/*
 * Copyright (c) 2008-2011 Atheros Communications Inc.
 *
 * 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/dma-mapping.h>
#include "ath9k.h"
#include "ar9003_mac.h"

#define SKB_CB_ATHBUF(__skb)    (*((struct ath_rxbuf **)__skb->cb))

static inline bool ath9k_check_auto_sleep(struct ath_softc *sc)
{
        return sc->ps_enabled &&
               (sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_AUTOSLEEP);
}

/*
 * Setup and link descriptors.
 *
 * 11N: we can no longer afford to self link the last descriptor.
 * MAC acknowledges BA status as long as it copies frames to host
 * buffer (or rx fifo). This can incorrectly acknowledge packets
 * to a sender if last desc is self-linked.
 */
static void ath_rx_buf_link(struct ath_softc *sc, struct ath_rxbuf *bf,
                            bool flush)
{
        struct ath_hw *ah = sc->sc_ah;
        struct ath_common *common = ath9k_hw_common(ah);
        struct ath_desc *ds;
        struct sk_buff *skb;

        ds = bf->bf_desc;
        ds->ds_link = 0; /* link to null */
        ds->ds_data = bf->bf_buf_addr;

        /* virtual addr of the beginning of the buffer. */
        skb = bf->bf_mpdu;
        BUG_ON(skb == NULL);
        ds->ds_vdata = skb->data;

        /*
         * setup rx descriptors. The rx_bufsize here tells the hardware
         * how much data it can DMA to us and that we are prepared
         * to process
         */
        ath9k_hw_setuprxdesc(ah, ds,
                             common->rx_bufsize,
                             0);

        if (sc->rx.rxlink)
                *sc->rx.rxlink = bf->bf_daddr;
        else if (!flush)
                ath9k_hw_putrxbuf(ah, bf->bf_daddr);

        sc->rx.rxlink = &ds->ds_link;
}

static void ath_rx_buf_relink(struct ath_softc *sc, struct ath_rxbuf *bf,
                              bool flush)
{
        if (sc->rx.buf_hold)
                ath_rx_buf_link(sc, sc->rx.buf_hold, flush);

        sc->rx.buf_hold = bf;
}

static void ath_setdefantenna(struct ath_softc *sc, u32 antenna)
{
        /* XXX block beacon interrupts */
        ath9k_hw_setantenna(sc->sc_ah, antenna);
        sc->rx.defant = antenna;
        sc->rx.rxotherant = 0;
}

static void ath_opmode_init(struct ath_softc *sc)
{
        struct ath_hw *ah = sc->sc_ah;
        struct ath_common *common = ath9k_hw_common(ah);

        u32 rfilt, mfilt[2];

        /* configure rx filter */
        rfilt = ath_calcrxfilter(sc);
        ath9k_hw_setrxfilter(ah, rfilt);

        /* configure bssid mask */
        ath_hw_setbssidmask(common);

        /* configure operational mode */
        ath9k_hw_setopmode(ah);

        /* calculate and install multicast filter */
        mfilt[0] = mfilt[1] = ~0;
        ath9k_hw_setmcastfilter(ah, mfilt[0], mfilt[1]);
}

static bool ath_rx_edma_buf_link(struct ath_softc *sc,
                                 enum ath9k_rx_qtype qtype)
{
        struct ath_hw *ah = sc->sc_ah;
        struct ath_rx_edma *rx_edma;
        struct sk_buff *skb;
        struct ath_rxbuf *bf;

        rx_edma = &sc->rx.rx_edma[qtype];
        if (skb_queue_len(&rx_edma->rx_fifo) >= rx_edma->rx_fifo_hwsize)
                return false;

        bf = list_first_entry(&sc->rx.rxbuf, struct ath_rxbuf, list);
        list_del_init(&bf->list);

        skb = bf->bf_mpdu;

        memset(skb->data, 0, ah->caps.rx_status_len);
        dma_sync_single_for_device(sc->dev, bf->bf_buf_addr,
                                ah->caps.rx_status_len, DMA_TO_DEVICE);

        SKB_CB_ATHBUF(skb) = bf;
        ath9k_hw_addrxbuf_edma(ah, bf->bf_buf_addr, qtype);
        __skb_queue_tail(&rx_edma->rx_fifo, skb);

        return true;
}

static void ath_rx_addbuffer_edma(struct ath_softc *sc,
                                  enum ath9k_rx_qtype qtype)
{
        struct ath_common *common = ath9k_hw_common(sc->sc_ah);
        struct ath_rxbuf *bf, *tbf;

        if (list_empty(&sc->rx.rxbuf)) {
                ath_dbg(common, QUEUE, "No free rx buf available\n");
                return;
        }

        list_for_each_entry_safe(bf, tbf, &sc->rx.rxbuf, list)
                if (!ath_rx_edma_buf_link(sc, qtype))
                        break;

