/*
 * Copyright (c) 2014, Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>
 *
 * 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/export.h>
#include "ath9k.h"
#include "hw.h"
#include "dynack.h"

#define COMPUTE_TO              (5 * HZ)
#define LATEACK_DELAY           (10 * HZ)
#define EWMA_LEVEL              96
#define EWMA_DIV                128

/**
 * ath_dynack_get_max_to - set max timeout according to channel width
 * @ah: ath hw
 *
 */
static u32 ath_dynack_get_max_to(struct ath_hw *ah)
{
        const struct ath9k_channel *chan = ah->curchan;

        if (!chan)
                return 300;

        if (IS_CHAN_HT40(chan))
                return 300;
        if (IS_CHAN_HALF_RATE(chan))
                return 750;
        if (IS_CHAN_QUARTER_RATE(chan))
                return 1500;
        return 600;
}

/*
 * ath_dynack_ewma - EWMA (Exponentially Weighted Moving Average) calculation
 */
static inline int ath_dynack_ewma(int old, int new)
{
        if (old > 0)
                return (new * (EWMA_DIV - EWMA_LEVEL) +
                        old * EWMA_LEVEL) / EWMA_DIV;
        else
                return new;
}

/**
 * ath_dynack_get_sifs - get sifs time based on phy used
 * @ah: ath hw
 * @phy: phy used
 *
 */
static inline u32 ath_dynack_get_sifs(struct ath_hw *ah, int phy)
{
        u32 sifs = CCK_SIFS_TIME;

        if (phy == WLAN_RC_PHY_OFDM) {
                if (IS_CHAN_QUARTER_RATE(ah->curchan))
                        sifs = OFDM_SIFS_TIME_QUARTER;
                else if (IS_CHAN_HALF_RATE(ah->curchan))
                        sifs = OFDM_SIFS_TIME_HALF;
                else
                        sifs = OFDM_SIFS_TIME;
        }
        return sifs;
}

/**
 * ath_dynack_bssidmask - filter out ACK frames based on BSSID mask
 * @ah: ath hw
 * @mac: receiver address
 */
static inline bool ath_dynack_bssidmask(struct ath_hw *ah, const u8 *mac)
{
        int i;
        struct ath_common *common = ath9k_hw_common(ah);

        for (i = 0; i < ETH_ALEN; i++) {
                if ((common->macaddr[i] & common->bssidmask[i]) !=
                    (mac[i] & common->bssidmask[i]))
                        return false;
        }

        return true;
}

/**
 * ath_dynack_set_timeout - configure timeouts/slottime registers
 * @ah: ath hw
 * @to: timeout value
 *
 */
static void ath_dynack_set_timeout(struct ath_hw *ah, int to)
{
        struct ath_common *common = ath9k_hw_common(ah);
        int slottime = (to - 3) / 2;

        ath_dbg(common, DYNACK, "ACK timeout %u slottime %u\n",
                to, slottime);
        ath9k_hw_setslottime(ah, slottime);
        ath9k_hw_set_ack_timeout(ah, to);
        ath9k_hw_set_cts_timeout(ah, to);
}

/**
 * ath_dynack_compute_ackto - compute ACK timeout as the maximum STA timeout
 * @ah: ath hw
 *
 * should be called while holding qlock
 */
static void ath_dynack_compute_ackto(struct ath_hw *ah)
{
        struct ath_dynack *da = &ah->dynack;
        struct ath_node *an;
        int to = 0;

        list_for_each_entry(an, &da->nodes, list)
                if (an->ackto > to)
                        to = an->ackto;

        if (to && da->ackto != to) {
                ath_dynack_set_timeout(ah, to);
                da->ackto = to;
        }
}

/**
 * ath_dynack_compute_to - compute STA ACK timeout
 * @ah: ath hw
 *
 * should be called while holding qlock
 */
static void ath_dynack_compute_to(struct ath_hw *ah)
{
        struct ath_dynack *da = &ah->dynack;
        u32 ackto, ack_ts, max_to;
        struct ieee80211_sta *sta;
        struct ts_info *st_ts;
        struct ath_node *an;
        u8 *dst, *src;

        rcu_read_lock();

        max_to = ath_dynack_get_max_to(ah);
        while (da->st_rbf.h_rb != da->st_rbf.t_rb &&
               da->ack_rbf.h_rb != da->ack_rbf.t_rb) {
                ack_ts = da->ack_rbf.tstamp[da->ack_rbf.h_rb];
                st_ts = &da->st_rbf.ts[da->st_rbf.h_rb];
                dst = da->st_rbf.addr[da->st_rbf.h_rb].h_dest;
                src = da->st_rbf.addr[da->st_rbf.h_rb].h_src;

