/*
   * 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
  static const int 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 wether 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
  ",
  			datalen, num_fft_packets);
  		if (num_fft_packets < (FFT_NUM_SAMPLES)) {
  			ath_dbg(common, DFS, "not enough packets for chirp
  ");
  			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
  ");
  		}
  		if (IS_CHAN_HT40MINUS(ah->curchan)) {
  			int temp = is_ctl;
  			is_ctl = is_ext;
  			is_ext = temp;
  		}
  		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
  ",
  			datalen, num_fft_packets);
  		if (num_fft_packets < (FFT_NUM_SAMPLES)) {
  			ath_dbg(common, DFS, "not enough packets for chirp
  ");
  			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]
  ",
  		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
  ", 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
  ",
  				ddelta);
  			return false;
  		}
  done:
  		ath_dbg(common, DFS, "CHIRP - %d: delta=%d, ddelta=%d
  ",
  			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 = (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;
  	}
  
  	/* 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))
  		return;
  	DFS_STAT_INC(sc, radar_detected);
  	ieee80211_radar_detected(sc->hw);
  }
  
  /*
   * 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
  ",
  			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 = (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))
  		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
  ",
  		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