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Commit 96ff5641 authored by Johannes Berg's avatar Johannes Berg Committed by Reinette Chatre
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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: default avatarJohannes Berg <johannes.berg@intel.com>
Signed-off-by: default avatarReinette Chatre <reinette.chatre@intel.com>
parent 0250ecec

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

+3 −1
Original line number Diff line number Diff line
@@ -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

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

+18 −5
Original line number Diff line number Diff line
@@ -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.

drivers/net/wireless/iwlwifi/iwl3945-base.c

+2 −1
Original line number Diff line number Diff line
@@ -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");