                ath_dbg(ath9k_hw_common(ah), DYNACK,
                        "ack_ts %u st_ts %u st_dur %u [%u-%u]\n",
                        ack_ts, st_ts->tstamp, st_ts->dur,
                        da->ack_rbf.h_rb, da->st_rbf.h_rb);

                if (ack_ts > st_ts->tstamp + st_ts->dur) {
                        ackto = ack_ts - st_ts->tstamp - st_ts->dur;

                        if (ackto < max_to) {
                                sta = ieee80211_find_sta_by_ifaddr(ah->hw, dst,
                                                                   src);
                                if (sta) {
                                        an = (struct ath_node *)sta->drv_priv;
                                        an->ackto = ath_dynack_ewma(an->ackto,
                                                                    ackto);
                                        ath_dbg(ath9k_hw_common(ah), DYNACK,
                                                "%pM to %d [%u]\n", dst,
                                                an->ackto, ackto);
                                        if (time_is_before_jiffies(da->lto)) {
                                                ath_dynack_compute_ackto(ah);
                                                da->lto = jiffies + COMPUTE_TO;
                                        }
                                }
                                INCR(da->ack_rbf.h_rb, ATH_DYN_BUF);
                        }
                        INCR(da->st_rbf.h_rb, ATH_DYN_BUF);
                } else {
                        INCR(da->ack_rbf.h_rb, ATH_DYN_BUF);
                }
        }

        rcu_read_unlock();
}

/**
 * ath_dynack_sample_tx_ts - status timestamp sampling method
 * @ah: ath hw
 * @skb: socket buffer
 * @ts: tx status info
 * @sta: station pointer
 *
 */
void ath_dynack_sample_tx_ts(struct ath_hw *ah, struct sk_buff *skb,
                             struct ath_tx_status *ts,
                             struct ieee80211_sta *sta)
{
        struct ieee80211_hdr *hdr;
        struct ath_dynack *da = &ah->dynack;
        struct ath_common *common = ath9k_hw_common(ah);
        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
        u32 dur = ts->duration;
        u8 ridx;

        if (!da->enabled || (info->flags & IEEE80211_TX_CTL_NO_ACK))
                return;

        spin_lock_bh(&da->qlock);

        hdr = (struct ieee80211_hdr *)skb->data;

        /* late ACK */
        if (ts->ts_status & ATH9K_TXERR_XRETRY) {
                if (ieee80211_is_assoc_req(hdr->frame_control) ||
                    ieee80211_is_assoc_resp(hdr->frame_control) ||
                    ieee80211_is_auth(hdr->frame_control)) {
                        u32 max_to = ath_dynack_get_max_to(ah);

                        ath_dbg(common, DYNACK, "late ack\n");
                        ath_dynack_set_timeout(ah, max_to);
                        if (sta) {
                                struct ath_node *an;

                                an = (struct ath_node *)sta->drv_priv;
                                an->ackto = -1;
                        }
                        da->lto = jiffies + LATEACK_DELAY;
                }

                spin_unlock_bh(&da->qlock);
                return;
        }

        ridx = ts->ts_rateindex;

        da->st_rbf.ts[da->st_rbf.t_rb].tstamp = ts->ts_tstamp;

        /* ether_addr_copy() gives a false warning on gcc-10 so use memcpy()
         * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97490
         */
        memcpy(da->st_rbf.addr[da->st_rbf.t_rb].h_dest, hdr->addr1, ETH_ALEN);
        memcpy(da->st_rbf.addr[da->st_rbf.t_rb].h_src, hdr->addr2, ETH_ALEN);

        if (!(info->status.rates[ridx].flags & IEEE80211_TX_RC_MCS)) {
                const struct ieee80211_rate *rate;
                struct ieee80211_tx_rate *rates = info->status.rates;
                u32 phy;

                rate = &common->sbands[info->band].bitrates[rates[ridx].idx];
                if (info->band == NL80211_BAND_2GHZ &&
                    !(rate->flags & IEEE80211_RATE_ERP_G))
                        phy = WLAN_RC_PHY_CCK;
                else
                        phy = WLAN_RC_PHY_OFDM;

                dur -= ath_dynack_get_sifs(ah, phy);
        }
        da->st_rbf.ts[da->st_rbf.t_rb].dur = dur;

