cpufreq: powernv: Fix crash in gpstate_timer_handler()

[deliverable/linux.git] / drivers / cpufreq / powernv-cpufreq.c

/*
 * POWERNV cpufreq driver for the IBM POWER processors
 *
 * (C) Copyright IBM 2014
 *
 * Author: Vaidyanathan Srinivasan <svaidy at linux.vnet.ibm.com>
 *
 * 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, or (at your option)
 * any later version.
 *
 * 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.  See the
 * GNU General Public License for more details.
 *
 */

#define pr_fmt(fmt)     "powernv-cpufreq: " fmt

#include <linux/kernel.h>
#include <linux/sysfs.h>
#include <linux/cpumask.h>
#include <linux/module.h>
#include <linux/cpufreq.h>
#include <linux/smp.h>
#include <linux/of.h>
#include <linux/reboot.h>
#include <linux/slab.h>
#include <linux/cpu.h>
#include <trace/events/power.h>

#include <asm/cputhreads.h>
#include <asm/firmware.h>
#include <asm/reg.h>
#include <asm/smp.h> /* Required for cpu_sibling_mask() in UP configs */
#include <asm/opal.h>
#include <linux/timer.h>

#define POWERNV_MAX_PSTATES     256
#define PMSR_PSAFE_ENABLE       (1UL << 30)
#define PMSR_SPR_EM_DISABLE     (1UL << 31)
#define PMSR_MAX(x)             ((x >> 32) & 0xFF)

#define MAX_RAMP_DOWN_TIME                              5120
/*
 * On an idle system we want the global pstate to ramp-down from max value to
 * min over a span of ~5 secs. Also we want it to initially ramp-down slowly and
 * then ramp-down rapidly later on.
 *
 * This gives a percentage rampdown for time elapsed in milliseconds.
 * ramp_down_percentage = ((ms * ms) >> 18)
 *                      ~= 3.8 * (sec * sec)
 *
 * At 0 ms      ramp_down_percent = 0
 * At 5120 ms   ramp_down_percent = 100
 */
#define ramp_down_percent(time)         ((time * time) >> 18)

/* Interval after which the timer is queued to bring down global pstate */
#define GPSTATE_TIMER_INTERVAL                          2000

/**
 * struct global_pstate_info -  Per policy data structure to maintain history of
 *                              global pstates
 * @highest_lpstate_idx:        The local pstate index from which we are
 *                              ramping down
 * @elapsed_time:               Time in ms spent in ramping down from
 *                              highest_lpstate_idx
 * @last_sampled_time:          Time from boot in ms when global pstates were
 *                              last set
 * @last_lpstate_idx,           Last set value of local pstate and global
 * last_gpstate_idx             pstate in terms of cpufreq table index
 * @timer:                      Is used for ramping down if cpu goes idle for
 *                              a long time with global pstate held high
 * @gpstate_lock:               A spinlock to maintain synchronization between
 *                              routines called by the timer handler and
 *                              governer's target_index calls
 */
struct global_pstate_info {
        int highest_lpstate_idx;
        unsigned int elapsed_time;
        unsigned int last_sampled_time;
        int last_lpstate_idx;
        int last_gpstate_idx;
        spinlock_t gpstate_lock;
        struct timer_list timer;
};

static struct cpufreq_frequency_table powernv_freqs[POWERNV_MAX_PSTATES+1];
static bool rebooting, throttled, occ_reset;

static const char * const throttle_reason[] = {
        "No throttling",
        "Power Cap",
        "Processor Over Temperature",
        "Power Supply Failure",
        "Over Current",
        "OCC Reset"
};

enum throttle_reason_type {
        NO_THROTTLE = 0,
        POWERCAP,
        CPU_OVERTEMP,
        POWER_SUPPLY_FAILURE,
        OVERCURRENT,
        OCC_RESET_THROTTLE,
        OCC_MAX_REASON
};

static struct chip {
        unsigned int id;
        bool throttled;
        bool restore;
        u8 throttle_reason;
        cpumask_t mask;
        struct work_struct throttle;
        int throttle_turbo;
        int throttle_sub_turbo;
        int reason[OCC_MAX_REASON];
} *chips;

static int nr_chips;
static DEFINE_PER_CPU(struct chip *, chip_info);

