hardware events map */
static const int tile_hw_event_map[] = {
        [PERF_COUNT_HW_CPU_CYCLES]              = 0x01, /* ONE */
        [PERF_COUNT_HW_INSTRUCTIONS]            = 0x06, /* MP_BUNDLE_RETIRED */
        [PERF_COUNT_HW_CACHE_REFERENCES]        = TILE_OP_UNSUPP,
        [PERF_COUNT_HW_CACHE_MISSES]            = TILE_OP_UNSUPP,
        [PERF_COUNT_HW_BRANCH_INSTRUCTIONS]     = 0x16, /*
                                          MP_CONDITIONAL_BRANCH_ISSUED */
        [PERF_COUNT_HW_BRANCH_MISSES]           = 0x14, /*
                                          MP_CONDITIONAL_BRANCH_MISSPREDICT */
        [PERF_COUNT_HW_BUS_CYCLES]              = TILE_OP_UNSUPP,
};
#else
/* TILEGx hardware events map */
static const int tile_hw_event_map[] = {
        [PERF_COUNT_HW_CPU_CYCLES]              = 0x181, /* ONE */
        [PERF_COUNT_HW_INSTRUCTIONS]            = 0xdb, /* INSTRUCTION_BUNDLE */
        [PERF_COUNT_HW_CACHE_REFERENCES]        = TILE_OP_UNSUPP,
        [PERF_COUNT_HW_CACHE_MISSES]            = TILE_OP_UNSUPP,
        [PERF_COUNT_HW_BRANCH_INSTRUCTIONS]     = 0xd9, /*
                                                COND_BRANCH_PRED_CORRECT */
        [PERF_COUNT_HW_BRANCH_MISSES]           = 0xda, /*
                                                COND_BRANCH_PRED_INCORRECT */
        [PERF_COUNT_HW_BUS_CYCLES]              = TILE_OP_UNSUPP,
};
#endif

#define C(x) PERF_COUNT_HW_CACHE_##x

/*
 * Generalized hw caching related hw_event table, filled
 * in on a per model basis. A value of -1 means
 * 'not supported', any other value means the
 * raw hw_event ID.
 */
#ifndef __tilegx__
/* TILEPro hardware cache event map */
static const int tile_cache_event_map[PERF_COUNT_HW_CACHE_MAX]
                                     [PERF_COUNT_HW_CACHE_OP_MAX]
                                     [PERF_COUNT_HW_CACHE_RESULT_MAX] = {
[C(L1D)] = {
        [C(OP_READ)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = 0x21, /* RD_MISS */
        },
        [C(OP_WRITE)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = 0x22, /* WR_MISS */
        },
        [C(OP_PREFETCH)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
},
[C(L1I)] = {
        [C(OP_READ)] = {
                [C(RESULT_ACCESS)] = 0x12, /* MP_ICACHE_HIT_ISSUED */
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
        [C(OP_WRITE)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
        [C(OP_PREFETCH)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
},
[C(LL)] = {
        [C(OP_READ)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
        [C(OP_WRITE)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
        [C(OP_PREFETCH)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
},
[C(DTLB)] = {
        [C(OP_READ)] = {
                [C(RESULT_ACCESS)] = 0x1d, /* TLB_CNT */
                [C(RESULT_MISS)] = 0x20, /* TLB_EXCEPTION */
        },
        [C(OP_WRITE)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
        [C(OP_PREFETCH)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
},
[C(ITLB)] = {
        [C(OP_READ)] = {
                [C(RESULT_ACCESS)] = 0x13, /* MP_ITLB_HIT_ISSUED */
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
        [C(OP_WRITE)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
        [C(OP_PREFETCH)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
},
[C(BPU)] = {
        [C(OP_READ)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
        [C(OP_WRITE)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
        [C(OP_PREFETCH)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
},
};
#else
/* TILEGx hardware events map */
static const int tile_cache_event_map[PERF_COUNT_HW_CACHE_MAX]
                                     [PERF_COUNT_HW_CACHE_OP_MAX]
                                     [PERF_COUNT_HW_CACHE_RESULT_MAX] = {
[C(L1D)] = {
        /*
         * Like some other architectures (e.g. ARM), the performance
         * counters don't differentiate between read and write
         * accesses/misses, so this isn't strictly correct, but it's the
         * best we can do. Writes and reads get combined.
         */
        [C(OP_READ)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = 0x44, /* RD_MISS */
        },
        [C(OP_WRITE)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = 0x45, /* WR_MISS */
        },
        [C(OP_PREFETCH)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
},
[C(L1I)] = {
        [C(OP_READ)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
        [C(OP_WRITE)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
        [C(OP_PREFETCH)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
},
[C(LL)] = {
        [C(OP_READ)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
        [C(OP_WRITE)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
        [C(OP_PREFETCH)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
},
[C(DTLB)] = {
        [C(OP_READ)] = {
                [C(RESULT_ACCESS)] = 0x40, /* TLB_CNT */
                [C(RESULT_MISS)] = 0x43, /* TLB_EXCEPTION */
        },
        [C(OP_WRITE)] = {
                [C(RESULT_ACCESS)] = 0x40, /* TLB_CNT */
                [C(RESULT_MISS)] = 0x43, /* TLB_EXCEPTION */
        },
        [C(OP_PREFETCH)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
},
[C(ITLB)] = {
        [C(OP_READ)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = 0xd4, /* ITLB_MISS_INT */
        },
        [C(OP_WRITE)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = 0xd4, /* ITLB_MISS_INT */
        },
        [C(OP_PREFETCH)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
},
[C(BPU)] = {
        [C(OP_READ)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
        [C(OP_WRITE)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
        [C(OP_PREFETCH)] = {
                [C(RESULT_ACCESS)] = TILE_OP_UNSUPP,
                [C(RESULT_MISS)] = TILE_OP_UNSUPP,
        },
},
};
#endif

