/*
 * Performance event support - powerpc architecture code
 *
 * Copyright 2008-2009 Paul Mackerras, IBM Corporation.
 *
 * 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; either version
 * 2 of the License, or (at your option) any later version.
 */
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/perf_event.h>
#include <linux/percpu.h>
#include <linux/hardirq.h>
#include <linux/uaccess.h>
#include <asm/reg.h>
#include <asm/pmc.h>
#include <asm/machdep.h>
#include <asm/firmware.h>
#include <asm/ptrace.h>
#include <asm/code-patching.h>

#define BHRB_MAX_ENTRIES        32
#define BHRB_TARGET             0x0000000000000002
#define BHRB_PREDICTION         0x0000000000000001
#define BHRB_EA                 0xFFFFFFFFFFFFFFFC

struct cpu_hw_events {
        int n_events;
        int n_percpu;
        int disabled;
        int n_added;
        int n_limited;
        u8  pmcs_enabled;
        struct perf_event *event[MAX_HWEVENTS];
        u64 events[MAX_HWEVENTS];
        unsigned int flags[MAX_HWEVENTS];
        unsigned long mmcr[3];
        struct perf_event *limited_counter[MAX_LIMITED_HWCOUNTERS];
        u8  limited_hwidx[MAX_LIMITED_HWCOUNTERS];
        u64 alternatives[MAX_HWEVENTS][MAX_EVENT_ALTERNATIVES];
        unsigned long amasks[MAX_HWEVENTS][MAX_EVENT_ALTERNATIVES];
        unsigned long avalues[MAX_HWEVENTS][MAX_EVENT_ALTERNATIVES];

        unsigned int group_flag;
        int n_txn_start;

        /* BHRB bits */
        u64                             bhrb_filter;    /* BHRB HW branch filter */
        int                             bhrb_users;
        void                            *bhrb_context;
        struct  perf_branch_stack       bhrb_stack;
        struct  perf_branch_entry       bhrb_entries[BHRB_MAX_ENTRIES];
};

DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events);

struct power_pmu *ppmu;

/*
 * Normally, to ignore kernel events we set the FCS (freeze counters
 * in supervisor mode) bit in MMCR0, but if the kernel runs with the
 * hypervisor bit set in the MSR, or if we are running on a processor
 * where the hypervisor bit is forced to 1 (as on Apple G5 processors),
 * then we need to use the FCHV bit to ignore kernel events.
 */
static unsigned int freeze_events_kernel = MMCR0_FCS;

/*
 * 32-bit doesn't have MMCRA but does have an MMCR2,
 * and a few other names are different.
 */
#ifdef CONFIG_PPC32

#define MMCR0_FCHV              0
#define MMCR0_PMCjCE            MMCR0_PMCnCE

#define SPRN_MMCRA              SPRN_MMCR2
#define MMCRA_SAMPLE_ENABLE     0

static inline unsigned long perf_ip_adjust(struct pt_regs *regs)
{
        return 0;
}
static inline void perf_get_data_addr(struct pt_regs *regs, u64 *addrp) { }
static inline u32 perf_get_misc_flags(struct pt_regs *regs)
{
        return 0;
}
static inline void perf_read_regs(struct pt_regs *regs)
{
        regs->result = 0;
}
static inline int perf_intr_is_nmi(struct pt_regs *regs)
{
        return 0;
}

static inline int siar_valid(struct pt_regs *regs)
{
        return 1;
}

static inline void power_pmu_bhrb_enable(struct perf_event *event) {}
static inline void power_pmu_bhrb_disable(struct perf_event *event) {}
void power_pmu_flush_branch_stack(void) {}
static inline void power_pmu_bhrb_read(struct cpu_hw_events *cpuhw) {}
#endif /* CONFIG_PPC32 */

static bool regs_use_siar(struct pt_regs *regs)
{
        return !!regs->result;
}

/*
 * Things that are specific to 64-bit implementations.
 */
#ifdef CONFIG_PPC64

static inline unsigned long perf_ip_adjust(struct pt_regs *regs)
{
        unsigned long mmcra = regs->dsisr;

        if ((ppmu->flags & PPMU_HAS_SSLOT) && (mmcra & MMCRA_SAMPLE_ENABLE)) {
                unsigned long slot = (mmcra & MMCRA_SLOT) >> MMCRA_SLOT_SHIFT;
                if (slot > 1)
                        return 4 * (slot - 1);
        }

        return 0;
}

/*
 * The user wants a data address recorded.
 * If we're not doing instruction sampling, give them the SDAR
 * (sampled data address).  If we are doing instruction sampling, then
 * only give them the SDAR if it corresponds to the instruction
 * pointed to by SIAR; this is indicated by the [POWER6_]MMCRA_SDSYNC, the
 * [POWER7P_]MMCRA_SDAR_VALID bit in MMCRA, or the SDAR_VALID bit in SIER.
 */
static inline void perf_get_data_addr(struct pt_regs *regs, u64 *addrp)
{
        unsigned long mmcra = regs->dsisr;
        bool sdar_valid;

        if (ppmu->flags & PPMU_HAS_SIER)
                sdar_valid = regs->dar & SIER_SDAR_VALID;
        else {
                unsigned long sdsync;

                if (ppmu->flags & PPMU_SIAR_VALID)
                        sdsync = POWER7P_MMCRA_SDAR_VALID;
                else if (ppmu->flags & PPMU_ALT_SIPR)
                        sdsync = POWER6_MMCRA_SDSYNC;
                else
                        sdsync = MMCRA_SDSYNC;

                sdar_valid = mmcra & sdsync;
        }

        if (!(mmcra & MMCRA_SAMPLE_ENABLE) || sdar_valid)
                *addrp = mfspr(SPRN_SDAR);
}

static bool regs_sihv(struct pt_regs *regs)
{
        unsigned long sihv = MMCRA_SIHV;

        if (ppmu->flags & PPMU_HAS_SIER)
                return !!(regs->dar & SIER_SIHV);

        if (ppmu->flags & PPMU_ALT_SIPR)
                sihv = POWER6_MMCRA_SIHV;

        return !!(regs->dsisr & sihv);
}

static bool regs_sipr(struct pt_regs *regs)
{
        unsigned long sipr = MMCRA_SIPR;

        if (ppmu->flags & PPMU_HAS_SIER)
                return !!(regs->dar & SIER_SIPR);

        if (ppmu->flags & PPMU_ALT_SIPR)
                sipr = POWER6_MMCRA_SIPR;

        return !!(regs->dsisr & sipr);
}

static inline u32 perf_flags_from_msr(struct pt_regs *regs)
{
        if (regs->msr & MSR_PR)
                return PERF_RECORD_MISC_USER;
        if ((regs->msr & MSR_HV) && freeze_events_kernel != MMCR0_FCHV)
                return PERF_RECORD_MISC_HYPERVISOR;
        return PERF_RECORD_MISC_KERNEL;
}

static inline u32 perf_get_misc_flags(struct pt_regs *regs)
{
        bool use_siar = regs_use_siar(regs);

        if (!use_siar)
                return perf_flags_from_msr(regs);