/*
 * Note:
 * The set of pstates consists of contiguous integers.
 * powernv_pstate_info stores the index of the frequency table for
 * max, min and nominal frequencies. It also stores number of
 * available frequencies.
 *
 * powernv_pstate_info.nominal indicates the index to the highest
 * non-turbo frequency.
 */
static struct powernv_pstate_info {
        unsigned int min;
        unsigned int max;
        unsigned int nominal;
        unsigned int nr_pstates;
} powernv_pstate_info;

/* Use following macros for conversions between pstate_id and index */
static inline int idx_to_pstate(unsigned int i)
{
        if (unlikely(i >= powernv_pstate_info.nr_pstates)) {
                pr_warn_once("index %u is out of bound\n", i);
                return powernv_freqs[powernv_pstate_info.nominal].driver_data;
        }

        return powernv_freqs[i].driver_data;
}

static inline unsigned int pstate_to_idx(int pstate)
{
        int min = powernv_freqs[powernv_pstate_info.min].driver_data;
        int max = powernv_freqs[powernv_pstate_info.max].driver_data;

        if (min > 0) {
                if (unlikely((pstate < max) || (pstate > min))) {
                        pr_warn_once("pstate %d is out of bound\n", pstate);
                        return powernv_pstate_info.nominal;
                }
        } else {
                if (unlikely((pstate > max) || (pstate < min))) {
                        pr_warn_once("pstate %d is out of bound\n", pstate);
                        return powernv_pstate_info.nominal;
                }
        }
        /*
         * abs() is deliberately used so that is works with
         * both monotonically increasing and decreasing
         * pstate values
         */
        return abs(pstate - idx_to_pstate(powernv_pstate_info.max));
}

static inline void reset_gpstates(struct cpufreq_policy *policy)
{
        struct global_pstate_info *gpstates = policy->driver_data;

        gpstates->highest_lpstate_idx = 0;
        gpstates->elapsed_time = 0;
        gpstates->last_sampled_time = 0;
        gpstates->last_lpstate_idx = 0;
        gpstates->last_gpstate_idx = 0;
}

/*
 * Initialize the freq table based on data obtained
 * from the firmware passed via device-tree
 */
static int init_powernv_pstates(void)
{
        struct device_node *power_mgt;
        int i, nr_pstates = 0;
        const __be32 *pstate_ids, *pstate_freqs;
        u32 len_ids, len_freqs;
        u32 pstate_min, pstate_max, pstate_nominal;

        power_mgt = of_find_node_by_path("/ibm,opal/power-mgt");
        if (!power_mgt) {
                pr_warn("power-mgt node not found\n");
                return -ENODEV;
        }

        if (of_property_read_u32(power_mgt, "ibm,pstate-min", &pstate_min)) {
                pr_warn("ibm,pstate-min node not found\n");
                return -ENODEV;
        }

        if (of_property_read_u32(power_mgt, "ibm,pstate-max", &pstate_max)) {
                pr_warn("ibm,pstate-max node not found\n");
                return -ENODEV;
        }

        if (of_property_read_u32(power_mgt, "ibm,pstate-nominal",
                                 &pstate_nominal)) {
                pr_warn("ibm,pstate-nominal not found\n");
                return -ENODEV;
        }
        pr_info("cpufreq pstate min %d nominal %d max %d\n", pstate_min,
                pstate_nominal, pstate_max);

        pstate_ids = of_get_property(power_mgt, "ibm,pstate-ids", &len_ids);
        if (!pstate_ids) {
                pr_warn("ibm,pstate-ids not found\n");
                return -ENODEV;
        }

        pstate_freqs = of_get_property(power_mgt, "ibm,pstate-frequencies-mhz",
                                      &len_freqs);
        if (!pstate_freqs) {
                pr_warn("ibm,pstate-frequencies-mhz not found\n");
                return -ENODEV;
        }

        if (len_ids != len_freqs) {
                pr_warn("Entries in ibm,pstate-ids and "
                        "ibm,pstate-frequencies-mhz does not match\n");
        }

        nr_pstates = min(len_ids, len_freqs) / sizeof(u32);
        if (!nr_pstates) {
                pr_warn("No PStates found\n");
                return -ENODEV;
        }

        powernv_pstate_info.nr_pstates = nr_pstates;
        pr_debug("NR PStates %d\n", nr_pstates);
        for (i = 0; i < nr_pstates; i++) {
                u32 id = be32_to_cpu(pstate_ids[i]);
                u32 freq = be32_to_cpu(pstate_freqs[i]);

                pr_debug("PState id %d freq %d MHz\n", id, freq);
                powernv_freqs[i].frequency = freq * 1000; /* kHz */
                powernv_freqs[i].driver_data = id;

                if (id == pstate_max)
                        powernv_pstate_info.max = i;
                else if (id == pstate_nominal)
                        powernv_pstate_info.nominal = i;
                else if (id == pstate_min)
                        powernv_pstate_info.min = i;
        }