static atomic_t tile_active_events;
static DEFINE_MUTEX(perf_intr_reserve_mutex);

static int tile_map_hw_event(u64 config);
static int tile_map_cache_event(u64 config);

static int tile_pmu_handle_irq(struct pt_regs *regs, int fault);

/*
 * To avoid new_raw_count getting larger then pre_raw_count
 * in tile_perf_event_update(), we limit the value of max_period to 2^31 - 1.
 */
static const struct tile_pmu tilepmu = {
#ifndef __tilegx__
        .name = "tilepro",
#else
        .name = "tilegx",
#endif
        .max_events = ARRAY_SIZE(tile_hw_event_map),
        .map_hw_event = tile_map_hw_event,
        .hw_events = tile_hw_event_map,
        .map_cache_event = tile_map_cache_event,
        .cache_events = &tile_cache_event_map,
        .cntval_bits = 32,
        .cntval_mask = (1ULL << 32) - 1,
        .max_period = (1ULL << 31) - 1,
        .num_counters = TILE_MAX_COUNTERS,
        .num_base_counters = TILE_BASE_COUNTERS,
};

static const struct tile_pmu *tile_pmu __read_mostly;

/*
 * Check whether perf event is enabled.
 */
int tile_perf_enabled(void)
{
        return atomic_read(&tile_active_events) != 0;
}

/*
 * Read Performance Counters.
 */
static inline u64 read_counter(int idx)
{
        u64 val = 0;