        /*
         * If we don't have flags in MMCRA, rather than using
         * the MSR, we intuit the flags from the address in
         * SIAR which should give slightly more reliable
         * results
         */
        if (ppmu->flags & PPMU_NO_SIPR) {
                unsigned long siar = mfspr(SPRN_SIAR);
                if (siar >= PAGE_OFFSET)
                        return PERF_RECORD_MISC_KERNEL;
                return PERF_RECORD_MISC_USER;
        }

        /* PR has priority over HV, so order below is important */
        if (regs_sipr(regs))
                return PERF_RECORD_MISC_USER;

        if (regs_sihv(regs) && (freeze_events_kernel != MMCR0_FCHV))
                return PERF_RECORD_MISC_HYPERVISOR;

        return PERF_RECORD_MISC_KERNEL;
}

/*
 * Overload regs->dsisr to store MMCRA so we only need to read it once
 * on each interrupt.
 * Overload regs->dar to store SIER if we have it.
 * Overload regs->result to specify whether we should use the MSR (result
 * is zero) or the SIAR (result is non zero).
 */
static inline void perf_read_regs(struct pt_regs *regs)
{
        unsigned long mmcra = mfspr(SPRN_MMCRA);
        int marked = mmcra & MMCRA_SAMPLE_ENABLE;
        int use_siar;

        regs->dsisr = mmcra;

        if (ppmu->flags & PPMU_HAS_SIER)
                regs->dar = mfspr(SPRN_SIER);

        /*
         * If this isn't a PMU exception (eg a software event) the SIAR is
         * not valid. Use pt_regs.
         *
         * If it is a marked event use the SIAR.
         *
         * If the PMU doesn't update the SIAR for non marked events use
         * pt_regs.
         *
         * If the PMU has HV/PR flags then check to see if they
         * place the exception in userspace. If so, use pt_regs. In
         * continuous sampling mode the SIAR and the PMU exception are
         * not synchronised, so they may be many instructions apart.
         * This can result in confusing backtraces. We still want
         * hypervisor samples as well as samples in the kernel with
         * interrupts off hence the userspace check.
         */
        if (TRAP(regs) != 0xf00)
                use_siar = 0;
        else if (marked)
                use_siar = 1;
        else if ((ppmu->flags & PPMU_NO_CONT_SAMPLING))
                use_siar = 0;
        else if (!(ppmu->flags & PPMU_NO_SIPR) && regs_sipr(regs))
                use_siar = 0;
        else
                use_siar = 1;

        regs->result = use_siar;
}

/*
 * If interrupts were soft-disabled when a PMU interrupt occurs, treat
 * it as an NMI.
 */
static inline int perf_intr_is_nmi(struct pt_regs *regs)
{
        return !regs->softe;
}

/*
 * On processors like P7+ that have the SIAR-Valid bit, marked instructions
 * must be sampled only if the SIAR-valid bit is set.
 *
 * For unmarked instructions and for processors that don't have the SIAR-Valid
 * bit, assume that SIAR is valid.
 */
static inline int siar_valid(struct pt_regs *regs)
{
        unsigned long mmcra = regs->dsisr;
        int marked = mmcra & MMCRA_SAMPLE_ENABLE;

        if (marked) {
                if (ppmu->flags & PPMU_HAS_SIER)
                        return regs->dar & SIER_SIAR_VALID;

                if (ppmu->flags & PPMU_SIAR_VALID)
                        return mmcra & POWER7P_MMCRA_SIAR_VALID;
        }

        return 1;
}


/* Reset all possible BHRB entries */
static void power_pmu_bhrb_reset(void)
{
        asm volatile(PPC_CLRBHRB);
}

static void power_pmu_bhrb_enable(struct perf_event *event)
{
        struct cpu_hw_events *cpuhw = &__get_cpu_var(cpu_hw_events);

        if (!ppmu->bhrb_nr)
                return;

        /* Clear BHRB if we changed task context to avoid data leaks */
        if (event->ctx->task && cpuhw->bhrb_context != event->ctx) {
                power_pmu_bhrb_reset();
                cpuhw->bhrb_context = event->ctx;
        }
        cpuhw->bhrb_users++;
}

static void power_pmu_bhrb_disable(struct perf_event *event)
{
        struct cpu_hw_events *cpuhw = &__get_cpu_var(cpu_hw_events);

        if (!ppmu->bhrb_nr)
                return;

        cpuhw->bhrb_users--;
        WARN_ON_ONCE(cpuhw->bhrb_users < 0);

        if (!cpuhw->disabled && !cpuhw->bhrb_users) {
                /* BHRB cannot be turned off when other
                 * events are active on the PMU.
                 */

                /* avoid stale pointer */
                cpuhw->bhrb_context = NULL;
        }
}

/* Called from ctxsw to prevent one process's branch entries to
 * mingle with the other process's entries during context switch.
 */
void power_pmu_flush_branch_stack(void)
{
        if (ppmu->bhrb_nr)
                power_pmu_bhrb_reset();
}
/* Calculate the to address for a branch */
static __u64 power_pmu_bhrb_to(u64 addr)
{
        unsigned int instr;
        int ret;
        __u64 target;

        if (is_kernel_addr(addr))
                return branch_target((unsigned int *)addr);

        /* Userspace: need copy instruction here then translate it */
        pagefault_disable();
        ret = __get_user_inatomic(instr, (unsigned int __user *)addr);
        if (ret) {
                pagefault_enable();
                return 0;
        }
        pagefault_enable();

        target = branch_target(&instr);
        if ((!target) || (instr & BRANCH_ABSOLUTE))
                return target;

        /* Translate relative branch target from kernel to user address */
        return target - (unsigned long)&instr + addr;
}

/* Processing BHRB entries */
void power_pmu_bhrb_read(struct cpu_hw_events *cpuhw)
{
        u64 val;
        u64 addr;
        int r_index, u_index, pred;

        r_index = 0;
        u_index = 0;
        while (r_index < ppmu->bhrb_nr) {
                /* Assembly read function */
                val = read_bhrb(r_index++);
                if (!val)
                        /* Terminal marker: End of valid BHRB entries */
                        break;
                else {
                        addr = val & BHRB_EA;
                        pred = val & BHRB_PREDICTION;

                        if (!addr)
                                /* invalid entry */
                                continue;

                        /* Branches are read most recent first (ie. mfbhrb 0 is
                         * the most recent branch).
                         * There are two types of valid entries:
                         * 1) a target entry which is the to address of a
                         *    computed goto like a blr,bctr,btar.  The next
                         *    entry read from the bhrb will be branch
                         *    corresponding to this target (ie. the actual
                         *    blr/bctr/btar instruction).
                         * 2) a from address which is an actual branch.  If a
                         *    target entry proceeds this, then this is the
                         *    matching branch for that target.  If this is not
                         *    following a target entry, then this is a branch
                         *    where the target is given as an immediate field
                         *    in the instruction (ie. an i or b form branch).
                         *    In this case we need to read the instruction from
                         *    memory to determine the target/to address.
                         */

