iwlwifi: Recover TX flow stall due to stuck queue

Monitors the internal TX queues periodically.  When a queue is stuck
for some unknown conditions causing the throughput to drop and the
transfer is stop, the driver will force firmware reload and bring the
system back to normal operational state.

The iwlwifi devices behave differently in this regard so this feature is
made part of the ops infrastructure so we can have more control on how to
monitor and recover from tx queue stall case per device.

Signed-off-by: Trieu 'Andrew' Nguyen <trieux.t.nguyen@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>

1 files changed, 93 insertions, 0 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl-core.c b/drivers/net/wireless/iwlwifi/iwl-core.c
index d4c2a3e..5180fb2 100644
--- a/drivers/net/wireless/iwlwifi/iwl-core.c
+++ b/drivers/net/wireless/iwlwifi/iwl-core.c
@@ -3051,6 +3051,99 @@ int iwl_force_reset(struct iwl_priv *priv, int mode)
 	}
 	return 0;
 }
+EXPORT_SYMBOL(iwl_force_reset);
+
+/**
+ * iwl_bg_monitor_recover - Timer callback to check for stuck queue and recover
+ *
+ * During normal condition (no queue is stuck), the timer is continually set to
+ * execute every monitor_recover_period milliseconds after the last timer
+ * expired.  When the queue read_ptr is at the same place, the timer is
+ * shorten to 100mSecs.  This is
+ *      1) to reduce the chance that the read_ptr may wrap around (not stuck)
+ *      2) to detect the stuck queues quicker before the station and AP can
+ *      disassociate each other.
+ *
+ * This function monitors all the tx queues and recover from it if any
+ * of the queues are stuck.
+ * 1. It first check the cmd queue for stuck conditions.  If it is stuck,
+ *      it will recover by resetting the firmware and return.
+ * 2. Then, it checks for station association.  If it associates it will check
+ *      other queues.  If any queue is stuck, it will recover by resetting
+ *      the firmware.
+ * Note: It the number of times the queue read_ptr to be at the same place to
+ *      be MAX_REPEAT+1 in order to consider to be stuck.
+ */
+/*
+ * The maximum number of times the read pointer of the tx queue at the
+ * same place without considering to be stuck.
+ */
+#define MAX_REPEAT      (2)
+static int iwl_check_stuck_queue(struct iwl_priv *priv, int cnt)
+{
+	struct iwl_tx_queue *txq;
+	struct iwl_queue *q;
+
+	txq = &priv->txq[cnt];
+	q = &txq->q;
+	/* queue is empty, skip */
+	if (q->read_ptr != q->write_ptr) {
+		if (q->read_ptr == q->last_read_ptr) {
+			/* a queue has not been read from last time */
+			if (q->repeat_same_read_ptr > MAX_REPEAT) {
+				IWL_ERR(priv,
+					"queue %d stuck %d time. Fw reload.\n",
+					q->id, q->repeat_same_read_ptr);
+				q->repeat_same_read_ptr = 0;
+				iwl_force_reset(priv, IWL_FW_RESET);
+			} else {
+				q->repeat_same_read_ptr++;
+				IWL_DEBUG_RADIO(priv,
+						"queue %d, not read %d time\n",
+						q->id,
+						q->repeat_same_read_ptr);
+				mod_timer(&priv->monitor_recover, jiffies +
+					msecs_to_jiffies(IWL_ONE_HUNDRED_MSECS));
+			}
+			return 1;
+		} else {
+			q->last_read_ptr = q->read_ptr;
+			q->repeat_same_read_ptr = 0;
+		}
+	}
+	return 0;
+}
+
+void iwl_bg_monitor_recover(unsigned long data)
+{
+	struct iwl_priv *priv = (struct iwl_priv *)data;
+	int cnt;
+
+	if (test_bit(STATUS_EXIT_PENDING, &priv->status))
+		return;
+
+	/* monitor and check for stuck cmd queue */
+	if (iwl_check_stuck_queue(priv, IWL_CMD_QUEUE_NUM))
+		return;
+
+	/* monitor and check for other stuck queues */
+	if (iwl_is_associated(priv)) {
+		for (cnt = 0; cnt < priv->hw_params.max_txq_num; cnt++) {
+			/* skip as we already checked the command queue */
+			if (cnt == IWL_CMD_QUEUE_NUM)
+				continue;
+			if (iwl_check_stuck_queue(priv, cnt))
+				return;
+		}
+	}
+	/*
+	 * Reschedule the timer to occur in
+	 * priv->cfg->monitor_recover_period
+	 */
+	mod_timer(&priv->monitor_recover,
+		jiffies + msecs_to_jiffies(priv->cfg->monitor_recover_period));
+}
+EXPORT_SYMBOL(iwl_bg_monitor_recover);
 
 #ifdef CONFIG_PM