dfs.c

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/*
 * 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;
};

/* 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;

    ath_dbg(ath9k_hw_common(sc->sc_ah), DFS,
        "pulse_bw_info=0x%x, pri,ext len/rssi=(%u/%u, %u/%u)\n",
        ard->pulse_bw_info,
        ard->pulse_length_pri, ard->rssi,
        ard->pulse_length_ext, ard->ext_rssi);

    /*
     * 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 = (ard->rssi < ard->ext_rssi) ? ard->ext_rssi : ard->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;
    }

    /*
     * TODO: check chirping pulses
     *   checks for chirping are dependent on the DFS regulatory domain
     *   used, which is yet TBD
     */

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

    DFS_STAT_INC(sc, pulses_detected);
    return true;
}
#undef PRI_CH_RADAR_FOUND
#undef EXT_CH_RADAR_FOUND

/*
 * 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_ctl0;
    ard.ext_rssi = rs->rs_rssi_ext0;

    /*
     * 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 = (char *)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)) {
        struct dfs_pattern_detector *pd = sc->dfs_detector;
        static u64 last_ts;
        ath_dbg(common, DFS,
            "ath9k_dfs_process_phyerr: channel=%d, ts=%llu, "
            "width=%d, rssi=%d, delta_ts=%llu\n",
            pe.freq, pe.ts, pe.width, pe.rssi, pe.ts-last_ts);
        last_ts = pe.ts;
        DFS_STAT_INC(sc, pulses_processed);
        if (pd != NULL && pd->add_pulse(pd, &pe)) {
            DFS_STAT_INC(sc, radar_detected);
            /*
             * TODO: forward radar event to DFS management layer
             */
        }
    }
}