                        if (val & BHRB_TARGET) {
                                /* Target branches use two entries
                                 * (ie. computed gotos/XL form)
                                 */
                                cpuhw->bhrb_entries[u_index].to = addr;
                                cpuhw->bhrb_entries[u_index].mispred = pred;
                                cpuhw->bhrb_entries[u_index].predicted = ~pred;

                                /* Get from address in next entry */
                                val = read_bhrb(r_index++);
                                addr = val & BHRB_EA;
                                if (val & BHRB_TARGET) {
                                        /* Shouldn't have two targets in a
                                           row.. Reset index and try again */
                                        r_index--;
                                        addr = 0;
                                }
                                cpuhw->bhrb_entries[u_index].from = addr;
                        } else {
                                /* Branches to immediate field 
                                   (ie I or B form) */
                                cpuhw->bhrb_entries[u_index].from = addr;
                                cpuhw->bhrb_entries[u_index].to =
                                        power_pmu_bhrb_to(addr);
                                cpuhw->bhrb_entries[u_index].mispred = pred;
                                cpuhw->bhrb_entries[u_index].predicted = ~pred;
                        }
                        u_index++;

                }
        }
        cpuhw->bhrb_stack.nr = u_index;
        return;
}

#endif /* CONFIG_PPC64 */

static void perf_event_interrupt(struct pt_regs *regs);

void perf_event_print_debug(void)
{
}

/*
 * Read one performance monitor counter (PMC).
 */
static unsigned long read_pmc(int idx)
{
        unsigned long val;

        switch (idx) {
        case 1:
                val = mfspr(SPRN_PMC1);
                break;
        case 2:
                val = mfspr(SPRN_PMC2);
                break;
        case 3:
                val = mfspr(SPRN_PMC3);
                break;
        case 4:
                val = mfspr(SPRN_PMC4);
                break;
        case 5:
                val = mfspr(SPRN_PMC5);
                break;
        case 6:
                val = mfspr(SPRN_PMC6);
                break;
#ifdef CONFIG_PPC64
        case 7:
                val = mfspr(SPRN_PMC7);
                break;
        case 8:
                val = mfspr(SPRN_PMC8);
                break;
#endif /* CONFIG_PPC64 */
        default:
                printk(KERN_ERR "oops trying to read PMC%d\n", idx);
                val = 0;
        }
        return val;
}

/*
 * Write one PMC.
 */
static void write_pmc(int idx, unsigned long val)
{
        switch (idx) {
        case 1:
                mtspr(SPRN_PMC1, val);
                break;
        case 2:
                mtspr(SPRN_PMC2, val);
                break;
        case 3:
                mtspr(SPRN_PMC3, val);
                break;
        case 4:
                mtspr(SPRN_PMC4, val);
                break;
        case 5:
                mtspr(SPRN_PMC5, val);
                break;
        case 6:
                mtspr(SPRN_PMC6, val);
                break;
#ifdef CONFIG_PPC64
        case 7:
                mtspr(SPRN_PMC7, val);
                break;
        case 8:
                mtspr(SPRN_PMC8, val);
                break;
#endif /* CONFIG_PPC64 */
        default:
                printk(KERN_ERR "oops trying to write PMC%d\n", idx);
        }
}

/*
 * Check if a set of events can all go on the PMU at once.
 * If they can't, this will look at alternative codes for the events
 * and see if any combination of alternative codes is feasible.
 * The feasible set is returned in event_id[].
 */
static int power_check_constraints(struct cpu_hw_events *cpuhw,
                                   u64 event_id[], unsigned int cflags[],
                                   int n_ev)
{
        unsigned long mask, value, nv;
        unsigned long smasks[MAX_HWEVENTS], svalues[MAX_HWEVENTS];
        int n_alt[MAX_HWEVENTS], choice[MAX_HWEVENTS];
        int i, j;
        unsigned long addf = ppmu->add_fields;
        unsigned long tadd = ppmu->test_adder;

        if (n_ev > ppmu->n_counter)
                return -1;

        /* First see if the events will go on as-is */
        for (i = 0; i < n_ev; ++i) {
                if ((cflags[i] & PPMU_LIMITED_PMC_REQD)
                    && !ppmu->limited_pmc_event(event_id[i])) {
                        ppmu->get_alternatives(event_id[i], cflags[i],
                                               cpuhw->alternatives[i]);
                        event_id[i] = cpuhw->alternatives[i][0];
                }
                if (ppmu->get_constraint(event_id[i], &cpuhw->amasks[i][0],
                                         &cpuhw->avalues[i][0]))
                        return -1;
        }
        value = mask = 0;
        for (i = 0; i < n_ev; ++i) {
                nv = (value | cpuhw->avalues[i][0]) +
                        (value & cpuhw->avalues[i][0] & addf);
                if ((((nv + tadd) ^ value) & mask) != 0 ||
                    (((nv + tadd) ^ cpuhw->avalues[i][0]) &
                     cpuhw->amasks[i][0]) != 0)
                        break;
                value = nv;
                mask |= cpuhw->amasks[i][0];
        }
        if (i == n_ev)
                return 0;       /* all OK */

        /* doesn't work, gather alternatives... */
        if (!ppmu->get_alternatives)
                return -1;
        for (i = 0; i < n_ev; ++i) {
                choice[i] = 0;
                n_alt[i] = ppmu->get_alternatives(event_id[i], cflags[i],
                                                  cpuhw->alternatives[i]);
                for (j = 1; j < n_alt[i]; ++j)
                        ppmu->get_constraint(cpuhw->alternatives[i][j],
                                             &cpuhw->amasks[i][j],
                                             &cpuhw->avalues[i][j]);
        }

        /* enumerate all possibilities and see if any will work */
        i = 0;
        j = -1;
        value = mask = nv = 0;
        while (i < n_ev) {
                if (j >= 0) {
                        /* we're backtracking, restore context */
                        value = svalues[i];
                        mask = smasks[i];
                        j = choice[i];
                }
                /*
                 * See if any alternative k for event_id i,
                 * where k > j, will satisfy the constraints.
                 */
                while (++j < n_alt[i]) {
                        nv = (value | cpuhw->avalues[i][j]) +
                                (value & cpuhw->avalues[i][j] & addf);
                        if ((((nv + tadd) ^ value) & mask) == 0 &&
                            (((nv + tadd) ^ cpuhw->avalues[i][j])
                             & cpuhw->amasks[i][j]) == 0)
                                break;
                }
                if (j >= n_alt[i]) {
                        /*
                         * No feasible alternative, backtrack
                         * to event_id i-1 and continue enumerating its
                         * alternatives from where we got up to.
                         */
                        if (--i < 0)
                                return -1;
                } else {
                        /*
                         * Found a feasible alternative for event_id i,
                         * remember where we got up to with this event_id,
                         * go on to the next event_id, and start with
                         * the first alternative for it.
                         */
                        choice[i] = j;
                        svalues[i] = value;
                        smasks[i] = mask;
                        value = nv;
                        mask |= cpuhw->amasks[i][j];
                        ++i;
                        j = -1;
                }
        }

