/*
 * In-Memory Collection (IMC) Performance Monitor counter support.
 *
 * Copyright (C) 2017 Madhavan Srinivasan, IBM Corporation.
 *           (C) 2017 Anju T Sudhakar, IBM Corporation.
 *           (C) 2017 Hemant K Shaw, 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 later version.
 */
#include <linux/perf_event.h>
#include <linux/slab.h>
#include <asm/opal.h>
#include <asm/imc-pmu.h>
#include <asm/cputhreads.h>
#include <asm/smp.h>
#include <linux/string.h>

/* Nest IMC data structures and variables */

/*
 * Used to avoid races in counting the nest-pmu units during hotplug
 * register and unregister
 */
static DEFINE_MUTEX(nest_init_lock);
static DEFINE_PER_CPU(struct imc_pmu_ref *, local_nest_imc_refc);
static struct imc_pmu **per_nest_pmu_arr;
static cpumask_t nest_imc_cpumask;
static struct imc_pmu_ref *nest_imc_refc;
static int nest_pmus;

/* Core IMC data structures and variables */

static cpumask_t core_imc_cpumask;
static struct imc_pmu_ref *core_imc_refc;
static struct imc_pmu *core_imc_pmu;

/* Thread IMC data structures and variables */

static DEFINE_PER_CPU(u64 *, thread_imc_mem);
static struct imc_pmu *thread_imc_pmu;
static int thread_imc_mem_size;

static struct imc_pmu *imc_event_to_pmu(struct perf_event *event)
{
        return container_of(event->pmu, struct imc_pmu, pmu);
}

PMU_FORMAT_ATTR(event, "config:0-40");
PMU_FORMAT_ATTR(offset, "config:0-31");
PMU_FORMAT_ATTR(rvalue, "config:32");
PMU_FORMAT_ATTR(mode, "config:33-40");
static struct attribute *imc_format_attrs[] = {
        &format_attr_event.attr,
        &format_attr_offset.attr,
        &format_attr_rvalue.attr,
        &format_attr_mode.attr,
        NULL,
};

static struct attribute_group imc_format_group = {
        .name = "format",
        .attrs = imc_format_attrs,
};

/* Get the cpumask printed to a buffer "buf" */
static ssize_t imc_pmu_cpumask_get_attr(struct device *dev,
                                        struct device_attribute *attr,
                                        char *buf)
{
        struct pmu *pmu = dev_get_drvdata(dev);
        struct imc_pmu *imc_pmu = container_of(pmu, struct imc_pmu, pmu);
        cpumask_t *active_mask;

        switch(imc_pmu->domain){
        case IMC_DOMAIN_NEST:
                active_mask = &nest_imc_cpumask;
                break;
        case IMC_DOMAIN_CORE:
                active_mask = &core_imc_cpumask;
                break;
        default:
                return 0;
        }

        return cpumap_print_to_pagebuf(true, buf, active_mask);
}

static DEVICE_ATTR(cpumask, S_IRUGO, imc_pmu_cpumask_get_attr, NULL);

static struct attribute *imc_pmu_cpumask_attrs[] = {
        &dev_attr_cpumask.attr,
        NULL,
};

static struct attribute_group imc_pmu_cpumask_attr_group = {
        .attrs = imc_pmu_cpumask_attrs,
};

/* device_str_attr_create : Populate event "name" and string "str" in attribute */
static struct attribute *device_str_attr_create(const char *name, const char *str)
{
        struct perf_pmu_events_attr *attr;

        attr = kzalloc(sizeof(*attr), GFP_KERNEL);
        if (!attr)
                return NULL;
        sysfs_attr_init(&attr->attr.attr);

        attr->event_str = str;
        attr->attr.attr.name = name;
        attr->attr.attr.mode = 0444;
        attr->attr.show = perf_event_sysfs_show;

        return &attr->attr.attr;
}

static int imc_parse_event(struct device_node *np, const char *scale,
                                  const char *unit, const char *prefix,
                                  u32 base, struct imc_events *event)
{
        const char *s;
        u32 reg;

        if (of_property_read_u32(np, "reg", &reg))
                goto error;
        /* Add the base_reg value to the "reg" */
        event->value = base + reg;

        if (of_property_read_string(np, "event-name", &s))
                goto error;

        event->name = kasprintf(GFP_KERNEL, "%s%s", prefix, s);
        if (!event->name)
                goto error;

        if (of_property_read_string(np, "scale", &s))
                s = scale;

        if (s) {
                event->scale = kstrdup(s, GFP_KERNEL);
                if (!event->scale)
                        goto error;
        }

        if (of_property_read_string(np, "unit", &s))
                s = unit;

        if (s) {
                event->unit = kstrdup(s, GFP_KERNEL);
                if (!event->unit)
                        goto error;
        }

        return 0;
error:
        kfree(event->unit);
        kfree(event->scale);
        kfree(event->name);
        return -EINVAL;
}

/*
 * imc_free_events: Function to cleanup the events list, having
 *                  "nr_entries".
 */
static void imc_free_events(struct imc_events *events, int nr_entries)
{
        int i;