}

static void ath_rx_remove_buffer(struct ath_softc *sc,
                                 enum ath9k_rx_qtype qtype)
{
        struct ath_rxbuf *bf;
        struct ath_rx_edma *rx_edma;
        struct sk_buff *skb;

        rx_edma = &sc->rx.rx_edma[qtype];

        while ((skb = __skb_dequeue(&rx_edma->rx_fifo)) != NULL) {
                bf = SKB_CB_ATHBUF(skb);
                BUG_ON(!bf);
                list_add_tail(&bf->list, &sc->rx.rxbuf);
        }
}

static void ath_rx_edma_cleanup(struct ath_softc *sc)
{
        struct ath_hw *ah = sc->sc_ah;
        struct ath_common *common = ath9k_hw_common(ah);
        struct ath_rxbuf *bf;

        ath_rx_remove_buffer(sc, ATH9K_RX_QUEUE_LP);
        ath_rx_remove_buffer(sc, ATH9K_RX_QUEUE_HP);

        list_for_each_entry(bf, &sc->rx.rxbuf, list) {
                if (bf->bf_mpdu) {
                        dma_unmap_single(sc->dev, bf->bf_buf_addr,
                                        common->rx_bufsize,
                                        DMA_BIDIRECTIONAL);
                        dev_kfree_skb_any(bf->bf_mpdu);
                        bf->bf_buf_addr = 0;
                        bf->bf_mpdu = NULL;
                }
        }
}

static void ath_rx_edma_init_queue(struct ath_rx_edma *rx_edma, int size)
{
        __skb_queue_head_init(&rx_edma->rx_fifo);
        rx_edma->rx_fifo_hwsize = size;
}

static int ath_rx_edma_init(struct ath_softc *sc, int nbufs)
{
        struct ath_common *common = ath9k_hw_common(sc->sc_ah);
        struct ath_hw *ah = sc->sc_ah;
        struct sk_buff *skb;
        struct ath_rxbuf *bf;
        int error = 0, i;
        u32 size;

        ath9k_hw_set_rx_bufsize(ah, common->rx_bufsize -
                                    ah->caps.rx_status_len);

        ath_rx_edma_init_queue(&sc->rx.rx_edma[ATH9K_RX_QUEUE_LP],
                               ah->caps.rx_lp_qdepth);
        ath_rx_edma_init_queue(&sc->rx.rx_edma[ATH9K_RX_QUEUE_HP],
                               ah->caps.rx_hp_qdepth);

        size = sizeof(struct ath_rxbuf) * nbufs;
        bf = devm_kzalloc(sc->dev, size, GFP_KERNEL);
        if (!bf)
                return -ENOMEM;

        INIT_LIST_HEAD(&sc->rx.rxbuf);

        for (i = 0; i < nbufs; i++, bf++) {
                skb = ath_rxbuf_alloc(common, common->rx_bufsize, GFP_KERNEL);
                if (!skb) {
                        error = -ENOMEM;
                        goto rx_init_fail;
                }

                memset(skb->data, 0, common->rx_bufsize);
                bf->bf_mpdu = skb;

                bf->bf_buf_addr = dma_map_single(sc->dev, skb->data,
                                                 common->rx_bufsize,
                                                 DMA_BIDIRECTIONAL);
                if (unlikely(dma_mapping_error(sc->dev,
                                                bf->bf_buf_addr))) {
                                dev_kfree_skb_any(skb);
                                bf->bf_mpdu = NULL;
                                bf->bf_buf_addr = 0;
                                ath_err(common,
                                        "dma_mapping_error() on RX init\n");
                                error = -ENOMEM;
                                goto rx_init_fail;
                }

                list_add_tail(&bf->list, &sc->rx.rxbuf);
        }

        return 0;

rx_init_fail:
        ath_rx_edma_cleanup(sc);
        return error;
}

static void ath_edma_start_recv(struct ath_softc *sc)
{
        ath9k_hw_rxena(sc->sc_ah);
        ath_rx_addbuffer_edma(sc, ATH9K_RX_QUEUE_HP);
        ath_rx_addbuffer_edma(sc, ATH9K_RX_QUEUE_LP);
        ath_opmode_init(sc);
        ath9k_hw_startpcureceive(sc->sc_ah, sc->cur_chan->offchannel);
}

static void ath_edma_stop_recv(struct ath_softc *sc)
{
        ath_rx_remove_buffer(sc, ATH9K_RX_QUEUE_HP);
        ath_rx_remove_buffer(sc, ATH9K_RX_QUEUE_LP);
}

int ath_rx_init(struct ath_softc *sc, int nbufs)
{
        struct ath_common *common = ath9k_hw_common(sc->sc_ah);
        struct sk_buff *skb;
        struct ath_rxbuf *bf;
        int error = 0;

        spin_lock_init(&sc->sc_pcu_lock);

        common->rx_bufsize = IEEE80211_MAX_MPDU_LEN / 2 +
                             sc->sc_ah->caps.rx_status_len;

        if (sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_EDMA)
                return ath_rx_edma_init(sc, nbufs);

        ath_dbg(common, CONFIG, "cachelsz %u rxbufsize %u\n",
                common->cachelsz, common->rx_bufsize);

        /* Initialize rx descriptors */

        error = ath_descdma_setup(sc, &sc->rx.rxdma, &sc->rx.rxbuf,
                                  "rx", nbufs, 1, 0);
        if (error != 0) {
                ath_err(common,
                        "failed to allocate rx descriptors: %d\n",
                        error);
                goto err;
        }

        list_for_each_entry(bf, &sc->rx.rxbuf, list) {
                skb = ath_rxbuf_alloc(common, common->rx_bufsize,
                                      GFP_KERNEL);
                if (skb == NULL) {
                        error = -ENOMEM;
                        goto err;
                }

                bf->bf_mpdu = skb;
                bf->bf_buf_addr = dma_map_single(sc->dev, skb->data,
                                                 common->rx_bufsize,
                                                 DMA_FROM_DEVICE);
                if (unlikely(dma_mapping_error(sc->dev,
                                               bf->bf_buf_addr))) {
                        dev_kfree_skb_any(skb);
                        bf->bf_mpdu = NULL;
                        bf->bf_buf_addr = 0;
                        ath_err(common,
                                "dma_mapping_error() on RX init\n");
                        error = -ENOMEM;
                        goto err;
                }
        }
        sc->rx.rxlink = NULL;
err:
        if (error)
                ath_rx_cleanup(sc);

        return error;
}

void ath_rx_cleanup(struct ath_softc *sc)
{
        struct ath_hw *ah = sc->sc_ah;
        struct ath_common *common = ath9k_hw_common(ah);
        struct sk_buff *skb;
        struct ath_rxbuf *bf;

        if (sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_EDMA) {
                ath_rx_edma_cleanup(sc);
                return;
        }

        list_for_each_entry(bf, &sc->rx.rxbuf, list) {
                skb = bf->bf_mpdu;
                if (skb) {
                        dma_unmap_single(sc->dev, bf->bf_buf_addr,
                                         common->rx_bufsize,
                                         DMA_FROM_DEVICE);
                        dev_kfree_skb(skb);
                        bf->bf_buf_addr = 0;
                        bf->bf_mpdu = NULL;
                }
        }
}

