1 files changed, 444 insertions, 0 deletions
diff --git a/net/mac80211/rc80211_pid_algo.c b/net/mac80211/rc80211_pid_algo.c
new file mode 100644
index 00000000000..3fac3a5d7e0
--- /dev/null
+++ b/net/mac80211/rc80211_pid_algo.c
@@ -0,0 +1,444 @@
+/*
+ * Copyright 2002-2005, Instant802 Networks, Inc.
+ * Copyright 2005, Devicescape Software, Inc.
+ * Copyright 2007, Mattias Nissler <mattias.nissler@gmx.de>
+ * Copyright 2007, Stefano Brivio <stefano.brivio@polimi.it>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/netdevice.h>
+#include <linux/types.h>
+#include <linux/skbuff.h>
+
+#include <net/mac80211.h>
+#include "ieee80211_rate.h"
+
+#include "rc80211_pid.h"
+
+
+/* This is an implementation of a TX rate control algorithm that uses a PID
+ * controller. Given a target failed frames rate, the controller decides about
+ * TX rate changes to meet the target failed frames rate.
+ *
+ * The controller basically computes the following:
+ *
+ * adj = CP * err + CI * err_avg + CD * (err - last_err) * (1 + sharpening)
+ *
+ * where
+ * 	adj	adjustment value that is used to switch TX rate (see below)
+ * 	err	current error: target vs. current failed frames percentage
+ * 	last_err	last error
+ * 	err_avg	average (i.e. poor man's integral) of recent errors
+ *	sharpening	non-zero when fast response is needed (i.e. right after
+ *			association or no frames sent for a long time), heading
+ * 			to zero over time
+ * 	CP	Proportional coefficient
+ * 	CI	Integral coefficient
+ * 	CD	Derivative coefficient
+ *
+ * CP, CI, CD are subject to careful tuning.
+ *
+ * The integral component uses a exponential moving average approach instead of
+ * an actual sliding window. The advantage is that we don't need to keep an
+ * array of the last N error values and computation is easier.
+ *
+ * Once we have the adj value, we map it to a rate by means of a learning
+ * algorithm. This algorithm keeps the state of the percentual failed frames
+ * difference between rates. The behaviour of the lowest available rate is kept
+ * as a reference value, and every time we switch between two rates, we compute
+ * the difference between the failed frames each rate exhibited. By doing so,
+ * we compare behaviours which different rates exhibited in adjacent timeslices,
+ * thus the comparison is minimally affected by external conditions. This
+ * difference gets propagated to the whole set of measurements, so that the
+ * reference is always the same. Periodically, we normalize this set so that
+ * recent events weigh the most. By comparing the adj value with this set, we
+ * avoid pejorative switches to lower rates and allow for switches to higher
+ * rates if they behaved well.
+ *
+ * Note that for the computations we use a fixed-point representation to avoid
+ * floating point arithmetic. Hence, all values are shifted left by
+ * RC_PID_ARITH_SHIFT.
+ */
+
+
+/* Shift the adjustment so that we won't switch to a lower rate if it exhibited
+ * a worse failed frames behaviour and we'll choose the highest rate whose
+ * failed frames behaviour is not worse than the one of the original rate
+ * target. While at it, check that the adjustment is within the ranges. Then,
+ * provide the new rate index. */
+static int rate_control_pid_shift_adjust(struct rc_pid_rateinfo *r,
+					 int adj, int cur, int l)
+{
+	int i, j, k, tmp;
+
+	if (cur + adj < 0)
+		return 0;
+	if (cur + adj >= l)
+		return l - 1;
+
+	i = r[cur + adj].rev_index;
+
+	j = r[cur].rev_index;
+
+	if (adj < 0) {
+			tmp = i;