        /* End of list marker entry */
        powernv_freqs[i].frequency = CPUFREQ_TABLE_END;
        return 0;
}

/* Returns the CPU frequency corresponding to the pstate_id. */
static unsigned int pstate_id_to_freq(int pstate_id)
{
        int i;

        i = pstate_to_idx(pstate_id);
        if (i >= powernv_pstate_info.nr_pstates || i < 0) {
                pr_warn("PState id %d outside of PState table, "
                        "reporting nominal id %d instead\n",
                        pstate_id, idx_to_pstate(powernv_pstate_info.nominal));
                i = powernv_pstate_info.nominal;
        }

        return powernv_freqs[i].frequency;
}

/*
 * cpuinfo_nominal_freq_show - Show the nominal CPU frequency as indicated by
 * the firmware
 */
static ssize_t cpuinfo_nominal_freq_show(struct cpufreq_policy *policy,
                                        char *buf)
{
        return sprintf(buf, "%u\n",
                powernv_freqs[powernv_pstate_info.nominal].frequency);
}

struct freq_attr cpufreq_freq_attr_cpuinfo_nominal_freq =
        __ATTR_RO(cpuinfo_nominal_freq);

static struct freq_attr *powernv_cpu_freq_attr[] = {
        &cpufreq_freq_attr_scaling_available_freqs,
        &cpufreq_freq_attr_cpuinfo_nominal_freq,
        NULL,
};

#define throttle_attr(name, member)                                     \
static ssize_t name##_show(struct cpufreq_policy *policy, char *buf)    \
{                                                                       \
        struct chip *chip = per_cpu(chip_info, policy->cpu);            \
                                                                        \
        return sprintf(buf, "%u\n", chip->member);                      \
}                                                                       \
                                                                        \
static struct freq_attr throttle_attr_##name = __ATTR_RO(name)          \

throttle_attr(unthrottle, reason[NO_THROTTLE]);
throttle_attr(powercap, reason[POWERCAP]);
throttle_attr(overtemp, reason[CPU_OVERTEMP]);
throttle_attr(supply_fault, reason[POWER_SUPPLY_FAILURE]);
throttle_attr(overcurrent, reason[OVERCURRENT]);
throttle_attr(occ_reset, reason[OCC_RESET_THROTTLE]);
throttle_attr(turbo_stat, throttle_turbo);
throttle_attr(sub_turbo_stat, throttle_sub_turbo);

static struct attribute *throttle_attrs[] = {
        &throttle_attr_unthrottle.attr,
        &throttle_attr_powercap.attr,
        &throttle_attr_overtemp.attr,
        &throttle_attr_supply_fault.attr,
        &throttle_attr_overcurrent.attr,
        &throttle_attr_occ_reset.attr,
        &throttle_attr_turbo_stat.attr,
        &throttle_attr_sub_turbo_stat.attr,
        NULL,
};

static const struct attribute_group throttle_attr_grp = {
        .name   = "throttle_stats",
        .attrs  = throttle_attrs,
};

/* Helper routines */

/* Access helpers to power mgt SPR */

static inline unsigned long get_pmspr(unsigned long sprn)
{
        switch (sprn) {
        case SPRN_PMCR:
                return mfspr(SPRN_PMCR);

        case SPRN_PMICR:
                return mfspr(SPRN_PMICR);

        case SPRN_PMSR:
                return mfspr(SPRN_PMSR);
        }
        BUG();
}

static inline void set_pmspr(unsigned long sprn, unsigned long val)
{
        switch (sprn) {
        case SPRN_PMCR:
                mtspr(SPRN_PMCR, val);
                return;

        case SPRN_PMICR:
                mtspr(SPRN_PMICR, val);
                return;
        }
        BUG();
}