        INCR(da->st_rbf.t_rb, ATH_DYN_BUF);
        if (da->st_rbf.t_rb == da->st_rbf.h_rb)
                INCR(da->st_rbf.h_rb, ATH_DYN_BUF);

        ath_dbg(common, DYNACK, "{%pM} tx sample %u [dur %u][h %u-t %u]\n",
                hdr->addr1, ts->ts_tstamp, dur, da->st_rbf.h_rb,
                da->st_rbf.t_rb);

        ath_dynack_compute_to(ah);

        spin_unlock_bh(&da->qlock);
}
EXPORT_SYMBOL(ath_dynack_sample_tx_ts);

/**
 * ath_dynack_sample_ack_ts - ACK timestamp sampling method
 * @ah: ath hw
 * @skb: socket buffer
 * @ts: rx timestamp
 *
 */
void ath_dynack_sample_ack_ts(struct ath_hw *ah, struct sk_buff *skb,
                              u32 ts)
{
        struct ath_dynack *da = &ah->dynack;
        struct ath_common *common = ath9k_hw_common(ah);
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;

        if (!da->enabled || !ath_dynack_bssidmask(ah, hdr->addr1))
                return;

        spin_lock_bh(&da->qlock);
        da->ack_rbf.tstamp[da->ack_rbf.t_rb] = ts;

        INCR(da->ack_rbf.t_rb, ATH_DYN_BUF);
        if (da->ack_rbf.t_rb == da->ack_rbf.h_rb)
                INCR(da->ack_rbf.h_rb, ATH_DYN_BUF);

        ath_dbg(common, DYNACK, "rx sample %u [h %u-t %u]\n",
                ts, da->ack_rbf.h_rb, da->ack_rbf.t_rb);

        ath_dynack_compute_to(ah);

        spin_unlock_bh(&da->qlock);
}
EXPORT_SYMBOL(ath_dynack_sample_ack_ts);

/**
 * ath_dynack_node_init - init ath_node related info
 * @ah: ath hw
 * @an: ath node
 *
 */
void ath_dynack_node_init(struct ath_hw *ah, struct ath_node *an)
{
        struct ath_dynack *da = &ah->dynack;

        an->ackto = da->ackto;

        spin_lock_bh(&da->qlock);
        list_add_tail(&an->list, &da->nodes);
        spin_unlock_bh(&da->qlock);
}
EXPORT_SYMBOL(ath_dynack_node_init);

/**
 * ath_dynack_node_deinit - deinit ath_node related info
 * @ah: ath hw
 * @an: ath node
 *
 */
void ath_dynack_node_deinit(struct ath_hw *ah, struct ath_node *an)
{
        struct ath_dynack *da = &ah->dynack;

        spin_lock_bh(&da->qlock);
        list_del(&an->list);
        spin_unlock_bh(&da->qlock);
}
EXPORT_SYMBOL(ath_dynack_node_deinit);

/**
 * ath_dynack_reset - reset dynack processing
 * @ah: ath hw
 *
 */
void ath_dynack_reset(struct ath_hw *ah)
{
        struct ath_dynack *da = &ah->dynack;
        struct ath_node *an;

        spin_lock_bh(&da->qlock);

        da->lto = jiffies + COMPUTE_TO;

        da->st_rbf.t_rb = 0;
        da->st_rbf.h_rb = 0;
        da->ack_rbf.t_rb = 0;
        da->ack_rbf.h_rb = 0;

        da->ackto = ath_dynack_get_max_to(ah);
        list_for_each_entry(an, &da->nodes, list)
                an->ackto = da->ackto;

        /* init acktimeout */
        ath_dynack_set_timeout(ah, da->ackto);

        spin_unlock_bh(&da->qlock);
}
EXPORT_SYMBOL(ath_dynack_reset);

/**
 * ath_dynack_init - init dynack data structure
 * @ah: ath hw
 *
 */
void ath_dynack_init(struct ath_hw *ah)
{
        struct ath_dynack *da = &ah->dynack;

        memset(da, 0, sizeof(struct ath_dynack));

        spin_lock_init(&da->qlock);
        INIT_LIST_HEAD(&da->nodes);
        /* ackto = slottime + sifs + air delay */
        da->ackto = 9 + 16 + 64;

        ah->hw->wiphy->features |= NL80211_FEATURE_ACKTO_ESTIMATION;
}