/*
 * Copyright (c) 2008-2011 Atheros Communications Inc.
 * Copyright (c) 2011 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 "hw.h"
#include "hw-ops.h"
#include "ath9k.h"
#include "dfs.h"
#include "dfs_debug.h"

/* internal struct to pass radar data */
struct ath_radar_data {
        u8 pulse_bw_info;
        u8 rssi;
        u8 ext_rssi;
        u8 pulse_length_ext;
        u8 pulse_length_pri;
};

/**** begin: CHIRP ************************************************************/

/* min and max gradients for defined FCC chirping pulses, given by
 * - 20MHz chirp width over a pulse width of  50us
 * -  5MHz chirp width over a pulse width of 100us
 */
static const int BIN_DELTA_MIN          = 1;
static const int BIN_DELTA_MAX          = 10;

/* we need at least 3 deltas / 4 samples for a reliable chirp detection */
#define NUM_DIFFS 3
#define FFT_NUM_SAMPLES         (NUM_DIFFS + 1)

/* Threshold for difference of delta peaks */
static const int MAX_DIFF               = 2;

/* width range to be checked for chirping */
static const int MIN_CHIRP_PULSE_WIDTH  = 20;
static const int MAX_CHIRP_PULSE_WIDTH  = 110;

struct ath9k_dfs_fft_20 {
        u8 bin[28];
        u8 lower_bins[3];
} __packed;
struct ath9k_dfs_fft_40 {
        u8 bin[64];
        u8 lower_bins[3];
        u8 upper_bins[3];
} __packed;

static inline int fft_max_index(u8 *bins)
{
        return (bins[2] & 0xfc) >> 2;
}
static inline int fft_max_magnitude(u8 *bins)
{
        return (bins[0] & 0xc0) >> 6 | bins[1] << 2 | (bins[2] & 0x03) << 10;
}
static inline u8 fft_bitmap_weight(u8 *bins)
{
        return bins[0] & 0x3f;
}

static int ath9k_get_max_index_ht40(struct ath9k_dfs_fft_40 *fft,
                                    bool is_ctl, bool is_ext)
{
        const int DFS_UPPER_BIN_OFFSET = 64;
        /* if detected radar on both channels, select the significant one */
        if (is_ctl && is_ext) {
                /* first check whether channels have 'strong' bins */
                is_ctl = fft_bitmap_weight(fft->lower_bins) != 0;
                is_ext = fft_bitmap_weight(fft->upper_bins) != 0;

                /* if still unclear, take higher magnitude */
                if (is_ctl && is_ext) {
                        int mag_lower = fft_max_magnitude(fft->lower_bins);
                        int mag_upper = fft_max_magnitude(fft->upper_bins);
                        if (mag_upper > mag_lower)
                                is_ctl = false;
                        else
                                is_ext = false;
                }
        }
        if (is_ctl)
                return fft_max_index(fft->lower_bins);
        return fft_max_index(fft->upper_bins) + DFS_UPPER_BIN_OFFSET;
}
static bool ath9k_check_chirping(struct ath_softc *sc, u8 *data,
                                 int datalen, bool is_ctl, bool is_ext)
{
        int i;
        int max_bin[FFT_NUM_SAMPLES];
        struct ath_hw *ah = sc->sc_ah;
        struct ath_common *common = ath9k_hw_common(ah);
        int prev_delta;

        if (IS_CHAN_HT40(ah->curchan)) {
                struct ath9k_dfs_fft_40 *fft = (struct ath9k_dfs_fft_40 *) data;
                int num_fft_packets = datalen / sizeof(*fft);
                if (num_fft_packets == 0)
                        return false;

                ath_dbg(common, DFS, "HT40: datalen=%d, num_fft_packets=%d\n",
                        datalen, num_fft_packets);
                if (num_fft_packets < FFT_NUM_SAMPLES) {
                        ath_dbg(common, DFS, "not enough packets for chirp\n");
                        return false;
                }
                /* HW sometimes adds 2 garbage bytes in front of FFT samples */
                if ((datalen % sizeof(*fft)) == 2) {
                        fft = (struct ath9k_dfs_fft_40 *) (data + 2);
                        ath_dbg(common, DFS, "fixing datalen by 2\n");
                }
                if (IS_CHAN_HT40MINUS(ah->curchan))
                        swap(is_ctl, is_ext);

