iwl-4965-rs.c

/******************************************************************************
 *
 * Copyright(c) 2005 - 2008 Intel Corporation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110, USA
 *
 * The full GNU General Public License is included in this distribution in the
 * file called LICENSE.
 *
 * Contact Information:
 * James P. Ketrenos <ipw2100-admin@linux.intel.com>
 * Intel Corporation, 5200 N.E. Elam Young Parkway, Hillsboro, OR 97124-6497
 *
 *****************************************************************************/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/skbuff.h>
#include <linux/wireless.h>
#include <net/mac80211.h>

#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/delay.h>

#include <linux/workqueue.h>

#include "../net/mac80211/rate.h"

#include "iwl-dev.h"
#include "iwl-core.h"
#include "iwl-helpers.h"

#define RS_NAME "iwl-4965-rs"

#define NUM_TRY_BEFORE_ANT_TOGGLE 1
#define IWL_NUMBER_TRY      1
#define IWL_HT_NUMBER_TRY   3

#define IWL_RATE_MAX_WINDOW		62	/* # tx in history window */
#define IWL_RATE_MIN_FAILURE_TH		6	/* min failures to calc tpt */
#define IWL_RATE_MIN_SUCCESS_TH		8	/* min successes to calc tpt */

/* max time to accum history 2 seconds */
#define IWL_RATE_SCALE_FLUSH_INTVL   (2*HZ)

static u8 rs_ht_to_legacy[] = {
	IWL_RATE_6M_INDEX, IWL_RATE_6M_INDEX,
	IWL_RATE_6M_INDEX, IWL_RATE_6M_INDEX,
	IWL_RATE_6M_INDEX,
	IWL_RATE_6M_INDEX, IWL_RATE_9M_INDEX,
	IWL_RATE_12M_INDEX, IWL_RATE_18M_INDEX,
	IWL_RATE_24M_INDEX, IWL_RATE_36M_INDEX,
	IWL_RATE_48M_INDEX, IWL_RATE_54M_INDEX
};

static const u8 ant_toggle_lookup[] = {
	/*ANT_NONE -> */ ANT_NONE,
	/*ANT_A    -> */ ANT_B,
	/*ANT_B    -> */ ANT_C,
	/*ANT_AB   -> */ ANT_BC,
	/*ANT_C    -> */ ANT_A,
	/*ANT_AC   -> */ ANT_AB,
	/*ANT_BC   -> */ ANT_AC,
	/*ANT_ABC  -> */ ANT_ABC,
};

/**
 * struct iwl4965_rate_scale_data -- tx success history for one rate
 */
struct iwl4965_rate_scale_data {
	u64 data;		/* bitmap of successful frames */
	s32 success_counter;	/* number of frames successful */
	s32 success_ratio;	/* per-cent * 128  */
	s32 counter;		/* number of frames attempted */
	s32 average_tpt;	/* success ratio * expected throughput */
	unsigned long stamp;
};

/**
 * struct iwl4965_scale_tbl_info -- tx params and success history for all rates
 *
 * There are two of these in struct iwl4965_lq_sta,
 * one for "active", and one for "search".
 */
struct iwl4965_scale_tbl_info {
	enum iwl_table_type lq_type;
	u8 ant_type;
	u8 is_SGI;	/* 1 = short guard interval */
	u8 is_fat;	/* 1 = 40 MHz channel width */
	u8 is_dup;	/* 1 = duplicated data streams */
	u8 action;	/* change modulation; IWL_[LEGACY/SISO/MIMO]_SWITCH_* */
	s32 *expected_tpt;	/* throughput metrics; expected_tpt_G, etc. */
	u32 current_rate;  /* rate_n_flags, uCode API format */
	struct iwl4965_rate_scale_data win[IWL_RATE_COUNT]; /* rate histories */
};

struct iwl4965_traffic_load {
	unsigned long time_stamp;	/* age of the oldest statistics */
	u32 packet_count[TID_QUEUE_MAX_SIZE];   /* packet count in this time
						 * slice */
	u32 total;			/* total num of packets during the
					 * last TID_MAX_TIME_DIFF */
	u8 queue_count;			/* number of queues that has
					 * been used since the last cleanup */
	u8 head;			/* start of the circular buffer */
};

/**
 * struct iwl4965_lq_sta -- driver's rate scaling private structure
 *
 * Pointer to this gets passed back and forth between driver and mac80211.
 */
struct iwl4965_lq_sta {
	u8 active_tbl;		/* index of active table, range 0-1 */
	u8 enable_counter;	/* indicates HT mode */
	u8 stay_in_tbl;		/* 1: disallow, 0: allow search for new mode */
	u8 search_better_tbl;	/* 1: currently trying alternate mode */
	s32 last_tpt;