/*
 * Calculate the receive filter according to the
 * operating mode and state:
 *
 * o always accept unicast, broadcast, and multicast traffic
 * o maintain current state of phy error reception (the hal
 *   may enable phy error frames for noise immunity work)
 * o probe request frames are accepted only when operating in
 *   hostap, adhoc, or monitor modes
 * o enable promiscuous mode according to the interface state
 * o accept beacons:
 *   - when operating in adhoc mode so the 802.11 layer creates
 *     node table entries for peers,
 *   - when operating in station mode for collecting rssi data when
 *     the station is otherwise quiet, or
 *   - when operating as a repeater so we see repeater-sta beacons
 *   - when scanning
 */

u32 ath_calcrxfilter(struct ath_softc *sc)
{
        struct ath_common *common = ath9k_hw_common(sc->sc_ah);
        u32 rfilt;

        if (IS_ENABLED(CONFIG_ATH9K_TX99))
                return 0;

        rfilt = ATH9K_RX_FILTER_UCAST | ATH9K_RX_FILTER_BCAST
                | ATH9K_RX_FILTER_MCAST;

        /* if operating on a DFS channel, enable radar pulse detection */
        if (sc->hw->conf.radar_enabled)
                rfilt |= ATH9K_RX_FILTER_PHYRADAR | ATH9K_RX_FILTER_PHYERR;

        spin_lock_bh(&sc->chan_lock);

        if (sc->cur_chan->rxfilter & FIF_PROBE_REQ)
                rfilt |= ATH9K_RX_FILTER_PROBEREQ;

        if (sc->sc_ah->is_monitoring)
                rfilt |= ATH9K_RX_FILTER_PROM;

        if ((sc->cur_chan->rxfilter & FIF_CONTROL) ||
            sc->sc_ah->dynack.enabled)
                rfilt |= ATH9K_RX_FILTER_CONTROL;

        if ((sc->sc_ah->opmode == NL80211_IFTYPE_STATION) &&
            (sc->cur_chan->nvifs <= 1) &&
            !(sc->cur_chan->rxfilter & FIF_BCN_PRBRESP_PROMISC))
                rfilt |= ATH9K_RX_FILTER_MYBEACON;
        else if (sc->sc_ah->opmode != NL80211_IFTYPE_OCB)
                rfilt |= ATH9K_RX_FILTER_BEACON;

        if ((sc->sc_ah->opmode == NL80211_IFTYPE_AP) ||
            (sc->cur_chan->rxfilter & FIF_PSPOLL))
                rfilt |= ATH9K_RX_FILTER_PSPOLL;

        if (sc->cur_chandef.width != NL80211_CHAN_WIDTH_20_NOHT)
                rfilt |= ATH9K_RX_FILTER_COMP_BAR;

        if (sc->cur_chan->nvifs > 1 || (sc->cur_chan->rxfilter & FIF_OTHER_BSS)) {
                /* This is needed for older chips */
                if (sc->sc_ah->hw_version.macVersion <= AR_SREV_VERSION_9160)
                        rfilt |= ATH9K_RX_FILTER_PROM;
                rfilt |= ATH9K_RX_FILTER_MCAST_BCAST_ALL;
        }

        if (AR_SREV_9550(sc->sc_ah) || AR_SREV_9531(sc->sc_ah) ||
            AR_SREV_9561(sc->sc_ah))
                rfilt |= ATH9K_RX_FILTER_4ADDRESS;

        if (AR_SREV_9462(sc->sc_ah) || AR_SREV_9565(sc->sc_ah))
                rfilt |= ATH9K_RX_FILTER_CONTROL_WRAPPER;

        if (ath9k_is_chanctx_enabled() &&
            test_bit(ATH_OP_SCANNING, &common->op_flags))
                rfilt |= ATH9K_RX_FILTER_BEACON;

        spin_unlock_bh(&sc->chan_lock);

        return rfilt;

}

void ath_startrecv(struct ath_softc *sc)
{
        struct ath_hw *ah = sc->sc_ah;
        struct ath_rxbuf *bf, *tbf;

        if (ah->caps.hw_caps & ATH9K_HW_CAP_EDMA) {
                ath_edma_start_recv(sc);
                return;
        }

        if (list_empty(&sc->rx.rxbuf))
                goto start_recv;

        sc->rx.buf_hold = NULL;
        sc->rx.rxlink = NULL;
        list_for_each_entry_safe(bf, tbf, &sc->rx.rxbuf, list) {
                ath_rx_buf_link(sc, bf, false);
        }