                for (i = 0; i < FFT_NUM_SAMPLES; i++)
                        max_bin[i] = ath9k_get_max_index_ht40(fft + i, is_ctl,
                                                              is_ext);
        } else {
                struct ath9k_dfs_fft_20 *fft = (struct ath9k_dfs_fft_20 *) data;
                int num_fft_packets = datalen / sizeof(*fft);
                if (num_fft_packets == 0)
                        return false;
                ath_dbg(common, DFS, "HT20: datalen=%d, num_fft_packets=%d\n",
                        datalen, num_fft_packets);
                if (num_fft_packets < FFT_NUM_SAMPLES) {
                        ath_dbg(common, DFS, "not enough packets for chirp\n");
                        return false;
                }
                /* in ht20, this is a 6-bit signed number => shift it to 0 */
                for (i = 0; i < FFT_NUM_SAMPLES; i++)
                        max_bin[i] = fft_max_index(fft[i].lower_bins) ^ 0x20;
        }
        ath_dbg(common, DFS, "bin_max = [%d, %d, %d, %d]\n",
                max_bin[0], max_bin[1], max_bin[2], max_bin[3]);

        /* Check for chirp attributes within specs
         * a) delta of adjacent max_bins is within range
         * b) delta of adjacent deltas are within tolerance
         */
        prev_delta = 0;
        for (i = 0; i < NUM_DIFFS; i++) {
                int ddelta = -1;
                int delta = max_bin[i + 1] - max_bin[i];

                /* ensure gradient is within valid range */
                if (abs(delta) < BIN_DELTA_MIN || abs(delta) > BIN_DELTA_MAX) {
                        ath_dbg(common, DFS, "CHIRP: invalid delta %d "
                                "in sample %d\n", delta, i);
                        return false;
                }
                if (i == 0)
                        goto done;
                ddelta = delta - prev_delta;
                if (abs(ddelta) > MAX_DIFF) {
                        ath_dbg(common, DFS, "CHIRP: ddelta %d too high\n",
                                ddelta);
                        return false;
                }
done:
                ath_dbg(common, DFS, "CHIRP - %d: delta=%d, ddelta=%d\n",
                        i, delta, ddelta);
                prev_delta = delta;
        }
        return true;
}
/**** end: CHIRP **************************************************************/

/* convert pulse duration to usecs, considering clock mode */
static u32 dur_to_usecs(struct ath_hw *ah, u32 dur)
{
        const u32 AR93X_NSECS_PER_DUR = 800;
        const u32 AR93X_NSECS_PER_DUR_FAST = (8000 / 11);
        u32 nsecs;

        if (IS_CHAN_A_FAST_CLOCK(ah, ah->curchan))
                nsecs = dur * AR93X_NSECS_PER_DUR_FAST;
        else
                nsecs = dur * AR93X_NSECS_PER_DUR;

        return (nsecs + 500) / 1000;
}

#define PRI_CH_RADAR_FOUND 0x01
#define EXT_CH_RADAR_FOUND 0x02
static bool
ath9k_postprocess_radar_event(struct ath_softc *sc,
                              struct ath_radar_data *ard,
                              struct pulse_event *pe)
{
        u8 rssi;
        u16 dur;

        /*
         * Only the last 2 bits of the BW info are relevant, they indicate
         * which channel the radar was detected in.
         */
        ard->pulse_bw_info &= 0x03;

        switch (ard->pulse_bw_info) {
        case PRI_CH_RADAR_FOUND:
                /* radar in ctrl channel */
                dur = ard->pulse_length_pri;
                DFS_STAT_INC(sc, pri_phy_errors);
                /*
                 * cannot use ctrl channel RSSI
                 * if extension channel is stronger
                 */
                rssi = (ard->ext_rssi >= (ard->rssi + 3)) ? 0 : ard->rssi;
                break;
        case EXT_CH_RADAR_FOUND:
                /* radar in extension channel */
                dur = ard->pulse_length_ext;
                DFS_STAT_INC(sc, ext_phy_errors);
                /*
                 * cannot use extension channel RSSI
                 * if control channel is stronger
                 */
                rssi = (ard->rssi >= (ard->ext_rssi + 12)) ? 0 : ard->ext_rssi;
                break;
        case (PRI_CH_RADAR_FOUND | EXT_CH_RADAR_FOUND):
                /*
                 * Conducted testing, when pulse is on DC, both pri and ext
                 * durations are reported to be same
                 *
                 * Radiated testing, when pulse is on DC, different pri and
                 * ext durations are reported, so take the larger of the two
                 */
                if (ard->pulse_length_ext >= ard->pulse_length_pri)
                        dur = ard->pulse_length_ext;
                else
                        dur = ard->pulse_length_pri;
                DFS_STAT_INC(sc, dc_phy_errors);

