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authorLars Ericsson <Lars_Ericsson@telia.com>2009-08-08 23:54:51 +0200
committerJohn W. Linville <linville@tuxdriver.com>2009-08-14 09:13:52 -0400
commit66679a65efffffb62dc2650960b3aff758d575f9 (patch)
tree75f3f323331e89fd7c4a8cc87339cceb1959037b /drivers/net/wireless/rt2x00/rt2x00link.c
parent193df183b15cda78f6b2373f576e243327ea0d8f (diff)
rt2x00: Fix rounding errors in RSSI average calculation
Small changes in signal level was not detected up by the MOVING_AVERAGE() due to a rounding error, using 'int' type. rt2x00lib_antenna_diversity_eval: rssi: -62 -62 -62 -62 -62 -62 -62 -62 -62 -62 -62 -62 -62 -62 -62 rssi_avg: -57 -57 -57 -57 -57 -57 -57 -57 -57 -57 -57 -57 -57 -57 -57 The signal level reported back could be significantly (5dBm) different from the actual value. A level +3dBm is the same as double the AP output power. Signed-off-by: Lars Ericsson <Lars_Ericsson@telia.com> Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com> Signed-off-by: John W. Linville <linville@tuxdriver.com>
Diffstat (limited to 'drivers/net/wireless/rt2x00/rt2x00link.c')
-rw-r--r--drivers/net/wireless/rt2x00/rt2x00link.c65
1 files changed, 39 insertions, 26 deletions
diff --git a/drivers/net/wireless/rt2x00/rt2x00link.c b/drivers/net/wireless/rt2x00/rt2x00link.c
index dd68f3a57b6..c64db0ba7f4 100644
--- a/drivers/net/wireless/rt2x00/rt2x00link.c
+++ b/drivers/net/wireless/rt2x00/rt2x00link.c
@@ -46,7 +46,15 @@
#define DEFAULT_PERCENTAGE 50
/*
- * Small helper macro to work with moving/walking averages.
+ * Small helper macro for percentage calculation
+ * This is a very simple macro with the only catch that it will
+ * produce a default value in case no total value was provided.
+ */
+#define PERCENTAGE(__value, __total) \
+ ( (__total) ? (((__value) * 100) / (__total)) : (DEFAULT_PERCENTAGE) )
+
+/*
+ * Helper struct and macro to work with moving/walking averages.
* When adding a value to the average value the following calculation
* is needed:
*
@@ -60,18 +68,28 @@
* for a few minutes but when the device is moved away from the AP
* the average will not decrease fast enough to compensate.
* The walking average compensates this and will move towards
- * the new values correctly allowing a effective link tuning.
+ * the new values correctly allowing a effective link tuning,
+ * the speed of the average moving towards other values depends
+ * on the value for the number of samples. The higher the number
+ * of samples, the slower the average will move.
+ * We use two variables to keep track of the average value to
+ * compensate for the rounding errors. This can be a significant
+ * error (>5dBm) if the factor is too low.
*/
-#define MOVING_AVERAGE(__avg, __val, __samples) \
- ( (((__avg) * ((__samples) - 1)) + (__val)) / (__samples) )
-
-/*
- * Small helper macro for percentage calculation
- * This is a very simple macro with the only catch that it will
- * produce a default value in case no total value was provided.
- */
-#define PERCENTAGE(__value, __total) \
- ( (__total) ? (((__value) * 100) / (__total)) : (DEFAULT_PERCENTAGE) )
+#define AVG_SAMPLES 8
+#define AVG_FACTOR 1000
+#define MOVING_AVERAGE(__avg, __val) \
+({ \
+ struct avg_val __new; \
+ __new.avg_weight = \
+ (__avg).avg_weight ? \
+ ((((__avg).avg_weight * ((AVG_SAMPLES) - 1)) + \
+ ((__val) * (AVG_FACTOR))) / \
+ (AVG_SAMPLES) ) : \
+ ((__val) * (AVG_FACTOR)); \
+ __new.avg = __new.avg_weight / (AVG_FACTOR); \
+ __new; \
+})
/*
* For calculating the Signal quality we have determined
@@ -98,8 +116,8 @@ static int rt2x00link_antenna_get_link_rssi(struct rt2x00_dev *rt2x00dev)
{
struct link_ant *ant = &rt2x00dev->link.ant;
- if (ant->rssi_ant && rt2x00dev->link.qual.rx_success)
- return ant->rssi_ant;
+ if (ant->rssi_ant.avg && rt2x00dev->link.qual.rx_success)
+ return ant->rssi_ant.avg;
return DEFAULT_RSSI;
}
@@ -121,7 +139,8 @@ static void rt2x00link_antenna_update_rssi_history(struct rt2x00_dev *rt2x00dev,
static void rt2x00link_antenna_reset(struct rt2x00_dev *rt2x00dev)
{
- rt2x00dev->link.ant.rssi_ant = 0;
+ rt2x00dev->link.ant.rssi_ant.avg = 0;
+ rt2x00dev->link.ant.rssi_ant.avg_weight = 0;
}
static void rt2x00lib_antenna_diversity_sample(struct rt2x00_dev *rt2x00dev)
@@ -258,8 +277,6 @@ void rt2x00link_update_stats(struct rt2x00_dev *rt2x00dev,
struct link_qual *qual = &rt2x00dev->link.qual;
struct link_ant *ant = &rt2x00dev->link.ant;
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
- int avg_rssi = rxdesc->rssi;
- int ant_rssi = rxdesc->rssi;
/*
* Frame was received successfully since non-succesfull
@@ -279,16 +296,12 @@ void rt2x00link_update_stats(struct rt2x00_dev *rt2x00dev,
/*
* Update global RSSI
*/
- if (link->avg_rssi)
- avg_rssi = MOVING_AVERAGE(link->avg_rssi, rxdesc->rssi, 8);
- link->avg_rssi = avg_rssi;
+ link->avg_rssi = MOVING_AVERAGE(link->avg_rssi, rxdesc->rssi);
/*
* Update antenna RSSI
*/
- if (ant->rssi_ant)
- ant_rssi = MOVING_AVERAGE(ant->rssi_ant, rxdesc->rssi, 8);
- ant->rssi_ant = ant_rssi;
+ ant->rssi_ant = MOVING_AVERAGE(ant->rssi_ant, rxdesc->rssi);
}
static void rt2x00link_precalculate_signal(struct rt2x00_dev *rt2x00dev)
@@ -421,10 +434,10 @@ static void rt2x00link_tuner(struct work_struct *work)
* collect the RSSI data we could use this. Otherwise we
* must fallback to the default RSSI value.
*/
- if (!link->avg_rssi || !qual->rx_success)
+ if (!link->avg_rssi.avg || !qual->rx_success)
qual->rssi = DEFAULT_RSSI;
else
- qual->rssi = link->avg_rssi;
+ qual->rssi = link->avg_rssi.avg;
/*
* Only perform the link tuning when Link tuning
@@ -442,7 +455,7 @@ static void rt2x00link_tuner(struct work_struct *work)
/*
* Send a signal to the led to update the led signal strength.
*/
- rt2x00leds_led_quality(rt2x00dev, link->avg_rssi);
+ rt2x00leds_led_quality(rt2x00dev, qual->rssi);
/*
* Evaluate antenna setup, make this the last step when