        /* We could have deleted elements so the list may be empty now */
        if (list_empty(&sc->rx.rxbuf))
                goto start_recv;

        bf = list_first_entry(&sc->rx.rxbuf, struct ath_rxbuf, list);
        ath9k_hw_putrxbuf(ah, bf->bf_daddr);
        ath9k_hw_rxena(ah);

start_recv:
        ath_opmode_init(sc);
        ath9k_hw_startpcureceive(ah, sc->cur_chan->offchannel);
}

static void ath_flushrecv(struct ath_softc *sc)
{
        if (sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_EDMA)
                ath_rx_tasklet(sc, 1, true);
        ath_rx_tasklet(sc, 1, false);
}

bool ath_stoprecv(struct ath_softc *sc)
{
        struct ath_hw *ah = sc->sc_ah;
        bool stopped, reset = false;

        ath9k_hw_abortpcurecv(ah);
        ath9k_hw_setrxfilter(ah, 0);
        stopped = ath9k_hw_stopdmarecv(ah, &reset);

        ath_flushrecv(sc);

        if (sc->sc_ah->caps.hw_caps & ATH9K_HW_CAP_EDMA)
                ath_edma_stop_recv(sc);
        else
                sc->rx.rxlink = NULL;

        if (!(ah->ah_flags & AH_UNPLUGGED) &&
            unlikely(!stopped)) {
                ath_dbg(ath9k_hw_common(sc->sc_ah), RESET,
                        "Failed to stop Rx DMA\n");
                RESET_STAT_INC(sc, RESET_RX_DMA_ERROR);
        }
        return stopped && !reset;
}

static bool ath_beacon_dtim_pending_cab(struct sk_buff *skb)
{
        /* Check whether the Beacon frame has DTIM indicating buffered bc/mc */
        struct ieee80211_mgmt *mgmt;
        u8 *pos, *end, id, elen;
        struct ieee80211_tim_ie *tim;

        mgmt = (struct ieee80211_mgmt *)skb->data;
        pos = mgmt->u.beacon.variable;
        end = skb->data + skb->len;

        while (pos + 2 < end) {
                id = *pos++;
                elen = *pos++;
                if (pos + elen > end)
                        break;

                if (id == WLAN_EID_TIM) {
                        if (elen < sizeof(*tim))
                                break;
                        tim = (struct ieee80211_tim_ie *) pos;
                        if (tim->dtim_count != 0)
                                break;
                        return tim->bitmap_ctrl & 0x01;
                }

                pos += elen;
        }

        return false;
}

static void ath_rx_ps_beacon(struct ath_softc *sc, struct sk_buff *skb)
{
        struct ath_common *common = ath9k_hw_common(sc->sc_ah);
        bool skip_beacon = false;

        if (skb->len < 24 + 8 + 2 + 2)
                return;

        sc->ps_flags &= ~PS_WAIT_FOR_BEACON;

        if (sc->ps_flags & PS_BEACON_SYNC) {
                sc->ps_flags &= ~PS_BEACON_SYNC;
                ath_dbg(common, PS,
                        "Reconfigure beacon timers based on synchronized timestamp\n");

#ifdef CONFIG_ATH9K_CHANNEL_CONTEXT
                if (ath9k_is_chanctx_enabled()) {
                        if (sc->cur_chan == &sc->offchannel.chan)
                                skip_beacon = true;
                }
#endif

                if (!skip_beacon &&
                    !(WARN_ON_ONCE(sc->cur_chan->beacon.beacon_interval == 0)))
                        ath9k_set_beacon(sc);

                ath9k_p2p_beacon_sync(sc);
        }

        if (ath_beacon_dtim_pending_cab(skb)) {
                /*
                 * Remain awake waiting for buffered broadcast/multicast
                 * frames. If the last broadcast/multicast frame is not
                 * received properly, the next beacon frame will work as
                 * a backup trigger for returning into NETWORK SLEEP state,
                 * so we are waiting for it as well.
                 */
                ath_dbg(common, PS,
                        "Received DTIM beacon indicating buffered broadcast/multicast frame(s)\n");
                sc->ps_flags |= PS_WAIT_FOR_CAB | PS_WAIT_FOR_BEACON;
                return;
        }

        if (sc->ps_flags & PS_WAIT_FOR_CAB) {
                /*
                 * This can happen if a broadcast frame is dropped or the AP
                 * fails to send a frame indicating that all CAB frames have
                 * been delivered.
                 */
                sc->ps_flags &= ~PS_WAIT_FOR_CAB;
                ath_dbg(common, PS, "PS wait for CAB frames timed out\n");
        }
}

static void ath_rx_ps(struct ath_softc *sc, struct sk_buff *skb, bool mybeacon)
{
        struct ieee80211_hdr *hdr;
        struct ath_common *common = ath9k_hw_common(sc->sc_ah);

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

        /* Process Beacon and CAB receive in PS state */
        if (((sc->ps_flags & PS_WAIT_FOR_BEACON) || ath9k_check_auto_sleep(sc))
            && mybeacon) {
                ath_rx_ps_beacon(sc, skb);
        } else if ((sc->ps_flags & PS_WAIT_FOR_CAB) &&
                   (ieee80211_is_data(hdr->frame_control) ||
                    ieee80211_is_action(hdr->frame_control)) &&
                   is_multicast_ether_addr(hdr->addr1) &&
                   !ieee80211_has_moredata(hdr->frame_control)) {
                /*
                 * No more broadcast/multicast frames to be received at this
                 * point.
                 */
                sc->ps_flags &= ~(PS_WAIT_FOR_CAB | PS_WAIT_FOR_BEACON);
                ath_dbg(common, PS,
                        "All PS CAB frames received, back to sleep\n");
        } else if ((sc->ps_flags & PS_WAIT_FOR_PSPOLL_DATA) &&
                   !is_multicast_ether_addr(hdr->addr1) &&
                   !ieee80211_has_morefrags(hdr->frame_control)) {
                sc->ps_flags &= ~PS_WAIT_FOR_PSPOLL_DATA;
                ath_dbg(common, PS,
                        "Going back to sleep after having received PS-Poll data (0x%lx)\n",
                        sc->ps_flags & (PS_WAIT_FOR_BEACON |
                                        PS_WAIT_FOR_CAB |
                                        PS_WAIT_FOR_PSPOLL_DATA |
                                        PS_WAIT_FOR_TX_ACK));
        }
}