	/* The following determine when to search for a new mode */
	u32 table_count_limit;
	u32 max_failure_limit;	/* # failed frames before new search */
	u32 max_success_limit;	/* # successful frames before new search */
	u32 table_count;
	u32 total_failed;	/* total failed frames, any/all rates */
	u32 total_success;	/* total successful frames, any/all rates */
	u32 flush_timer;	/* time staying in mode before new search */

	u8 action_counter;	/* # mode-switch actions tried */
	u8 is_green;
	u8 is_dup;
	enum ieee80211_band band;
	u8 ibss_sta_added;

	/* The following are bitmaps of rates; IWL_RATE_6M_MASK, etc. */
	u32 supp_rates;
	u16 active_legacy_rate;
	u16 active_siso_rate;
	u16 active_mimo2_rate;
	u16 active_mimo3_rate;
	u16 active_rate_basic;

	struct iwl_link_quality_cmd lq;
	struct iwl4965_scale_tbl_info lq_info[LQ_SIZE]; /* "active", "search" */
	struct iwl4965_traffic_load load[TID_MAX_LOAD_COUNT];
	u8 tx_agg_tid_en;
#ifdef CONFIG_MAC80211_DEBUGFS
	struct dentry *rs_sta_dbgfs_scale_table_file;
	struct dentry *rs_sta_dbgfs_stats_table_file;
	struct dentry *rs_sta_dbgfs_tx_agg_tid_en_file;
	u32 dbg_fixed_rate;
#endif
	struct iwl_priv *drv;
};

static void rs_rate_scale_perform(struct iwl_priv *priv,
				   struct net_device *dev,
				   struct ieee80211_hdr *hdr,
				   struct sta_info *sta);
static void rs_fill_link_cmd(const struct iwl_priv *priv,
			     struct iwl4965_lq_sta *lq_sta,
			     u32 rate_n_flags);


#ifdef CONFIG_MAC80211_DEBUGFS
static void rs_dbgfs_set_mcs(struct iwl4965_lq_sta *lq_sta,
					u32 *rate_n_flags, int index);
#else
static void rs_dbgfs_set_mcs(struct iwl4965_lq_sta *lq_sta,
					u32 *rate_n_flags, int index)
{}
#endif

/*
 * Expected throughput metrics for following rates:
 * 1, 2, 5.5, 11, 6, 9, 12, 18, 24, 36, 48, 54, 60 MBits
 * "G" is the only table that supports CCK (the first 4 rates).
 */
/*FIXME:RS:need to spearate tables for MIMO2/MIMO3*/
static s32 expected_tpt_A[IWL_RATE_COUNT] = {
	0, 0, 0, 0, 40, 57, 72, 98, 121, 154, 177, 186, 186
};

static s32 expected_tpt_G[IWL_RATE_COUNT] = {
	7, 13, 35, 58, 40, 57, 72, 98, 121, 154, 177, 186, 186
};

static s32 expected_tpt_siso20MHz[IWL_RATE_COUNT] = {
	0, 0, 0, 0, 42, 42, 76, 102, 124, 159, 183, 193, 202
};

static s32 expected_tpt_siso20MHzSGI[IWL_RATE_COUNT] = {
	0, 0, 0, 0, 46, 46, 82, 110, 132, 168, 192, 202, 211
};

static s32 expected_tpt_mimo20MHz[IWL_RATE_COUNT] = {
	0, 0, 0, 0, 74, 74, 123, 155, 179, 214, 236, 244, 251
};

static s32 expected_tpt_mimo20MHzSGI[IWL_RATE_COUNT] = {
	0, 0, 0, 0, 81, 81, 131, 164, 188, 222, 243, 251, 257
};

static s32 expected_tpt_siso40MHz[IWL_RATE_COUNT] = {
	0, 0, 0, 0, 77, 77, 127, 160, 184, 220, 242, 250, 257
};

static s32 expected_tpt_siso40MHzSGI[IWL_RATE_COUNT] = {
	0, 0, 0, 0, 83, 83, 135, 169, 193, 229, 250, 257, 264
};

static s32 expected_tpt_mimo40MHz[IWL_RATE_COUNT] = {
	0, 0, 0, 0, 123, 123, 182, 214, 235, 264, 279, 285, 289
};

static s32 expected_tpt_mimo40MHzSGI[IWL_RATE_COUNT] = {
	0, 0, 0, 0, 131, 131, 191, 222, 242, 270, 284, 289, 293
};

static inline u8 rs_extract_rate(u32 rate_n_flags)
{
	return (u8)(rate_n_flags & 0xFF);
}

static void rs_rate_scale_clear_window(struct iwl4965_rate_scale_data *window)
{
	window->data = 0;
	window->success_counter = 0;
	window->success_ratio = IWL_INVALID_VALUE;
	window->counter = 0;
	window->average_tpt = IWL_INVALID_VALUE;
	window->stamp = 0;
}

static inline u8 rs_is_valid_ant(u8 valid_antenna, u8 ant_type)
{
	return ((ant_type & valid_antenna) == ant_type);
}