        /* Nothing to clean, return */
        if (!events)
                return;
        for (i = 0; i < nr_entries; i++) {
                kfree(events[i].unit);
                kfree(events[i].scale);
                kfree(events[i].name);
        }

        kfree(events);
}

/*
 * update_events_in_group: Update the "events" information in an attr_group
 *                         and assign the attr_group to the pmu "pmu".
 */
static int update_events_in_group(struct device_node *node, struct imc_pmu *pmu)
{
        struct attribute_group *attr_group;
        struct attribute **attrs, *dev_str;
        struct device_node *np, *pmu_events;
        u32 handle, base_reg;
        int i = 0, j = 0, ct, ret;
        const char *prefix, *g_scale, *g_unit;
        const char *ev_val_str, *ev_scale_str, *ev_unit_str;

        if (!of_property_read_u32(node, "events", &handle))
                pmu_events = of_find_node_by_phandle(handle);
        else
                return 0;

        /* Did not find any node with a given phandle */
        if (!pmu_events)
                return 0;

        /* Get a count of number of child nodes */
        ct = of_get_child_count(pmu_events);

        /* Get the event prefix */
        if (of_property_read_string(node, "events-prefix", &prefix))
                return 0;

        /* Get a global unit and scale data if available */
        if (of_property_read_string(node, "scale", &g_scale))
                g_scale = NULL;

        if (of_property_read_string(node, "unit", &g_unit))
                g_unit = NULL;

        /* "reg" property gives out the base offset of the counters data */
        of_property_read_u32(node, "reg", &base_reg);

        /* Allocate memory for the events */
        pmu->events = kcalloc(ct, sizeof(struct imc_events), GFP_KERNEL);
        if (!pmu->events)
                return -ENOMEM;

        ct = 0;
        /* Parse the events and update the struct */
        for_each_child_of_node(pmu_events, np) {
                ret = imc_parse_event(np, g_scale, g_unit, prefix, base_reg, &pmu->events[ct]);
                if (!ret)
                        ct++;
        }

        /* Allocate memory for attribute group */
        attr_group = kzalloc(sizeof(*attr_group), GFP_KERNEL);
        if (!attr_group) {
                imc_free_events(pmu->events, ct);
                return -ENOMEM;
        }

        /*
         * Allocate memory for attributes.
         * Since we have count of events for this pmu, we also allocate
         * memory for the scale and unit attribute for now.
         * "ct" has the total event structs added from the events-parent node.
         * So allocate three times the "ct" (this includes event, event_scale and
         * event_unit).
         */
        attrs = kcalloc(((ct * 3) + 1), sizeof(struct attribute *), GFP_KERNEL);
        if (!attrs) {
                kfree(attr_group);
                imc_free_events(pmu->events, ct);
                return -ENOMEM;
        }

        attr_group->name = "events";
        attr_group->attrs = attrs;
        do {
                ev_val_str = kasprintf(GFP_KERNEL, "event=0x%x", pmu->events[i].value);
                dev_str = device_str_attr_create(pmu->events[i].name, ev_val_str);
                if (!dev_str)
                        continue;

                attrs[j++] = dev_str;
                if (pmu->events[i].scale) {
                        ev_scale_str = kasprintf(GFP_KERNEL, "%s.scale", pmu->events[i].name);
                        dev_str = device_str_attr_create(ev_scale_str, pmu->events[i].scale);
                        if (!dev_str)
                                continue;

                        attrs[j++] = dev_str;
                }

                if (pmu->events[i].unit) {
                        ev_unit_str = kasprintf(GFP_KERNEL, "%s.unit", pmu->events[i].name);
                        dev_str = device_str_attr_create(ev_unit_str, pmu->events[i].unit);
                        if (!dev_str)
                                continue;

                        attrs[j++] = dev_str;
                }
        } while (++i < ct);

        /* Save the event attribute */
        pmu->attr_groups[IMC_EVENT_ATTR] = attr_group;

        return 0;
}

/* get_nest_pmu_ref: Return the imc_pmu_ref struct for the given node */
static struct imc_pmu_ref *get_nest_pmu_ref(int cpu)
{
        return per_cpu(local_nest_imc_refc, cpu);
}

static void nest_change_cpu_context(int old_cpu, int new_cpu)
{
        struct imc_pmu **pn = per_nest_pmu_arr;

        if (old_cpu < 0 || new_cpu < 0)
                return;

        while (*pn) {
                perf_pmu_migrate_context(&(*pn)->pmu, old_cpu, new_cpu);
                pn++;
        }
}

static int ppc_nest_imc_cpu_offline(unsigned int cpu)
{
        int nid, target = -1;
        const struct cpumask *l_cpumask;
        struct imc_pmu_ref *ref;

        /*
         * Check in the designated list for this cpu. Dont bother
         * if not one of them.
         */
        if (!cpumask_test_and_clear_cpu(cpu, &nest_imc_cpumask))
                return 0;

        /*
         * Check whether nest_imc is registered. We could end up here if the
         * cpuhotplug callback registration fails. i.e, callback invokes the
         * offline path for all successfully registered nodes. At this stage,
         * nest_imc pmu will not be registered and we should return here.
         *
         * We return with a zero since this is not an offline failure. And
         * cpuhp_setup_state() returns the actual failure reason to the caller,
         * which in turn will call the cleanup routine.
         */
        if (!nest_pmus)
                return 0;

        /*
         * Now that this cpu is one of the designated,
         * find a next cpu a) which is online and b) in same chip.
         */
        nid = cpu_to_node(cpu);
        l_cpumask = cpumask_of_node(nid);
        target = cpumask_any_but(l_cpumask, cpu);