        /* __insn_mfspr() only takes an immediate argument */
        switch (idx) {
        case PERF_COUNT_0_IDX:
                val = __insn_mfspr(SPR_PERF_COUNT_0);
                break;
        case PERF_COUNT_1_IDX:
                val = __insn_mfspr(SPR_PERF_COUNT_1);
                break;
        case AUX_PERF_COUNT_0_IDX:
                val = __insn_mfspr(SPR_AUX_PERF_COUNT_0);
                break;
        case AUX_PERF_COUNT_1_IDX:
                val = __insn_mfspr(SPR_AUX_PERF_COUNT_1);
                break;
        default:
                WARN_ON_ONCE(idx > AUX_PERF_COUNT_1_IDX ||
                                idx < PERF_COUNT_0_IDX);
        }

        return val;
}

/*
 * Write Performance Counters.
 */
static inline void write_counter(int idx, u64 value)
{
        /* __insn_mtspr() only takes an immediate argument */
        switch (idx) {
        case PERF_COUNT_0_IDX:
                __insn_mtspr(SPR_PERF_COUNT_0, value);
                break;
        case PERF_COUNT_1_IDX:
                __insn_mtspr(SPR_PERF_COUNT_1, value);
                break;
        case AUX_PERF_COUNT_0_IDX:
                __insn_mtspr(SPR_AUX_PERF_COUNT_0, value);
                break;
        case AUX_PERF_COUNT_1_IDX:
                __insn_mtspr(SPR_AUX_PERF_COUNT_1, value);
                break;
        default:
                WARN_ON_ONCE(idx > AUX_PERF_COUNT_1_IDX ||
                                idx < PERF_COUNT_0_IDX);
        }
}

/*
 * Enable performance event by setting
 * Performance Counter Control registers.
 */
static inline void tile_pmu_enable_event(struct perf_event *event)
{
        struct hw_perf_event *hwc = &event->hw;
        unsigned long cfg, mask;
        int shift, idx = hwc->idx;

        /*
         * prevent early activation from tile_pmu_start() in hw_perf_enable
         */

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

        if (idx < tile_pmu->num_base_counters)
                cfg = __insn_mfspr(SPR_PERF_COUNT_CTL);
        else
                cfg = __insn_mfspr(SPR_AUX_PERF_COUNT_CTL);

        switch (idx) {
        case PERF_COUNT_0_IDX:
        case AUX_PERF_COUNT_0_IDX:
                mask = TILE_EVENT_MASK;
                shift = 0;
                break;
        case PERF_COUNT_1_IDX:
        case AUX_PERF_COUNT_1_IDX:
                mask = TILE_EVENT_MASK << 16;
                shift = 16;
                break;
        default:
                WARN_ON_ONCE(idx < PERF_COUNT_0_IDX ||
                        idx > AUX_PERF_COUNT_1_IDX);
                return;
        }

        /* Clear mask bits to enable the event. */
        cfg &= ~mask;
        cfg |= hwc->config << shift;

        if (idx < tile_pmu->num_base_counters)
                __insn_mtspr(SPR_PERF_COUNT_CTL, cfg);
        else
                __insn_mtspr(SPR_AUX_PERF_COUNT_CTL, cfg);
}

/*
 * Disable performance event by clearing
 * Performance Counter Control registers.
 */
static inline void tile_pmu_disable_event(struct perf_event *event)
{
        struct hw_perf_event *hwc = &event->hw;
        unsigned long cfg, mask;
        int idx = hwc->idx;

        if (idx == -1)
                return;

        if (idx < tile_pmu->num_base_counters)
                cfg = __insn_mfspr(SPR_PERF_COUNT_CTL);
        else
                cfg = __insn_mfspr(SPR_AUX_PERF_COUNT_CTL);

        switch (idx) {
        case PERF_COUNT_0_IDX:
        case AUX_PERF_COUNT_0_IDX:
                mask = TILE_PLM_MASK;
                break;
        case PERF_COUNT_1_IDX:
        case AUX_PERF_COUNT_1_IDX:
                mask = TILE_PLM_MASK << 16;
                break;
        default:
                WARN_ON_ONCE(idx < PERF_COUNT_0_IDX ||
                        idx > AUX_PERF_COUNT_1_IDX);
                return;
        }

        /* Set mask bits to disable the event. */
        cfg |= mask;

        if (idx < tile_pmu->num_base_counters)
                __insn_mtspr(SPR_PERF_COUNT_CTL, cfg);
        else
                __insn_mtspr(SPR_AUX_PERF_COUNT_CTL, cfg);
}