static bool ath_edma_get_buffers(struct ath_softc *sc,
                                 enum ath9k_rx_qtype qtype,
                                 struct ath_rx_status *rs,
                                 struct ath_rxbuf **dest)
{
        struct ath_rx_edma *rx_edma = &sc->rx.rx_edma[qtype];
        struct ath_hw *ah = sc->sc_ah;
        struct ath_common *common = ath9k_hw_common(ah);
        struct sk_buff *skb;
        struct ath_rxbuf *bf;
        int ret;

        skb = skb_peek(&rx_edma->rx_fifo);
        if (!skb)
                return false;

        bf = SKB_CB_ATHBUF(skb);
        BUG_ON(!bf);

        dma_sync_single_for_cpu(sc->dev, bf->bf_buf_addr,
                                common->rx_bufsize, DMA_FROM_DEVICE);

        ret = ath9k_hw_process_rxdesc_edma(ah, rs, skb->data);
        if (ret == -EINPROGRESS) {
                /*let device gain the buffer again*/
                dma_sync_single_for_device(sc->dev, bf->bf_buf_addr,
                                common->rx_bufsize, DMA_FROM_DEVICE);
                return false;
        }

        __skb_unlink(skb, &rx_edma->rx_fifo);
        if (ret == -EINVAL) {
                /* corrupt descriptor, skip this one and the following one */
                list_add_tail(&bf->list, &sc->rx.rxbuf);
                ath_rx_edma_buf_link(sc, qtype);

                skb = skb_peek(&rx_edma->rx_fifo);
                if (skb) {
                        bf = SKB_CB_ATHBUF(skb);
                        BUG_ON(!bf);

                        __skb_unlink(skb, &rx_edma->rx_fifo);
                        list_add_tail(&bf->list, &sc->rx.rxbuf);
                        ath_rx_edma_buf_link(sc, qtype);
                }

                bf = NULL;
        }

        *dest = bf;
        return true;
}

static struct ath_rxbuf *ath_edma_get_next_rx_buf(struct ath_softc *sc,
                                                struct ath_rx_status *rs,
                                                enum ath9k_rx_qtype qtype)
{
        struct ath_rxbuf *bf = NULL;

        while (ath_edma_get_buffers(sc, qtype, rs, &bf)) {
                if (!bf)
                        continue;

                return bf;
        }
        return NULL;
}

static struct ath_rxbuf *ath_get_next_rx_buf(struct ath_softc *sc,
                                           struct ath_rx_status *rs)
{
        struct ath_hw *ah = sc->sc_ah;
        struct ath_common *common = ath9k_hw_common(ah);
        struct ath_desc *ds;
        struct ath_rxbuf *bf;
        int ret;

        if (list_empty(&sc->rx.rxbuf)) {
                sc->rx.rxlink = NULL;
                return NULL;
        }

        bf = list_first_entry(&sc->rx.rxbuf, struct ath_rxbuf, list);
        if (bf == sc->rx.buf_hold)
                return NULL;

        ds = bf->bf_desc;

        /*
         * Must provide the virtual address of the current
         * descriptor, the physical address, and the virtual
         * address of the next descriptor in the h/w chain.
         * This allows the HAL to look ahead to see if the
         * hardware is done with a descriptor by checking the
         * done bit in the following descriptor and the address
         * of the current descriptor the DMA engine is working
         * on.  All this is necessary because of our use of
         * a self-linked list to avoid rx overruns.
         */
        ret = ath9k_hw_rxprocdesc(ah, ds, rs);
        if (ret == -EINPROGRESS) {
                struct ath_rx_status trs;
                struct ath_rxbuf *tbf;
                struct ath_desc *tds;

                memset(&trs, 0, sizeof(trs));
                if (list_is_last(&bf->list, &sc->rx.rxbuf)) {
                        sc->rx.rxlink = NULL;
                        return NULL;
                }

                tbf = list_entry(bf->list.next, struct ath_rxbuf, list);

                /*
                 * On some hardware the descriptor status words could
                 * get corrupted, including the done bit. Because of
                 * this, check if the next descriptor's done bit is
                 * set or not.
                 *
                 * If the next descriptor's done bit is set, the current
                 * descriptor has been corrupted. Force s/w to discard
                 * this descriptor and continue...
                 */

                tds = tbf->bf_desc;
                ret = ath9k_hw_rxprocdesc(ah, tds, &trs);
                if (ret == -EINPROGRESS)
                        return NULL;

                /*
                 * Re-check previous descriptor, in case it has been filled
                 * in the mean time.
                 */
                ret = ath9k_hw_rxprocdesc(ah, ds, rs);
                if (ret == -EINPROGRESS) {
                        /*
                         * mark descriptor as zero-length and set the 'more'
                         * flag to ensure that both buffers get discarded
                         */
                        rs->rs_datalen = 0;
                        rs->rs_more = true;
                }
        }

        list_del(&bf->list);
        if (!bf->bf_mpdu)
                return bf;

