iwlwifi: work around passive scan issue

Some firmware versions don't behave properly when
passive scanning is requested on radar channels
without enabling active scanning on receiving a
good frame. Work around that issue by asking the
firmware to only enable the active scanning after
receiving a huge number of good frames, a number
that can never be reached during our dwell time.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>

diff --git a/drivers/net/wireless/iwlwifi/iwl-commands.h b/drivers/net/wireless/iwlwifi/iwl-commands.h
index 6383d9f..f4e59ae 100644 (file)
--- a/drivers/net/wireless/iwlwifi/iwl-commands.h
+++ b/drivers/net/wireless/iwlwifi/iwl-commands.h
@@ -2621,7 +2621,9 @@ struct iwl_ssid_ie {
 #define PROBE_OPTION_MAX_3945          4
 #define PROBE_OPTION_MAX               20
 #define TX_CMD_LIFE_TIME_INFINITE      cpu_to_le32(0xFFFFFFFF)
-#define IWL_GOOD_CRC_TH                        cpu_to_le16(1)
+#define IWL_GOOD_CRC_TH_DISABLED       0
+#define IWL_GOOD_CRC_TH_DEFAULT                cpu_to_le16(1)
+#define IWL_GOOD_CRC_TH_NEVER          cpu_to_le16(0xffff)
 #define IWL_MAX_SCAN_SIZE 1024
 #define IWL_MAX_CMD_SIZE 4096
 #define IWL_MAX_PROBE_REQUEST          200

diff --git a/drivers/net/wireless/iwlwifi/iwl-scan.c b/drivers/net/wireless/iwlwifi/iwl-scan.c
index 5062f4e..2367286 100644 (file)
--- a/drivers/net/wireless/iwlwifi/iwl-scan.c
+++ b/drivers/net/wireless/iwlwifi/iwl-scan.c
@@ -812,16 +812,29 @@ static void iwl_bg_request_scan(struct work_struct *data)
                        rate = IWL_RATE_1M_PLCP;
                        rate_flags = RATE_MCS_CCK_MSK;
                }
-               scan->good_CRC_th = 0;
+               scan->good_CRC_th = IWL_GOOD_CRC_TH_DISABLED;
        } else if (priv->scan_bands & BIT(IEEE80211_BAND_5GHZ)) {
                band = IEEE80211_BAND_5GHZ;
                rate = IWL_RATE_6M_PLCP;
                /*
-                * If active scaning is requested but a certain channel
-                * is marked passive, we can do active scanning if we
-                * detect transmissions.
+                * If active scanning is requested but a certain channel is
+                * marked passive, we can do active scanning if we detect
+                * transmissions.
+                *
+                * There is an issue with some firmware versions that triggers
+                * a sysassert on a "good CRC threshold" of zero (== disabled),
+                * on a radar channel even though this means that we should NOT
+                * send probes.
+                *
+                * The "good CRC threshold" is the number of frames that we
+                * need to receive during our dwell time on a channel before
+                * sending out probes -- setting this to a huge value will
+                * mean we never reach it, but at the same time work around
+                * the aforementioned issue. Thus use IWL_GOOD_CRC_TH_NEVER
+                * here instead of IWL_GOOD_CRC_TH_DISABLED.
                 */
-               scan->good_CRC_th = is_active ? IWL_GOOD_CRC_TH : 0;
+               scan->good_CRC_th = is_active ? IWL_GOOD_CRC_TH_DEFAULT :
+                                               IWL_GOOD_CRC_TH_NEVER;
 
                /* Force use of chains B and C (0x6) for scan Rx for 4965
                 * Avoid A (0x1) because of its off-channel reception on A-band.

diff --git a/drivers/net/wireless/iwlwifi/iwl3945-base.c b/drivers/net/wireless/iwlwifi/iwl3945-base.c
index e276f2a..2f47d93 100644 (file)
--- a/drivers/net/wireless/iwlwifi/iwl3945-base.c
+++ b/drivers/net/wireless/iwlwifi/iwl3945-base.c
@@ -2966,7 +2966,8 @@ static void iwl3945_bg_request_scan(struct work_struct *data)
                 * is marked passive, we can do active scanning if we
                 * detect transmissions.
                 */
-               scan->good_CRC_th = is_active ? IWL_GOOD_CRC_TH : 0;
+               scan->good_CRC_th = is_active ? IWL_GOOD_CRC_TH_DEFAULT :
+                                               IWL_GOOD_CRC_TH_DISABLED;
                band = IEEE80211_BAND_5GHZ;
        } else {
                IWL_WARN(priv, "Invalid scan band count\n");