wl1271: Optimize scan duration

Currently then dwell times for each channel in scans is set to an overly
long value, and excessive number of probe-requests are transmitted on each
channel (for active scans.)

Based on testing, comparable results can be received with smaller dwell-time,
and, with fever probe-requests - in fact, reducing the number of probe-requests
to 2 seems to increase the number of found results.

Configure more optimal values for per channel dwell times. Comparison for the
different scan configurations (in my current office environment):

dwell-time 60000   3x probe-req == ~60 results
           40000   3x probe-req == ~50 results
           30000   3x probe-req == ~40 results

dwell-time 60000   2x probe-req == ~70 results
           40000   2x probe-req == ~60 results
           30000   2x probe-req == ~58 results

The above are results for a cumulative 3 scan run. For individual scans, the
number of results drop slightly more.
Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Reviewed-by: Teemu Paasikivi <ext-teemu.3.paasikivi@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>

drivers/net/wireless/wl12xx/wl1271_conf.h

@@ -1016,6 +1016,44 @@ struct conf_roam_trigger_settings {
 	u8 avg_weight_snr_data;
 };
 
+struct conf_scan_settings {
+	/*
+	 * The minimum time to wait on each channel for active scans
+	 *
+	 * Range: 0 - 65536 tu
+	 */
+	u16 min_dwell_time_active;
+
+	/*
+	 * The maximum time to wait on each channel for active scans
+	 *
+	 * Range: 0 - 65536 tu
+	 */
+	u16 max_dwell_time_active;
+
+	/*
+	 * The maximum time to wait on each channel for passive scans
+	 *
+	 * Range: 0 - 65536 tu
+	 */
+	u16 min_dwell_time_passive;
+
+	/*
+	 * The maximum time to wait on each channel for passive scans
+	 *
+	 * Range: 0 - 65536 tu
+	 */
+	u16 max_dwell_time_passive;
+
+	/*
+	 * Number of probe requests to transmit on each active scan channel
+	 *
+	 * Range: u8
+	 */
+	u16 num_probe_reqs;
+
+};
+
 struct conf_drv_settings {
 	struct conf_sg_settings sg;
 	struct conf_rx_settings rx;
@@ -1024,6 +1062,7 @@ struct conf_drv_settings {
 	struct conf_itrim_settings itrim;
 	struct conf_pm_config_settings pm_config;
 	struct conf_roam_trigger_settings roam_trigger;
+	struct conf_scan_settings scan;
 };
 
 #endif

drivers/net/wireless/wl12xx/wl1271_main.c

@@ -232,7 +232,14 @@ static struct conf_drv_settings default_conf = {
 		.avg_weight_rssi_data         = 10,
 		.avg_weight_snr_beacon        = 20,
 		.avg_weight_snr_data          = 10
-	}
+	},
+	.scan = {
+		.min_dwell_time_active        = 7500,
+		.max_dwell_time_active        = 30000,
+		.min_dwell_time_passive       = 30000,
+		.max_dwell_time_passive       = 60000,
+		.num_probe_reqs               = 2,
+	},
 };
 
 static void __wl1271_op_remove_interface(struct wl1271 *wl);

drivers/net/wireless/wl12xx/wl1271_scan.c

@@ -64,6 +64,7 @@ static int wl1271_get_scan_channels(struct wl1271 *wl,
 				    struct basic_scan_channel_params *channels,
 				    enum ieee80211_band band, bool passive)
 {
+	struct conf_scan_settings *c = &wl->conf.scan;
 	int i, j;
 	u32 flags;
 
@@ -91,10 +92,17 @@ static int wl1271_get_scan_channels(struct wl1271 *wl,
 			wl1271_debug(DEBUG_SCAN, "beacon_found %d",
 				     req->channels[i]->beacon_found);
 
+			if (!passive) {
 				channels[j].min_duration =
-				cpu_to_le32(WL1271_SCAN_CHAN_MIN_DURATION);
+					cpu_to_le32(c->min_dwell_time_active);
 				channels[j].max_duration =
-				cpu_to_le32(WL1271_SCAN_CHAN_MAX_DURATION);
+					cpu_to_le32(c->max_dwell_time_active);
+			} else {
+				channels[j].min_duration =
+					cpu_to_le32(c->min_dwell_time_passive);
+				channels[j].max_duration =
+					cpu_to_le32(c->max_dwell_time_passive);
+			}
 			channels[j].early_termination = 0;
 			channels[j].tx_power_att = req->channels[i]->max_power;
 			channels[j].channel = req->channels[i]->hw_value;
@@ -151,7 +159,7 @@ static int wl1271_scan_send(struct wl1271 *wl, enum ieee80211_band band,
 	cmd->params.rx_filter_options =
 		cpu_to_le32(CFG_RX_PRSP_EN | CFG_RX_MGMT_EN | CFG_RX_BCN_EN);
 
-	cmd->params.n_probe_reqs = WL1271_SCAN_PROBE_REQS;
+	cmd->params.n_probe_reqs = wl->conf.scan.num_probe_reqs;
 	cmd->params.tx_rate = cpu_to_le32(basic_rate);
 	cmd->params.tid_trigger = 0;
 	cmd->params.scan_tag = WL1271_SCAN_DEFAULT_TAG;

drivers/net/wireless/wl12xx/wl1271_scan.h

@@ -40,11 +40,8 @@ void wl1271_scan_complete_work(struct work_struct *work);
 #define WL1271_SCAN_OPT_ACTIVE         0
 #define WL1271_SCAN_OPT_PASSIVE	       1
 #define WL1271_SCAN_OPT_PRIORITY_HIGH  4
-#define WL1271_SCAN_CHAN_MIN_DURATION  30000  /* TU */
-#define WL1271_SCAN_CHAN_MAX_DURATION  60000  /* TU */
 #define WL1271_SCAN_BAND_2_4_GHZ 0
 #define WL1271_SCAN_BAND_5_GHZ 1
-#define WL1271_SCAN_PROBE_REQS 3
 
 #define WL1271_SCAN_TIMEOUT    10000 /* msec */