+			for (k = j; k >= i; k--)
+				if (r[k].diff <= r[j].diff)
+					tmp = k;
+			return r[tmp].index;
+	} else if (adj > 0) {
+			tmp = i;
+			for (k = i + 1; k + i < l; k++)
+				if (r[k].diff <= r[i].diff)
+					tmp = k;
+			return r[tmp].index;
+	}
+	return cur + adj;
+}
+
+static void rate_control_pid_adjust_rate(struct ieee80211_local *local,
+					 struct sta_info *sta, int adj,
+					 struct rc_pid_rateinfo *rinfo)
+{
+	struct ieee80211_sub_if_data *sdata;
+	struct ieee80211_hw_mode *mode;
+	int newidx;
+	int maxrate;
+	int back = (adj > 0) ? 1 : -1;
+
+	sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);
+	if (sdata->bss && sdata->bss->force_unicast_rateidx > -1) {
+		/* forced unicast rate - do not change STA rate */
+		return;
+	}
+
+	mode = local->oper_hw_mode;
+	maxrate = sdata->bss ? sdata->bss->max_ratectrl_rateidx : -1;
+
+	newidx = rate_control_pid_shift_adjust(rinfo, adj, sta->txrate,
+					       mode->num_rates);
+
+	while (newidx != sta->txrate) {
+		if (rate_supported(sta, mode, newidx) &&
+		    (maxrate < 0 || newidx <= maxrate)) {
+			sta->txrate = newidx;
+			break;
+		}
+
+		newidx += back;
+	}
+
+#ifdef CONFIG_MAC80211_DEBUGFS
+	rate_control_pid_event_rate_change(
+		&((struct rc_pid_sta_info *)sta->rate_ctrl_priv)->events,
+		newidx, mode->rates[newidx].rate);
+#endif
+}
+
+/* Normalize the failed frames per-rate differences. */
+static void rate_control_pid_normalize(struct rc_pid_rateinfo *r, int l)
+{
+	int i;
+
+	if (r[0].diff > RC_PID_NORM_OFFSET)
+		r[0].diff -= RC_PID_NORM_OFFSET;
+	else if (r[0].diff < -RC_PID_NORM_OFFSET)
+		r[0].diff += RC_PID_NORM_OFFSET;
+	for (i = 0; i < l - 1; i++)
+		if (r[i + 1].diff > r[i].diff + RC_PID_NORM_OFFSET)
+			r[i + 1].diff -= RC_PID_NORM_OFFSET;
+		else if (r[i + 1].diff <= r[i].diff)
+			r[i + 1].diff += RC_PID_NORM_OFFSET;
+}
+
+static void rate_control_pid_sample(struct rc_pid_info *pinfo,
+				    struct ieee80211_local *local,
+				    struct sta_info *sta)
+{
+	struct rc_pid_sta_info *spinfo = sta->rate_ctrl_priv;
+	struct rc_pid_rateinfo *rinfo = pinfo->rinfo;
+	struct ieee80211_hw_mode *mode;
+	u32 pf;
+	s32 err_avg;
+	s32 err_prop;
+	s32 err_int;
+	s32 err_der;
+	int adj, i, j, tmp;
+
+	mode = local->oper_hw_mode;
+	spinfo = sta->rate_ctrl_priv;
+
+	/* In case nothing happened during the previous control interval, turn
+	 * the sharpening factor on. */
+	if (jiffies - spinfo->last_sample > 2 * RC_PID_INTERVAL)
+		spinfo->sharp_cnt = RC_PID_SHARPENING_DURATION;
+
+	spinfo->last_sample = jiffies;
+
+	/* This should never happen, but in case, we assume the old sample is
+	 * still a good measurement and copy it. */
+	if (unlikely(spinfo->tx_num_xmit == 0))
+		pf = spinfo->last_pf;
+	else {
+		pf = spinfo->tx_num_failed * 100 / spinfo->tx_num_xmit;
+		pf <<= RC_PID_ARITH_SHIFT;
+	}
+
+	spinfo->tx_num_xmit = 0;
+	spinfo->tx_num_failed = 0;
+
+	/* If we just switched rate, update the rate behaviour info. */
+	if (pinfo->oldrate != sta->txrate) {
+
+		i = rinfo[pinfo->oldrate].rev_index;
+		j = rinfo[sta->txrate].rev_index;
+
+		tmp = (pf - spinfo->last_pf);
+		tmp = RC_PID_DO_ARITH_RIGHT_SHIFT(tmp, RC_PID_ARITH_SHIFT);
+
+		rinfo[j].diff = rinfo[i].diff + tmp;
+		pinfo->oldrate = sta->txrate;
+	}
+	rate_control_pid_normalize(rinfo, mode->num_rates);
+
+	/* Compute the proportional, integral and derivative errors. */
+	err_prop = RC_PID_TARGET_PF - pf;
+
+	err_avg = spinfo->err_avg_sc >> RC_PID_SMOOTHING_SHIFT;
+	spinfo->err_avg_sc = spinfo->err_avg_sc - err_avg + err_prop;
+	err_int = spinfo->err_avg_sc >> RC_PID_SMOOTHING_SHIFT;