/*
 * Use objects of this type to query/update
 * pstates on a remote CPU via smp_call_function.
 */
struct powernv_smp_call_data {
        unsigned int freq;
        int pstate_id;
        int gpstate_id;
};

/*
 * powernv_read_cpu_freq: Reads the current frequency on this CPU.
 *
 * Called via smp_call_function.
 *
 * Note: The caller of the smp_call_function should pass an argument of
 * the type 'struct powernv_smp_call_data *' along with this function.
 *
 * The current frequency on this CPU will be returned via
 * ((struct powernv_smp_call_data *)arg)->freq;
 */
static void powernv_read_cpu_freq(void *arg)
{
        unsigned long pmspr_val;
        s8 local_pstate_id;
        struct powernv_smp_call_data *freq_data = arg;

        pmspr_val = get_pmspr(SPRN_PMSR);

        /*
         * The local pstate id corresponds bits 48..55 in the PMSR.
         * Note: Watch out for the sign!
         */
        local_pstate_id = (pmspr_val >> 48) & 0xFF;
        freq_data->pstate_id = local_pstate_id;
        freq_data->freq = pstate_id_to_freq(freq_data->pstate_id);

        pr_debug("cpu %d pmsr %016lX pstate_id %d frequency %d kHz\n",
                raw_smp_processor_id(), pmspr_val, freq_data->pstate_id,
                freq_data->freq);
}

/*
 * powernv_cpufreq_get: Returns the CPU frequency as reported by the
 * firmware for CPU 'cpu'. This value is reported through the sysfs
 * file cpuinfo_cur_freq.
 */
static unsigned int powernv_cpufreq_get(unsigned int cpu)
{
        struct powernv_smp_call_data freq_data;

        smp_call_function_any(cpu_sibling_mask(cpu), powernv_read_cpu_freq,
                        &freq_data, 1);

        return freq_data.freq;
}

/*
 * set_pstate: Sets the pstate on this CPU.
 *
 * This is called via an smp_call_function.
 *
 * The caller must ensure that freq_data is of the type
 * (struct powernv_smp_call_data *) and the pstate_id which needs to be set
 * on this CPU should be present in freq_data->pstate_id.
 */
static void set_pstate(void *data)
{
        unsigned long val;
        struct powernv_smp_call_data *freq_data = data;
        unsigned long pstate_ul = freq_data->pstate_id;
        unsigned long gpstate_ul = freq_data->gpstate_id;

        val = get_pmspr(SPRN_PMCR);
        val = val & 0x0000FFFFFFFFFFFFULL;

        pstate_ul = pstate_ul & 0xFF;
        gpstate_ul = gpstate_ul & 0xFF;

        /* Set both global(bits 56..63) and local(bits 48..55) PStates */
        val = val | (gpstate_ul << 56) | (pstate_ul << 48);

        pr_debug("Setting cpu %d pmcr to %016lX\n",
                        raw_smp_processor_id(), val);
        set_pmspr(SPRN_PMCR, val);
}

/*
 * get_nominal_index: Returns the index corresponding to the nominal
 * pstate in the cpufreq table
 */
static inline unsigned int get_nominal_index(void)
{
        return powernv_pstate_info.nominal;
}

static void powernv_cpufreq_throttle_check(void *data)
{
        struct chip *chip;
        unsigned int cpu = smp_processor_id();
        unsigned long pmsr;
        int pmsr_pmax;
        unsigned int pmsr_pmax_idx;

        pmsr = get_pmspr(SPRN_PMSR);
        chip = this_cpu_read(chip_info);

        /* Check for Pmax Capping */
        pmsr_pmax = (s8)PMSR_MAX(pmsr);
        pmsr_pmax_idx = pstate_to_idx(pmsr_pmax);
        if (pmsr_pmax_idx != powernv_pstate_info.max) {
                if (chip->throttled)
                        goto next;
                chip->throttled = true;
                if (pmsr_pmax_idx > powernv_pstate_info.nominal) {
                        pr_warn_once("CPU %d on Chip %u has Pmax(%d) reduced below nominal frequency(%d)\n",
                                     cpu, chip->id, pmsr_pmax,
                                     idx_to_pstate(powernv_pstate_info.nominal));
                        chip->throttle_sub_turbo++;
                } else {
                        chip->throttle_turbo++;
                }
                trace_powernv_throttle(chip->id,
                                      throttle_reason[chip->throttle_reason],
                                      pmsr_pmax);
        } else if (chip->throttled) {
                chip->throttled = false;
                trace_powernv_throttle(chip->id,
                                      throttle_reason[chip->throttle_reason],
                                      pmsr_pmax);
        }