/*
 * Propagate event elapsed time into the generic event.
 * Can only be executed on the CPU where the event is active.
 * Returns the delta events processed.
 */
static u64 tile_perf_event_update(struct perf_event *event)
{
        struct hw_perf_event *hwc = &event->hw;
        int shift = 64 - tile_pmu->cntval_bits;
        u64 prev_raw_count, new_raw_count;
        u64 oldval;
        int idx = hwc->idx;
        u64 delta;

        /*
         * Careful: an NMI might modify the previous event value.
         *
         * 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 event atomically:
         */
again:
        prev_raw_count = local64_read(&hwc->prev_count);
        new_raw_count = read_counter(idx);

        oldval = local64_cmpxchg(&hwc->prev_count, prev_raw_count,
                                 new_raw_count);
        if (oldval != 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
         * (event-)time and add that to the generic event.
         *
         * 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);
        local64_sub(delta, &hwc->period_left);

        return new_raw_count;
}

/*
 * Set the next IRQ period, based on the hwc->period_left value.
 * To be called with the event disabled in hw:
 */
static int tile_event_set_period(struct perf_event *event)
{
        struct hw_perf_event *hwc = &event->hw;
        int idx = hwc->idx;
        s64 left = local64_read(&hwc->period_left);
        s64 period = hwc->sample_period;
        int ret = 0;

        /*
         * If we are way outside a reasonable range then just skip forward:
         */
        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 > tile_pmu->max_period)
                left = tile_pmu->max_period;

        /*
         * The hw event starts counting from this event offset,
         * mark it to be able to extra future deltas:
         */
        local64_set(&hwc->prev_count, (u64)-left);

        write_counter(idx, (u64)(-left) & tile_pmu->cntval_mask);

        perf_event_update_userpage(event);

        return ret;
}

/*
 * Stop the event but do not release the PMU counter
 */
static void tile_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 (__test_and_clear_bit(idx, cpuc->active_mask)) {
                tile_pmu_disable_event(event);
                cpuc->events[hwc->idx] = NULL;
                WARN_ON_ONCE(hwc->state & PERF_HES_STOPPED);
                hwc->state |= PERF_HES_STOPPED;
        }

        if ((flags & PERF_EF_UPDATE) && !(hwc->state & PERF_HES_UPTODATE)) {
                /*
                 * Drain the remaining delta count out of a event
                 * that we are disabling:
                 */
                tile_perf_event_update(event);
                hwc->state |= PERF_HES_UPTODATE;
        }
}

/*
 * Start an event (without re-assigning counter)
 */
static void tile_pmu_start(struct perf_event *event, int flags)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
        int idx = event->hw.idx;

        if (WARN_ON_ONCE(!(event->hw.state & PERF_HES_STOPPED)))
                return;

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

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

        event->hw.state = 0;

        cpuc->events[idx] = event;
        __set_bit(idx, cpuc->active_mask);

        unmask_pmc_interrupts();

        tile_pmu_enable_event(event);

        perf_event_update_userpage(event);
}

/*
 * Add a single event to the PMU.
 *
 * The event is added to the group of enabled events
 * but only if it can be scehduled with existing events.
 */
static int tile_pmu_add(struct perf_event *event, int flags)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
        struct hw_perf_event *hwc;
        unsigned long mask;
        int b, max_cnt;

        hwc = &event->hw;

        /*
         * We are full.
         */
        if (cpuc->n_events == tile_pmu->num_counters)
                return -ENOSPC;

        cpuc->event_list[cpuc->n_events] = event;
        cpuc->n_events++;

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

        /*
         * Find first empty counter.
         */
        max_cnt = tile_pmu->num_counters;
        mask = ~cpuc->used_mask;

        /* Find next free counter. */
        b = find_next_bit(&mask, max_cnt, 0);

        /* Should not happen. */
        if (WARN_ON_ONCE(b == max_cnt))
                return -ENOSPC;