        /* OK, we have a feasible combination, tell the caller the solution */
        for (i = 0; i < n_ev; ++i)
                event_id[i] = cpuhw->alternatives[i][choice[i]];
        return 0;
}

/*
 * Check if newly-added events have consistent settings for
 * exclude_{user,kernel,hv} with each other and any previously
 * added events.
 */
static int check_excludes(struct perf_event **ctrs, unsigned int cflags[],
                          int n_prev, int n_new)
{
        int eu = 0, ek = 0, eh = 0;
        int i, n, first;
        struct perf_event *event;

        n = n_prev + n_new;
        if (n <= 1)
                return 0;

        first = 1;
        for (i = 0; i < n; ++i) {
                if (cflags[i] & PPMU_LIMITED_PMC_OK) {
                        cflags[i] &= ~PPMU_LIMITED_PMC_REQD;
                        continue;
                }
                event = ctrs[i];
                if (first) {
                        eu = event->attr.exclude_user;
                        ek = event->attr.exclude_kernel;
                        eh = event->attr.exclude_hv;
                        first = 0;
                } else if (event->attr.exclude_user != eu ||
                           event->attr.exclude_kernel != ek ||
                           event->attr.exclude_hv != eh) {
                        return -EAGAIN;
                }
        }

        if (eu || ek || eh)
                for (i = 0; i < n; ++i)
                        if (cflags[i] & PPMU_LIMITED_PMC_OK)
                                cflags[i] |= PPMU_LIMITED_PMC_REQD;

        return 0;
}

static u64 check_and_compute_delta(u64 prev, u64 val)
{
        u64 delta = (val - prev) & 0xfffffffful;

        /*
         * POWER7 can roll back counter values, if the new value is smaller
         * than the previous value it will cause the delta and the counter to
         * have bogus values unless we rolled a counter over.  If a coutner is
         * rolled back, it will be smaller, but within 256, which is the maximum
         * number of events to rollback at once.  If we dectect a rollback
         * return 0.  This can lead to a small lack of precision in the
         * counters.
         */
        if (prev > val && (prev - val) < 256)
                delta = 0;

        return delta;
}

static void power_pmu_read(struct perf_event *event)
{
        s64 val, delta, prev;

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

        if (!event->hw.idx)
                return;
        /*
         * Performance monitor interrupts come even when interrupts
         * are soft-disabled, as long as interrupts are hard-enabled.
         * Therefore we treat them like NMIs.
         */
        do {
                prev = local64_read(&event->hw.prev_count);
                barrier();
                val = read_pmc(event->hw.idx);
                delta = check_and_compute_delta(prev, val);
                if (!delta)
                        return;
        } while (local64_cmpxchg(&event->hw.prev_count, prev, val) != prev);

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

/*
 * On some machines, PMC5 and PMC6 can't be written, don't respect
 * the freeze conditions, and don't generate interrupts.  This tells
 * us if `event' is using such a PMC.
 */
static int is_limited_pmc(int pmcnum)
{
        return (ppmu->flags & PPMU_LIMITED_PMC5_6)
                && (pmcnum == 5 || pmcnum == 6);
}

static void freeze_limited_counters(struct cpu_hw_events *cpuhw,
                                    unsigned long pmc5, unsigned long pmc6)
{
        struct perf_event *event;
        u64 val, prev, delta;
        int i;

        for (i = 0; i < cpuhw->n_limited; ++i) {
                event = cpuhw->limited_counter[i];
                if (!event->hw.idx)
                        continue;
                val = (event->hw.idx == 5) ? pmc5 : pmc6;
                prev = local64_read(&event->hw.prev_count);
                event->hw.idx = 0;
                delta = check_and_compute_delta(prev, val);
                if (delta)
                        local64_add(delta, &event->count);
        }
}

static void thaw_limited_counters(struct cpu_hw_events *cpuhw,
                                  unsigned long pmc5, unsigned long pmc6)
{
        struct perf_event *event;
        u64 val, prev;
        int i;

        for (i = 0; i < cpuhw->n_limited; ++i) {
                event = cpuhw->limited_counter[i];
                event->hw.idx = cpuhw->limited_hwidx[i];
                val = (event->hw.idx == 5) ? pmc5 : pmc6;
                prev = local64_read(&event->hw.prev_count);
                if (check_and_compute_delta(prev, val))
                        local64_set(&event->hw.prev_count, val);
                perf_event_update_userpage(event);
        }
}

/*
 * Since limited events don't respect the freeze conditions, we
 * have to read them immediately after freezing or unfreezing the
 * other events.  We try to keep the values from the limited
 * events as consistent as possible by keeping the delay (in
 * cycles and instructions) between freezing/unfreezing and reading
 * the limited events as small and consistent as possible.
 * Therefore, if any limited events are in use, we read them
 * both, and always in the same order, to minimize variability,
 * and do it inside the same asm that writes MMCR0.
 */
static void write_mmcr0(struct cpu_hw_events *cpuhw, unsigned long mmcr0)
{
        unsigned long pmc5, pmc6;

        if (!cpuhw->n_limited) {
                mtspr(SPRN_MMCR0, mmcr0);
                return;
        }

        /*
         * Write MMCR0, then read PMC5 and PMC6 immediately.
         * To ensure we don't get a performance monitor interrupt
         * between writing MMCR0 and freezing/thawing the limited
         * events, we first write MMCR0 with the event overflow
         * interrupt enable bits turned off.
         */
        asm volatile("mtspr %3,%2; mfspr %0,%4; mfspr %1,%5"
                     : "=&r" (pmc5), "=&r" (pmc6)
                     : "r" (mmcr0 & ~(MMCR0_PMC1CE | MMCR0_PMCjCE)),
                       "i" (SPRN_MMCR0),
                       "i" (SPRN_PMC5), "i" (SPRN_PMC6));

        if (mmcr0 & MMCR0_FC)
                freeze_limited_counters(cpuhw, pmc5, pmc6);
        else
                thaw_limited_counters(cpuhw, pmc5, pmc6);

        /*
         * Write the full MMCR0 including the event overflow interrupt
         * enable bits, if necessary.
         */
        if (mmcr0 & (MMCR0_PMC1CE | MMCR0_PMCjCE))
                mtspr(SPRN_MMCR0, mmcr0);
}

/*
 * Disable all events to prevent PMU interrupts and to allow
 * events to be added or removed.
 */
static void power_pmu_disable(struct pmu *pmu)
{
        struct cpu_hw_events *cpuhw;
        unsigned long flags;

        if (!ppmu)
                return;
        local_irq_save(flags);
        cpuhw = &__get_cpu_var(cpu_hw_events);

        if (!cpuhw->disabled) {
                cpuhw->disabled = 1;
                cpuhw->n_added = 0;

