/*
Copyright (C) 2004 - 2009 rt2x00 SourceForge Project
<http://rt2x00.serialmonkey.com>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the
Free Software Foundation, Inc.,
59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
/*
Module: rt2x00lib
Abstract: rt2x00 generic link tuning routines.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include "rt2x00.h"
#include "rt2x00lib.h"
/*
* When we lack RSSI information return something less then -80 to
* tell the driver to tune the device to maximum sensitivity.
*/
#define DEFAULT_RSSI -128
/*
* When no TX/RX percentage could be calculated due to lack of
* frames on the air, we fallback to a percentage of 50%.
* This will assure we will get at least get some decent value
* when the link tuner starts.
* The value will be dropped and overwritten with the correct (measured)
* value anyway during the first run of the link tuner.
*/
#define DEFAULT_PERCENTAGE 50
/*
* 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:
*
* avg_rssi = ((avg_rssi * 7) + rssi) / 8;
*
* The advantage of this approach is that we only need 1 variable
* to store the average in (No need for a count and a total).
* But more importantly, normal average values will over time
* move less and less towards newly added values this results
* that with link tuning, the device can have a very good RSSI
* 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 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 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
* the total number of success and failed RX and TX frames.
* With the addition of the average RSSI value we can determine
* the link quality using the following algorithm:
*
* rssi_percentage = (avg_rssi * 100) / rssi_offset
* rx_percentage = (rx_success * 100) / rx_total
* tx_percentage = (tx_success * 100) / tx_total
* avg_signal = ((WEIGHT_RSSI * avg_rssi) +
* (WEIGHT_TX * tx_percentage) +
* (WEIGHT_RX * rx_percentage)) / 100
*
* This value should then be checked to not be greater then 100.
* This means the values of WEIGHT_RSSI, WEIGHT_RX, WEIGHT_TX must
* sum up to 100 as well.
*/
#define WEIGHT_RSSI 20
#define WEIGHT_RX 40
#define WEIGHT_TX 40
static int rt2x00link_antenna_get_link_rssi(struct rt2x00_dev *rt2x00dev)
{
struct link_ant *ant = &rt2x00dev->link.ant;
if (ant->rssi_ant.avg && rt2x00dev->link.qual.rx_success)
return ant->rssi_ant.avg;
return DEFAULT_RSSI;
}
static int rt2x00link_antenna_get_rssi_history(struct rt2x00_dev *rt2x00dev)
{
struct link_ant *ant = &rt2x00dev->link.ant;
if (ant->rssi_history)
return ant->rssi_history;
return DEFAULT_RSSI;
}
static void rt2x00link_antenna_update_rssi_history(struct rt2x00_dev *rt2x00dev,
int rssi)
{
struct link_ant *ant = &rt2x00dev->link.ant;
ant->rssi_history = rssi;
}
static void rt2x00link_antenna_reset(struct rt2x00_dev *rt2x00dev)
{
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)
{
struct link_ant *ant = &rt2x00dev->link.ant;
struct antenna_setup new_ant;
int other_antenna;
int sample_current = rt2x00link_antenna_get_link_rssi(rt2x00dev);
int sample_other = rt2x00link_antenna_get_rssi_history(rt2x00dev);
memcpy(&new_ant, &ant->active, sizeof(new_ant));
/*
* We are done sampling. Now we should evaluate the results.
*/
ant->flags &= ~ANTENNA_MODE_SAMPLE;
/*
* During the last period we have sampled the RSSI
* from both antennas. It now is time to determine
* which antenna demonstrated the best performance.
* When we are already on the antenna with the best
* performance, just create a good starting point
* for the history and we are done.
*/
if (sample_current >= sample_other) {
rt2x00link_antenna_update_rssi_history(rt2x00dev,
sample_current);
return;
}
other_antenna = (ant->active.rx == ANTENNA_A) ? ANTENNA_B : ANTENNA_A;
if (ant->flags & ANTENNA_RX_DIVERSITY)
new_ant.rx = other_antenna;
if (ant->flags & ANTENNA_TX_DIVERSITY)
new_ant.tx = other_antenna;
rt2x00lib_config_antenna(rt2x00dev, new_ant);
}
static void rt2x00lib_antenna_diversity_eval(struct rt2x00_dev *rt2x00dev)
{
struct link_ant *ant = &rt2x00dev->link.ant;
struct antenna_setup new_ant;
int rssi_curr;
int rssi_old;
memcpy(&new_ant, &ant->active, sizeof(new_ant));
/*
* Get current RSSI value along with the historical value,
* after that update the history with the current value.