        /* Check if Psafe_mode_active is set in PMSR. */
next:
        if (pmsr & PMSR_PSAFE_ENABLE) {
                throttled = true;
                pr_info("Pstate set to safe frequency\n");
        }

        /* Check if SPR_EM_DISABLE is set in PMSR */
        if (pmsr & PMSR_SPR_EM_DISABLE) {
                throttled = true;
                pr_info("Frequency Control disabled from OS\n");
        }

        if (throttled) {
                pr_info("PMSR = %16lx\n", pmsr);
                pr_warn("CPU Frequency could be throttled\n");
        }
}

/**
 * calc_global_pstate - Calculate global pstate
 * @elapsed_time:               Elapsed time in milliseconds
 * @local_pstate_idx:           New local pstate
 * @highest_lpstate_idx:        pstate from which its ramping down
 *
 * Finds the appropriate global pstate based on the pstate from which its
 * ramping down and the time elapsed in ramping down. It follows a quadratic
 * equation which ensures that it reaches ramping down to pmin in 5sec.
 */
static inline int calc_global_pstate(unsigned int elapsed_time,
                                     int highest_lpstate_idx,
                                     int local_pstate_idx)
{
        int index_diff;

        /*
         * Using ramp_down_percent we get the percentage of rampdown
         * that we are expecting to be dropping. Difference between
         * highest_lpstate_idx and powernv_pstate_info.min will give a absolute
         * number of how many pstates we will drop eventually by the end of
         * 5 seconds, then just scale it get the number pstates to be dropped.
         */
        index_diff =  ((int)ramp_down_percent(elapsed_time) *
                        (powernv_pstate_info.min - highest_lpstate_idx)) / 100;

        /* Ensure that global pstate is >= to local pstate */
        if (highest_lpstate_idx + index_diff >= local_pstate_idx)
                return local_pstate_idx;
        else
                return highest_lpstate_idx + index_diff;
}

static inline void  queue_gpstate_timer(struct global_pstate_info *gpstates)
{
        unsigned int timer_interval;

        /*
         * Setting up timer to fire after GPSTATE_TIMER_INTERVAL ms, But
         * if it exceeds MAX_RAMP_DOWN_TIME ms for ramp down time.
         * Set timer such that it fires exactly at MAX_RAMP_DOWN_TIME
         * seconds of ramp down time.
         */
        if ((gpstates->elapsed_time + GPSTATE_TIMER_INTERVAL)
             > MAX_RAMP_DOWN_TIME)
                timer_interval = MAX_RAMP_DOWN_TIME - gpstates->elapsed_time;
        else
                timer_interval = GPSTATE_TIMER_INTERVAL;

        mod_timer_pinned(&gpstates->timer, jiffies +
                        msecs_to_jiffies(timer_interval));
}

/**
 * gpstate_timer_handler
 *
 * @data: pointer to cpufreq_policy on which timer was queued
 *
 * This handler brings down the global pstate closer to the local pstate
 * according quadratic equation. Queues a new timer if it is still not equal
 * to local pstate
 */
void gpstate_timer_handler(unsigned long data)
{
        struct cpufreq_policy *policy = (struct cpufreq_policy *)data;
        struct global_pstate_info *gpstates = policy->driver_data;
        int gpstate_idx;
        unsigned int time_diff = jiffies_to_msecs(jiffies)
                                        - gpstates->last_sampled_time;
        struct powernv_smp_call_data freq_data;

        if (!spin_trylock(&gpstates->gpstate_lock))
                return;

        gpstates->last_sampled_time += time_diff;
        gpstates->elapsed_time += time_diff;
        freq_data.pstate_id = idx_to_pstate(gpstates->last_lpstate_idx);

        if ((gpstates->last_gpstate_idx == gpstates->last_lpstate_idx) ||
            (gpstates->elapsed_time > MAX_RAMP_DOWN_TIME)) {
                gpstate_idx = pstate_to_idx(freq_data.pstate_id);
                reset_gpstates(policy);
                gpstates->highest_lpstate_idx = gpstate_idx;
        } else {
                gpstate_idx = calc_global_pstate(gpstates->elapsed_time,
                                                 gpstates->highest_lpstate_idx,
                                                 gpstates->last_lpstate_idx);
        }

