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>
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@ -133,6 +133,17 @@
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#define SHORT_EIFS ( SIFS + SHORT_DIFS + \
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#define SHORT_EIFS ( SIFS + SHORT_DIFS + \
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GET_DURATION(IEEE80211_HEADER + ACK_SIZE, 10) )
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GET_DURATION(IEEE80211_HEADER + ACK_SIZE, 10) )
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/*
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* Structure for average calculation
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* The avg field contains the actual average value,
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* but avg_weight is internally used during calculations
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* to prevent rounding errors.
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*/
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struct avg_val {
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int avg;
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int avg_weight;
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};
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/*
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/*
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* Chipset identification
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* Chipset identification
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* The chipset on the device is composed of a RT and RF chip.
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* The chipset on the device is composed of a RT and RF chip.
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@ -256,7 +267,7 @@ struct link_ant {
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* Similar to the avg_rssi in the link_qual structure
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* Similar to the avg_rssi in the link_qual structure
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* this value is updated by using the walking average.
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* this value is updated by using the walking average.
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*/
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*/
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int rssi_ant;
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struct avg_val rssi_ant;
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};
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};
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/*
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/*
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@ -285,7 +296,7 @@ struct link {
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/*
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/*
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* Currently active average RSSI value
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* Currently active average RSSI value
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*/
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*/
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int avg_rssi;
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struct avg_val avg_rssi;
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/*
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/*
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* Currently precalculated percentages of successful
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* Currently precalculated percentages of successful
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@ -46,7 +46,15 @@
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#define DEFAULT_PERCENTAGE 50
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#define DEFAULT_PERCENTAGE 50
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/*
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/*
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* Small helper macro to work with moving/walking averages.
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* Small helper macro for percentage calculation
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* This is a very simple macro with the only catch that it will
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* produce a default value in case no total value was provided.
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*/
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#define PERCENTAGE(__value, __total) \
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( (__total) ? (((__value) * 100) / (__total)) : (DEFAULT_PERCENTAGE) )
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/*
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* Helper struct and macro to work with moving/walking averages.
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* When adding a value to the average value the following calculation
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* When adding a value to the average value the following calculation
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* is needed:
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* is needed:
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*
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*
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@ -60,18 +68,28 @@
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* for a few minutes but when the device is moved away from the AP
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* for a few minutes but when the device is moved away from the AP
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* the average will not decrease fast enough to compensate.
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* the average will not decrease fast enough to compensate.
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* The walking average compensates this and will move towards
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* The walking average compensates this and will move towards
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* the new values correctly allowing a effective link tuning.
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* the new values correctly allowing a effective link tuning,
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* the speed of the average moving towards other values depends
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* on the value for the number of samples. The higher the number
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* of samples, the slower the average will move.
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* We use two variables to keep track of the average value to
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* compensate for the rounding errors. This can be a significant
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* error (>5dBm) if the factor is too low.
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*/
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*/
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#define MOVING_AVERAGE(__avg, __val, __samples) \
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#define AVG_SAMPLES 8
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( (((__avg) * ((__samples) - 1)) + (__val)) / (__samples) )
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#define AVG_FACTOR 1000
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#define MOVING_AVERAGE(__avg, __val) \
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/*
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({ \
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* Small helper macro for percentage calculation
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struct avg_val __new; \
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* This is a very simple macro with the only catch that it will
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__new.avg_weight = \
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* produce a default value in case no total value was provided.
