Back-port of the following upstream commit...

commit d4d59e88cb746165c6fe33eacb6f582d525c6ef1
Author: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Date:   Fri Jan 22 14:22:45 2010 -0800

    iwlwifi: Logic to control how frequent radio should be reset if needed
    
    Add additional logic for internal scan routine to control how
    frequent this function should be performed.
    
    The intent of this function is to reset/re-tune the radio and bring the
    RF/PHY back to normal state, it does not make sense calling it too
    frequent,
    if reset the radio can not bring it back to normal state, it indicate
    there are other reason to cause the radio not operate correctly.
    
    Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
    Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
    Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff -up linux-2.6.32.noarch/drivers/net/wireless/iwlwifi/iwl-dev.h.orig linux-2.6.32.noarch/drivers/net/wireless/iwlwifi/iwl-dev.h
--- linux-2.6.32.noarch/drivers/net/wireless/iwlwifi/iwl-dev.h.orig	2010-03-22 11:26:18.000000000 -0400
+++ linux-2.6.32.noarch/drivers/net/wireless/iwlwifi/iwl-dev.h	2010-03-22 14:12:32.000000000 -0400
@@ -1013,6 +1013,7 @@ struct iwl_priv {
 	unsigned long scan_start;
 	unsigned long scan_pass_start;
 	unsigned long scan_start_tsf;
+	unsigned long last_internal_scan_jiffies;
 	void *scan;
 	int scan_bands;
 	struct cfg80211_scan_request *scan_request;
diff -up linux-2.6.32.noarch/drivers/net/wireless/iwlwifi/iwl-scan.c.orig linux-2.6.32.noarch/drivers/net/wireless/iwlwifi/iwl-scan.c
--- linux-2.6.32.noarch/drivers/net/wireless/iwlwifi/iwl-scan.c.orig	2010-03-22 11:26:18.000000000 -0400
+++ linux-2.6.32.noarch/drivers/net/wireless/iwlwifi/iwl-scan.c	2010-03-22 14:15:28.000000000 -0400
@@ -206,7 +206,8 @@ static void iwl_rx_scan_results_notif(st
 #endif
 
 	priv->last_scan_jiffies = jiffies;
-	priv->next_scan_jiffies = 0;
+	if (!priv->is_internal_short_scan)
+		priv->next_scan_jiffies = 0;
 }
 
 /* Service SCAN_COMPLETE_NOTIFICATION (0x84) */
@@ -252,8 +253,11 @@ static void iwl_rx_scan_complete_notif(s
 			goto reschedule;
 	}
 
-	priv->last_scan_jiffies = jiffies;
-	priv->next_scan_jiffies = 0;
+	if (!priv->is_internal_short_scan)
+		priv->next_scan_jiffies = 0;
+	else
+		priv->last_internal_scan_jiffies = jiffies;
+
 	IWL_DEBUG_INFO(priv, "Setting scan to off\n");
 
 	clear_bit(STATUS_SCANNING, &priv->status);
@@ -560,6 +564,8 @@ EXPORT_SYMBOL(iwl_mac_hw_scan);
  * internal short scan, this function should only been called while associated.
  * It will reset and tune the radio to prevent possible RF related problem
  */
+#define IWL_DELAY_NEXT_INTERNAL_SCAN (HZ*1)
+
 int iwl_internal_short_hw_scan(struct iwl_priv *priv)
 {
 	int ret = 0;
@@ -579,6 +585,13 @@ int iwl_internal_short_hw_scan(struct iw
 		ret = -EAGAIN;
 		goto out;
 	}
+	if (priv->last_internal_scan_jiffies &&
+	    time_after(priv->last_internal_scan_jiffies +
+		       IWL_DELAY_NEXT_INTERNAL_SCAN, jiffies)) {
+		IWL_DEBUG_SCAN(priv, "internal scan rejected\n");
+		goto out;
+	}
+
 	priv->scan_bands = 0;
 	if (priv->band == IEEE80211_BAND_5GHZ)
 		priv->scan_bands |= BIT(IEEE80211_BAND_5GHZ);