        /*
         * Update the cpumask with the target cpu and
         * migrate the context if needed
         */
        if (target >= 0 && target < nr_cpu_ids) {
                cpumask_set_cpu(target, &nest_imc_cpumask);
                nest_change_cpu_context(cpu, target);
        } else {
                opal_imc_counters_stop(OPAL_IMC_COUNTERS_NEST,
                                       get_hard_smp_processor_id(cpu));
                /*
                 * If this is the last cpu in this chip then, skip the reference
                 * count mutex lock and make the reference count on this chip zero.
                 */
                ref = get_nest_pmu_ref(cpu);
                if (!ref)
                        return -EINVAL;

                ref->refc = 0;
        }
        return 0;
}

static int ppc_nest_imc_cpu_online(unsigned int cpu)
{
        const struct cpumask *l_cpumask;
        static struct cpumask tmp_mask;
        int res;

        /* Get the cpumask of this node */
        l_cpumask = cpumask_of_node(cpu_to_node(cpu));

        /*
         * If this is not the first online CPU on this node, then
         * just return.
         */
        if (cpumask_and(&tmp_mask, l_cpumask, &nest_imc_cpumask))
                return 0;

        /*
         * If this is the first online cpu on this node
         * disable the nest counters by making an OPAL call.
         */
        res = opal_imc_counters_stop(OPAL_IMC_COUNTERS_NEST,
                                     get_hard_smp_processor_id(cpu));
        if (res)
                return res;

        /* Make this CPU the designated target for counter collection */
        cpumask_set_cpu(cpu, &nest_imc_cpumask);
        return 0;
}

static int nest_pmu_cpumask_init(void)
{
        return cpuhp_setup_state(CPUHP_AP_PERF_POWERPC_NEST_IMC_ONLINE,
                                 "perf/powerpc/imc:online",
                                 ppc_nest_imc_cpu_online,
                                 ppc_nest_imc_cpu_offline);
}

static void nest_imc_counters_release(struct perf_event *event)
{
        int rc, node_id;
        struct imc_pmu_ref *ref;

        if (event->cpu < 0)
                return;

        node_id = cpu_to_node(event->cpu);

        /*
         * See if we need to disable the nest 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
         * enable or disable the nest counters.
         */
        ref = get_nest_pmu_ref(event->cpu);
        if (!ref)
                return;

        /* Take the mutex lock for this node and then decrement the reference count */
        mutex_lock(&ref->lock);
        if (ref->refc == 0) {
                /*
                 * The scenario where this is true is, when perf session is
                 * started, followed by offlining of all cpus in a given node.
                 *
                 * In the cpuhotplug offline path, ppc_nest_imc_cpu_offline()
                 * function set the ref->count to zero, if the cpu which is
                 * about to offline is the last cpu in a given node and make
                 * an OPAL call to disable the engine in that node.
                 *
                 */
                mutex_unlock(&ref->lock);
                return;
        }
        ref->refc--;
        if (ref->refc == 0) {
                rc = opal_imc_counters_stop(OPAL_IMC_COUNTERS_NEST,
                                            get_hard_smp_processor_id(event->cpu));
                if (rc) {
                        mutex_unlock(&ref->lock);
                        pr_err("nest-imc: Unable to stop the counters for core %d\n", node_id);
                        return;
                }
        } else if (ref->refc < 0) {
                WARN(1, "nest-imc: Invalid event reference count\n");
                ref->refc = 0;
        }
        mutex_unlock(&ref->lock);
}

static int nest_imc_event_init(struct perf_event *event)
{
        int chip_id, rc, node_id;
        u32 l_config, config = event->attr.config;
        struct imc_mem_info *pcni;
        struct imc_pmu *pmu;
        struct imc_pmu_ref *ref;
        bool flag = false;

        if (event->attr.type != event->pmu->type)
                return -ENOENT;

        /* Sampling not supported */
        if (event->hw.sample_period)
                return -EINVAL;

        if (event->cpu < 0)
                return -EINVAL;

        pmu = imc_event_to_pmu(event);

        /* Sanity check for config (event offset) */
        if ((config & IMC_EVENT_OFFSET_MASK) > pmu->counter_mem_size)
                return -EINVAL;

        /*
         * Nest HW counter memory resides in a per-chip reserve-memory (HOMER).
         * Get the base memory addresss for this cpu.
         */
        chip_id = cpu_to_chip_id(event->cpu);
        pcni = pmu->mem_info;
        do {
                if (pcni->id == chip_id) {
                        flag = true;
                        break;
                }
                pcni++;
        } while (pcni);

        if (!flag)
                return -ENODEV;

        /*
         * Add the event offset to the base address.
         */
        l_config = config & IMC_EVENT_OFFSET_MASK;
        event->hw.event_base = (u64)pcni->vbase + l_config;
        node_id = cpu_to_node(event->cpu);

        /*
         * Get the imc_pmu_ref struct for this node.
         * Take the mutex lock and then increment the count of nest pmu events
         * inited.
         */
        ref = get_nest_pmu_ref(event->cpu);
        if (!ref)
                return -EINVAL;

        mutex_lock(&ref->lock);
        if (ref->refc == 0) {
                rc = opal_imc_counters_start(OPAL_IMC_COUNTERS_NEST,
                                             get_hard_smp_processor_id(event->cpu));
                if (rc) {
                        mutex_unlock(&ref->lock);
                        pr_err("nest-imc: Unable to start the counters for node %d\n",
                                                                        node_id);
                        return rc;
                }
        }
        ++ref->refc;
        mutex_unlock(&ref->lock);

        event->destroy = nest_imc_counters_release;
        return 0;
}

/*
 * core_imc_mem_init : Initializes memory for the current core.
 *
 * Uses alloc_pages_node() and uses the returned address as an argument to
 * an opal call to configure the pdbar. The address sent as an argument is
 * converted to physical address before the opal call is made. This is the
 * base address at which the core imc counters are populated.
 */
static int core_imc_mem_init(int cpu, int size)
{
        int nid, rc = 0, core_id = (cpu / threads_per_core);
        struct imc_mem_info *mem_info;