        /*
         * If local pstate is equal to global pstate, rampdown is over
         * So timer is not required to be queued.
         */
        if (gpstate_idx != gpstates->last_lpstate_idx)
                queue_gpstate_timer(gpstates);

        freq_data.gpstate_id = idx_to_pstate(gpstate_idx);
        gpstates->last_gpstate_idx = pstate_to_idx(freq_data.gpstate_id);
        gpstates->last_lpstate_idx = pstate_to_idx(freq_data.pstate_id);

        spin_unlock(&gpstates->gpstate_lock);

        /* Timer may get migrated to a different cpu on cpu hot unplug */
        smp_call_function_any(policy->cpus, set_pstate, &freq_data, 1);
}

/*
 * powernv_cpufreq_target_index: Sets the frequency corresponding to
 * the cpufreq table entry indexed by new_index on the cpus in the
 * mask policy->cpus
 */
static int powernv_cpufreq_target_index(struct cpufreq_policy *policy,
                                        unsigned int new_index)
{
        struct powernv_smp_call_data freq_data;
        unsigned int cur_msec, gpstate_idx;
        struct global_pstate_info *gpstates = policy->driver_data;

        if (unlikely(rebooting) && new_index != get_nominal_index())
                return 0;

        if (!throttled)
                powernv_cpufreq_throttle_check(NULL);

        cur_msec = jiffies_to_msecs(get_jiffies_64());

        spin_lock(&gpstates->gpstate_lock);
        freq_data.pstate_id = idx_to_pstate(new_index);

        if (!gpstates->last_sampled_time) {
                gpstate_idx = new_index;
                gpstates->highest_lpstate_idx = new_index;
                goto gpstates_done;
        }

        if (gpstates->last_gpstate_idx < new_index) {
                gpstates->elapsed_time += cur_msec -
                                                 gpstates->last_sampled_time;

                /*
                 * If its has been ramping down for more than MAX_RAMP_DOWN_TIME
                 * we should be resetting all global pstate related data. Set it
                 * equal to local pstate to start fresh.
                 */
                if (gpstates->elapsed_time > MAX_RAMP_DOWN_TIME) {
                        reset_gpstates(policy);
                        gpstates->highest_lpstate_idx = new_index;
                        gpstate_idx = new_index;
                } else {
                /* Elaspsed_time is less than 5 seconds, continue to rampdown */
                        gpstate_idx = calc_global_pstate(gpstates->elapsed_time,
                                                         gpstates->highest_lpstate_idx,
                                                         new_index);
                }
        } else {
                reset_gpstates(policy);
                gpstates->highest_lpstate_idx = new_index;
                gpstate_idx = new_index;
        }

        /*
         * If local pstate is equal to global pstate, rampdown is over
         * So timer is not required to be queued.
         */
        if (gpstate_idx != new_index)
                queue_gpstate_timer(gpstates);
        else
                del_timer_sync(&gpstates->timer);

gpstates_done:
        freq_data.gpstate_id = idx_to_pstate(gpstate_idx);
        gpstates->last_sampled_time = cur_msec;
        gpstates->last_gpstate_idx = gpstate_idx;
        gpstates->last_lpstate_idx = new_index;

        spin_unlock(&gpstates->gpstate_lock);

        /*
         * Use smp_call_function to send IPI and execute the
         * mtspr on target CPU.  We could do that without IPI
         * if current CPU is within policy->cpus (core)
         */
        smp_call_function_any(policy->cpus, set_pstate, &freq_data, 1);
        return 0;
}

static int powernv_cpufreq_cpu_init(struct cpufreq_policy *policy)
{
        int base, i, ret;
        struct kernfs_node *kn;
        struct global_pstate_info *gpstates;

        base = cpu_first_thread_sibling(policy->cpu);

        for (i = 0; i < threads_per_core; i++)
                cpumask_set_cpu(base + i, policy->cpus);

        kn = kernfs_find_and_get(policy->kobj.sd, throttle_attr_grp.name);
        if (!kn) {
                int ret;

                ret = sysfs_create_group(&policy->kobj, &throttle_attr_grp);
                if (ret) {
                        pr_info("Failed to create throttle stats directory for cpu %d\n",
                                policy->cpu);
                        return ret;
                }
        } else {
                kernfs_put(kn);
        }

        gpstates =  kzalloc(sizeof(*gpstates), GFP_KERNEL);
        if (!gpstates)
                return -ENOMEM;

        policy->driver_data = gpstates;