        /*
         * Synchronize the DMA transfer with CPU before
         * 1. accessing the frame
         * 2. requeueing the same buffer to h/w
         */
        dma_sync_single_for_cpu(sc->dev, bf->bf_buf_addr,
                        common->rx_bufsize,
                        DMA_FROM_DEVICE);

        return bf;
}

static void ath9k_process_tsf(struct ath_rx_status *rs,
                              struct ieee80211_rx_status *rxs,
                              u64 tsf)
{
        u32 tsf_lower = tsf & 0xffffffff;

        rxs->mactime = (tsf & ~0xffffffffULL) | rs->rs_tstamp;
        if (rs->rs_tstamp > tsf_lower &&
            unlikely(rs->rs_tstamp - tsf_lower > 0x10000000))
                rxs->mactime -= 0x100000000ULL;

        if (rs->rs_tstamp < tsf_lower &&
            unlikely(tsf_lower - rs->rs_tstamp > 0x10000000))
                rxs->mactime += 0x100000000ULL;
}

/*
 * For Decrypt or Demic errors, we only mark packet status here and always push
 * up the frame up to let mac80211 handle the actual error case, be it no
 * decryption key or real decryption error. This let us keep statistics there.
 */
static int ath9k_rx_skb_preprocess(struct ath_softc *sc,
                                   struct sk_buff *skb,
                                   struct ath_rx_status *rx_stats,
                                   struct ieee80211_rx_status *rx_status,
                                   bool *decrypt_error, u64 tsf)
{
        struct ieee80211_hw *hw = sc->hw;
        struct ath_hw *ah = sc->sc_ah;
        struct ath_common *common = ath9k_hw_common(ah);
        struct ieee80211_hdr *hdr;
        bool discard_current = sc->rx.discard_next;
        bool is_phyerr;

        /*
         * Discard corrupt descriptors which are marked in
         * ath_get_next_rx_buf().
         */
        if (discard_current)
                goto corrupt;

        sc->rx.discard_next = false;

        /*
         * Discard zero-length packets and packets smaller than an ACK
         * which are not PHY_ERROR (short radar pulses have a length of 3)
         */
        is_phyerr = rx_stats->rs_status & ATH9K_RXERR_PHY;
        if (!rx_stats->rs_datalen ||
            (rx_stats->rs_datalen < 10 && !is_phyerr)) {
                RX_STAT_INC(sc, rx_len_err);
                goto corrupt;
        }

        /*
         * rs_status follows rs_datalen so if rs_datalen is too large
         * we can take a hint that hardware corrupted it, so ignore
         * those frames.
         */
        if (rx_stats->rs_datalen > (common->rx_bufsize - ah->caps.rx_status_len)) {
                RX_STAT_INC(sc, rx_len_err);
                goto corrupt;
        }

        /* Only use status info from the last fragment */
        if (rx_stats->rs_more)
                return 0;

        /*
         * Return immediately if the RX descriptor has been marked
         * as corrupt based on the various error bits.
         *
         * This is different from the other corrupt descriptor
         * condition handled above.
         */
        if (rx_stats->rs_status & ATH9K_RXERR_CORRUPT_DESC)
                goto corrupt;

        hdr = (struct ieee80211_hdr *) (skb->data + ah->caps.rx_status_len);

        ath9k_process_tsf(rx_stats, rx_status, tsf);
        ath_debug_stat_rx(sc, rx_stats);

        /*
         * Process PHY errors and return so that the packet
         * can be dropped.
         */
        if (rx_stats->rs_status & ATH9K_RXERR_PHY) {
                /*
                 * DFS and spectral are mutually exclusive
                 *
                 * Since some chips use PHYERR_RADAR as indication for both, we
                 * need to double check which feature is enabled to prevent
                 * feeding spectral or dfs-detector with wrong frames.
                 */
                if (hw->conf.radar_enabled) {
                        ath9k_dfs_process_phyerr(sc, hdr, rx_stats,
                                                 rx_status->mactime);
                } else if (sc->spec_priv.spectral_mode != SPECTRAL_DISABLED &&
                           ath_cmn_process_fft(&sc->spec_priv, hdr, rx_stats,
                                               rx_status->mactime)) {
                        RX_STAT_INC(sc, rx_spectral);
                }
                return -EINVAL;
        }

        /*
         * everything but the rate is checked here, the rate check is done
         * separately to avoid doing two lookups for a rate for each frame.
         */
        spin_lock_bh(&sc->chan_lock);
        if (!ath9k_cmn_rx_accept(common, hdr, rx_status, rx_stats, decrypt_error,
                                 sc->cur_chan->rxfilter)) {
                spin_unlock_bh(&sc->chan_lock);
                return -EINVAL;
        }
        spin_unlock_bh(&sc->chan_lock);

        if (ath_is_mybeacon(common, hdr)) {
                RX_STAT_INC(sc, rx_beacons);
                rx_stats->is_mybeacon = true;
        }

        /*
         * This shouldn't happen, but have a safety check anyway.
         */
        if (WARN_ON(!ah->curchan))
                return -EINVAL;

        if (ath9k_cmn_process_rate(common, hw, rx_stats, rx_status)) {
                /*
                 * No valid hardware bitrate found -- we should not get here
                 * because hardware has already validated this frame as OK.
                 */
                ath_dbg(common, ANY, "unsupported hw bitrate detected 0x%02x using 1 Mbit\n",
                        rx_stats->rs_rate);
                RX_STAT_INC(sc, rx_rate_err);
                return -EINVAL;
        }

        if (ath9k_is_chanctx_enabled()) {
                if (rx_stats->is_mybeacon)
                        ath_chanctx_beacon_recv_ev(sc,
                                           ATH_CHANCTX_EVENT_BEACON_RECEIVED);
        }

        ath9k_cmn_process_rssi(common, hw, rx_stats, rx_status);

        rx_status->band = ah->curchan->chan->band;
        rx_status->freq = ah->curchan->chan->center_freq;
        rx_status->antenna = rx_stats->rs_antenna;
        rx_status->flag |= RX_FLAG_MACTIME_END;