        /*
         * alloc_pages_node() will allocate memory for core in the
         * local node only.
         */
        nid = cpu_to_node(cpu);
        mem_info = &core_imc_pmu->mem_info[core_id];
        mem_info->id = core_id;

        /* We need only vbase for core counters */
        mem_info->vbase = page_address(alloc_pages_node(nid,
                                          GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE |
                                          __GFP_NOWARN, get_order(size)));
        if (!mem_info->vbase)
                return -ENOMEM;

        /* Init the mutex */
        core_imc_refc[core_id].id = core_id;
        mutex_init(&core_imc_refc[core_id].lock);

        rc = opal_imc_counters_init(OPAL_IMC_COUNTERS_CORE,
                                __pa((void *)mem_info->vbase),
                                get_hard_smp_processor_id(cpu));
        if (rc) {
                free_pages((u64)mem_info->vbase, get_order(size));
                mem_info->vbase = NULL;
        }

        return rc;
}

static bool is_core_imc_mem_inited(int cpu)
{
        struct imc_mem_info *mem_info;
        int core_id = (cpu / threads_per_core);

        mem_info = &core_imc_pmu->mem_info[core_id];
        if (!mem_info->vbase)
                return false;

        return true;
}

static int ppc_core_imc_cpu_online(unsigned int cpu)
{
        const struct cpumask *l_cpumask;
        static struct cpumask tmp_mask;
        int ret = 0;

        /* Get the cpumask for this core */
        l_cpumask = cpu_sibling_mask(cpu);

        /* If a cpu for this core is already set, then, don't do anything */
        if (cpumask_and(&tmp_mask, l_cpumask, &core_imc_cpumask))
                return 0;

        if (!is_core_imc_mem_inited(cpu)) {
                ret = core_imc_mem_init(cpu, core_imc_pmu->counter_mem_size);
                if (ret) {
                        pr_info("core_imc memory allocation for cpu %d failed\n", cpu);
                        return ret;
                }
        }

        /* set the cpu in the mask */
        cpumask_set_cpu(cpu, &core_imc_cpumask);
        return 0;
}

static int ppc_core_imc_cpu_offline(unsigned int cpu)
{
        unsigned int core_id;
        int ncpu;
        struct imc_pmu_ref *ref;

        /*
         * clear this cpu out of the mask, if not present in the mask,
         * don't bother doing anything.
         */
        if (!cpumask_test_and_clear_cpu(cpu, &core_imc_cpumask))
                return 0;

        /*
         * Check whether core_imc is registered. We could end up here
         * if the cpuhotplug callback registration fails. i.e, callback
         * invokes the offline path for all sucessfully registered cpus.
         * At this stage, core_imc pmu will not be registered and we
         * should return here.
         *
         * We return with a zero since this is not an offline failure.
         * And cpuhp_setup_state() returns the actual failure reason
         * to the caller, which inturn will call the cleanup routine.
         */
        if (!core_imc_pmu->pmu.event_init)
                return 0;

        /* Find any online cpu in that core except the current "cpu" */
        ncpu = cpumask_any_but(cpu_sibling_mask(cpu), cpu);

        if (ncpu >= 0 && ncpu < nr_cpu_ids) {
                cpumask_set_cpu(ncpu, &core_imc_cpumask);
                perf_pmu_migrate_context(&core_imc_pmu->pmu, cpu, ncpu);
        } else {
                /*
                 * If this is the last cpu in this core then, skip taking refernce
                 * count mutex lock for this core and directly zero "refc" for
                 * this core.
                 */
                opal_imc_counters_stop(OPAL_IMC_COUNTERS_CORE,
                                       get_hard_smp_processor_id(cpu));
                core_id = cpu / threads_per_core;
                ref = &core_imc_refc[core_id];
                if (!ref)
                        return -EINVAL;

                ref->refc = 0;
        }
        return 0;
}

static int core_imc_pmu_cpumask_init(void)
{
        return cpuhp_setup_state(CPUHP_AP_PERF_POWERPC_CORE_IMC_ONLINE,
                                 "perf/powerpc/imc_core:online",
                                 ppc_core_imc_cpu_online,
                                 ppc_core_imc_cpu_offline);
}

static void core_imc_counters_release(struct perf_event *event)
{
        int rc, core_id;
        struct imc_pmu_ref *ref;

        if (event->cpu < 0)
                return;
        /*
         * See if we need to disable the IMC 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
         * enable or disable the core counters.
         */
        core_id = event->cpu / threads_per_core;