/*
 *	removes the old data from the statistics. All data that is older than
 *	TID_MAX_TIME_DIFF, will be deleted.
 */
static void rs_tl_rm_old_stats(struct iwl4965_traffic_load *tl, u32 curr_time)
{
	/* The oldest age we want to keep */
	u32 oldest_time = curr_time - TID_MAX_TIME_DIFF;

	while (tl->queue_count &&
	       (tl->time_stamp < oldest_time)) {
		tl->total -= tl->packet_count[tl->head];
		tl->packet_count[tl->head] = 0;
		tl->time_stamp += TID_QUEUE_CELL_SPACING;
		tl->queue_count--;
		tl->head++;
		if (tl->head >= TID_QUEUE_MAX_SIZE)
			tl->head = 0;
	}
}

/*
 *	increment traffic load value for tid and also remove
 *	any old values if passed the certain time period
 */
static void rs_tl_add_packet(struct iwl4965_lq_sta *lq_data,
			     struct ieee80211_hdr *hdr)
{
	u32 curr_time = jiffies_to_msecs(jiffies);
	u32 time_diff;
	s32 index;
	struct iwl4965_traffic_load *tl = NULL;
	u16 fc = le16_to_cpu(hdr->frame_control);
	u8 tid;

	if (ieee80211_is_qos_data(fc)) {
		u8 *qc = ieee80211_get_qos_ctrl(hdr, ieee80211_get_hdrlen(fc));
		tid = qc[0] & 0xf;
	} else
		return;

	tl = &lq_data->load[tid];

	curr_time -= curr_time % TID_ROUND_VALUE;

	/* Happens only for the first packet. Initialize the data */
	if (!(tl->queue_count)) {
		tl->total = 1;
		tl->time_stamp = curr_time;
		tl->queue_count = 1;
		tl->head = 0;
		tl->packet_count[0] = 1;
		return;
	}

	time_diff = TIME_WRAP_AROUND(tl->time_stamp, curr_time);
	index = time_diff / TID_QUEUE_CELL_SPACING;

	/* The history is too long: remove data that is older than */
	/* TID_MAX_TIME_DIFF */
	if (index >= TID_QUEUE_MAX_SIZE)
		rs_tl_rm_old_stats(tl, curr_time);

	index = (tl->head + index) % TID_QUEUE_MAX_SIZE;
	tl->packet_count[index] = tl->packet_count[index] + 1;
	tl->total = tl->total + 1;

	if ((index + 1) > tl->queue_count)
		tl->queue_count = index + 1;
}

/*
	get the traffic load value for tid
*/
static u32 rs_tl_get_load(struct iwl4965_lq_sta *lq_data, u8 tid)
{
	u32 curr_time = jiffies_to_msecs(jiffies);
	u32 time_diff;
	s32 index;
	struct iwl4965_traffic_load *tl = NULL;

	if (tid >= TID_MAX_LOAD_COUNT)
		return 0;

	tl = &(lq_data->load[tid]);

	curr_time -= curr_time % TID_ROUND_VALUE;

	if (!(tl->queue_count))
		return 0;

	time_diff = TIME_WRAP_AROUND(tl->time_stamp, curr_time);
	index = time_diff / TID_QUEUE_CELL_SPACING;

	/* The history is too long: remove data that is older than */
	/* TID_MAX_TIME_DIFF */
	if (index >= TID_QUEUE_MAX_SIZE)
		rs_tl_rm_old_stats(tl, curr_time);

	return tl->total;
}

static void rs_tl_turn_on_agg_for_tid(struct iwl_priv *priv,
				struct iwl4965_lq_sta *lq_data, u8 tid,
				struct sta_info *sta)
{
	unsigned long state;
	DECLARE_MAC_BUF(mac);

	spin_lock_bh(&sta->lock);
	state = sta->ampdu_mlme.tid_state_tx[tid];
	spin_unlock_bh(&sta->lock);

	if (state == HT_AGG_STATE_IDLE &&
	    rs_tl_get_load(lq_data, tid) > IWL_AGG_LOAD_THRESHOLD) {
		IWL_DEBUG_HT("Starting Tx agg: STA: %s tid: %d\n",
				print_mac(mac, sta->addr), tid);
		ieee80211_start_tx_ba_session(priv->hw, sta->addr, tid);
	}
}

static void rs_tl_turn_on_agg(struct iwl_priv *priv, u8 tid,
				struct iwl4965_lq_sta *lq_data,
				struct sta_info *sta)
{
	if ((tid < TID_MAX_LOAD_COUNT))
		rs_tl_turn_on_agg_for_tid(priv, lq_data, tid, sta);
	else if (tid == IWL_AGG_ALL_TID)
		for (tid = 0; tid < TID_MAX_LOAD_COUNT; tid++)
			rs_tl_turn_on_agg_for_tid(priv, lq_data, tid, sta);
}

static inline int get_num_of_ant_from_rate(u32 rate_n_flags)
{
	return (!!(rate_n_flags & RATE_MCS_ANT_A_MSK) +
		!!(rate_n_flags & RATE_MCS_ANT_B_MSK) +
		!!(rate_n_flags & RATE_MCS_ANT_C_MSK));
}

