iwlwifi: avoid too frequent recover from statistics

Usually H/W generate statistics notify once per about 100ms, but
sometimes we can receive notify in shorter time, even 2 ms.

This can be problem for plcp health and ack health checking.

I.e. with 2 plcp errors happens randomly in 2 ms duration, we
exceed plcp delta threshold equal to 100 (2*100/2).

Also checking ack's in short time, can results not necessary false
positive and firmware reset, for example when channel is noised and
we do not receive ACKs frames or when remote device does not send
ACKs at the moment.

Patch change code to do statistic check and possible recovery only
if 99ms elapsed from last check. Forced delay should assure we have
good statistic data to estimate hardware state.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-agn.c

@@ -3737,6 +3737,8 @@ static int iwl_init_drv(struct iwl_priv *priv)
 	priv->force_reset[IWL_FW_RESET].reset_duration =
 		IWL_DELAY_NEXT_FORCE_FW_RELOAD;
 
+	priv->rx_statistics_jiffies = jiffies;
+
 	/* Choose which receivers/antennas to use */
 	if (priv->cfg->ops->hcmd->set_rxon_chain)
 		priv->cfg->ops->hcmd->set_rxon_chain(priv,

drivers/net/wireless/iwlwifi/iwl-dev.h

@@ -1261,8 +1261,8 @@ struct iwl_priv {
 	/* track IBSS manager (last beacon) status */
 	u32 ibss_manager;
 
-	/* storing the jiffies when the plcp error rate is received */
-	unsigned long plcp_jiffies;
+	/* jiffies when last recovery from statistics was performed */
+	unsigned long rx_statistics_jiffies;
 
 	/* force reset */
 	struct iwl_force_reset force_reset[IWL_MAX_FORCE_RESET];

drivers/net/wireless/iwlwifi/iwl-rx.c

@@ -449,10 +449,8 @@ static bool iwl_good_ack_health(struct iwl_priv *priv, struct iwl_rx_packet *pkt
  * to improve the throughput.
  */
 static bool iwl_good_plcp_health(struct iwl_priv *priv,
-				 struct iwl_rx_packet *pkt)
+				 struct iwl_rx_packet *pkt, unsigned int msecs)
 {
-	unsigned int msecs;
-	unsigned long stamp;
 	int delta;
 	int threshold = priv->cfg->base_params->plcp_delta_threshold;
 
@@ -461,13 +459,6 @@ static bool iwl_good_plcp_health(struct iwl_priv *priv,
 		return true;
 	}
 
-	stamp = jiffies;
-	msecs = jiffies_to_msecs(stamp - priv->plcp_jiffies);
-	priv->plcp_jiffies = stamp;
-
-	if (msecs == 0)
-		return true;
-
 	if (iwl_bt_statistics(priv)) {
 		struct statistics_rx_bt *cur, *old;
 
@@ -508,9 +499,21 @@ static void iwl_recover_from_statistics(struct iwl_priv *priv,
 					struct iwl_rx_packet *pkt)
 {
 	const struct iwl_mod_params *mod_params = priv->cfg->mod_params;
+	unsigned int msecs;
+	unsigned long stamp;
 
-	if (test_bit(STATUS_EXIT_PENDING, &priv->status) ||
-	    !iwl_is_any_associated(priv))
+	if (test_bit(STATUS_EXIT_PENDING, &priv->status))
+		return;
+
+	stamp = jiffies;
+	msecs = jiffies_to_msecs(stamp - priv->rx_statistics_jiffies);
+
+	/* Only gather statistics and update time stamp when not associated */
+	if (!iwl_is_any_associated(priv))
+		goto out;
+
+	/* Do not check/recover when do not have enough statistics data */
+	if (msecs < 99)
 		return;
 
 	if (mod_params->ack_check && !iwl_good_ack_health(priv, pkt)) {
@@ -519,8 +522,18 @@ static void iwl_recover_from_statistics(struct iwl_priv *priv,
 			return;
 	}
 
-	if (mod_params->plcp_check && !iwl_good_plcp_health(priv, pkt))
+	if (mod_params->plcp_check && !iwl_good_plcp_health(priv, pkt, msecs))
 		iwl_force_reset(priv, IWL_RF_RESET, false);
+
+out:
+	if (iwl_bt_statistics(priv))
+		memcpy(&priv->_agn.statistics_bt, &pkt->u.stats_bt,
+			sizeof(priv->_agn.statistics_bt));
+	else
+		memcpy(&priv->_agn.statistics, &pkt->u.stats,
+			sizeof(priv->_agn.statistics));
+
+	priv->rx_statistics_jiffies = stamp;
 }
 
 /* Calculate noise level, based on measurements during network silence just
@@ -669,13 +682,6 @@ static void iwl_rx_statistics(struct iwl_priv *priv,
 
 	iwl_recover_from_statistics(priv, pkt);
 
-	if (iwl_bt_statistics(priv))
-		memcpy(&priv->_agn.statistics_bt, &pkt->u.stats_bt,
-			sizeof(priv->_agn.statistics_bt));
-	else
-		memcpy(&priv->_agn.statistics, &pkt->u.stats,
-			sizeof(priv->_agn.statistics));
-
 	set_bit(STATUS_STATISTICS, &priv->status);
 
 	/* Reschedule the statistics timer to occur in