        /* Take the mutex lock and decrement the refernce count for this core */
        ref = &core_imc_refc[core_id];
        if (!ref)
                return;

        mutex_lock(&ref->lock);
        if (ref->refc == 0) {
                /*
                 * The scenario where this is true is, when perf session is
                 * started, followed by offlining of all cpus in a given core.
                 *
                 * In the cpuhotplug offline path, ppc_core_imc_cpu_offline()
                 * function set the ref->count to zero, if the cpu which is
                 * about to offline is the last cpu in a given core and make
                 * an OPAL call to disable the engine in that core.
                 *
                 */
                mutex_unlock(&ref->lock);
                return;
        }
        ref->refc--;
        if (ref->refc == 0) {
                rc = opal_imc_counters_stop(OPAL_IMC_COUNTERS_CORE,
                                            get_hard_smp_processor_id(event->cpu));
                if (rc) {
                        mutex_unlock(&ref->lock);
                        pr_err("IMC: Unable to stop the counters for core %d\n", core_id);
                        return;
                }
        } else if (ref->refc < 0) {
                WARN(1, "core-imc: Invalid event reference count\n");
                ref->refc = 0;
        }
        mutex_unlock(&ref->lock);
}

static int core_imc_event_init(struct perf_event *event)
{
        int core_id, rc;
        u64 config = event->attr.config;
        struct imc_mem_info *pcmi;
        struct imc_pmu *pmu;
        struct imc_pmu_ref *ref;

        if (event->attr.type != event->pmu->type)
                return -ENOENT;

        /* Sampling not supported */
        if (event->hw.sample_period)
                return -EINVAL;

        if (event->cpu < 0)
                return -EINVAL;

        event->hw.idx = -1;
        pmu = imc_event_to_pmu(event);

        /* Sanity check for config (event offset) */
        if (((config & IMC_EVENT_OFFSET_MASK) > pmu->counter_mem_size))
                return -EINVAL;

        if (!is_core_imc_mem_inited(event->cpu))
                return -ENODEV;

        core_id = event->cpu / threads_per_core;
        pcmi = &core_imc_pmu->mem_info[core_id];
        if ((!pcmi->vbase))
                return -ENODEV;

        /* Get the core_imc mutex for this core */
        ref = &core_imc_refc[core_id];
        if (!ref)
                return -EINVAL;

        /*
         * Core pmu units are enabled only when it is used.
         * See if this is triggered for the first time.
         * If yes, take the mutex lock and enable the core counters.
         * If not, just increment the count in core_imc_refc struct.
         */
        mutex_lock(&ref->lock);
        if (ref->refc == 0) {
                rc = opal_imc_counters_start(OPAL_IMC_COUNTERS_CORE,
                                             get_hard_smp_processor_id(event->cpu));
                if (rc) {
                        mutex_unlock(&ref->lock);
                        pr_err("core-imc: Unable to start the counters for core %d\n",
                                                                        core_id);
                        return rc;
                }
        }
        ++ref->refc;
        mutex_unlock(&ref->lock);

        event->hw.event_base = (u64)pcmi->vbase + (config & IMC_EVENT_OFFSET_MASK);
        event->destroy = core_imc_counters_release;
        return 0;
}

/*
 * Allocates a page of memory for each of the online cpus, and write the
 * physical base address of that page to the LDBAR for that cpu.
 *
 * LDBAR Register Layout:
 *
 *  0          4         8         12        16        20        24        28
 * | - - - - | - - - - | - - - - | - - - - | - - - - | - - - - | - - - - | - - - - |
 *   | |       [   ]    [                   Counter Address [8:50]
 *   | * Mode    |
 *   |           * PB Scope
 *   * Enable/Disable
 *
 *  32        36        40        44        48        52        56        60
 * | - - - - | - - - - | - - - - | - - - - | - - - - | - - - - | - - - - | - - - - |
 *           Counter Address [8:50]              ]
 *
 */
static int thread_imc_mem_alloc(int cpu_id, int size)
{
        u64 ldbar_value, *local_mem = per_cpu(thread_imc_mem, cpu_id);
        int nid = cpu_to_node(cpu_id);

        if (!local_mem) {
                /*
                 * This case could happen only once at start, since we dont
                 * free the memory in cpu offline path.
                 */
                local_mem = page_address(alloc_pages_node(nid,
                                  GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE |
                                  __GFP_NOWARN, get_order(size)));
                if (!local_mem)
                        return -ENOMEM;

                per_cpu(thread_imc_mem, cpu_id) = local_mem;
        }

        ldbar_value = ((u64)local_mem & THREAD_IMC_LDBAR_MASK) | THREAD_IMC_ENABLE;

        mtspr(SPRN_LDBAR, ldbar_value);
        return 0;
}

static int ppc_thread_imc_cpu_online(unsigned int cpu)
{
        return thread_imc_mem_alloc(cpu, thread_imc_mem_size);
}

static int ppc_thread_imc_cpu_offline(unsigned int cpu)
{
        mtspr(SPRN_LDBAR, 0);
        return 0;
}

static int thread_imc_cpu_init(void)
{
        return cpuhp_setup_state(CPUHP_AP_PERF_POWERPC_THREAD_IMC_ONLINE,
                          "perf/powerpc/imc_thread:online",
                          ppc_thread_imc_cpu_online,
                          ppc_thread_imc_cpu_offline);
}

static int thread_imc_event_init(struct perf_event *event)
{
        u32 config = event->attr.config;
        struct task_struct *target;
        struct imc_pmu *pmu;

        if (event->attr.type != event->pmu->type)
                return -ENOENT;

        /* Sampling not supported */
        if (event->hw.sample_period)
                return -EINVAL;

        event->hw.idx = -1;
        pmu = imc_event_to_pmu(event);