                /*
                 * Check if we ever enabled the PMU on this cpu.
                 */
                if (!cpuhw->pmcs_enabled) {
                        ppc_enable_pmcs();
                        cpuhw->pmcs_enabled = 1;
                }

                /*
                 * Disable instruction sampling if it was enabled
                 */
                if (cpuhw->mmcr[2] & MMCRA_SAMPLE_ENABLE) {
                        mtspr(SPRN_MMCRA,
                              cpuhw->mmcr[2] & ~MMCRA_SAMPLE_ENABLE);
                        mb();
                }

                /*
                 * Set the 'freeze counters' bit.
                 * The barrier is to make sure the mtspr has been
                 * executed and the PMU has frozen the events
                 * before we return.
                 */
                write_mmcr0(cpuhw, mfspr(SPRN_MMCR0) | MMCR0_FC);
                mb();
        }
        local_irq_restore(flags);
}

/*
 * Re-enable all events if disable == 0.
 * If we were previously disabled and events were added, then
 * put the new config on the PMU.
 */
static void power_pmu_enable(struct pmu *pmu)
{
        struct perf_event *event;
        struct cpu_hw_events *cpuhw;
        unsigned long flags;
        long i;
        unsigned long val;
        s64 left;
        unsigned int hwc_index[MAX_HWEVENTS];
        int n_lim;
        int idx;

        if (!ppmu)
                return;
        local_irq_save(flags);
        cpuhw = &__get_cpu_var(cpu_hw_events);
        if (!cpuhw->disabled) {
                local_irq_restore(flags);
                return;
        }
        cpuhw->disabled = 0;

        /*
         * If we didn't change anything, or only removed events,
         * no need to recalculate MMCR* settings and reset the PMCs.
         * Just reenable the PMU with the current MMCR* settings
         * (possibly updated for removal of events).
         */
        if (!cpuhw->n_added) {
                mtspr(SPRN_MMCRA, cpuhw->mmcr[2] & ~MMCRA_SAMPLE_ENABLE);
                mtspr(SPRN_MMCR1, cpuhw->mmcr[1]);
                if (cpuhw->n_events == 0)
                        ppc_set_pmu_inuse(0);
                goto out_enable;
        }

        /*
         * Compute MMCR* values for the new set of events
         */
        if (ppmu->compute_mmcr(cpuhw->events, cpuhw->n_events, hwc_index,
                               cpuhw->mmcr)) {
                /* shouldn't ever get here */
                printk(KERN_ERR "oops compute_mmcr failed\n");
                goto out;
        }

        /*
         * Add in MMCR0 freeze bits corresponding to the
         * attr.exclude_* bits for the first event.
         * We have already checked that all events have the
         * same values for these bits as the first event.
         */
        event = cpuhw->event[0];
        if (event->attr.exclude_user)
                cpuhw->mmcr[0] |= MMCR0_FCP;
        if (event->attr.exclude_kernel)
                cpuhw->mmcr[0] |= freeze_events_kernel;
        if (event->attr.exclude_hv)
                cpuhw->mmcr[0] |= MMCR0_FCHV;

        /*
         * Write the new configuration to MMCR* with the freeze
         * bit set and set the hardware events to their initial values.
         * Then unfreeze the events.
         */
        ppc_set_pmu_inuse(1);
        mtspr(SPRN_MMCRA, cpuhw->mmcr[2] & ~MMCRA_SAMPLE_ENABLE);
        mtspr(SPRN_MMCR1, cpuhw->mmcr[1]);
        mtspr(SPRN_MMCR0, (cpuhw->mmcr[0] & ~(MMCR0_PMC1CE | MMCR0_PMCjCE))
                                | MMCR0_FC);

        /*
         * Read off any pre-existing events that need to move
         * to another PMC.
         */
        for (i = 0; i < cpuhw->n_events; ++i) {
                event = cpuhw->event[i];
                if (event->hw.idx && event->hw.idx != hwc_index[i] + 1) {
                        power_pmu_read(event);
                        write_pmc(event->hw.idx, 0);
                        event->hw.idx = 0;
                }
        }

        /*
         * Initialize the PMCs for all the new and moved events.
         */
        cpuhw->n_limited = n_lim = 0;
        for (i = 0; i < cpuhw->n_events; ++i) {
                event = cpuhw->event[i];
                if (event->hw.idx)
                        continue;
                idx = hwc_index[i] + 1;
                if (is_limited_pmc(idx)) {
                        cpuhw->limited_counter[n_lim] = event;
                        cpuhw->limited_hwidx[n_lim] = idx;
                        ++n_lim;
                        continue;
                }
                val = 0;
                if (event->hw.sample_period) {

                        left = local64_read(&event->hw.period_left);
                        if (left < 0x80000000L)
                                val = 0x80000000L - left;
                }
                local64_set(&event->hw.prev_count, val);
                event->hw.idx = idx;
                if (event->hw.state & PERF_HES_STOPPED)
                        val = 0;
                write_pmc(idx, val);
                perf_event_update_userpage(event);
        }
        cpuhw->n_limited = n_lim;
        cpuhw->mmcr[0] |= MMCR0_PMXE | MMCR0_FCECE;

 out_enable:
        mb();
        write_mmcr0(cpuhw, cpuhw->mmcr[0]);

        /*
         * Enable instruction sampling if necessary
         */
        if (cpuhw->mmcr[2] & MMCRA_SAMPLE_ENABLE) {
                mb();
                mtspr(SPRN_MMCRA, cpuhw->mmcr[2]);
        }

 out:
        if (cpuhw->bhrb_users)
                ppmu->config_bhrb(cpuhw->bhrb_filter);

        local_irq_restore(flags);
}

static int collect_events(struct perf_event *group, int max_count,
                          struct perf_event *ctrs[], u64 *events,
                          unsigned int *flags)
{
        int n = 0;
        struct perf_event *event;

        if (!is_software_event(group)) {
                if (n >= max_count)
                        return -1;
                ctrs[n] = group;
                flags[n] = group->hw.event_base;
                events[n++] = group->hw.config;
        }
        list_for_each_entry(event, &group->sibling_list, group_entry) {
                if (!is_software_event(event) &&
                    event->state != PERF_EVENT_STATE_OFF) {
                        if (n >= max_count)
                                return -1;
                        ctrs[n] = event;
                        flags[n] = event->hw.event_base;
                        events[n++] = event->hw.config;
                }
        }
        return n;
}

/*
 * Add a event to the PMU.
 * If all events are not already frozen, then we disable and
 * re-enable the PMU in order to get hw_perf_enable to do the
 * actual work of reconfiguring the PMU.
 */
static int power_pmu_add(struct perf_event *event, int ef_flags)
{
        struct cpu_hw_events *cpuhw;
        unsigned long flags;
        int n0;
        int ret = -EAGAIN;

