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>

1 files changed, 168 insertions, 0 deletions

diff --git a/net/mac80211/debugfs.c b/net/mac80211/debugfs.c
index 5c090e41d9bb..fa16e54980a1 100644
--- a/net/mac80211/debugfs.c
+++ b/net/mac80211/debugfs.c
@@ -17,6 +17,172 @@
 
 #define DEBUGFS_FORMAT_BUFFER_SIZE 100
 
+#define TX_LATENCY_BIN_DELIMTER_C ','
+#define TX_LATENCY_BIN_DELIMTER_S ","
+#define TX_LATENCY_BINS_DISABLED "enable(bins disabled)\n"
+#define TX_LATENCY_DISABLED "disable\n"
+
+
+/*
+ * Display if Tx latency statistics & bins are enabled/disabled
+ */
+static ssize_t sta_tx_latency_stat_read(struct file *file,
+					char __user *userbuf,
+					size_t count, loff_t *ppos)
+{
+	struct ieee80211_local *local = file->private_data;
+	struct ieee80211_tx_latency_bin_ranges  *tx_latency;
+	char *buf;
+	int bufsz, i, ret;
+	int pos = 0;
+
+	rcu_read_lock();
+
+	tx_latency = rcu_dereference(local->tx_latency);
+
+	if (tx_latency && tx_latency->n_ranges) {
+		bufsz = tx_latency->n_ranges * 15;
+		buf = kzalloc(bufsz, GFP_ATOMIC);
+		if (!buf)
+			goto err;
+
+		for (i = 0; i < tx_latency->n_ranges; i++)
+			pos += scnprintf(buf + pos, bufsz - pos, "%d,",
+					 tx_latency->ranges[i]);
+		pos += scnprintf(buf + pos, bufsz - pos, "\n");
+	} else if (tx_latency) {
+		bufsz = sizeof(TX_LATENCY_BINS_DISABLED) + 1;
+		buf = kzalloc(bufsz, GFP_ATOMIC);
+		if (!buf)
+			goto err;
+
+		pos += scnprintf(buf + pos, bufsz - pos, "%s\n",
+				 TX_LATENCY_BINS_DISABLED);
+	} else {
+		bufsz = sizeof(TX_LATENCY_DISABLED) + 1;
+		buf = kzalloc(bufsz, GFP_ATOMIC);
+		if (!buf)
+			goto err;
+
+		pos += scnprintf(buf + pos, bufsz - pos, "%s\n",
+				 TX_LATENCY_DISABLED);
+	}
+
+	rcu_read_unlock();
+
+	ret = simple_read_from_buffer(userbuf, count, ppos, buf, pos);
+	kfree(buf);
+
+	return ret;
+err:
+	rcu_read_unlock();
+	return -ENOMEM;
+}
+
+/*
+ * Receive input from user regarding Tx latency statistics
+ * The input should indicate if Tx latency statistics and bins are
+ * enabled/disabled.
+ * If bins are enabled input should indicate the amount of different bins and
+ * their ranges. Each bin will count how many Tx frames transmitted within the
+ * appropriate latency.
+ * Legal input is:
+ * a) "enable(bins disabled)" - to enable only general statistics
+ * b) "a,b,c,d,...z" - to enable general statistics and bins, where all are
+ * numbers and a < b < c < d.. < z
+ * c) "disable" - disable all statistics
+ * NOTE: must configure Tx latency statistics bins before stations connected.
+ */
+
+static ssize_t sta_tx_latency_stat_write(struct file *file,
+					 const char __user *userbuf,
+					 size_t count, loff_t *ppos)
+{
+	struct ieee80211_local *local = file->private_data;
+	char buf[128] = {};
+	char *bins = buf;
+	char *token;
+	int buf_size, i, alloc_size;
+	int prev_bin = 0;
+	int n_ranges = 0;
+	int ret = count;
+	struct ieee80211_tx_latency_bin_ranges  *tx_latency;
+
+	if (sizeof(buf) <= count)
+		return -EINVAL;
+	buf_size = count;
+	if (copy_from_user(buf, userbuf, buf_size))
+		return -EFAULT;
+
+	mutex_lock(&local->sta_mtx);
+
+	/* cannot change config once we have stations */
+	if (local->num_sta)
+		goto unlock;
+
+	tx_latency =
+		rcu_dereference_protected(local->tx_latency,
+					  lockdep_is_held(&local->sta_mtx));
+
+	/* disable Tx statistics */
+	if (!strcmp(buf, TX_LATENCY_DISABLED)) {
+		if (!tx_latency)
+			goto unlock;
+		rcu_assign_pointer(local->tx_latency, NULL);
+		synchronize_rcu();
+		kfree(tx_latency);
+		goto unlock;
+	}
+
+	/* Tx latency already enabled */
+	if (tx_latency)
+		goto unlock;
+
+	if (strcmp(TX_LATENCY_BINS_DISABLED, buf)) {
+		/* check how many bins and between what ranges user requested */
+		token = buf;
+		while (*token != '\0') {
+			if (*token == TX_LATENCY_BIN_DELIMTER_C)
+				n_ranges++;
+			token++;
+		}
+		n_ranges++;
+	}
+
+	alloc_size = sizeof(struct ieee80211_tx_latency_bin_ranges) +
+		     n_ranges * sizeof(u32);
+	tx_latency = kzalloc(alloc_size, GFP_ATOMIC);
+	if (!tx_latency) {
+		ret = -ENOMEM;
+		goto unlock;
+	}
+	tx_latency->n_ranges = n_ranges;
+	for (i = 0; i < n_ranges; i++) { /* setting bin ranges */
+		token = strsep(&bins, TX_LATENCY_BIN_DELIMTER_S);
+		sscanf(token, "%d", &tx_latency->ranges[i]);
+		/* bins values should be in ascending order */
+		if (prev_bin >= tx_latency->ranges[i]) {
+			ret = -EINVAL;
+			kfree(tx_latency);
+			goto unlock;
+		}
+		prev_bin = tx_latency->ranges[i];
+	}
+	rcu_assign_pointer(local->tx_latency, tx_latency);
+
+unlock:
+	mutex_unlock(&local->sta_mtx);
+
+	return ret;
+}
+
+static const struct file_operations stats_tx_latency_ops = {
+	.write = sta_tx_latency_stat_write,
+	.read = sta_tx_latency_stat_read,
+	.open = simple_open,
+	.llseek = generic_file_llseek,
+};
+
 int mac80211_format_buffer(char __user *userbuf, size_t count,
 				  loff_t *ppos, char *fmt, ...)
 {
@@ -315,4 +481,6 @@ void debugfs_hw_add(struct ieee80211_local *local)
 	DEBUGFS_DEVSTATS_ADD(dot11RTSFailureCount);
 	DEBUGFS_DEVSTATS_ADD(dot11FCSErrorCount);
 	DEBUGFS_DEVSTATS_ADD(dot11RTSSuccessCount);
+
+	DEBUGFS_DEVSTATS_ADD(tx_latency);
 }