        /* Sanity check for config offset */
        if (((config & IMC_EVENT_OFFSET_MASK) > pmu->counter_mem_size))
                return -EINVAL;

        target = event->hw.target;
        if (!target)
                return -EINVAL;

        event->pmu->task_ctx_nr = perf_sw_context;
        return 0;
}

static bool is_thread_imc_pmu(struct perf_event *event)
{
        if (!strncmp(event->pmu->name, "thread_imc", strlen("thread_imc")))
                return true;

        return false;
}

static u64 * get_event_base_addr(struct perf_event *event)
{
        u64 addr;

        if (is_thread_imc_pmu(event)) {
                addr = (u64)per_cpu(thread_imc_mem, smp_processor_id());
                return (u64 *)(addr + (event->attr.config & IMC_EVENT_OFFSET_MASK));
        }

        return (u64 *)event->hw.event_base;
}

static void thread_imc_pmu_start_txn(struct pmu *pmu,
                                     unsigned int txn_flags)
{
        if (txn_flags & ~PERF_PMU_TXN_ADD)
                return;
        perf_pmu_disable(pmu);
}

static void thread_imc_pmu_cancel_txn(struct pmu *pmu)
{
        perf_pmu_enable(pmu);
}

static int thread_imc_pmu_commit_txn(struct pmu *pmu)
{
        perf_pmu_enable(pmu);
        return 0;
}

static u64 imc_read_counter(struct perf_event *event)
{
        u64 *addr, data;

        /*
         * In-Memory Collection (IMC) counters are free flowing counters.
         * So we take a snapshot of the counter value on enable and save it
         * to calculate the delta at later stage to present the event counter
         * value.
         */
        addr = get_event_base_addr(event);
        data = be64_to_cpu(READ_ONCE(*addr));
        local64_set(&event->hw.prev_count, data);

        return data;
}

static void imc_event_update(struct perf_event *event)
{
        u64 counter_prev, counter_new, final_count;

        counter_prev = local64_read(&event->hw.prev_count);
        counter_new = imc_read_counter(event);
        final_count = counter_new - counter_prev;

        /* Update the delta to the event count */
        local64_add(final_count, &event->count);
}

static void imc_event_start(struct perf_event *event, int flags)
{
        /*
         * In Memory Counters are free flowing counters. HW or the microcode
         * keeps adding to the counter offset in memory. To get event
         * counter value, we snapshot the value here and we calculate
         * delta at later point.
         */
        imc_read_counter(event);
}

static void imc_event_stop(struct perf_event *event, int flags)
{
        /*
         * Take a snapshot and calculate the delta and update
         * the event counter values.
         */
        imc_event_update(event);
}

static int imc_event_add(struct perf_event *event, int flags)
{
        if (flags & PERF_EF_START)
                imc_event_start(event, flags);

        return 0;
}

static int thread_imc_event_add(struct perf_event *event, int flags)
{
        int core_id;
        struct imc_pmu_ref *ref;

        if (flags & PERF_EF_START)
                imc_event_start(event, flags);

        if (!is_core_imc_mem_inited(smp_processor_id()))
                return -EINVAL;

        core_id = smp_processor_id() / threads_per_core;
        /*
         * imc pmus are enabled only when it is used.
         * See if this is triggered for the first time.
         * If yes, take the mutex lock and enable the counters.
         * If not, just increment the count in ref count struct.
         */
        ref = &core_imc_refc[core_id];
        if (!ref)
                return -EINVAL;

        mutex_lock(&ref->lock);
        if (ref->refc == 0) {
                if (opal_imc_counters_start(OPAL_IMC_COUNTERS_CORE,

                    get_hard_smp_processor_id(smp_processor_id()))) {
                        mutex_unlock(&ref->lock);
                        pr_err("thread-imc: Unable to start the counter\
                                for core %d\n", core_id);
                        return -EINVAL;
                }
        }
        ++ref->refc;
        mutex_unlock(&ref->lock);
        return 0;
}

static void thread_imc_event_del(struct perf_event *event, int flags)
{

        int core_id;
        struct imc_pmu_ref *ref;

        /*
         * Take a snapshot and calculate the delta and update
         * the event counter values.
         */
        imc_event_update(event);

        core_id = smp_processor_id() / threads_per_core;
        ref = &core_imc_refc[core_id];

        mutex_lock(&ref->lock);
        ref->refc--;
        if (ref->refc == 0) {
                if (opal_imc_counters_stop(OPAL_IMC_COUNTERS_CORE,
                    get_hard_smp_processor_id(smp_processor_id()))) {
                        mutex_unlock(&ref->lock);
                        pr_err("thread-imc: Unable to stop the counters\
                                for core %d\n", core_id);
                        return;
                }
        } else if (ref->refc < 0) {
                ref->refc = 0;
        }
        mutex_unlock(&ref->lock);
}

/* update_pmu_ops : Populate the appropriate operations for "pmu" */
static int update_pmu_ops(struct imc_pmu *pmu)
{
        pmu->pmu.task_ctx_nr = perf_invalid_context;
        pmu->pmu.add = imc_event_add;
        pmu->pmu.del = imc_event_stop;
        pmu->pmu.start = imc_event_start;
        pmu->pmu.stop = imc_event_stop;
        pmu->pmu.read = imc_event_update;
        pmu->pmu.attr_groups = pmu->attr_groups;
        pmu->pmu.capabilities = PERF_PMU_CAP_NO_EXCLUDE;
        pmu->attr_groups[IMC_FORMAT_ATTR] = &imc_format_group;

