/*
 * Copyright (c) 2012 Neratec Solutions AG
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <linux/slab.h>
#include <linux/spinlock.h>

#include "ath.h"
#include "dfs_pattern_detector.h"
#include "dfs_pri_detector.h"

struct ath_dfs_pool_stats global_dfs_pool_stats = {};

#define DFS_POOL_STAT_INC(c) (global_dfs_pool_stats.c++)
#define DFS_POOL_STAT_DEC(c) (global_dfs_pool_stats.c--)

/**
 * struct pulse_elem - elements in pulse queue
 * @ts: time stamp in usecs
 */
struct pulse_elem {
        struct list_head head;
        u64 ts;
};

/**
 * pde_get_multiple() - get number of multiples considering a given tolerance
 * @return factor if abs(val - factor*fraction) <= tolerance, 0 otherwise
 */
static u32 pde_get_multiple(u32 val, u32 fraction, u32 tolerance)
{
        u32 remainder;
        u32 factor;
        u32 delta;

        if (fraction == 0)
                return 0;

        delta = (val < fraction) ? (fraction - val) : (val - fraction);

        if (delta <= tolerance)
                /* val and fraction are within tolerance */
                return 1;

        factor = val / fraction;
        remainder = val % fraction;
        if (remainder > tolerance) {
                /* no exact match */
                if ((fraction - remainder) <= tolerance)
                        /* remainder is within tolerance */
                        factor++;
                else
                        factor = 0;
        }
        return factor;
}

/**
 * DOC: Singleton Pulse and Sequence Pools
 *
 * Instances of pri_sequence and pulse_elem are kept in singleton pools to
 * reduce the number of dynamic allocations. They are shared between all
 * instances and grow up to the peak number of simultaneously used objects.
 *
 * Memory is freed after all references to the pools are released.
 */
static u32 singleton_pool_references;
static LIST_HEAD(pulse_pool);
static LIST_HEAD(pseq_pool);
static DEFINE_SPINLOCK(pool_lock);

static void pool_register_ref(void)
{
        spin_lock_bh(&pool_lock);
        singleton_pool_references++;
        DFS_POOL_STAT_INC(pool_reference);
        spin_unlock_bh(&pool_lock);
}

static void pool_deregister_ref(void)
{
        spin_lock_bh(&pool_lock);
        singleton_pool_references--;
        DFS_POOL_STAT_DEC(pool_reference);
        if (singleton_pool_references == 0) {
                /* free singleton pools with no references left */
                struct pri_sequence *ps, *ps0;
                struct pulse_elem *p, *p0;

                list_for_each_entry_safe(p, p0, &pulse_pool, head) {
                        list_del(&p->head);
                        DFS_POOL_STAT_DEC(pulse_allocated);
                        kfree(p);
                }
                list_for_each_entry_safe(ps, ps0, &pseq_pool, head) {
                        list_del(&ps->head);
                        DFS_POOL_STAT_DEC(pseq_allocated);
                        kfree(ps);
                }
        }
        spin_unlock_bh(&pool_lock);
}

static void pool_put_pulse_elem(struct pulse_elem *pe)
{
        spin_lock_bh(&pool_lock);
        list_add(&pe->head, &pulse_pool);
        DFS_POOL_STAT_DEC(pulse_used);
        spin_unlock_bh(&pool_lock);
}

static void pool_put_pseq_elem(struct pri_sequence *pse)
{
        spin_lock_bh(&pool_lock);
        list_add(&pse->head, &pseq_pool);
        DFS_POOL_STAT_DEC(pseq_used);
        spin_unlock_bh(&pool_lock);
}

static struct pri_sequence *pool_get_pseq_elem(void)
{
        struct pri_sequence *pse = NULL;
        spin_lock_bh(&pool_lock);
        if (!list_empty(&pseq_pool)) {
                pse = list_first_entry(&pseq_pool, struct pri_sequence, head);
                list_del(&pse->head);
                DFS_POOL_STAT_INC(pseq_used);
        }
        spin_unlock_bh(&pool_lock);
        return pse;
}

static struct pulse_elem *pool_get_pulse_elem(void)
{
        struct pulse_elem *pe = NULL;
        spin_lock_bh(&pool_lock);
        if (!list_empty(&pulse_pool)) {
                pe = list_first_entry(&pulse_pool, struct pulse_elem, head);
                list_del(&pe->head);
                DFS_POOL_STAT_INC(pulse_used);
        }
        spin_unlock_bh(&pool_lock);
        return pe;
}