+
+	err_der = pf - spinfo->last_pf
+		  * (1 + RC_PID_SHARPENING_FACTOR * spinfo->sharp_cnt);
+	spinfo->last_pf = pf;
+	if (spinfo->sharp_cnt)
+			spinfo->sharp_cnt--;
+
+#ifdef CONFIG_MAC80211_DEBUGFS
+	rate_control_pid_event_pf_sample(&spinfo->events, pf, err_prop, err_int,
+					 err_der);
+#endif
+
+	/* Compute the controller output. */
+	adj = (err_prop * pinfo->coeff_p + err_int * pinfo->coeff_i
+	      + err_der * pinfo->coeff_d);
+	adj = RC_PID_DO_ARITH_RIGHT_SHIFT(adj, 2 * RC_PID_ARITH_SHIFT);
+
+	/* Change rate. */
+	if (adj)
+		rate_control_pid_adjust_rate(local, sta, adj, rinfo);
+}
+
+static void rate_control_pid_tx_status(void *priv, struct net_device *dev,
+				       struct sk_buff *skb,
+				       struct ieee80211_tx_status *status)
+{
+	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
+	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
+	struct rc_pid_info *pinfo = priv;
+	struct sta_info *sta;
+	struct rc_pid_sta_info *spinfo;
+
+	sta = sta_info_get(local, hdr->addr1);
+
+	if (!sta)
+		return;
+
+	/* Ignore all frames that were sent with a different rate than the rate
+	 * we currently advise mac80211 to use. */
+	if (status->control.rate != &local->oper_hw_mode->rates[sta->txrate])
+		return;
+
+	spinfo = sta->rate_ctrl_priv;
+	spinfo->tx_num_xmit++;
+
+#ifdef CONFIG_MAC80211_DEBUGFS
+	rate_control_pid_event_tx_status(&spinfo->events, status);
+#endif
+
+	/* We count frames that totally failed to be transmitted as two bad
+	 * frames, those that made it out but had some retries as one good and
+	 * one bad frame. */
+	if (status->excessive_retries) {
+		spinfo->tx_num_failed += 2;
+		spinfo->tx_num_xmit++;
+	} else if (status->retry_count) {
+		spinfo->tx_num_failed++;
+		spinfo->tx_num_xmit++;
+	}
+
+	if (status->excessive_retries) {
+		sta->tx_retry_failed++;
+		sta->tx_num_consecutive_failures++;
+		sta->tx_num_mpdu_fail++;
+	} else {
+		sta->last_ack_rssi[0] = sta->last_ack_rssi[1];
+		sta->last_ack_rssi[1] = sta->last_ack_rssi[2];
+		sta->last_ack_rssi[2] = status->ack_signal;
+		sta->tx_num_consecutive_failures = 0;
+		sta->tx_num_mpdu_ok++;
+	}
+	sta->tx_retry_count += status->retry_count;
+	sta->tx_num_mpdu_fail += status->retry_count;
+
+	/* Update PID controller state. */
+	if (time_after(jiffies, spinfo->last_sample + RC_PID_INTERVAL))
+		rate_control_pid_sample(pinfo, local, sta);
+
+	sta_info_put(sta);
+}
+
+static void rate_control_pid_get_rate(void *priv, struct net_device *dev,
+				      struct ieee80211_hw_mode *mode,
+				      struct sk_buff *skb,
+				      struct rate_selection *sel)
+{
+	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
+	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
+	struct sta_info *sta;
+	int rateidx;
+
+	sta = sta_info_get(local, hdr->addr1);
+
+	if (!sta) {
+		sel->rate = rate_lowest(local, mode, NULL);
+		sta_info_put(sta);
+		return;
+	}
+
+	rateidx = sta->txrate;
+
+	if (rateidx >= mode->num_rates)
+		rateidx = mode->num_rates - 1;
+
+	sta_info_put(sta);
+
+	sel->rate = &mode->rates[rateidx];
+
+#ifdef CONFIG_MAC80211_DEBUGFS
+	rate_control_pid_event_tx_rate(
+		&((struct rc_pid_sta_info *) sta->rate_ctrl_priv)->events,
+		rateidx, mode->rates[rateidx].rate);
+#endif
+}
+
+static void rate_control_pid_rate_init(void *priv, void *priv_sta,
+					  struct ieee80211_local *local,
+					  struct sta_info *sta)
+{
+	/* TODO: This routine should consider using RSSI from previous packets
+	 * as we need to have IEEE 802.1X auth succeed immediately after assoc..