/**
 * rs_collect_tx_data - Update the success/failure sliding window
 *
 * We keep a sliding window of the last 62 packets transmitted
 * at this rate.  window->data contains the bitmask of successful
 * packets.
 */
static int rs_collect_tx_data(struct iwl4965_rate_scale_data *windows,
			      int scale_index, s32 tpt, int retries,
			      int successes)
{
	struct iwl4965_rate_scale_data *window = NULL;
	static const u64 mask = (((u64)1) << (IWL_RATE_MAX_WINDOW - 1));
	s32 fail_count;

	if (scale_index < 0 || scale_index >= IWL_RATE_COUNT)
		return -EINVAL;

	/* Select data for current tx bit rate */
	window = &(windows[scale_index]);

	/*
	 * Keep track of only the latest 62 tx frame attempts in this rate's
	 * history window; anything older isn't really relevant any more.
	 * If we have filled up the sliding window, drop the oldest attempt;
	 * if the oldest attempt (highest bit in bitmap) shows "success",
	 * subtract "1" from the success counter (this is the main reason
	 * we keep these bitmaps!).
	 */
	while (retries > 0) {
		if (window->counter >= IWL_RATE_MAX_WINDOW) {

			/* remove earliest */
			window->counter = IWL_RATE_MAX_WINDOW - 1;

			if (window->data & mask) {
				window->data &= ~mask;
				window->success_counter--;
			}
		}

		/* Increment frames-attempted counter */
		window->counter++;

		/* Shift bitmap by one frame (throw away oldest history),
		 * OR in "1", and increment "success" if this
		 * frame was successful. */
		window->data <<= 1;;
		if (successes > 0) {
			window->success_counter++;
			window->data |= 0x1;
			successes--;
		}

		retries--;
	}

	/* Calculate current success ratio, avoid divide-by-0! */
	if (window->counter > 0)
		window->success_ratio = 128 * (100 * window->success_counter)
					/ window->counter;
	else
		window->success_ratio = IWL_INVALID_VALUE;

	fail_count = window->counter - window->success_counter;

	/* Calculate average throughput, if we have enough history. */
	if ((fail_count >= IWL_RATE_MIN_FAILURE_TH) ||
	    (window->success_counter >= IWL_RATE_MIN_SUCCESS_TH))
		window->average_tpt = (window->success_ratio * tpt + 64) / 128;
	else
		window->average_tpt = IWL_INVALID_VALUE;

	/* Tag this window as having been updated */
	window->stamp = jiffies;

	return 0;
}

/*
 * Fill uCode API rate_n_flags field, based on "search" or "active" table.
 */
/* FIXME:RS:remove this function and put the flags statically in the table */
static u32 rate_n_flags_from_tbl(struct iwl4965_scale_tbl_info *tbl,
				       int index, u8 use_green)
{
	u32 rate_n_flags = 0;

	if (is_legacy(tbl->lq_type)) {
		rate_n_flags = iwl_rates[index].plcp;
		if (index >= IWL_FIRST_CCK_RATE && index <= IWL_LAST_CCK_RATE)
			rate_n_flags |= RATE_MCS_CCK_MSK;

	} else if (is_Ht(tbl->lq_type)) {
		if (index > IWL_LAST_OFDM_RATE) {
			IWL_ERROR("invalid HT rate index %d\n", index);
			index = IWL_LAST_OFDM_RATE;
		}
		rate_n_flags = RATE_MCS_HT_MSK;

		if (is_siso(tbl->lq_type))
			rate_n_flags |=	iwl_rates[index].plcp_siso;
		else if (is_mimo2(tbl->lq_type))
			rate_n_flags |=	iwl_rates[index].plcp_mimo2;
		else
			rate_n_flags |=	iwl_rates[index].plcp_mimo3;
	} else {
		IWL_ERROR("Invalid tbl->lq_type %d\n", tbl->lq_type);
	}

	rate_n_flags |= ((tbl->ant_type << RATE_MCS_ANT_POS) &
						     RATE_MCS_ANT_ABC_MSK);

	if (is_Ht(tbl->lq_type)) {
		if (tbl->is_fat) {
			if (tbl->is_dup)
				rate_n_flags |= RATE_MCS_DUP_MSK;
			else
				rate_n_flags |= RATE_MCS_FAT_MSK;
		}
		if (tbl->is_SGI)
			rate_n_flags |= RATE_MCS_SGI_MSK;

		if (use_green) {
			rate_n_flags |= RATE_MCS_GF_MSK;
			if (is_siso(tbl->lq_type) && tbl->is_SGI) {
				rate_n_flags &= ~RATE_MCS_SGI_MSK;
				IWL_ERROR("GF was set with SGI:SISO\n");
			}
		}
	}
	return rate_n_flags;
}