static struct pulse_elem *pulse_queue_get_tail(struct pri_detector *pde)
{
        struct list_head *l = &pde->pulses;
        if (list_empty(l))
                return NULL;
        return list_entry(l->prev, struct pulse_elem, head);
}

static bool pulse_queue_dequeue(struct pri_detector *pde)
{
        struct pulse_elem *p = pulse_queue_get_tail(pde);
        if (p != NULL) {
                list_del_init(&p->head);
                pde->count--;
                /* give it back to pool */
                pool_put_pulse_elem(p);
        }
        return (pde->count > 0);
}

/* remove pulses older than window */
static void pulse_queue_check_window(struct pri_detector *pde)
{
        u64 min_valid_ts;
        struct pulse_elem *p;

        /* there is no delta time with less than 2 pulses */
        if (pde->count < 2)
                return;

        if (pde->last_ts <= pde->window_size)
                return;

        min_valid_ts = pde->last_ts - pde->window_size;
        while ((p = pulse_queue_get_tail(pde)) != NULL) {
                if (p->ts >= min_valid_ts)
                        return;
                pulse_queue_dequeue(pde);
        }
}

static bool pulse_queue_enqueue(struct pri_detector *pde, u64 ts)
{
        struct pulse_elem *p = pool_get_pulse_elem();
        if (p == NULL) {
                p = kmalloc(sizeof(*p), GFP_ATOMIC);
                if (p == NULL) {
                        DFS_POOL_STAT_INC(pulse_alloc_error);
                        return false;
                }
                DFS_POOL_STAT_INC(pulse_allocated);
                DFS_POOL_STAT_INC(pulse_used);
        }
        INIT_LIST_HEAD(&p->head);
        p->ts = ts;
        list_add(&p->head, &pde->pulses);
        pde->count++;
        pde->last_ts = ts;
        pulse_queue_check_window(pde);
        if (pde->count >= pde->max_count)
                pulse_queue_dequeue(pde);
        return true;
}

static bool pseq_handler_create_sequences(struct pri_detector *pde,
                                          u64 ts, u32 min_count)
{
        struct pulse_elem *p;
        list_for_each_entry(p, &pde->pulses, head) {
                struct pri_sequence ps, *new_ps;
                struct pulse_elem *p2;
                u32 tmp_false_count;
                u64 min_valid_ts;
                u32 delta_ts = ts - p->ts;

                if (delta_ts < pde->rs->pri_min)
                        /* ignore too small pri */
                        continue;

                if (delta_ts > pde->rs->pri_max)
                        /* stop on too large pri (sorted list) */
                        break;

                /* build a new sequence with new potential pri */
                ps.count = 2;
                ps.count_falses = 0;
                ps.first_ts = p->ts;
                ps.last_ts = ts;
                ps.pri = ts - p->ts;
                ps.dur = ps.pri * (pde->rs->ppb - 1)
                                + 2 * pde->rs->max_pri_tolerance;

                p2 = p;
                tmp_false_count = 0;
                min_valid_ts = ts - ps.dur;
                /* check which past pulses are candidates for new sequence */
                list_for_each_entry_continue(p2, &pde->pulses, head) {
                        u32 factor;
                        if (p2->ts < min_valid_ts)
                                /* stop on crossing window border */
                                break;
                        /* check if pulse match (multi)PRI */
                        factor = pde_get_multiple(ps.last_ts - p2->ts, ps.pri,
                                                  pde->rs->max_pri_tolerance);
                        if (factor > 0) {
                                ps.count++;
                                ps.first_ts = p2->ts;
                                /*
                                 * on match, add the intermediate falses
                                 * and reset counter
                                 */
                                ps.count_falses += tmp_false_count;
                                tmp_false_count = 0;
                        } else {
                                /* this is a potential false one */
                                tmp_false_count++;
                        }
                }
                if (ps.count < min_count)
                        /* did not reach minimum count, drop sequence */
                        continue;