*/
rssi_curr = rt2x00link_antenna_get_link_rssi(rt2x00dev);
rssi_old = rt2x00link_antenna_get_rssi_history(rt2x00dev);
rt2x00link_antenna_update_rssi_history(rt2x00dev, rssi_curr);
/*
* Legacy driver indicates that we should swap antenna's
* when the difference in RSSI is greater that 5. This
* also should be done when the RSSI was actually better
* then the previous sample.
* When the difference exceeds the threshold we should
* sample the rssi from the other antenna to make a valid
* comparison between the 2 antennas.
*/
if (abs(rssi_curr - rssi_old) < 5)
return;
ant->flags |= ANTENNA_MODE_SAMPLE;
if (ant->flags & ANTENNA_RX_DIVERSITY)
new_ant.rx = (new_ant.rx == ANTENNA_A) ? ANTENNA_B : ANTENNA_A;
if (ant->flags & ANTENNA_TX_DIVERSITY)
new_ant.tx = (new_ant.tx == ANTENNA_A) ? ANTENNA_B : ANTENNA_A;
rt2x00lib_config_antenna(rt2x00dev, new_ant);
}
static bool rt2x00lib_antenna_diversity(struct rt2x00_dev *rt2x00dev)
{
struct link_ant *ant = &rt2x00dev->link.ant;
unsigned int flags = ant->flags;
/*
* Determine if software diversity is enabled for
* either the TX or RX antenna (or both).
* Always perform this check since within the link
* tuner interval the configuration might have changed.
*/
flags &= ~ANTENNA_RX_DIVERSITY;
flags &= ~ANTENNA_TX_DIVERSITY;
if (rt2x00dev->default_ant.rx == ANTENNA_SW_DIVERSITY)
flags |= ANTENNA_RX_DIVERSITY;
if (rt2x00dev->default_ant.tx == ANTENNA_SW_DIVERSITY)
flags |= ANTENNA_TX_DIVERSITY;
if (!(ant->flags & ANTENNA_RX_DIVERSITY) &&
!(ant->flags & ANTENNA_TX_DIVERSITY)) {
ant->flags = 0;
return true;
}
/* Update flags */
ant->flags = flags;
/*
* If we have only sampled the data over the last period
* we should now harvest the data. Otherwise just evaluate
* the data. The latter should only be performed once
* every 2 seconds.
*/
if (ant->flags & ANTENNA_MODE_SAMPLE) {
rt2x00lib_antenna_diversity_sample(rt2x00dev);
return true;
} else if (rt2x00dev->link.count & 1) {
rt2x00lib_antenna_diversity_eval(rt2x00dev);
return true;
}
return false;
}
void rt2x00link_update_stats(struct rt2x00_dev *rt2x00dev,
struct sk_buff *skb,
struct rxdone_entry_desc *rxdesc)
{
struct link *link = &rt2x00dev->link;
struct link_qual *qual = &rt2x00dev->link.qual;
struct link_ant *ant = &rt2x00dev->link.ant;
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
/*
* Frame was received successfully since non-succesfull
* frames would have been dropped by the hardware.
*/
qual->rx_success++;
/*
* We are only interested in quality statistics from
* beacons which came from the BSS which we are
* associated with.
*/
if (!ieee80211_is_beacon(hdr->frame_control) ||
!(rxdesc->dev_flags & RXDONE_MY_BSS))
return;
/*
* Update global RSSI
*/
link->avg_rssi = MOVING_AVERAGE(link->avg_rssi, rxdesc->rssi);
/*
* Update antenna RSSI
*/
ant->rssi_ant = MOVING_AVERAGE(ant->rssi_ant, rxdesc->rssi);
}
static void rt2x00link_precalculate_signal(struct rt2x00_dev *rt2x00dev)
{
struct link *link = &rt2x00dev->link;
struct link_qual *qual = &rt2x00dev->link.qual;
link->rx_percentage =
PERCENTAGE(qual->rx_success, qual->rx_failed + qual->rx_success);
link->tx_percentage =
PERCENTAGE(qual->tx_success, qual->tx_failed + qual->tx_success);
}
int rt2x00link_calculate_signal(struct rt2x00_dev *rt2x00dev, int rssi)
{
struct link *link = &rt2x00dev->link;
int rssi_percentage = 0;
int signal;
/*
* We need a positive value for the RSSI.
*/
if (rssi < 0)
rssi += rt2x00dev->rssi_offset;
/*
* Calculate the different percentages,
* which will be used for the signal.