/*
 * Interpret uCode API's rate_n_flags format,
 * fill "search" or "active" tx mode table.
 */
static int rs_get_tbl_info_from_mcs(const u32 rate_n_flags,
				    enum ieee80211_band band,
				    struct iwl4965_scale_tbl_info *tbl,
				    int *rate_idx)
{
	u32 ant_msk = (rate_n_flags & RATE_MCS_ANT_ABC_MSK);
	u8 num_of_ant = get_num_of_ant_from_rate(rate_n_flags);
	u8 mcs;

	*rate_idx = iwl4965_hwrate_to_plcp_idx(rate_n_flags);

	if (*rate_idx  == IWL_RATE_INVALID) {
		*rate_idx = -1;
		return -EINVAL;
	}
	tbl->is_SGI = 0;	/* default legacy setup */
	tbl->is_fat = 0;
	tbl->is_dup = 0;
	tbl->ant_type = (ant_msk >> RATE_MCS_ANT_POS);
	tbl->lq_type = LQ_NONE;

	/* legacy rate format */
	if (!(rate_n_flags & RATE_MCS_HT_MSK)) {
		if (num_of_ant == 1) {
			if (band == IEEE80211_BAND_5GHZ)
				tbl->lq_type = LQ_A;
			else
				tbl->lq_type = LQ_G;
		}
	/* HT rate format */
	} else {
		if (rate_n_flags & RATE_MCS_SGI_MSK)
			tbl->is_SGI = 1;

		if ((rate_n_flags & RATE_MCS_FAT_MSK) ||
		    (rate_n_flags & RATE_MCS_DUP_MSK))
			tbl->is_fat = 1;

		if (rate_n_flags & RATE_MCS_DUP_MSK)
			tbl->is_dup = 1;

		mcs = rs_extract_rate(rate_n_flags);

		/* SISO */
		if (mcs <= IWL_RATE_SISO_60M_PLCP) {
			if (num_of_ant == 1)
				tbl->lq_type = LQ_SISO; /*else NONE*/
		/* MIMO2 */
		} else if (mcs <= IWL_RATE_MIMO2_60M_PLCP) {
			if (num_of_ant == 2)
				tbl->lq_type = LQ_MIMO2;
		/* MIMO3 */
		} else {
			if (num_of_ant == 3)
				tbl->lq_type = LQ_MIMO3;
		}
	}
	return 0;
}

/* switch to another antenna/antennas and return 1 */
/* if no other valid antenna found, return 0 */
static int rs_toggle_antenna(u32 valid_ant, u32 *rate_n_flags,
			      struct iwl4965_scale_tbl_info *tbl)
{
	u8 new_ant_type;

	if (!tbl->ant_type || tbl->ant_type > ANT_ABC)
		return 0;

	if (!rs_is_valid_ant(valid_ant, tbl->ant_type))
		return 0;

	new_ant_type = ant_toggle_lookup[tbl->ant_type];

	while ((new_ant_type != tbl->ant_type) &&
	       !rs_is_valid_ant(valid_ant, new_ant_type))
		new_ant_type = ant_toggle_lookup[new_ant_type];

	if (new_ant_type == tbl->ant_type)
		return 0;

	tbl->ant_type = new_ant_type;
	*rate_n_flags &= ~RATE_MCS_ANT_ABC_MSK;
	*rate_n_flags |= new_ant_type << RATE_MCS_ANT_POS;
	return 1;
}

/* FIXME:RS: in 4965 we don't use greenfield at all */
/* FIXME:RS: don't use greenfield for now in TX */
#if 0
static inline u8 rs_use_green(struct iwl_priv *priv, struct ieee80211_conf *conf)
{
	return ((conf->flags & IEEE80211_CONF_SUPPORT_HT_MODE) &&
		priv->current_ht_config.is_green_field &&
		!priv->current_ht_config.non_GF_STA_present);
}
#endif
static inline u8 rs_use_green(struct iwl_priv *priv, struct ieee80211_conf *conf)
{
	return 0;
}