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

        /*
         * Add the event to the list (if there is room)
         * and check whether the total set is still feasible.
         */
        cpuhw = &__get_cpu_var(cpu_hw_events);
        n0 = cpuhw->n_events;
        if (n0 >= ppmu->n_counter)
                goto out;
        cpuhw->event[n0] = event;
        cpuhw->events[n0] = event->hw.config;
        cpuhw->flags[n0] = event->hw.event_base;

        /*
         * This event may have been disabled/stopped in record_and_restart()
         * because we exceeded the ->event_limit. If re-starting the event,
         * clear the ->hw.state (STOPPED and UPTODATE flags), so the user
         * notification is re-enabled.
         */
        if (!(ef_flags & PERF_EF_START))
                event->hw.state = PERF_HES_STOPPED | PERF_HES_UPTODATE;
        else
                event->hw.state = 0;

        /*
         * If group events scheduling transaction was started,
         * skip the schedulability test here, it will be performed
         * at commit time(->commit_txn) as a whole
         */
        if (cpuhw->group_flag & PERF_EVENT_TXN)
                goto nocheck;

        if (check_excludes(cpuhw->event, cpuhw->flags, n0, 1))
                goto out;
        if (power_check_constraints(cpuhw, cpuhw->events, cpuhw->flags, n0 + 1))
                goto out;
        event->hw.config = cpuhw->events[n0];

nocheck:
        ++cpuhw->n_events;
        ++cpuhw->n_added;

        ret = 0;
 out:
        if (has_branch_stack(event))
                power_pmu_bhrb_enable(event);

        perf_pmu_enable(event->pmu);
        local_irq_restore(flags);
        return ret;
}

/*
 * Remove a event from the PMU.
 */
static void power_pmu_del(struct perf_event *event, int ef_flags)
{
        struct cpu_hw_events *cpuhw;
        long i;
        unsigned long flags;

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

        power_pmu_read(event);

        cpuhw = &__get_cpu_var(cpu_hw_events);
        for (i = 0; i < cpuhw->n_events; ++i) {
                if (event == cpuhw->event[i]) {
                        while (++i < cpuhw->n_events) {
                                cpuhw->event[i-1] = cpuhw->event[i];
                                cpuhw->events[i-1] = cpuhw->events[i];
                                cpuhw->flags[i-1] = cpuhw->flags[i];
                        }
                        --cpuhw->n_events;
                        ppmu->disable_pmc(event->hw.idx - 1, cpuhw->mmcr);
                        if (event->hw.idx) {
                                write_pmc(event->hw.idx, 0);
                                event->hw.idx = 0;
                        }
                        perf_event_update_userpage(event);
                        break;
                }
        }
        for (i = 0; i < cpuhw->n_limited; ++i)
                if (event == cpuhw->limited_counter[i])
                        break;
        if (i < cpuhw->n_limited) {
                while (++i < cpuhw->n_limited) {
                        cpuhw->limited_counter[i-1] = cpuhw->limited_counter[i];
                        cpuhw->limited_hwidx[i-1] = cpuhw->limited_hwidx[i];
                }
                --cpuhw->n_limited;
        }
        if (cpuhw->n_events == 0) {
                /* disable exceptions if no events are running */
                cpuhw->mmcr[0] &= ~(MMCR0_PMXE | MMCR0_FCECE);
        }

        if (has_branch_stack(event))
                power_pmu_bhrb_disable(event);

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

/*
 * POWER-PMU does not support disabling individual counters, hence
 * program their cycle counter to their max value and ignore the interrupts.
 */

static void power_pmu_start(struct perf_event *event, int ef_flags)
{
        unsigned long flags;
        s64 left;
        unsigned long val;

        if (!event->hw.idx || !event->hw.sample_period)
                return;

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

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

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

        event->hw.state = 0;
        left = local64_read(&event->hw.period_left);

        val = 0;
        if (left < 0x80000000L)
                val = 0x80000000L - left;

        write_pmc(event->hw.idx, val);

        perf_event_update_userpage(event);
        perf_pmu_enable(event->pmu);
        local_irq_restore(flags);
}

static void power_pmu_stop(struct perf_event *event, int ef_flags)
{
        unsigned long flags;

        if (!event->hw.idx || !event->hw.sample_period)
                return;

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

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

        power_pmu_read(event);
        event->hw.state |= PERF_HES_STOPPED | PERF_HES_UPTODATE;
        write_pmc(event->hw.idx, 0);

        perf_event_update_userpage(event);
        perf_pmu_enable(event->pmu);
        local_irq_restore(flags);
}

/*
 * Start group events scheduling transaction
 * Set the flag to make pmu::enable() not perform the
 * schedulability test, it will be performed at commit time
 */
void power_pmu_start_txn(struct pmu *pmu)
{
        struct cpu_hw_events *cpuhw = &__get_cpu_var(cpu_hw_events);

        perf_pmu_disable(pmu);
        cpuhw->group_flag |= PERF_EVENT_TXN;
        cpuhw->n_txn_start = cpuhw->n_events;
}

/*
 * Stop group events scheduling transaction
 * Clear the flag and pmu::enable() will perform the
 * schedulability test.
 */
void power_pmu_cancel_txn(struct pmu *pmu)
{
        struct cpu_hw_events *cpuhw = &__get_cpu_var(cpu_hw_events);

        cpuhw->group_flag &= ~PERF_EVENT_TXN;
        perf_pmu_enable(pmu);
}

/*
 * Commit group events scheduling transaction
 * Perform the group schedulability test as a whole
 * Return 0 if success
 */
int power_pmu_commit_txn(struct pmu *pmu)
{
        struct cpu_hw_events *cpuhw;
        long i, n;

        if (!ppmu)
                return -EAGAIN;
        cpuhw = &__get_cpu_var(cpu_hw_events);
        n = cpuhw->n_events;
        if (check_excludes(cpuhw->event, cpuhw->flags, 0, n))
                return -EAGAIN;
        i = power_check_constraints(cpuhw, cpuhw->events, cpuhw->flags, n);
        if (i < 0)
                return -EAGAIN;

        for (i = cpuhw->n_txn_start; i < n; ++i)
                cpuhw->event[i]->hw.config = cpuhw->events[i];

        cpuhw->group_flag &= ~PERF_EVENT_TXN;
        perf_pmu_enable(pmu);
        return 0;
}

/*
 * Return 1 if we might be able to put event on a limited PMC,
 * or 0 if not.
 * A event can only go on a limited PMC if it counts something
 * that a limited PMC can count, doesn't require interrupts, and
 * doesn't exclude any processor mode.
 */
static int can_go_on_limited_pmc(struct perf_event *event, u64 ev,
                                 unsigned int flags)
{
        int n;
        u64 alt[MAX_EVENT_ALTERNATIVES];

        if (event->attr.exclude_user
            || event->attr.exclude_kernel
            || event->attr.exclude_hv
            || event->attr.sample_period)
                return 0;

        if (ppmu->limited_pmc_event(ev))
                return 1;