                /* this is a valid one, add it */
                ps.deadline_ts = ps.first_ts + ps.dur;
                new_ps = pool_get_pseq_elem();
                if (new_ps == NULL) {
                        new_ps = kmalloc(sizeof(*new_ps), GFP_ATOMIC);
                        if (new_ps == NULL) {
                                DFS_POOL_STAT_INC(pseq_alloc_error);
                                return false;
                        }
                        DFS_POOL_STAT_INC(pseq_allocated);
                        DFS_POOL_STAT_INC(pseq_used);
                }
                memcpy(new_ps, &ps, sizeof(ps));
                INIT_LIST_HEAD(&new_ps->head);
                list_add(&new_ps->head, &pde->sequences);
        }
        return true;
}

/* check new ts and add to all matching existing sequences */
static u32
pseq_handler_add_to_existing_seqs(struct pri_detector *pde, u64 ts)
{
        u32 max_count = 0;
        struct pri_sequence *ps, *ps2;
        list_for_each_entry_safe(ps, ps2, &pde->sequences, head) {
                u32 delta_ts;
                u32 factor;

                /* first ensure that sequence is within window */
                if (ts > ps->deadline_ts) {
                        list_del_init(&ps->head);
                        pool_put_pseq_elem(ps);
                        continue;
                }

                delta_ts = ts - ps->last_ts;
                factor = pde_get_multiple(delta_ts, ps->pri,
                                          pde->rs->max_pri_tolerance);
                if (factor > 0) {
                        ps->last_ts = ts;
                        ps->count++;

                        if (max_count < ps->count)
                                max_count = ps->count;
                } else {
                        ps->count_falses++;
                }
        }
        return max_count;
}

static struct pri_sequence *
pseq_handler_check_detection(struct pri_detector *pde)
{
        struct pri_sequence *ps;

        if (list_empty(&pde->sequences))
                return NULL;

        list_for_each_entry(ps, &pde->sequences, head) {
                /*
                 * we assume to have enough matching confidence if we
                 * 1) have enough pulses
                 * 2) have more matching than false pulses
                 */
                if ((ps->count >= pde->rs->ppb_thresh) &&
                    (ps->count * pde->rs->num_pri >= ps->count_falses))
                        return ps;
        }
        return NULL;
}


/* free pulse queue and sequences list and give objects back to pools */
static void pri_detector_reset(struct pri_detector *pde, u64 ts)
{
        struct pri_sequence *ps, *ps0;
        struct pulse_elem *p, *p0;
        list_for_each_entry_safe(ps, ps0, &pde->sequences, head) {
                list_del_init(&ps->head);
                pool_put_pseq_elem(ps);
        }
        list_for_each_entry_safe(p, p0, &pde->pulses, head) {
                list_del_init(&p->head);
                pool_put_pulse_elem(p);
        }
        pde->count = 0;
        pde->last_ts = ts;
}

static void pri_detector_exit(struct pri_detector *de)
{
        pri_detector_reset(de, 0);
        pool_deregister_ref();
        kfree(de);
}

static struct pri_sequence *pri_detector_add_pulse(struct pri_detector *de,
                                                   struct pulse_event *event)
{
        u32 max_updated_seq;
        struct pri_sequence *ps;
        u64 ts = event->ts;
        const struct radar_detector_specs *rs = de->rs;

        /* ignore pulses not within width range */
        if ((rs->width_min > event->width) || (rs->width_max < event->width))
                return NULL;

        if ((ts - de->last_ts) < rs->max_pri_tolerance)
                /* if delta to last pulse is too short, don't use this pulse */
                return NULL;
        de->last_ts = ts;

        max_updated_seq = pseq_handler_add_to_existing_seqs(de, ts);

        if (!pseq_handler_create_sequences(de, ts, max_updated_seq)) {
                pri_detector_reset(de, ts);
                return NULL;
        }

        ps = pseq_handler_check_detection(de);

        if (ps == NULL)
                pulse_queue_enqueue(de, ts);

        return ps;
}

struct pri_detector *pri_detector_init(const struct radar_detector_specs *rs)
{
        struct pri_detector *de;

        de = kzalloc(sizeof(*de), GFP_ATOMIC);
        if (de == NULL)
                return NULL;
        de->exit = pri_detector_exit;
        de->add_pulse = pri_detector_add_pulse;
        de->reset = pri_detector_reset;

        INIT_LIST_HEAD(&de->sequences);
        INIT_LIST_HEAD(&de->pulses);
        de->window_size = rs->pri_max * rs->ppb * rs->num_pri;
        de->max_count = rs->ppb * 2;
        de->rs = rs;

        pool_register_ref();
        return de;
}