/**
 * rs_get_supported_rates - get the available rates
 *
 * if management frame or broadcast frame only return
 * basic available rates.
 *
 */
static u16 rs_get_supported_rates(struct iwl4965_lq_sta *lq_sta,
				   struct ieee80211_hdr *hdr,
				   enum iwl_table_type rate_type)
{
	if (hdr && is_multicast_ether_addr(hdr->addr1) &&
	    lq_sta->active_rate_basic)
		return lq_sta->active_rate_basic;

	if (is_legacy(rate_type)) {
		return lq_sta->active_legacy_rate;
	} else {
		if (is_siso(rate_type))
			return lq_sta->active_siso_rate;
		else if (is_mimo2(rate_type))
			return lq_sta->active_mimo2_rate;
		else
			return lq_sta->active_mimo3_rate;
	}
}

static u16 rs_get_adjacent_rate(struct iwl_priv *priv, u8 index, u16 rate_mask,
				int rate_type)
{
	u8 high = IWL_RATE_INVALID;
	u8 low = IWL_RATE_INVALID;

	/* 802.11A or ht walks to the next literal adjacent rate in
	 * the rate table */
	if (is_a_band(rate_type) || !is_legacy(rate_type)) {
		int i;
		u32 mask;

		/* Find the previous rate that is in the rate mask */
		i = index - 1;
		for (mask = (1 << i); i >= 0; i--, mask >>= 1) {
			if (rate_mask & mask) {
				low = i;
				break;
			}
		}

		/* Find the next rate that is in the rate mask */
		i = index + 1;
		for (mask = (1 << i); i < IWL_RATE_COUNT; i++, mask <<= 1) {
			if (rate_mask & mask) {
				high = i;
				break;
			}
		}

		return (high << 8) | low;
	}

	low = index;
	while (low != IWL_RATE_INVALID) {
		low = iwl_rates[low].prev_rs;
		if (low == IWL_RATE_INVALID)
			break;
		if (rate_mask & (1 << low))
			break;
		IWL_DEBUG_RATE("Skipping masked lower rate: %d\n", low);
	}

	high = index;
	while (high != IWL_RATE_INVALID) {
		high = iwl_rates[high].next_rs;
		if (high == IWL_RATE_INVALID)
			break;
		if (rate_mask & (1 << high))
			break;
		IWL_DEBUG_RATE("Skipping masked higher rate: %d\n", high);
	}

	return (high << 8) | low;
}

static u32 rs_get_lower_rate(struct iwl4965_lq_sta *lq_sta,
			     struct iwl4965_scale_tbl_info *tbl, u8 scale_index,
			     u8 ht_possible)
{
	s32 low;
	u16 rate_mask;
	u16 high_low;
	u8 switch_to_legacy = 0;
	u8 is_green = lq_sta->is_green;

	/* check if we need to switch from HT to legacy rates.
	 * assumption is that mandatory rates (1Mbps or 6Mbps)
	 * are always supported (spec demand) */
	if (!is_legacy(tbl->lq_type) && (!ht_possible || !scale_index)) {
		switch_to_legacy = 1;
		scale_index = rs_ht_to_legacy[scale_index];
		if (lq_sta->band == IEEE80211_BAND_5GHZ)
			tbl->lq_type = LQ_A;
		else
			tbl->lq_type = LQ_G;

		if (num_of_ant(tbl->ant_type) > 1)
			tbl->ant_type = ANT_A;/*FIXME:RS*/

		tbl->is_fat = 0;
		tbl->is_SGI = 0;
	}

	rate_mask = rs_get_supported_rates(lq_sta, NULL, tbl->lq_type);

	/* Mask with station rate restriction */
	if (is_legacy(tbl->lq_type)) {
		/* supp_rates has no CCK bits in A mode */
		if (lq_sta->band == IEEE80211_BAND_5GHZ)
			rate_mask  = (u16)(rate_mask &
			   (lq_sta->supp_rates << IWL_FIRST_OFDM_RATE));
		else
			rate_mask = (u16)(rate_mask & lq_sta->supp_rates);
	}

	/* If we switched from HT to legacy, check current rate */
	if (switch_to_legacy && (rate_mask & (1 << scale_index))) {
		low = scale_index;
		goto out;
	}

	high_low = rs_get_adjacent_rate(lq_sta->drv, scale_index, rate_mask,
					tbl->lq_type);
	low = high_low & 0xff;

	if (low == IWL_RATE_INVALID)
		low = scale_index;

out:
	return rate_n_flags_from_tbl(tbl, low, is_green);
}

/*
 * mac80211 sends us Tx status
 */
static void rs_tx_status(void *priv_rate, struct net_device *dev,
			 struct sk_buff *skb)
{
	int status;
	u8 retries;
	int rs_index, index = 0;
	struct iwl4965_lq_sta *lq_sta;
	struct iwl_link_quality_cmd *table;
	struct sta_info *sta;
	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
	struct iwl_priv *priv = (struct iwl_priv *)priv_rate;
	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
	struct ieee80211_hw *hw = local_to_hw(local);
	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
	struct iwl4965_rate_scale_data *window = NULL;
	struct iwl4965_rate_scale_data *search_win = NULL;
	u32 tx_rate;
	struct iwl4965_scale_tbl_info tbl_type;
	struct iwl4965_scale_tbl_info *curr_tbl, *search_tbl;
	u8 active_index = 0;
	u16 fc = le16_to_cpu(hdr->frame_control);
	s32 tpt = 0;