*/
rssi_percentage = PERCENTAGE(rssi, rt2x00dev->rssi_offset);
/*
* Add the individual percentages and use the WEIGHT
* defines to calculate the current link signal.
*/
signal = ((WEIGHT_RSSI * rssi_percentage) +
(WEIGHT_TX * link->tx_percentage) +
(WEIGHT_RX * link->rx_percentage)) / 100;
return max_t(int, signal, 100);
}
void rt2x00link_start_tuner(struct rt2x00_dev *rt2x00dev)
{
struct link *link = &rt2x00dev->link;
/*
* Link tuning should only be performed when
* an active sta or master interface exists.
* Single monitor mode interfaces should never have
* work with link tuners.
*/
if (!rt2x00dev->intf_ap_count && !rt2x00dev->intf_sta_count)
return;
link->rx_percentage = DEFAULT_PERCENTAGE;
link->tx_percentage = DEFAULT_PERCENTAGE;
rt2x00link_reset_tuner(rt2x00dev, false);
if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
ieee80211_queue_delayed_work(rt2x00dev->hw,
&link->work, LINK_TUNE_INTERVAL);
}
void rt2x00link_stop_tuner(struct rt2x00_dev *rt2x00dev)
{
cancel_delayed_work_sync(&rt2x00dev->link.work);
}
void rt2x00link_reset_tuner(struct rt2x00_dev *rt2x00dev, bool antenna)
{
struct link_qual *qual = &rt2x00dev->link.qual;
if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
return;
/*
* Reset link information.
* Both the currently active vgc level as well as
* the link tuner counter should be reset. Resetting
* the counter is important for devices where the
* device should only perform link tuning during the
* first minute after being enabled.
*/
rt2x00dev->link.count = 0;
memset(qual, 0, sizeof(*qual));
/*
* Reset the link tuner.
*/
rt2x00dev->ops->lib->reset_tuner(rt2x00dev, qual);
if (antenna)
rt2x00link_antenna_reset(rt2x00dev);
}
static void rt2x00link_reset_qual(struct rt2x00_dev *rt2x00dev)
{
struct link_qual *qual = &rt2x00dev->link.qual;
qual->rx_success = 0;
qual->rx_failed = 0;
qual->tx_success = 0;
qual->tx_failed = 0;
}
static void rt2x00link_tuner(struct work_struct *work)
{
struct rt2x00_dev *rt2x00dev =
container_of(work, struct rt2x00_dev, link.work.work);
struct link *link = &rt2x00dev->link;
struct link_qual *qual = &rt2x00dev->link.qual;
/*
* When the radio is shutting down we should
* immediately cease all link tuning.
*/
if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
return;
/*
* Update statistics.
*/
rt2x00dev->ops->lib->link_stats(rt2x00dev, qual);
rt2x00dev->low_level_stats.dot11FCSErrorCount += qual->rx_failed;
/*
* Update quality RSSI for link tuning,
* when we have received some frames and we managed to
* collect the RSSI data we could use this. Otherwise we
* must fallback to the default RSSI value.
*/
if (!link->avg_rssi.avg || !qual->rx_success)
qual->rssi = DEFAULT_RSSI;
else
qual->rssi = link->avg_rssi.avg;
/*
* Only perform the link tuning when Link tuning
* has been enabled (This could have been disabled from the EEPROM).
*/
if (!test_bit(CONFIG_DISABLE_LINK_TUNING, &rt2x00dev->flags))
rt2x00dev->ops->lib->link_tuner(rt2x00dev, qual, link->count);
/*
* Precalculate a portion of the link signal which is
* in based on the tx/rx success/failure counters.
*/
rt2x00link_precalculate_signal(rt2x00dev);
/*
* Send a signal to the led to update the led signal strength.
*/
rt2x00leds_led_quality(rt2x00dev, qual->rssi);
/*
* Evaluate antenna setup, make this the last step when
* rt2x00lib_antenna_diversity made changes the quality
* statistics will be reset.
*/
if (rt2x00lib_antenna_diversity(rt2x00dev))
rt2x00link_reset_qual(rt2x00dev);
/*
* Increase tuner counter, and reschedule the next link tuner run.
*/
link->count++;
if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
ieee80211_queue_delayed_work(rt2x00dev->hw,
&link->work, LINK_TUNE_INTERVAL);
}
void rt2x00link_register(struct rt2x00_dev *rt2x00dev)
{
INIT_DELAYED_WORK(&rt2x00dev->link.work, rt2x00link_tuner);
}
