linux/drivers/net/wireless/ath/ath9k/ani.c

/*
 * 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/kernel.h>
#include <linux/export.h>
#include "hw.h"
#include "hw-ops.h"

struct ani_ofdm_level_entry { … };

/* values here are relative to the INI */

/*
 * Legend:
 *
 * SI: Spur immunity
 * FS: FIR Step
 * WS: OFDM / CCK Weak Signal detection
 * MRC-CCK: Maximal Ratio Combining for CCK
 */

static const struct ani_ofdm_level_entry ofdm_level_table[] = …;
#define ATH9K_ANI_OFDM_NUM_LEVEL …
#define ATH9K_ANI_OFDM_MAX_LEVEL …
#define ATH9K_ANI_OFDM_DEF_LEVEL …

/*
 * MRC (Maximal Ratio Combining) has always been used with multi-antenna ofdm.
 * With OFDM for single stream you just add up all antenna inputs, you're
 * only interested in what you get after FFT. Signal alignment is also not
 * required for OFDM because any phase difference adds up in the frequency
 * domain.
 *
 * MRC requires extra work for use with CCK. You need to align the antenna
 * signals from the different antenna before you can add the signals together.
 * You need alignment of signals as CCK is in time domain, so addition can cancel
 * your signal completely if phase is 180 degrees (think of adding sine waves).
 * You also need to remove noise before the addition and this is where ANI
 * MRC CCK comes into play. One of the antenna inputs may be stronger but
 * lower SNR, so just adding after alignment can be dangerous.
 *
 * Regardless of alignment in time, the antenna signals add constructively after
 * FFT and improve your reception. For more information:
 *
 * https://en.wikipedia.org/wiki/Maximal-ratio_combining
 */

struct ani_cck_level_entry { … };

static const struct ani_cck_level_entry cck_level_table[] = …;

#define ATH9K_ANI_CCK_NUM_LEVEL …
#define ATH9K_ANI_CCK_MAX_LEVEL …
#define ATH9K_ANI_CCK_MAX_LEVEL_LOW_RSSI …
#define ATH9K_ANI_CCK_DEF_LEVEL …

static void ath9k_hw_update_mibstats(struct ath_hw *ah,
				     struct ath9k_mib_stats *stats)
{ … }

static void ath9k_ani_restart(struct ath_hw *ah)
{ … }

/* Adjust the OFDM Noise Immunity Level */
static void ath9k_hw_set_ofdm_nil(struct ath_hw *ah, u8 immunityLevel,
				  bool scan)
{ … }

static void ath9k_hw_ani_ofdm_err_trigger(struct ath_hw *ah)
{ … }

/*
 * Set the ANI settings to match an CCK level.
 */
static void ath9k_hw_set_cck_nil(struct ath_hw *ah, u_int8_t immunityLevel,
				 bool scan)
{ … }

static void ath9k_hw_ani_cck_err_trigger(struct ath_hw *ah)
{ … }

/*
 * only lower either OFDM or CCK errors per turn
 * we lower the other one next time
 */
static void ath9k_hw_ani_lower_immunity(struct ath_hw *ah)
{ … }

/*
 * Restore the ANI parameters in the HAL and reset the statistics.
 * This routine should be called for every hardware reset and for
 * every channel change.
 */
void ath9k_ani_reset(struct ath_hw *ah, bool is_scanning)
{ … }

static bool ath9k_hw_ani_read_counters(struct ath_hw *ah)
{ … }

void ath9k_hw_ani_monitor(struct ath_hw *ah, struct ath9k_channel *chan)
{ … }
EXPORT_SYMBOL(…);

void ath9k_enable_mib_counters(struct ath_hw *ah)
{ … }

/* Freeze the MIB counters, get the stats and then clear them */
void ath9k_hw_disable_mib_counters(struct ath_hw *ah)
{ … }
EXPORT_SYMBOL(…);

void ath9k_hw_ani_init(struct ath_hw *ah)
{ … }