        /*
         * Assign counter to event.
         */
        event->hw.idx = b;
        __set_bit(b, &cpuc->used_mask);

        /*
         * Start if requested.
         */
        if (flags & PERF_EF_START)
                tile_pmu_start(event, PERF_EF_RELOAD);

        return 0;
}

/*
 * Delete a single event from the PMU.
 *
 * The event is deleted from the group of enabled events.
 * If it is the last event, disable PMU interrupt.
 */
static void tile_pmu_del(struct perf_event *event, int flags)
{
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
        int i;

        /*
         * Remove event from list, compact list if necessary.
         */
        for (i = 0; i < cpuc->n_events; i++) {
                if (cpuc->event_list[i] == event) {
                        while (++i < cpuc->n_events)
                                cpuc->event_list[i-1] = cpuc->event_list[i];
                        --cpuc->n_events;
                        cpuc->events[event->hw.idx] = NULL;
                        __clear_bit(event->hw.idx, &cpuc->used_mask);
                        tile_pmu_stop(event, PERF_EF_UPDATE);
                        break;
                }
        }
        /*
         * If there are no events left, then mask PMU interrupt.
         */
        if (cpuc->n_events == 0)
                mask_pmc_interrupts();
        perf_event_update_userpage(event);
}

/*
 * Propagate event elapsed time into the event.
 */
static inline void tile_pmu_read(struct perf_event *event)
{
        tile_perf_event_update(event);
}

/*
 * Map generic events to Tile PMU.
 */
static int tile_map_hw_event(u64 config)
{
        if (config >= tile_pmu->max_events)
                return -EINVAL;
        return tile_pmu->hw_events[config];
}

/*
 * Map generic hardware cache events to Tile PMU.
 */
static int tile_map_cache_event(u64 config)
{
        unsigned int cache_type, cache_op, cache_result;
        int code;

        if (!tile_pmu->cache_events)
                return -ENOENT;

        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;

        code = (*tile_pmu->cache_events)[cache_type][cache_op][cache_result];
        if (code == TILE_OP_UNSUPP)
                return -EINVAL;

        return code;
}

static void tile_event_destroy(struct perf_event *event)
{
        if (atomic_dec_return(&tile_active_events) == 0)
                release_pmc_hardware();
}

static int __tile_event_init(struct perf_event *event)
{
        struct perf_event_attr *attr = &event->attr;
        struct hw_perf_event *hwc = &event->hw;
        int code;

        switch (attr->type) {
        case PERF_TYPE_HARDWARE:
                code = tile_pmu->map_hw_event(attr->config);
                break;
        case PERF_TYPE_HW_CACHE:
                code = tile_pmu->map_cache_event(attr->config);
                break;
        case PERF_TYPE_RAW:
                code = attr->config & TILE_EVENT_MASK;
                break;
        default:
                /* Should not happen. */
                return -EOPNOTSUPP;
        }

        if (code < 0)
                return code;

        hwc->config = code;
        hwc->idx = -1;

        if (attr->exclude_user)
                hwc->config |= TILE_CTL_EXCL_USER;

        if (attr->exclude_kernel)
                hwc->config |= TILE_CTL_EXCL_KERNEL;

        if (attr->exclude_hv)
                hwc->config |= TILE_CTL_EXCL_HV;

        if (!hwc->sample_period) {
                hwc->sample_period = tile_pmu->max_period;
                hwc->last_period = hwc->sample_period;
                local64_set(&hwc->period_left, hwc->sample_period);
        }
        event->destroy = tile_event_destroy;
        return 0;
}

static int tile_event_init(struct perf_event *event)
{
        int err = 0;
        perf_irq_t old_irq_handler = NULL;

        if (atomic_inc_return(&tile_active_events) == 1)
                old_irq_handler = reserve_pmc_hardware(tile_pmu_handle_irq);

        if (old_irq_handler) {
                pr_warn("PMC hardware busy (reserved by oprofile)\n");

                atomic_dec(&tile_active_events);
                return -EBUSY;
        }

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

        default:
                return -ENOENT;
        }

        err = __tile_event_init(event);
        if (err) {
                if (event->destroy)
                        event->destroy(event);
        }
        return err;
}

static struct pmu tilera_pmu = {
        .event_init     = tile_event_init,
        .add            = tile_pmu_add,
        .del            = tile_pmu_del,