        switch (pmu->domain) {
        case IMC_DOMAIN_NEST:
                pmu->pmu.event_init = nest_imc_event_init;
                pmu->attr_groups[IMC_CPUMASK_ATTR] = &imc_pmu_cpumask_attr_group;
                break;
        case IMC_DOMAIN_CORE:
                pmu->pmu.event_init = core_imc_event_init;
                pmu->attr_groups[IMC_CPUMASK_ATTR] = &imc_pmu_cpumask_attr_group;
                break;
        case IMC_DOMAIN_THREAD:
                pmu->pmu.event_init = thread_imc_event_init;
                pmu->pmu.add = thread_imc_event_add;
                pmu->pmu.del = thread_imc_event_del;
                pmu->pmu.start_txn = thread_imc_pmu_start_txn;
                pmu->pmu.cancel_txn = thread_imc_pmu_cancel_txn;
                pmu->pmu.commit_txn = thread_imc_pmu_commit_txn;
                break;
        default:
                break;
        }

        return 0;
}

/* init_nest_pmu_ref: Initialize the imc_pmu_ref struct for all the nodes */
static int init_nest_pmu_ref(void)
{
        int nid, i, cpu;

        nest_imc_refc = kcalloc(num_possible_nodes(), sizeof(*nest_imc_refc),
                                                                GFP_KERNEL);

        if (!nest_imc_refc)
                return -ENOMEM;

        i = 0;
        for_each_node(nid) {
                /*
                 * Mutex lock to avoid races while tracking the number of
                 * sessions using the chip's nest pmu units.
                 */
                mutex_init(&nest_imc_refc[i].lock);

                /*
                 * Loop to init the "id" with the node_id. Variable "i" initialized to
                 * 0 and will be used as index to the array. "i" will not go off the
                 * end of the array since the "for_each_node" loops for "N_POSSIBLE"
                 * nodes only.
                 */
                nest_imc_refc[i++].id = nid;
        }

        /*
         * Loop to init the per_cpu "local_nest_imc_refc" with the proper
         * "nest_imc_refc" index. This makes get_nest_pmu_ref() alot simple.
         */
        for_each_possible_cpu(cpu) {
                nid = cpu_to_node(cpu);
                for (i = 0; i < num_possible_nodes(); i++) {
                        if (nest_imc_refc[i].id == nid) {
                                per_cpu(local_nest_imc_refc, cpu) = &nest_imc_refc[i];
                                break;
                        }
                }
        }
        return 0;
}

static void cleanup_all_core_imc_memory(void)
{
        int i, nr_cores = DIV_ROUND_UP(num_possible_cpus(), threads_per_core);
        struct imc_mem_info *ptr = core_imc_pmu->mem_info;
        int size = core_imc_pmu->counter_mem_size;

        /* mem_info will never be NULL */
        for (i = 0; i < nr_cores; i++) {
                if (ptr[i].vbase)
                        free_pages((u64)ptr[i].vbase, get_order(size));
        }

        kfree(ptr);
        kfree(core_imc_refc);
}

static void thread_imc_ldbar_disable(void *dummy)
{
        /*
         * By Zeroing LDBAR, we disable thread-imc
         * updates.
         */
        mtspr(SPRN_LDBAR, 0);
}

void thread_imc_disable(void)
{
        on_each_cpu(thread_imc_ldbar_disable, NULL, 1);
}

static void cleanup_all_thread_imc_memory(void)
{
        int i, order = get_order(thread_imc_mem_size);

        for_each_online_cpu(i) {
                if (per_cpu(thread_imc_mem, i))
                        free_pages((u64)per_cpu(thread_imc_mem, i), order);

        }
}

/* Function to free the attr_groups which are dynamically allocated */
static void imc_common_mem_free(struct imc_pmu *pmu_ptr)
{
        if (pmu_ptr->attr_groups[IMC_EVENT_ATTR])
                kfree(pmu_ptr->attr_groups[IMC_EVENT_ATTR]->attrs);
        kfree(pmu_ptr->attr_groups[IMC_EVENT_ATTR]);
}

/*
 * Common function to unregister cpu hotplug callback and
 * free the memory.
 * TODO: Need to handle pmu unregistering, which will be
 * done in followup series.
 */
static void imc_common_cpuhp_mem_free(struct imc_pmu *pmu_ptr)
{
        if (pmu_ptr->domain == IMC_DOMAIN_NEST) {
                mutex_lock(&nest_init_lock);
                if (nest_pmus == 1) {
                        cpuhp_remove_state(CPUHP_AP_PERF_POWERPC_NEST_IMC_ONLINE);
                        kfree(nest_imc_refc);
                        kfree(per_nest_pmu_arr);
                        per_nest_pmu_arr = NULL;
                }

                if (nest_pmus > 0)
                        nest_pmus--;
                mutex_unlock(&nest_init_lock);
        }

        /* Free core_imc memory */
        if (pmu_ptr->domain == IMC_DOMAIN_CORE) {
                cpuhp_remove_state(CPUHP_AP_PERF_POWERPC_CORE_IMC_ONLINE);
                cleanup_all_core_imc_memory();
        }

        /* Free thread_imc memory */
        if (pmu_ptr->domain == IMC_DOMAIN_THREAD) {
                cpuhp_remove_state(CPUHP_AP_PERF_POWERPC_THREAD_IMC_ONLINE);
                cleanup_all_thread_imc_memory();
        }
}

/*
 * Function to unregister thread-imc if core-imc
 * is not registered.
 */
void unregister_thread_imc(void)
{
        imc_common_cpuhp_mem_free(thread_imc_pmu);
        imc_common_mem_free(thread_imc_pmu);
        perf_pmu_unregister(&thread_imc_pmu->pmu);
}