        /* initialize timer */
        init_timer_deferrable(&gpstates->timer);
        gpstates->timer.data = (unsigned long)policy;
        gpstates->timer.function = gpstate_timer_handler;
        gpstates->timer.expires = jiffies +
                                msecs_to_jiffies(GPSTATE_TIMER_INTERVAL);
        spin_lock_init(&gpstates->gpstate_lock);
        ret = cpufreq_table_validate_and_show(policy, powernv_freqs);

        if (ret < 0)
                kfree(policy->driver_data);

        return ret;
}

static int powernv_cpufreq_cpu_exit(struct cpufreq_policy *policy)
{
        /* timer is deleted in cpufreq_cpu_stop() */
        kfree(policy->driver_data);

        return 0;
}

static int powernv_cpufreq_reboot_notifier(struct notifier_block *nb,
                                unsigned long action, void *unused)
{
        int cpu;
        struct cpufreq_policy cpu_policy;

        rebooting = true;
        for_each_online_cpu(cpu) {
                cpufreq_get_policy(&cpu_policy, cpu);
                powernv_cpufreq_target_index(&cpu_policy, get_nominal_index());
        }

        return NOTIFY_DONE;
}

static struct notifier_block powernv_cpufreq_reboot_nb = {
        .notifier_call = powernv_cpufreq_reboot_notifier,
};

void powernv_cpufreq_work_fn(struct work_struct *work)
{
        struct chip *chip = container_of(work, struct chip, throttle);
        unsigned int cpu;
        cpumask_t mask;

        get_online_cpus();
        cpumask_and(&mask, &chip->mask, cpu_online_mask);
        smp_call_function_any(&mask,
                              powernv_cpufreq_throttle_check, NULL, 0);

        if (!chip->restore)
                goto out;

        chip->restore = false;
        for_each_cpu(cpu, &mask) {
                int index;
                struct cpufreq_policy policy;

                cpufreq_get_policy(&policy, cpu);
                index = cpufreq_table_find_index_c(&policy, policy.cur);
                powernv_cpufreq_target_index(&policy, index);
                cpumask_andnot(&mask, &mask, policy.cpus);
        }
out:
        put_online_cpus();
}

static int powernv_cpufreq_occ_msg(struct notifier_block *nb,
                                   unsigned long msg_type, void *_msg)
{
        struct opal_msg *msg = _msg;
        struct opal_occ_msg omsg;
        int i;

        if (msg_type != OPAL_MSG_OCC)
                return 0;

        omsg.type = be64_to_cpu(msg->params[0]);

        switch (omsg.type) {
        case OCC_RESET:
                occ_reset = true;
                pr_info("OCC (On Chip Controller - enforces hard thermal/power limits) Resetting\n");
                /*
                 * powernv_cpufreq_throttle_check() is called in
                 * target() callback which can detect the throttle state
                 * for governors like ondemand.
                 * But static governors will not call target() often thus
                 * report throttling here.
                 */
                if (!throttled) {
                        throttled = true;
                        pr_warn("CPU frequency is throttled for duration\n");
                }

                break;
        case OCC_LOAD:
                pr_info("OCC Loading, CPU frequency is throttled until OCC is started\n");
                break;
        case OCC_THROTTLE:
                omsg.chip = be64_to_cpu(msg->params[1]);
                omsg.throttle_status = be64_to_cpu(msg->params[2]);

                if (occ_reset) {
                        occ_reset = false;
                        throttled = false;
                        pr_info("OCC Active, CPU frequency is no longer throttled\n");

                        for (i = 0; i < nr_chips; i++) {
                                chips[i].restore = true;
                                schedule_work(&chips[i].throttle);
                        }

