/* Copyright (C) 2004 - 2009 Ivo van Doorn 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 #include #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 /* * 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; \ }) 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); } void rt2x00link_start_tuner(struct rt2x00_dev *rt2x00dev) { struct link *link = &rt2x00dev->link; /* * Link tuning should only be performed when * an active sta interface exists. AP interfaces * don't need link tuning and monitor mode interfaces * should never have to work with link tuners. */ if (!rt2x00dev->intf_sta_count) return; /** * While scanning, link tuning is disabled. By default * the most sensitive settings will be used to make sure * that all beacons and probe responses will be recieved * during the scan. */ if (test_bit(DEVICE_STATE_SCANNING, &rt2x00dev->flags)) return; 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; u8 vgc_level = qual->vgc_level_reg; 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)); /* * Restore the VGC level as stored in the registers, * the driver can use this to determine if the register * must be updated during reset or not. */ qual->vgc_level_reg = vgc_level; /* * 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) || test_bit(DEVICE_STATE_SCANNING, &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; /* * Check if link tuning is supported by the hardware, some hardware * do not support link tuning at all, while other devices can disable * the feature from the EEPROM. */ if (test_bit(DRIVER_SUPPORT_LINK_TUNING, &rt2x00dev->flags)) rt2x00dev->ops->lib->link_tuner(rt2x00dev, qual, link->count); /* * 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); }