                /* when both are present use stronger one */
                rssi = max(ard->rssi, ard->ext_rssi);
                break;
        default:
                /*
                 * Bogus bandwidth info was received in descriptor,
                 * so ignore this PHY error
                 */
                DFS_STAT_INC(sc, bwinfo_discards);
                return false;
        }

        if (rssi == 0) {
                DFS_STAT_INC(sc, rssi_discards);
                return false;
        }

        /* convert duration to usecs */
        pe->width = dur_to_usecs(sc->sc_ah, dur);
        pe->rssi = rssi;

        DFS_STAT_INC(sc, pulses_detected);
        return true;
}

static void
ath9k_dfs_process_radar_pulse(struct ath_softc *sc, struct pulse_event *pe)
{
        struct dfs_pattern_detector *pd = sc->dfs_detector;
        DFS_STAT_INC(sc, pulses_processed);
        if (pd == NULL)
                return;
        if (!pd->add_pulse(pd, pe, NULL))
                return;
        DFS_STAT_INC(sc, radar_detected);
        ieee80211_radar_detected(sc->hw, NULL);
}

/*
 * DFS: check PHY-error for radar pulse and feed the detector
 */
void ath9k_dfs_process_phyerr(struct ath_softc *sc, void *data,
                              struct ath_rx_status *rs, u64 mactime)
{
        struct ath_radar_data ard;
        u16 datalen;
        char *vdata_end;
        struct pulse_event pe;
        struct ath_hw *ah = sc->sc_ah;
        struct ath_common *common = ath9k_hw_common(ah);

        DFS_STAT_INC(sc, pulses_total);
        if ((rs->rs_phyerr != ATH9K_PHYERR_RADAR) &&
            (rs->rs_phyerr != ATH9K_PHYERR_FALSE_RADAR_EXT)) {
                ath_dbg(common, DFS,
                        "Error: rs_phyer=0x%x not a radar error\n",
                        rs->rs_phyerr);
                DFS_STAT_INC(sc, pulses_no_dfs);
                return;
        }

        datalen = rs->rs_datalen;
        if (datalen == 0) {
                DFS_STAT_INC(sc, datalen_discards);
                return;
        }

        ard.rssi = rs->rs_rssi_ctl[0];
        ard.ext_rssi = rs->rs_rssi_ext[0];

        /*
         * hardware stores this as 8 bit signed value.
         * we will cap it at 0 if it is a negative number
         */
        if (ard.rssi & 0x80)
                ard.rssi = 0;
        if (ard.ext_rssi & 0x80)
                ard.ext_rssi = 0;

        vdata_end = data + datalen;
        ard.pulse_bw_info = vdata_end[-1];
        ard.pulse_length_ext = vdata_end[-2];
        ard.pulse_length_pri = vdata_end[-3];
        pe.freq = ah->curchan->channel;
        pe.ts = mactime;
        if (!ath9k_postprocess_radar_event(sc, &ard, &pe))
                return;

        if (pe.width > MIN_CHIRP_PULSE_WIDTH &&
            pe.width < MAX_CHIRP_PULSE_WIDTH) {
                bool is_ctl = !!(ard.pulse_bw_info & PRI_CH_RADAR_FOUND);
                bool is_ext = !!(ard.pulse_bw_info & EXT_CH_RADAR_FOUND);
                int clen = datalen - 3;
                pe.chirp = ath9k_check_chirping(sc, data, clen, is_ctl, is_ext);
        } else {
                pe.chirp = false;
        }

        ath_dbg(common, DFS,
                "ath9k_dfs_process_phyerr: type=%d, freq=%d, ts=%llu, "
                "width=%d, rssi=%d, delta_ts=%llu\n",
                ard.pulse_bw_info, pe.freq, pe.ts, pe.width, pe.rssi,
                pe.ts - sc->dfs_prev_pulse_ts);
        sc->dfs_prev_pulse_ts = pe.ts;
        if (ard.pulse_bw_info & PRI_CH_RADAR_FOUND)
                ath9k_dfs_process_radar_pulse(sc, &pe);
        if (IS_CHAN_HT40(ah->curchan) &&
            ard.pulse_bw_info & EXT_CH_RADAR_FOUND) {
                pe.freq += IS_CHAN_HT40PLUS(ah->curchan) ? 20 : -20;
                ath9k_dfs_process_radar_pulse(sc, &pe);
        }
}
#undef PRI_CH_RADAR_FOUND
#undef EXT_CH_RADAR_FOUND