                        return 0;
                }

                for (i = 0; i < nr_chips; i++)
                        if (chips[i].id == omsg.chip)
                                break;

                if (omsg.throttle_status >= 0 &&
                    omsg.throttle_status <= OCC_MAX_THROTTLE_STATUS) {
                        chips[i].throttle_reason = omsg.throttle_status;
                        chips[i].reason[omsg.throttle_status]++;
                }

                if (!omsg.throttle_status)
                        chips[i].restore = true;

                schedule_work(&chips[i].throttle);
        }
        return 0;
}

static struct notifier_block powernv_cpufreq_opal_nb = {
        .notifier_call  = powernv_cpufreq_occ_msg,
        .next           = NULL,
        .priority       = 0,
};

static void powernv_cpufreq_stop_cpu(struct cpufreq_policy *policy)
{
        struct powernv_smp_call_data freq_data;
        struct global_pstate_info *gpstates = policy->driver_data;

        freq_data.pstate_id = idx_to_pstate(powernv_pstate_info.min);
        freq_data.gpstate_id = idx_to_pstate(powernv_pstate_info.min);
        smp_call_function_single(policy->cpu, set_pstate, &freq_data, 1);
        del_timer_sync(&gpstates->timer);
}

static struct cpufreq_driver powernv_cpufreq_driver = {
        .name           = "powernv-cpufreq",
        .flags          = CPUFREQ_CONST_LOOPS,
        .init           = powernv_cpufreq_cpu_init,
        .exit           = powernv_cpufreq_cpu_exit,
        .verify         = cpufreq_generic_frequency_table_verify,
        .target_index   = powernv_cpufreq_target_index,
        .get            = powernv_cpufreq_get,
        .stop_cpu       = powernv_cpufreq_stop_cpu,
        .attr           = powernv_cpu_freq_attr,
};

static int init_chip_info(void)
{
        unsigned int chip[256];
        unsigned int cpu, i;
        unsigned int prev_chip_id = UINT_MAX;

        for_each_possible_cpu(cpu) {
                unsigned int id = cpu_to_chip_id(cpu);

                if (prev_chip_id != id) {
                        prev_chip_id = id;
                        chip[nr_chips++] = id;
                }
        }

        chips = kcalloc(nr_chips, sizeof(struct chip), GFP_KERNEL);
        if (!chips)
                return -ENOMEM;

        for (i = 0; i < nr_chips; i++) {
                chips[i].id = chip[i];
                cpumask_copy(&chips[i].mask, cpumask_of_node(chip[i]));
                INIT_WORK(&chips[i].throttle, powernv_cpufreq_work_fn);
                for_each_cpu(cpu, &chips[i].mask)
                        per_cpu(chip_info, cpu) =  &chips[i];
        }

        return 0;
}

static inline void clean_chip_info(void)
{
        kfree(chips);
}

static inline void unregister_all_notifiers(void)
{
        opal_message_notifier_unregister(OPAL_MSG_OCC,
                                         &powernv_cpufreq_opal_nb);
        unregister_reboot_notifier(&powernv_cpufreq_reboot_nb);
}

static int __init powernv_cpufreq_init(void)
{
        int rc = 0;

        /* Don't probe on pseries (guest) platforms */
        if (!firmware_has_feature(FW_FEATURE_OPAL))
                return -ENODEV;

        /* Discover pstates from device tree and init */
        rc = init_powernv_pstates();
        if (rc)
                goto out;

        /* Populate chip info */
        rc = init_chip_info();
        if (rc)
                goto out;

        register_reboot_notifier(&powernv_cpufreq_reboot_nb);
        opal_message_notifier_register(OPAL_MSG_OCC, &powernv_cpufreq_opal_nb);

        rc = cpufreq_register_driver(&powernv_cpufreq_driver);
        if (!rc)
                return 0;

        pr_info("Failed to register the cpufreq driver (%d)\n", rc);
        unregister_all_notifiers();
        clean_chip_info();
out:
        pr_info("Platform driver disabled. System does not support PState control\n");
        return rc;
}
module_init(powernv_cpufreq_init);

static void __exit powernv_cpufreq_exit(void)
{
        cpufreq_unregister_driver(&powernv_cpufreq_driver);
        unregister_all_notifiers();
        clean_chip_info();
}
module_exit(powernv_cpufreq_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Vaidyanathan Srinivasan <svaidy at linux.vnet.ibm.com>");