        /*
         * The requested event_id isn't on a limited PMC already;
         * see if any alternative code goes on a limited PMC.
         */
        if (!ppmu->get_alternatives)
                return 0;

        flags |= PPMU_LIMITED_PMC_OK | PPMU_LIMITED_PMC_REQD;
        n = ppmu->get_alternatives(ev, flags, alt);

        return n > 0;
}

/*
 * Find an alternative event_id that goes on a normal PMC, if possible,
 * and return the event_id code, or 0 if there is no such alternative.
 * (Note: event_id code 0 is "don't count" on all machines.)
 */
static u64 normal_pmc_alternative(u64 ev, unsigned long flags)
{
        u64 alt[MAX_EVENT_ALTERNATIVES];
        int n;

        flags &= ~(PPMU_LIMITED_PMC_OK | PPMU_LIMITED_PMC_REQD);
        n = ppmu->get_alternatives(ev, flags, alt);
        if (!n)
                return 0;
        return alt[0];
}

/* 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);

/*
 * 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);
        }
}

/*
 * Translate a generic cache event_id config to a raw event_id code.
 */
static int hw_perf_cache_event(u64 config, u64 *eventp)
{
        unsigned long type, op, result;
        int ev;

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

static int power_pmu_event_init(struct perf_event *event)
{
        u64 ev;
        unsigned long flags;
        struct perf_event *ctrs[MAX_HWEVENTS];
        u64 events[MAX_HWEVENTS];
        unsigned int cflags[MAX_HWEVENTS];
        int n;
        int err;
        struct cpu_hw_events *cpuhw;

        if (!ppmu)
                return -ENOENT;

        if (has_branch_stack(event)) {
                /* PMU has BHRB enabled */
                if (!(ppmu->flags & PPMU_BHRB))
                        return -EOPNOTSUPP;
        }

        switch (event->attr.type) {
        case PERF_TYPE_HARDWARE:
                ev = event->attr.config;
                if (ev >= ppmu->n_generic || ppmu->generic_events[ev] == 0)
                        return -EOPNOTSUPP;
                ev = ppmu->generic_events[ev];
                break;
        case PERF_TYPE_HW_CACHE:
                err = hw_perf_cache_event(event->attr.config, &ev);
                if (err)
                        return err;
                break;
        case PERF_TYPE_RAW:
                ev = event->attr.config;
                break;
        default:
                return -ENOENT;
        }

        event->hw.config_base = ev;
        event->hw.idx = 0;

        /*
         * If we are not running on a hypervisor, force the
         * exclude_hv bit to 0 so that we don't care what
         * the user set it to.
         */
        if (!firmware_has_feature(FW_FEATURE_LPAR))
                event->attr.exclude_hv = 0;

        /*
         * If this is a per-task event, then we can use
         * PM_RUN_* events interchangeably with their non RUN_*
         * equivalents, e.g. PM_RUN_CYC instead of PM_CYC.
         * XXX we should check if the task is an idle task.
         */
        flags = 0;
        if (event->attach_state & PERF_ATTACH_TASK)
                flags |= PPMU_ONLY_COUNT_RUN;

        /*
         * If this machine has limited events, check whether this
         * event_id could go on a limited event.
         */
        if (ppmu->flags & PPMU_LIMITED_PMC5_6) {
                if (can_go_on_limited_pmc(event, ev, flags)) {
                        flags |= PPMU_LIMITED_PMC_OK;
                } else if (ppmu->limited_pmc_event(ev)) {
                        /*
                         * The requested event_id is on a limited PMC,
                         * but we can't use a limited PMC; see if any
                         * alternative goes on a normal PMC.
                         */
                        ev = normal_pmc_alternative(ev, flags);
                        if (!ev)
                                return -EINVAL;
                }
        }

        /*
         * If this is in a group, check if it can go on with all the
         * other hardware events in the group.  We assume the event
         * hasn't been linked into its leader's sibling list at this point.
         */
        n = 0;
        if (event->group_leader != event) {
                n = collect_events(event->group_leader, ppmu->n_counter - 1,
                                   ctrs, events, cflags);
                if (n < 0)
                        return -EINVAL;
        }
        events[n] = ev;
        ctrs[n] = event;
        cflags[n] = flags;
        if (check_excludes(ctrs, cflags, n, 1))
                return -EINVAL;

        cpuhw = &get_cpu_var(cpu_hw_events);
        err = power_check_constraints(cpuhw, events, cflags, n + 1);

        if (has_branch_stack(event)) {
                cpuhw->bhrb_filter = ppmu->bhrb_filter_map(
                                        event->attr.branch_sample_type);

                if(cpuhw->bhrb_filter == -1)
                        return -EOPNOTSUPP;
        }

        put_cpu_var(cpu_hw_events);
        if (err)
                return -EINVAL;

        event->hw.config = events[n];
        event->hw.event_base = cflags[n];
        event->hw.last_period = event->hw.sample_period;
        local64_set(&event->hw.period_left, event->hw.last_period);

        /*
         * See if we need to reserve the PMU.
         * 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(perf_event_interrupt))
                        err = -EBUSY;
                else
                        atomic_inc(&num_events);
                mutex_unlock(&pmc_reserve_mutex);
        }
        event->destroy = hw_perf_event_destroy;

        return err;
}

static int power_pmu_event_idx(struct perf_event *event)
{
        return event->hw.idx;
}

ssize_t power_events_sysfs_show(struct device *dev,
                                struct device_attribute *attr, char *page)
{
        struct perf_pmu_events_attr *pmu_attr;

        pmu_attr = container_of(attr, struct perf_pmu_events_attr, attr);

        return sprintf(page, "event=0x%02llx\n", pmu_attr->id);
}

struct pmu power_pmu = {
        .pmu_enable     = power_pmu_enable,
        .pmu_disable    = power_pmu_disable,
        .event_init     = power_pmu_event_init,
        .add            = power_pmu_add,
        .del            = power_pmu_del,
        .start          = power_pmu_start,
        .stop           = power_pmu_stop,
        .read           = power_pmu_read,
        .start_txn      = power_pmu_start_txn,
        .cancel_txn     = power_pmu_cancel_txn,
        .commit_txn     = power_pmu_commit_txn,
        .event_idx      = power_pmu_event_idx,
        .flush_branch_stack = power_pmu_flush_branch_stack,
};

/*
 * A counter has overflowed; update its count and record
 * things if requested.  Note that interrupts are hard-disabled
 * here so there is no possibility of being interrupted.
 */
static void record_and_restart(struct perf_event *event, unsigned long val,
                               struct pt_regs *regs)
{
        u64 period = event->hw.sample_period;
        s64 prev, delta, left;
        int record = 0;

        if (event->hw.state & PERF_HES_STOPPED) {
                write_pmc(event->hw.idx, 0);
                return;
        }

        /* we don't have to worry about interrupts here */
        prev = local64_read(&event->hw.prev_count);
        delta = check_and_compute_delta(prev, val);
        local64_add(delta, &event->count);

