iwlwifi: Tune radio to prevent unexpected behavior

We have seen the throughput dropped due to external noisy environment
and the radio is out of tune.  There are lot of plcp errors indicating
this condition. Eventually the station can get de-authenticated by the
Access Point.  By resetting and tuning the radio, the plcp errors are
reduced or eliminated and the throughput starts to rise.

To prevent unexpected behavior such as drop in throughput or deauthentication,
- The change provides the driver feature to monitor and tune the radio base on
the statistics notification from the uCode.
- It also allows the setting of the plcp error rate threshold via
the plcp_delta under debugfs interface.

Signed-off-by: Trieu 'Andrew' Nguyen <trieux.t.nguyen@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 54 insertions, 0 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl-rx.c b/drivers/net/wireless/iwlwifi/iwl-rx.c
index dc06c7bb0f5..ea309f42a78 100644
--- a/drivers/net/wireless/iwlwifi/iwl-rx.c
+++ b/drivers/net/wireless/iwlwifi/iwl-rx.c
@@ -602,11 +602,15 @@ static void iwl_accumulative_statistics(struct iwl_priv *priv,
 
 #define REG_RECALIB_PERIOD (60)
 
+#define PLCP_MSG "plcp_err exceeded %u, %u, %u, %u, %u, %d, %u mSecs\n"
 void iwl_rx_statistics(struct iwl_priv *priv,
 			      struct iwl_rx_mem_buffer *rxb)
 {
 	int change;
 	struct iwl_rx_packet *pkt = rxb_addr(rxb);
+	int combined_plcp_delta;
+	unsigned int plcp_msec;
+	unsigned long plcp_received_jiffies;
 
 	IWL_DEBUG_RX(priv, "Statistics notification received (%d vs %d).\n",
 		     (int)sizeof(priv->statistics),
@@ -621,6 +625,56 @@ void iwl_rx_statistics(struct iwl_priv *priv,
 #ifdef CONFIG_IWLWIFI_DEBUG
 	iwl_accumulative_statistics(priv, (__le32 *)&pkt->u.stats);
 #endif
+	/*
+	 * check for plcp_err and trigger radio reset if it exceeds
+	 * the plcp error threshold plcp_delta.
+	 */
+	plcp_received_jiffies = jiffies;
+	plcp_msec = jiffies_to_msecs((long) plcp_received_jiffies -
+					(long) priv->plcp_jiffies);
+	priv->plcp_jiffies = plcp_received_jiffies;
+	/*
+	 * check to make sure plcp_msec is not 0 to prevent division
+	 * by zero.
+	 */
+	if (plcp_msec) {
+		combined_plcp_delta =
+			(le32_to_cpu(pkt->u.stats.rx.ofdm.plcp_err) -
+			le32_to_cpu(priv->statistics.rx.ofdm.plcp_err)) +
+			(le32_to_cpu(pkt->u.stats.rx.ofdm_ht.plcp_err) -
+			le32_to_cpu(priv->statistics.rx.ofdm_ht.plcp_err));
+
+		if ((combined_plcp_delta > 0) &&
+			((combined_plcp_delta * 100) / plcp_msec) >
+			priv->cfg->plcp_delta_threshold) {
+			/*
+			 * if plcp_err exceed the threshold, the following
+			 * data is printed in csv format:
+			 *    Text: plcp_err exceeded %d,
+			 *    Received ofdm.plcp_err,
+			 *    Current ofdm.plcp_err,
+			 *    Received ofdm_ht.plcp_err,
+			 *    Current ofdm_ht.plcp_err,
+			 *    combined_plcp_delta,
+			 *    plcp_msec
+			 */
+			IWL_DEBUG_RADIO(priv, PLCP_MSG,
+				priv->cfg->plcp_delta_threshold,
+				le32_to_cpu(pkt->u.stats.rx.ofdm.plcp_err),
+				le32_to_cpu(priv->statistics.rx.ofdm.plcp_err),
+				le32_to_cpu(pkt->u.stats.rx.ofdm_ht.plcp_err),
+				le32_to_cpu(
+					priv->statistics.rx.ofdm_ht.plcp_err),
+				combined_plcp_delta, plcp_msec);
+
+			/*
+			 * Reset the RF radio due to the high plcp
+			 * error rate
+			 */
+			iwl_force_rf_reset(priv);
+		}
+	}
+
 	memcpy(&priv->statistics, &pkt->u.stats, sizeof(priv->statistics));
 
 	set_bit(STATUS_STATISTICS, &priv->status);