/*
 * imc_mem_init : Function to support memory allocation for core imc.
 */
static int imc_mem_init(struct imc_pmu *pmu_ptr, struct device_node *parent,
                                                                int pmu_index)
{
        const char *s;
        int nr_cores, cpu, res = -ENOMEM;

        if (of_property_read_string(parent, "name", &s))
                return -ENODEV;

        switch (pmu_ptr->domain) {
        case IMC_DOMAIN_NEST:
                /* Update the pmu name */
                pmu_ptr->pmu.name = kasprintf(GFP_KERNEL, "%s%s_imc", "nest_", s);
                if (!pmu_ptr->pmu.name)
                        goto err;

                /* Needed for hotplug/migration */
                if (!per_nest_pmu_arr) {
                        per_nest_pmu_arr = kcalloc(get_max_nest_dev() + 1,
                                                sizeof(struct imc_pmu *),
                                                GFP_KERNEL);
                        if (!per_nest_pmu_arr)
                                goto err;
                }
                per_nest_pmu_arr[pmu_index] = pmu_ptr;
                break;
        case IMC_DOMAIN_CORE:
                /* Update the pmu name */
                pmu_ptr->pmu.name = kasprintf(GFP_KERNEL, "%s%s", s, "_imc");
                if (!pmu_ptr->pmu.name)
                        goto err;

                nr_cores = DIV_ROUND_UP(num_possible_cpus(), threads_per_core);
                pmu_ptr->mem_info = kcalloc(nr_cores, sizeof(struct imc_mem_info),
                                                                GFP_KERNEL);

                if (!pmu_ptr->mem_info)
                        goto err;

                core_imc_refc = kcalloc(nr_cores, sizeof(struct imc_pmu_ref),
                                                                GFP_KERNEL);

                if (!core_imc_refc) {
                        kfree(pmu_ptr->mem_info);
                        goto err;
                }

                core_imc_pmu = pmu_ptr;
                break;
        case IMC_DOMAIN_THREAD:
                /* Update the pmu name */
                pmu_ptr->pmu.name = kasprintf(GFP_KERNEL, "%s%s", s, "_imc");
                if (!pmu_ptr->pmu.name)
                        goto err;

                thread_imc_mem_size = pmu_ptr->counter_mem_size;
                for_each_online_cpu(cpu) {
                        res = thread_imc_mem_alloc(cpu, pmu_ptr->counter_mem_size);
                        if (res) {
                                cleanup_all_thread_imc_memory();
                                goto err;
                        }
                }

                thread_imc_pmu = pmu_ptr;
                break;
        default:
                return -EINVAL;
        }

        return 0;
err:
        return res;
}

/*
 * init_imc_pmu : Setup and register the IMC pmu device.
 *
 * @parent:     Device tree unit node
 * @pmu_ptr:    memory allocated for this pmu
 * @pmu_idx:    Count of nest pmc registered
 *
 * init_imc_pmu() setup pmu cpumask and registers for a cpu hotplug callback.
 * Handles failure cases and accordingly frees memory.
 */
int init_imc_pmu(struct device_node *parent, struct imc_pmu *pmu_ptr, int pmu_idx)
{
        int ret;

        ret = imc_mem_init(pmu_ptr, parent, pmu_idx);
        if (ret)
                goto err_free_mem;

        switch (pmu_ptr->domain) {
        case IMC_DOMAIN_NEST:
                /*
                * Nest imc pmu need only one cpu per chip, we initialize the
                * cpumask for the first nest imc pmu and use the same for the
                * rest. To handle the cpuhotplug callback unregister, we track
                * the number of nest pmus in "nest_pmus".
                */
                mutex_lock(&nest_init_lock);
                if (nest_pmus == 0) {
                        ret = init_nest_pmu_ref();
                        if (ret) {
                                mutex_unlock(&nest_init_lock);
                                kfree(per_nest_pmu_arr);
                                per_nest_pmu_arr = NULL;
                                goto err_free_mem;
                        }
                        /* Register for cpu hotplug notification. */
                        ret = nest_pmu_cpumask_init();
                        if (ret) {
                                mutex_unlock(&nest_init_lock);
                                kfree(nest_imc_refc);
                                kfree(per_nest_pmu_arr);
                                per_nest_pmu_arr = NULL;
                                goto err_free_mem;
                        }
                }
                nest_pmus++;
                mutex_unlock(&nest_init_lock);
                break;
        case IMC_DOMAIN_CORE:
                ret = core_imc_pmu_cpumask_init();
                if (ret) {
                        cleanup_all_core_imc_memory();
                        goto err_free_mem;
                }

                break;
        case IMC_DOMAIN_THREAD:
                ret = thread_imc_cpu_init();
                if (ret) {
                        cleanup_all_thread_imc_memory();
                        goto err_free_mem;
                }

                break;
        default:
                return  -EINVAL;        /* Unknown domain */
        }

        ret = update_events_in_group(parent, pmu_ptr);
        if (ret)
                goto err_free_cpuhp_mem;

        ret = update_pmu_ops(pmu_ptr);
        if (ret)
                goto err_free_cpuhp_mem;

        ret = perf_pmu_register(&pmu_ptr->pmu, pmu_ptr->pmu.name, -1);
        if (ret)
                goto err_free_cpuhp_mem;

        pr_debug("%s performance monitor hardware support registered\n",
                                                        pmu_ptr->pmu.name);

        return 0;

err_free_cpuhp_mem:
        imc_common_cpuhp_mem_free(pmu_ptr);
err_free_mem:
        imc_common_mem_free(pmu_ptr);
        return ret;
}