#ifdef CONFIG_ATH9K_BTCOEX_SUPPORT
        if (ieee80211_is_data_present(hdr->frame_control) &&
            !ieee80211_is_qos_nullfunc(hdr->frame_control))
                sc->rx.num_pkts++;
#endif

        return 0;

corrupt:
        sc->rx.discard_next = rx_stats->rs_more;
        return -EINVAL;
}

/*
 * Run the LNA combining algorithm only in these cases:
 *
 * Standalone WLAN cards with both LNA/Antenna diversity
 * enabled in the EEPROM.
 *
 * WLAN+BT cards which are in the supported card list
 * in ath_pci_id_table and the user has loaded the
 * driver with "bt_ant_diversity" set to true.
 */
static void ath9k_antenna_check(struct ath_softc *sc,
                                struct ath_rx_status *rs)
{
        struct ath_hw *ah = sc->sc_ah;
        struct ath9k_hw_capabilities *pCap = &ah->caps;
        struct ath_common *common = ath9k_hw_common(ah);

        if (!(ah->caps.hw_caps & ATH9K_HW_CAP_ANT_DIV_COMB))
                return;

        /*
         * Change the default rx antenna if rx diversity
         * chooses the other antenna 3 times in a row.
         */
        if (sc->rx.defant != rs->rs_antenna) {
                if (++sc->rx.rxotherant >= 3)
                        ath_setdefantenna(sc, rs->rs_antenna);
        } else {
                sc->rx.rxotherant = 0;
        }

        if (pCap->hw_caps & ATH9K_HW_CAP_BT_ANT_DIV) {
                if (common->bt_ant_diversity)
                        ath_ant_comb_scan(sc, rs);
        } else {
                ath_ant_comb_scan(sc, rs);
        }
}

static void ath9k_apply_ampdu_details(struct ath_softc *sc,
        struct ath_rx_status *rs, struct ieee80211_rx_status *rxs)
{
        if (rs->rs_isaggr) {
                rxs->flag |= RX_FLAG_AMPDU_DETAILS | RX_FLAG_AMPDU_LAST_KNOWN;

                rxs->ampdu_reference = sc->rx.ampdu_ref;

                if (!rs->rs_moreaggr) {
                        rxs->flag |= RX_FLAG_AMPDU_IS_LAST;

                        sc->rx.ampdu_ref++;
                }

                if (rs->rs_flags & ATH9K_RX_DELIM_CRC_PRE)
                        rxs->flag |= RX_FLAG_AMPDU_DELIM_CRC_ERROR;
        }
}

static void ath_rx_count_airtime(struct ath_softc *sc,
                                 struct ath_rx_status *rs,
                                 struct sk_buff *skb)
{
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
        struct ath_hw *ah = sc->sc_ah;
        struct ath_common *common = ath9k_hw_common(ah);
        struct ieee80211_sta *sta;
        struct ieee80211_rx_status *rxs;
        const struct ieee80211_rate *rate;
        bool is_sgi, is_40, is_sp;
        int phy;
        u16 len = rs->rs_datalen;
        u32 airtime = 0;
        u8 tidno;

        if (!ieee80211_is_data(hdr->frame_control))
                return;

        rcu_read_lock();

        sta = ieee80211_find_sta_by_ifaddr(sc->hw, hdr->addr2, NULL);
        if (!sta)
                goto exit;
        tidno = skb->priority & IEEE80211_QOS_CTL_TID_MASK;

        rxs = IEEE80211_SKB_RXCB(skb);

        is_sgi = !!(rxs->enc_flags & RX_ENC_FLAG_SHORT_GI);
        is_40 = !!(rxs->bw == RATE_INFO_BW_40);
        is_sp = !!(rxs->enc_flags & RX_ENC_FLAG_SHORTPRE);

        if (!!(rxs->encoding == RX_ENC_HT)) {
                /* MCS rates */

                airtime += ath_pkt_duration(sc, rxs->rate_idx, len,
                                        is_40, is_sgi, is_sp);
        } else {

                phy = IS_CCK_RATE(rs->rs_rate) ? WLAN_RC_PHY_CCK : WLAN_RC_PHY_OFDM;
                rate = &common->sbands[rxs->band].bitrates[rxs->rate_idx];
                airtime += ath9k_hw_computetxtime(ah, phy, rate->bitrate * 100,
                                                len, rxs->rate_idx, is_sp);
        }

        ieee80211_sta_register_airtime(sta, tidno, 0, airtime);
exit:
        rcu_read_unlock();
}

int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp)
{
        struct ath_rxbuf *bf;
        struct sk_buff *skb = NULL, *requeue_skb, *hdr_skb;
        struct ieee80211_rx_status *rxs;
        struct ath_hw *ah = sc->sc_ah;
        struct ath_common *common = ath9k_hw_common(ah);
        struct ieee80211_hw *hw = sc->hw;
        int retval;
        struct ath_rx_status rs;
        enum ath9k_rx_qtype qtype;
        bool edma = !!(ah->caps.hw_caps & ATH9K_HW_CAP_EDMA);
        int dma_type;
        u64 tsf = 0;
        unsigned long flags;
        dma_addr_t new_buf_addr;
        unsigned int budget = 512;
        struct ieee80211_hdr *hdr;

        if (edma)
                dma_type = DMA_BIDIRECTIONAL;
        else
                dma_type = DMA_FROM_DEVICE;

        qtype = hp ? ATH9K_RX_QUEUE_HP : ATH9K_RX_QUEUE_LP;

        tsf = ath9k_hw_gettsf64(ah);

        do {
                bool decrypt_error = false;

                memset(&rs, 0, sizeof(rs));
                if (edma)
                        bf = ath_edma_get_next_rx_buf(sc, &rs, qtype);
                else
                        bf = ath_get_next_rx_buf(sc, &rs);

                if (!bf)
                        break;

                skb = bf->bf_mpdu;
                if (!skb)
                        continue;

