mac80211: Tx frame latency statistics

Measure TX latency and jitter statistics per station per TID.
These Measurements are disabled by default and can be enabled
via debugfs.

Features included for each station's TID:

1. Keep count of the maximum and average latency of Tx frames.
2. Keep track of many frames arrived in a specific time range
   (need to enable through debugfs and configure the bins ranges)

Signed-off-by: Matti Gottlieb <matti.gottlieb@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/debugfs_sta.c

@@ -38,6 +38,13 @@ static const struct file_operations sta_ ##name## _ops = {		\
 	.llseek = generic_file_llseek,					\
 }
 
+#define STA_OPS_W(name)							\
+static const struct file_operations sta_ ##name## _ops = {		\
+	.write = sta_##name##_write,					\
+	.open = simple_open,						\
+	.llseek = generic_file_llseek,					\
+}
+
 #define STA_OPS_RW(name)						\
 static const struct file_operations sta_ ##name## _ops = {		\
 	.read = sta_##name##_read,					\
@@ -388,6 +395,131 @@ static ssize_t sta_last_rx_rate_read(struct file *file, char __user *userbuf,
 }
 STA_OPS(last_rx_rate);
 
+static int
+sta_tx_latency_stat_header(struct ieee80211_tx_latency_bin_ranges *tx_latency,
+			   char *buf, int pos, int bufsz)
+{
+	int i;
+	int range_count = tx_latency->n_ranges;
+	u32 *bin_ranges = tx_latency->ranges;
+
+	pos += scnprintf(buf + pos, bufsz - pos,
+			  "Station\t\t\tTID\tMax\tAvg");
+	if (range_count) {
+		pos += scnprintf(buf + pos, bufsz - pos,
+				  "\t<=%d", bin_ranges[0]);
+		for (i = 0; i < range_count - 1; i++)
+			pos += scnprintf(buf + pos, bufsz - pos, "\t%d-%d",
+					  bin_ranges[i], bin_ranges[i+1]);
+		pos += scnprintf(buf + pos, bufsz - pos,
+				  "\t%d<", bin_ranges[range_count - 1]);
+	}
+
+	pos += scnprintf(buf + pos, bufsz - pos, "\n");
+
+	return pos;
+}
+
+static int
+sta_tx_latency_stat_table(struct ieee80211_tx_latency_bin_ranges *tx_lat_range,
+			  struct ieee80211_tx_latency_stat *tx_lat,
+			  char *buf, int pos, int bufsz, int tid)
+{
+	u32 avg = 0;
+	int j;
+	int bin_count = tx_lat->bin_count;
+
+	pos += scnprintf(buf + pos, bufsz - pos, "\t\t\t%d", tid);
+	/* make sure you don't divide in 0 */
+	if (tx_lat->counter)
+		avg = tx_lat->sum / tx_lat->counter;
+
+	pos += scnprintf(buf + pos, bufsz - pos, "\t%d\t%d",
+			  tx_lat->max, avg);
+
+	if (tx_lat_range->n_ranges && tx_lat->bins)
+		for (j = 0; j < bin_count; j++)
+			pos += scnprintf(buf + pos, bufsz - pos,
+					  "\t%d", tx_lat->bins[j]);
+	pos += scnprintf(buf + pos, bufsz - pos, "\n");
+
+	return pos;
+}
+
+/*
+ * Output Tx latency statistics station && restart all statistics information
+ */
+static ssize_t sta_tx_latency_stat_read(struct file *file,
+					char __user *userbuf,
+					size_t count, loff_t *ppos)
+{
+	struct sta_info *sta = file->private_data;
+	struct ieee80211_local *local = sta->local;
+	struct ieee80211_tx_latency_bin_ranges *tx_latency;
+	char *buf;
+	int bufsz, ret, i;
+	int pos = 0;
+
+	bufsz = 20 * IEEE80211_NUM_TIDS *
+		sizeof(struct ieee80211_tx_latency_stat);
+	buf = kzalloc(bufsz, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	rcu_read_lock();
+
+	tx_latency = rcu_dereference(local->tx_latency);
+
+	if (!sta->tx_lat) {
+		pos += scnprintf(buf + pos, bufsz - pos,
+				 "Tx latency statistics are not enabled\n");
+		goto unlock;
+	}
+
+	pos = sta_tx_latency_stat_header(tx_latency, buf, pos, bufsz);
+
+	pos += scnprintf(buf + pos, bufsz - pos, "%pM\n", sta->sta.addr);
+	for (i = 0; i < IEEE80211_NUM_TIDS; i++)
+		pos = sta_tx_latency_stat_table(tx_latency, &sta->tx_lat[i],
+						buf, pos, bufsz, i);
+unlock:
+	rcu_read_unlock();
+
+	ret = simple_read_from_buffer(userbuf, count, ppos, buf, pos);
+	kfree(buf);
+
+	return ret;
+}
+STA_OPS(tx_latency_stat);
+
+static ssize_t sta_tx_latency_stat_reset_write(struct file *file,
+					       const char __user *userbuf,
+					       size_t count, loff_t *ppos)
+{
+	u32 *bins;
+	int bin_count;
+	struct sta_info *sta = file->private_data;
+	int i;
+
+	if (!sta->tx_lat)
+		return -EINVAL;
+
+	for (i = 0; i < IEEE80211_NUM_TIDS; i++) {
+		bins = sta->tx_lat[i].bins;
+		bin_count = sta->tx_lat[i].bin_count;
+
+		sta->tx_lat[i].max = 0;
+		sta->tx_lat[i].sum = 0;
+		sta->tx_lat[i].counter = 0;
+
+		if (bin_count)
+			memset(bins, 0, bin_count * sizeof(u32));
+	}
+
+	return count;
+}
+STA_OPS_W(tx_latency_stat_reset);
+
 #define DEBUGFS_ADD(name) \
 	debugfs_create_file(#name, 0400, \
 		sta->debugfs.dir, sta, &sta_ ##name## _ops);
@@ -441,6 +573,8 @@ void ieee80211_sta_debugfs_add(struct sta_info *sta)
 	DEBUGFS_ADD(last_ack_signal);
 	DEBUGFS_ADD(current_tx_rate);
 	DEBUGFS_ADD(last_rx_rate);
+	DEBUGFS_ADD(tx_latency_stat);
+	DEBUGFS_ADD(tx_latency_stat_reset);
 
 	DEBUGFS_ADD_COUNTER(rx_packets, rx_packets);
 	DEBUGFS_ADD_COUNTER(tx_packets, tx_packets);