        .start          = tile_pmu_start,
        .stop           = tile_pmu_stop,

        .read           = tile_pmu_read,
};

/*
 * PMU's IRQ handler, PMU has 2 interrupts, they share the same handler.
 */
int tile_pmu_handle_irq(struct pt_regs *regs, int fault)
{
        struct perf_sample_data data;
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
        struct perf_event *event;
        struct hw_perf_event *hwc;
        u64 val;
        unsigned long status;
        int bit;

        __this_cpu_inc(perf_irqs);

        if (!atomic_read(&tile_active_events))
                return 0;

        status = pmc_get_overflow();
        pmc_ack_overflow(status);

        for_each_set_bit(bit, &status, tile_pmu->num_counters) {

                event = cpuc->events[bit];

                if (!event)
                        continue;

                if (!test_bit(bit, cpuc->active_mask))
                        continue;

                hwc = &event->hw;

                val = tile_perf_event_update(event);
                if (val & (1ULL << (tile_pmu->cntval_bits - 1)))
                        continue;

                perf_sample_data_init(&data, 0, event->hw.last_period);
                if (!tile_event_set_period(event))
                        continue;

                if (perf_event_overflow(event, &data, regs))
                        tile_pmu_stop(event, 0);
        }

        return 0;
}

static bool __init supported_pmu(void)
{
        tile_pmu = &tilepmu;
        return true;
}

int __init init_hw_perf_events(void)
{
        supported_pmu();
        perf_pmu_register(&tilera_pmu, "cpu", PERF_TYPE_RAW);
        return 0;
}
arch_initcall(init_hw_perf_events);

/* Callchain handling code. */

/*
 * Tile specific backtracing code for perf_events.
 */
static inline void perf_callchain(struct perf_callchain_entry_ctx *entry,
                    struct pt_regs *regs)
{
        struct KBacktraceIterator kbt;
        unsigned int i;

        /*
         * Get the address just after the "jalr" instruction that
         * jumps to the handler for a syscall.  When we find this
         * address in a backtrace, we silently ignore it, which gives
         * us a one-step backtrace connection from the sys_xxx()
         * function in the kernel to the xxx() function in libc.
         * Otherwise, we lose the ability to properly attribute time
         * from the libc calls to the kernel implementations, since
         * oprofile only considers PCs from backtraces a pair at a time.
         */
        unsigned long handle_syscall_pc = handle_syscall_link_address();

        KBacktraceIterator_init(&kbt, NULL, regs);
        kbt.profile = 1;

        /*
         * The sample for the pc is already recorded.  Now we are adding the
         * address of the callsites on the stack.  Our iterator starts
         * with the frame of the (already sampled) call site.  If our
         * iterator contained a "return address" field, we could have just
         * used it and wouldn't have needed to skip the first
         * frame.  That's in effect what the arm and x86 versions do.
         * Instead we peel off the first iteration to get the equivalent
         * behavior.
         */

        if (KBacktraceIterator_end(&kbt))
                return;
        KBacktraceIterator_next(&kbt);

        /*
         * Set stack depth to 16 for user and kernel space respectively, that
         * is, total 32 stack frames.
         */
        for (i = 0; i < 16; ++i) {
                unsigned long pc;
                if (KBacktraceIterator_end(&kbt))
                        break;
                pc = kbt.it.pc;
                if (pc != handle_syscall_pc)
                        perf_callchain_store(entry, pc);
                KBacktraceIterator_next(&kbt);
        }
}

void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
                    struct pt_regs *regs)
{
        perf_callchain(entry, regs);
}

void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
                      struct pt_regs *regs)
{
        perf_callchain(entry, regs);
}