	IWL_DEBUG_RATE_LIMIT("get frame ack response, update rate scale window\n");

	if (!ieee80211_is_data(fc) || is_multicast_ether_addr(hdr->addr1))
		return;

	/* This packet was aggregated but doesn't carry rate scale info */
	if ((info->flags & IEEE80211_TX_CTL_AMPDU) &&
	    !(info->flags & IEEE80211_TX_STAT_AMPDU))
		return;

	retries = info->status.retry_count;

	if (retries > 15)
		retries = 15;

	rcu_read_lock();

	sta = sta_info_get(local, hdr->addr1);

	if (!sta || !sta->rate_ctrl_priv)
		goto out;


	lq_sta = (struct iwl4965_lq_sta *)sta->rate_ctrl_priv;

	if (!priv->lq_mngr.lq_ready)
		goto out;

	if ((priv->iw_mode == IEEE80211_IF_TYPE_IBSS) &&
	    !lq_sta->ibss_sta_added)
		goto out;

	table = &lq_sta->lq;
	active_index = lq_sta->active_tbl;

	curr_tbl = &(lq_sta->lq_info[active_index]);
	search_tbl = &(lq_sta->lq_info[(1 - active_index)]);
	window = (struct iwl4965_rate_scale_data *)
	    &(curr_tbl->win[0]);
	search_win = (struct iwl4965_rate_scale_data *)
	    &(search_tbl->win[0]);

	/*
	 * Ignore this Tx frame response if its initial rate doesn't match
	 * that of latest Link Quality command.  There may be stragglers
	 * from a previous Link Quality command, but we're no longer interested
	 * in those; they're either from the "active" mode while we're trying
	 * to check "search" mode, or a prior "search" mode after we've moved
	 * to a new "search" mode (which might become the new "active" mode).
	 */
	tx_rate = le32_to_cpu(table->rs_table[0].rate_n_flags);
	rs_get_tbl_info_from_mcs(tx_rate, priv->band, &tbl_type, &rs_index);
	if (priv->band == IEEE80211_BAND_5GHZ)
		rs_index -= IWL_FIRST_OFDM_RATE;

	if ((info->tx_rate_idx < 0) ||
	    (tbl_type.is_SGI ^
		!!(info->flags & IEEE80211_TX_CTL_SHORT_GI)) ||
	    (tbl_type.is_fat ^
		!!(info->flags & IEEE80211_TX_CTL_40_MHZ_WIDTH)) ||
	    (tbl_type.is_dup ^
		!!(info->flags & IEEE80211_TX_CTL_DUP_DATA)) ||
	    (tbl_type.ant_type ^ info->antenna_sel_tx) ||
	    (!!(tx_rate & RATE_MCS_HT_MSK) ^
		!!(info->flags & IEEE80211_TX_CTL_OFDM_HT)) ||
	    (!!(tx_rate & RATE_MCS_GF_MSK) ^
		!!(info->flags & IEEE80211_TX_CTL_GREEN_FIELD)) ||
	    (hw->wiphy->bands[priv->band]->bitrates[rs_index].bitrate !=
	     hw->wiphy->bands[info->band]->bitrates[info->tx_rate_idx].bitrate)) {
		IWL_DEBUG_RATE("initial rate does not match 0x%x\n", tx_rate);
		goto out;
	}

	/* Update frame history window with "failure" for each Tx retry. */
	while (retries) {
		/* Look up the rate and other info used for each tx attempt.
		 * Each tx attempt steps one entry deeper in the rate table. */
		tx_rate = le32_to_cpu(table->rs_table[index].rate_n_flags);
		rs_get_tbl_info_from_mcs(tx_rate, priv->band,
					  &tbl_type, &rs_index);

		/* If type matches "search" table,
		 * add failure to "search" history */
		if ((tbl_type.lq_type == search_tbl->lq_type) &&
		    (tbl_type.ant_type == search_tbl->ant_type) &&
		    (tbl_type.is_SGI == search_tbl->is_SGI)) {
			if (search_tbl->expected_tpt)
				tpt = search_tbl->expected_tpt[rs_index];
			else
				tpt = 0;
			rs_collect_tx_data(search_win, rs_index, tpt, 1, 0);