                /*
                 * Take frame header from the first fragment and RX status from
                 * the last one.
                 */
                if (sc->rx.frag)
                        hdr_skb = sc->rx.frag;
                else
                        hdr_skb = skb;

                rxs = IEEE80211_SKB_RXCB(hdr_skb);
                memset(rxs, 0, sizeof(struct ieee80211_rx_status));

                retval = ath9k_rx_skb_preprocess(sc, hdr_skb, &rs, rxs,
                                                 &decrypt_error, tsf);
                if (retval)
                        goto requeue_drop_frag;

                /* Ensure we always have an skb to requeue once we are done
                 * processing the current buffer's skb */
                requeue_skb = ath_rxbuf_alloc(common, common->rx_bufsize, GFP_ATOMIC);

                /* If there is no memory we ignore the current RX'd frame,
                 * tell hardware it can give us a new frame using the old
                 * skb and put it at the tail of the sc->rx.rxbuf list for
                 * processing. */
                if (!requeue_skb) {
                        RX_STAT_INC(sc, rx_oom_err);
                        goto requeue_drop_frag;
                }

                /* We will now give hardware our shiny new allocated skb */
                new_buf_addr = dma_map_single(sc->dev, requeue_skb->data,
                                              common->rx_bufsize, dma_type);
                if (unlikely(dma_mapping_error(sc->dev, new_buf_addr))) {
                        dev_kfree_skb_any(requeue_skb);
                        goto requeue_drop_frag;
                }

                /* Unmap the frame */
                dma_unmap_single(sc->dev, bf->bf_buf_addr,
                                 common->rx_bufsize, dma_type);

                bf->bf_mpdu = requeue_skb;
                bf->bf_buf_addr = new_buf_addr;

                skb_put(skb, rs.rs_datalen + ah->caps.rx_status_len);
                if (ah->caps.rx_status_len)
                        skb_pull(skb, ah->caps.rx_status_len);

                if (!rs.rs_more)
                        ath9k_cmn_rx_skb_postprocess(common, hdr_skb, &rs,
                                                     rxs, decrypt_error);

                if (rs.rs_more) {
                        RX_STAT_INC(sc, rx_frags);
                        /*
                         * rs_more indicates chained descriptors which can be
                         * used to link buffers together for a sort of
                         * scatter-gather operation.
                         */
                        if (sc->rx.frag) {
                                /* too many fragments - cannot handle frame */
                                dev_kfree_skb_any(sc->rx.frag);
                                dev_kfree_skb_any(skb);
                                RX_STAT_INC(sc, rx_too_many_frags_err);
                                skb = NULL;
                        }
                        sc->rx.frag = skb;
                        goto requeue;
                }

                if (sc->rx.frag) {
                        int space = skb->len - skb_tailroom(hdr_skb);

                        if (pskb_expand_head(hdr_skb, 0, space, GFP_ATOMIC) < 0) {
                                dev_kfree_skb(skb);
                                RX_STAT_INC(sc, rx_oom_err);
                                goto requeue_drop_frag;
                        }

                        sc->rx.frag = NULL;

                        skb_copy_from_linear_data(skb, skb_put(hdr_skb, skb->len),
                                                  skb->len);
                        dev_kfree_skb_any(skb);
                        skb = hdr_skb;
                }

                if (rxs->flag & RX_FLAG_MMIC_STRIPPED)
                        skb_trim(skb, skb->len - 8);

                spin_lock_irqsave(&sc->sc_pm_lock, flags);
                if ((sc->ps_flags & (PS_WAIT_FOR_BEACON |
                                     PS_WAIT_FOR_CAB |
                                     PS_WAIT_FOR_PSPOLL_DATA)) ||
                    ath9k_check_auto_sleep(sc))
                        ath_rx_ps(sc, skb, rs.is_mybeacon);
                spin_unlock_irqrestore(&sc->sc_pm_lock, flags);

                ath9k_antenna_check(sc, &rs);
                ath9k_apply_ampdu_details(sc, &rs, rxs);
                ath_debug_rate_stats(sc, &rs, skb);
                ath_rx_count_airtime(sc, &rs, skb);

                hdr = (struct ieee80211_hdr *)skb->data;
                if (ieee80211_is_ack(hdr->frame_control))
                        ath_dynack_sample_ack_ts(sc->sc_ah, skb, rs.rs_tstamp);

                ieee80211_rx(hw, skb);

requeue_drop_frag:
                if (sc->rx.frag) {
                        dev_kfree_skb_any(sc->rx.frag);
                        sc->rx.frag = NULL;
                }
requeue:
                list_add_tail(&bf->list, &sc->rx.rxbuf);

                if (!edma) {
                        ath_rx_buf_relink(sc, bf, flush);
                        if (!flush)
                                ath9k_hw_rxena(ah);
                } else if (!flush) {
                        ath_rx_edma_buf_link(sc, qtype);
                }

                if (!budget--)
                        break;
        } while (1);

        if (!(ah->imask & ATH9K_INT_RXEOL)) {
                ah->imask |= (ATH9K_INT_RXEOL | ATH9K_INT_RXORN);
                ath9k_hw_set_interrupts(ah);
        }

        return 0;
}