        /*
         * See if the total period for this event has expired,
         * and update for the next period.
         */
        val = 0;
        left = local64_read(&event->hw.period_left) - delta;
        if (delta == 0)
                left++;
        if (period) {
                if (left <= 0) {
                        left += period;
                        if (left <= 0)
                                left = period;
                        record = siar_valid(regs);
                        event->hw.last_period = event->hw.sample_period;
                }
                if (left < 0x80000000LL)
                        val = 0x80000000LL - left;
        }

        write_pmc(event->hw.idx, val);
        local64_set(&event->hw.prev_count, val);
        local64_set(&event->hw.period_left, left);
        perf_event_update_userpage(event);

        /*
         * Finally record data if requested.
         */
        if (record) {
                struct perf_sample_data data;

                perf_sample_data_init(&data, ~0ULL, event->hw.last_period);

                if (event->attr.sample_type & PERF_SAMPLE_ADDR)
                        perf_get_data_addr(regs, &data.addr);

                if (event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK) {
                        struct cpu_hw_events *cpuhw;
                        cpuhw = &__get_cpu_var(cpu_hw_events);
                        power_pmu_bhrb_read(cpuhw);
                        data.br_stack = &cpuhw->bhrb_stack;
                }

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

/*
 * Called from generic code to get the misc flags (i.e. processor mode)
 * for an event_id.
 */
unsigned long perf_misc_flags(struct pt_regs *regs)
{
        u32 flags = perf_get_misc_flags(regs);

        if (flags)
                return flags;
        return user_mode(regs) ? PERF_RECORD_MISC_USER :
                PERF_RECORD_MISC_KERNEL;
}

/*
 * Called from generic code to get the instruction pointer
 * for an event_id.
 */
unsigned long perf_instruction_pointer(struct pt_regs *regs)
{
        bool use_siar = regs_use_siar(regs);

        if (use_siar && siar_valid(regs))
                return mfspr(SPRN_SIAR) + perf_ip_adjust(regs);
        else if (use_siar)
                return 0;               // no valid instruction pointer
        else
                return regs->nip;
}

static bool pmc_overflow_power7(unsigned long val)
{
        /*
         * Events on POWER7 can roll back if a speculative event doesn't
         * eventually complete. Unfortunately in some rare cases they will
         * raise a performance monitor exception. We need to catch this to
         * ensure we reset the PMC. In all cases the PMC will be 256 or less
         * cycles from overflow.
         *
         * We only do this if the first pass fails to find any overflowing
         * PMCs because a user might set a period of less than 256 and we
         * don't want to mistakenly reset them.
         */
        if ((0x80000000 - val) <= 256)
                return true;

        return false;
}

static bool pmc_overflow(unsigned long val)
{
        if ((int)val < 0)
                return true;

        return false;
}

/*
 * Performance monitor interrupt stuff
 */
static void perf_event_interrupt(struct pt_regs *regs)
{
        int i, j;
        struct cpu_hw_events *cpuhw = &__get_cpu_var(cpu_hw_events);
        struct perf_event *event;
        unsigned long val[8];
        int found, active;
        int nmi;

        if (cpuhw->n_limited)
                freeze_limited_counters(cpuhw, mfspr(SPRN_PMC5),
                                        mfspr(SPRN_PMC6));

        perf_read_regs(regs);

        nmi = perf_intr_is_nmi(regs);
        if (nmi)
                nmi_enter();
        else
                irq_enter();

        /* Read all the PMCs since we'll need them a bunch of times */
        for (i = 0; i < ppmu->n_counter; ++i)
                val[i] = read_pmc(i + 1);

        /* Try to find what caused the IRQ */
        found = 0;
        for (i = 0; i < ppmu->n_counter; ++i) {
                if (!pmc_overflow(val[i]))
                        continue;
                if (is_limited_pmc(i + 1))
                        continue; /* these won't generate IRQs */
                /*
                 * We've found one that's overflowed.  For active
                 * counters we need to log this.  For inactive
                 * counters, we need to reset it anyway
                 */
                found = 1;
                active = 0;
                for (j = 0; j < cpuhw->n_events; ++j) {
                        event = cpuhw->event[j];
                        if (event->hw.idx == (i + 1)) {
                                active = 1;
                                record_and_restart(event, val[i], regs);
                                break;
                        }
                }
                if (!active)
                        /* reset non active counters that have overflowed */
                        write_pmc(i + 1, 0);
        }
        if (!found && pvr_version_is(PVR_POWER7)) {
                /* check active counters for special buggy p7 overflow */
                for (i = 0; i < cpuhw->n_events; ++i) {
                        event = cpuhw->event[i];
                        if (!event->hw.idx || is_limited_pmc(event->hw.idx))
                                continue;
                        if (pmc_overflow_power7(val[event->hw.idx - 1])) {
                                /* event has overflowed in a buggy way*/
                                found = 1;
                                record_and_restart(event,
                                                   val[event->hw.idx - 1],
                                                   regs);
                        }
                }
        }
        if (!found && !nmi && printk_ratelimit())
                printk(KERN_WARNING "Can't find PMC that caused IRQ\n");

        /*
         * Reset MMCR0 to its normal value.  This will set PMXE and
         * clear FC (freeze counters) and PMAO (perf mon alert occurred)
         * and thus allow interrupts to occur again.
         * XXX might want to use MSR.PM to keep the events frozen until
         * we get back out of this interrupt.
         */
        write_mmcr0(cpuhw, cpuhw->mmcr[0]);

        if (nmi)
                nmi_exit();
        else
                irq_exit();
}

static void power_pmu_setup(int cpu)
{
        struct cpu_hw_events *cpuhw = &per_cpu(cpu_hw_events, cpu);

        if (!ppmu)
                return;
        memset(cpuhw, 0, sizeof(*cpuhw));
        cpuhw->mmcr[0] = MMCR0_FC;
}

static int __cpuinit
power_pmu_notifier(struct notifier_block *self, unsigned long action, void *hcpu)
{
        unsigned int cpu = (long)hcpu;

        switch (action & ~CPU_TASKS_FROZEN) {
        case CPU_UP_PREPARE:
                power_pmu_setup(cpu);
                break;

        default:
                break;
        }

        return NOTIFY_OK;
}

int __cpuinit register_power_pmu(struct power_pmu *pmu)
{
        if (ppmu)
                return -EBUSY;          /* something's already registered */

        ppmu = pmu;
        pr_info("%s performance monitor hardware support registered\n",
                pmu->name);

        power_pmu.attr_groups = ppmu->attr_groups;

#ifdef MSR_HV
        /*
         * Use FCHV to ignore kernel events if MSR.HV is set.
         */
        if (mfmsr() & MSR_HV)
                freeze_events_kernel = MMCR0_FCHV;
#endif /* CONFIG_PPC64 */

        perf_pmu_register(&power_pmu, "cpu", PERF_TYPE_RAW);
        perf_cpu_notifier(power_pmu_notifier);

        return 0;
}