		/* Else if type matches "current/active" table,
		 * add failure to "current/active" history */
		} else if ((tbl_type.lq_type == curr_tbl->lq_type) &&
			   (tbl_type.ant_type == curr_tbl->ant_type) &&
			   (tbl_type.is_SGI == curr_tbl->is_SGI)) {
			if (curr_tbl->expected_tpt)
				tpt = curr_tbl->expected_tpt[rs_index];
			else
				tpt = 0;
			rs_collect_tx_data(window, rs_index, tpt, 1, 0);
		}

		/* If not searching for a new mode, increment failed counter
		 * ... this helps determine when to start searching again */
		if (lq_sta->stay_in_tbl)
			lq_sta->total_failed++;
		--retries;
		index++;

	}

	/*
	 * Find (by rate) the history window to update with final Tx attempt;
	 * if Tx was successful first try, use original rate,
	 * else look up the rate that was, finally, successful.
	 */
	tx_rate = le32_to_cpu(table->rs_table[index].rate_n_flags);
	rs_get_tbl_info_from_mcs(tx_rate, priv->band, &tbl_type, &rs_index);

	/* Update frame history window with "success" if Tx got ACKed ... */
	status = !!(info->flags & IEEE80211_TX_STAT_ACK);

	/* If type matches "search" table,
	 * add final tx status to "search" history */
	if ((tbl_type.lq_type == search_tbl->lq_type) &&
	    (tbl_type.ant_type == search_tbl->ant_type) &&
	    (tbl_type.is_SGI == search_tbl->is_SGI)) {
		if (search_tbl->expected_tpt)
			tpt = search_tbl->expected_tpt[rs_index];
		else
			tpt = 0;
		if (info->flags & IEEE80211_TX_CTL_AMPDU)
			rs_collect_tx_data(search_win, rs_index, tpt,
					   info->status.ampdu_ack_len,
					   info->status.ampdu_ack_map);
		else
			rs_collect_tx_data(search_win, rs_index, tpt,
					   1, status);
	/* Else if type matches "current/active" table,
	 * add final tx status to "current/active" history */
	} else if ((tbl_type.lq_type == curr_tbl->lq_type) &&
		   (tbl_type.ant_type == curr_tbl->ant_type) &&
		   (tbl_type.is_SGI == curr_tbl->is_SGI)) {
		if (curr_tbl->expected_tpt)
			tpt = curr_tbl->expected_tpt[rs_index];
		else
			tpt = 0;
		if (info->flags & IEEE80211_TX_CTL_AMPDU)
			rs_collect_tx_data(window, rs_index, tpt,
					   info->status.ampdu_ack_len,
					   info->status.ampdu_ack_map);
		else
			rs_collect_tx_data(window, rs_index, tpt,
					   1, status);
	}

	/* If not searching for new mode, increment success/failed counter
	 * ... these help determine when to start searching again */
	if (lq_sta->stay_in_tbl) {
		if (info->flags & IEEE80211_TX_CTL_AMPDU) {
			lq_sta->total_success += info->status.ampdu_ack_map;
			lq_sta->total_failed +=
			     (info->status.ampdu_ack_len - info->status.ampdu_ack_map);
		} else {
			if (status)
				lq_sta->total_success++;
			else
				lq_sta->total_failed++;
		}
	}

	/* See if there's a better rate or modulation mode to try. */
	rs_rate_scale_perform(priv, dev, hdr, sta);
out:
	rcu_read_unlock();
	return;
}

/*
 * Begin a period of staying with a selected modulation mode.
 * Set "stay_in_tbl" flag to prevent any mode switches.
 * Set frame tx success limits according to legacy vs. high-throughput,
 * and reset overall (spanning all rates) tx success history statistics.
 * These control how long we stay using same modulation mode before
 * searching for a new mode.
 */
static void rs_set_stay_in_table(struct iwl_priv *priv, u8 is_legacy,
				 struct iwl4965_lq_sta *lq_sta)
{
	IWL_DEBUG_RATE("we are staying in the same table\n");
	lq_sta->stay_in_tbl = 1;	/* only place this gets set */
	if (is_legacy) {
		lq_sta->table_count_limit = IWL_LEGACY_TABLE_COUNT;
		lq_sta->max_failure_limit = IWL_LEGACY_FAILURE_LIMIT;
		lq_sta->max_success_limit = IWL_LEGACY_SUCCESS_LIMIT;
	} else {
		lq_sta->table_count_limit = IWL_NONE_LEGACY_TABLE_COUNT;
		lq_sta->max_failure_limit = IWL_NONE_LEGACY_FAILURE_LIMIT;
		lq_sta->max_success_limit = IWL_NONE_LEGACY_SUCCESS_LIMIT;
	}
	lq_sta->table_count = 0;
	lq_sta->total_failed = 0;