+	 * Until that method is implemented, we will use the lowest supported
+	 * rate as a workaround. */
+	sta->txrate = rate_lowest_index(local, local->oper_hw_mode, sta);
+}
+
+static void *rate_control_pid_alloc(struct ieee80211_local *local)
+{
+	struct rc_pid_info *pinfo;
+	struct rc_pid_rateinfo *rinfo;
+	struct ieee80211_hw_mode *mode;
+	int i, j, tmp;
+	bool s;
+
+	pinfo = kmalloc(sizeof(*pinfo), GFP_ATOMIC);
+	if (!pinfo)
+		return NULL;
+
+	/* We can safely assume that oper_hw_mode won't change unless we get
+	 * reinitialized. */
+	mode = local->oper_hw_mode;
+	rinfo = kmalloc(sizeof(*rinfo) * mode->num_rates, GFP_ATOMIC);
+	if (!rinfo) {
+		kfree(pinfo);
+		return NULL;
+	}
+
+	/* Sort the rates. This is optimized for the most common case (i.e.
+	 * almost-sorted CCK+OFDM rates). Kind of bubble-sort with reversed
+	 * mapping too. */
+	for (i = 0; i < mode->num_rates; i++) {
+		rinfo[i].index = i;
+		rinfo[i].rev_index = i;
+		if (RC_PID_FAST_START)
+			rinfo[i].diff = 0;
+		else
+			rinfo[i].diff = i * RC_PID_NORM_OFFSET;
+	}
+	for (i = 1; i < mode->num_rates; i++) {
+		s = 0;
+		for (j = 0; j < mode->num_rates - i; j++)
+			if (unlikely(mode->rates[rinfo[j].index].rate >
+				     mode->rates[rinfo[j + 1].index].rate)) {
+				tmp = rinfo[j].index;
+				rinfo[j].index = rinfo[j + 1].index;
+				rinfo[j + 1].index = tmp;
+				rinfo[rinfo[j].index].rev_index = j;
+				rinfo[rinfo[j + 1].index].rev_index = j + 1;
+				s = 1;
+			}
+		if (!s)
+			break;
+	}
+
+	pinfo->target = RC_PID_TARGET_PF;
+	pinfo->coeff_p = RC_PID_COEFF_P;
+	pinfo->coeff_i = RC_PID_COEFF_I;
+	pinfo->coeff_d = RC_PID_COEFF_D;
+	pinfo->rinfo = rinfo;
+	pinfo->oldrate = 0;
+
+	return pinfo;
+}
+
+static void rate_control_pid_free(void *priv)
+{
+	struct rc_pid_info *pinfo = priv;
+	kfree(pinfo->rinfo);
+	kfree(pinfo);
+}
+
+static void rate_control_pid_clear(void *priv)
+{
+}
+
+static void *rate_control_pid_alloc_sta(void *priv, gfp_t gfp)
+{
+	struct rc_pid_sta_info *spinfo;
+
+	spinfo = kzalloc(sizeof(*spinfo), gfp);
+	if (spinfo == NULL)
+		return NULL;
+
+#ifdef CONFIG_MAC80211_DEBUGFS
+	spin_lock_init(&spinfo->events.lock);
+	init_waitqueue_head(&spinfo->events.waitqueue);
+#endif
+
+	return spinfo;
+}
+
+static void rate_control_pid_free_sta(void *priv, void *priv_sta)
+{
+	struct rc_pid_sta_info *spinfo = priv_sta;
+	kfree(spinfo);
+}
+
+struct rate_control_ops mac80211_rcpid = {
+	.name = "pid",
+	.tx_status = rate_control_pid_tx_status,
+	.get_rate = rate_control_pid_get_rate,
+	.rate_init = rate_control_pid_rate_init,
+	.clear = rate_control_pid_clear,
+	.alloc = rate_control_pid_alloc,
+	.free = rate_control_pid_free,
+	.alloc_sta = rate_control_pid_alloc_sta,
+	.free_sta = rate_control_pid_free_sta,
+#ifdef CONFIG_MAC80211_DEBUGFS
+	.add_sta_debugfs = rate_control_pid_add_sta_debugfs,
+	.remove_sta_debugfs = rate_control_pid_remove_sta_debugfs,
+#endif
+};