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(__avg).avg_weight ? \
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*/
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((((__avg).avg_weight * ((AVG_SAMPLES) - 1)) + \
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#define PERCENTAGE(__value, __total) \
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((__val) * (AVG_FACTOR))) / \
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( (__total) ? (((__value) * 100) / (__total)) : (DEFAULT_PERCENTAGE) )
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(AVG_SAMPLES) ) : \
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((__val) * (AVG_FACTOR)); \
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__new.avg = __new.avg_weight / (AVG_FACTOR); \
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__new; \
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})
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/*
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/*
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* For calculating the Signal quality we have determined
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* For calculating the Signal quality we have determined
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@ -98,8 +116,8 @@ static int rt2x00link_antenna_get_link_rssi(struct rt2x00_dev *rt2x00dev)
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{
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{
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struct link_ant *ant = &rt2x00dev->link.ant;
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struct link_ant *ant = &rt2x00dev->link.ant;
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if (ant->rssi_ant && rt2x00dev->link.qual.rx_success)
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if (ant->rssi_ant.avg && rt2x00dev->link.qual.rx_success)
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return ant->rssi_ant;
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return ant->rssi_ant.avg;
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return DEFAULT_RSSI;
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return DEFAULT_RSSI;
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}
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}
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@ -121,7 +139,8 @@ static void rt2x00link_antenna_update_rssi_history(struct rt2x00_dev *rt2x00dev,
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static void rt2x00link_antenna_reset(struct rt2x00_dev *rt2x00dev)
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static void rt2x00link_antenna_reset(struct rt2x00_dev *rt2x00dev)
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{
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{
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rt2x00dev->link.ant.rssi_ant = 0;
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rt2x00dev->link.ant.rssi_ant.avg = 0;
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rt2x00dev->link.ant.rssi_ant.avg_weight = 0;
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}
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}
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static void rt2x00lib_antenna_diversity_sample(struct rt2x00_dev *rt2x00dev)
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static void rt2x00lib_antenna_diversity_sample(struct rt2x00_dev *rt2x00dev)
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@ -258,8 +277,6 @@ void rt2x00link_update_stats(struct rt2x00_dev *rt2x00dev,
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struct link_qual *qual = &rt2x00dev->link.qual;
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struct link_qual *qual = &rt2x00dev->link.qual;
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struct link_ant *ant = &rt2x00dev->link.ant;
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struct link_ant *ant = &rt2x00dev->link.ant;
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struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
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struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
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int avg_rssi = rxdesc->rssi;
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int ant_rssi = rxdesc->rssi;
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/*
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/*
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* Frame was received successfully since non-succesfull
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* Frame was received successfully since non-succesfull
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@ -279,16 +296,12 @@ void rt2x00link_update_stats(struct rt2x00_dev *rt2x00dev,
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/*
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/*
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* Update global RSSI
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* Update global RSSI
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*/
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*/
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if (link->avg_rssi)
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link->avg_rssi = MOVING_AVERAGE(link->avg_rssi, rxdesc->rssi);
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avg_rssi = MOVING_AVERAGE(link->avg_rssi, rxdesc->rssi, 8);
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link->avg_rssi = avg_rssi;
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/*
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/*
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* Update antenna RSSI
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* Update antenna RSSI
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*/
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*/
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if (ant->rssi_ant)
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ant->rssi_ant = MOVING_AVERAGE(ant->rssi_ant, rxdesc->rssi);
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ant_rssi = MOVING_AVERAGE(ant->rssi_ant, rxdesc->rssi, 8);
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ant->rssi_ant = ant_rssi;
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}
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}
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static void rt2x00link_precalculate_signal(struct rt2x00_dev *rt2x00dev)
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static void rt2x00link_precalculate_signal(struct rt2x00_dev *rt2x00dev)
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@ -421,10 +434,10 @@ static void rt2x00link_tuner(struct work_struct *work)
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* collect the RSSI data we could use this. Otherwise we
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* collect the RSSI data we could use this. Otherwise we
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* must fallback to the default RSSI value.
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* must fallback to the default RSSI value.
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*/
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*/
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if (!link->avg_rssi || !qual->rx_success)
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if (!link->avg_rssi.avg || !qual->rx_success)
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qual->rssi = DEFAULT_RSSI;
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qual->rssi = DEFAULT_RSSI;
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else
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else
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qual->rssi = link->avg_rssi;
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qual->rssi = link->avg_rssi.avg;
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/*
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/*
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* Only perform the link tuning when Link tuning
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* Only perform the link tuning when Link tuning
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@ -442,7 +455,7 @@ static void rt2x00link_tuner(struct work_struct *work)
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/*
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/*
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* Send a signal to the led to update the led signal strength.
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* Send a signal to the led to update the led signal strength.
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*/
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*/
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rt2x00leds_led_quality(rt2x00dev, link->avg_rssi);
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rt2x00leds_led_quality(rt2x00dev, qual->rssi);
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/*
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/*
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* Evaluate antenna setup, make this the last step when
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* Evaluate antenna setup, make this the last step when
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