drivers/net/wireless/rt2x00/rt2x00link.c

   1 /*
   2         Copyright (C) 2004 - 2009 Ivo van Doorn <IvDoorn@gmail.com>
   3         <http://rt2x00.serialmonkey.com>
   4
   5         This program is free software; you can redistribute it and/or modify
   6         it under the terms of the GNU General Public License as published by
   7         the Free Software Foundation; either version 2 of the License, or
   8         (at your option) any later version.
   9
  10         This program is distributed in the hope that it will be useful,
  11         but WITHOUT ANY WARRANTY; without even the implied warranty of
  12         MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13         GNU General Public License for more details.
  14
  15         You should have received a copy of the GNU General Public License
  16         along with this program; if not, write to the
  17         Free Software Foundation, Inc.,
  18         59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  19  */
  20
  21 /*
  22         Module: rt2x00lib
  23         Abstract: rt2x00 generic link tuning routines.
  24  */
  25
  26 #include <linux/kernel.h>
  27 #include <linux/module.h>
  28
  29 #include "rt2x00.h"
  30 #include "rt2x00lib.h"
  31
  32 /*
  33  * When we lack RSSI information return something less then -80 to
  34  * tell the driver to tune the device to maximum sensitivity.
  35  */
  36 #define DEFAULT_RSSI            -128
  37
  38 /*
  39  * Helper struct and macro to work with moving/walking averages.
  40  * When adding a value to the average value the following calculation
  41  * is needed:
  42  *
  43  *        avg_rssi = ((avg_rssi * 7) + rssi) / 8;
  44  *
  45  * The advantage of this approach is that we only need 1 variable
  46  * to store the average in (No need for a count and a total).
  47  * But more importantly, normal average values will over time
  48  * move less and less towards newly added values this results
  49  * that with link tuning, the device can have a very good RSSI
  50  * for a few minutes but when the device is moved away from the AP
  51  * the average will not decrease fast enough to compensate.
  52  * The walking average compensates this and will move towards
  53  * the new values correctly allowing a effective link tuning,
  54  * the speed of the average moving towards other values depends
  55  * on the value for the number of samples. The higher the number
  56  * of samples, the slower the average will move.
  57  * We use two variables to keep track of the average value to
  58  * compensate for the rounding errors. This can be a significant
  59  * error (>5dBm) if the factor is too low.
  60  */
  61 #define AVG_SAMPLES     8
  62 #define AVG_FACTOR      1000
  63 #define MOVING_AVERAGE(__avg, __val) \
  64 ({ \
  65         struct avg_val __new; \
  66         __new.avg_weight = \
  67             (__avg).avg_weight  ? \
  68                 ((((__avg).avg_weight * ((AVG_SAMPLES) - 1)) + \
  69                   ((__val) * (AVG_FACTOR))) / \
  70                  (AVG_SAMPLES) ) : \
  71                 ((__val) * (AVG_FACTOR)); \
  72         __new.avg = __new.avg_weight / (AVG_FACTOR); \
  73         __new; \
  74 })
  75
  76 static int rt2x00link_antenna_get_link_rssi(struct rt2x00_dev *rt2x00dev)
  77 {
  78         struct link_ant *ant = &rt2x00dev->link.ant;
  79
  80         if (ant->rssi_ant.avg && rt2x00dev->link.qual.rx_success)
  81                 return ant->rssi_ant.avg;
  82         return DEFAULT_RSSI;
  83 }
  84
  85 static int rt2x00link_antenna_get_rssi_history(struct rt2x00_dev *rt2x00dev)
  86 {
  87         struct link_ant *ant = &rt2x00dev->link.ant;
  88
  89         if (ant->rssi_history)
  90                 return ant->rssi_history;
  91         return DEFAULT_RSSI;
  92 }
  93
  94 static void rt2x00link_antenna_update_rssi_history(struct rt2x00_dev *rt2x00dev,
  95                                                    int rssi)
  96 {
  97         struct link_ant *ant = &rt2x00dev->link.ant;
  98         ant->rssi_history = rssi;
  99 }
 100
 101 static void rt2x00link_antenna_reset(struct rt2x00_dev *rt2x00dev)
 102 {
 103         rt2x00dev->link.ant.rssi_ant.avg = 0;
 104         rt2x00dev->link.ant.rssi_ant.avg_weight = 0;
 105 }
 106
 107 static void rt2x00lib_antenna_diversity_sample(struct rt2x00_dev *rt2x00dev)
 108 {
 109         struct link_ant *ant = &rt2x00dev->link.ant;
 110         struct antenna_setup new_ant;
 111         int other_antenna;
 112
 113         int sample_current = rt2x00link_antenna_get_link_rssi(rt2x00dev);
 114         int sample_other = rt2x00link_antenna_get_rssi_history(rt2x00dev);
 115
 116         memcpy(&new_ant, &ant->active, sizeof(new_ant));
 117
 118         /*
 119          * We are done sampling. Now we should evaluate the results.
 120          */
 121         ant->flags &= ~ANTENNA_MODE_SAMPLE;
 122
 123         /*
 124          * During the last period we have sampled the RSSI
 125          * from both antennas. It now is time to determine
 126          * which antenna demonstrated the best performance.
 127          * When we are already on the antenna with the best
 128          * performance, just create a good starting point
 129          * for the history and we are done.
 130          */
 131         if (sample_current >= sample_other) {
 132                 rt2x00link_antenna_update_rssi_history(rt2x00dev,
 133                         sample_current);
 134                 return;
 135         }
 136
 137         other_antenna = (ant->active.rx == ANTENNA_A) ? ANTENNA_B : ANTENNA_A;
 138
 139         if (ant->flags & ANTENNA_RX_DIVERSITY)
 140                 new_ant.rx = other_antenna;
 141
 142         if (ant->flags & ANTENNA_TX_DIVERSITY)
 143                 new_ant.tx = other_antenna;
 144
 145         rt2x00lib_config_antenna(rt2x00dev, new_ant);
 146 }
 147
 148 static void rt2x00lib_antenna_diversity_eval(struct rt2x00_dev *rt2x00dev)
 149 {
 150         struct link_ant *ant = &rt2x00dev->link.ant;
 151         struct antenna_setup new_ant;
 152         int rssi_curr;
 153         int rssi_old;
 154
 155         memcpy(&new_ant, &ant->active, sizeof(new_ant));
 156
 157         /*
 158          * Get current RSSI value along with the historical value,
 159          * after that update the history with the current value.
 160          */
 161         rssi_curr = rt2x00link_antenna_get_link_rssi(rt2x00dev);
 162         rssi_old = rt2x00link_antenna_get_rssi_history(rt2x00dev);
 163         rt2x00link_antenna_update_rssi_history(rt2x00dev, rssi_curr);
 164
 165         /*
 166          * Legacy driver indicates that we should swap antenna's
 167          * when the difference in RSSI is greater that 5. This
 168          * also should be done when the RSSI was actually better
 169          * then the previous sample.
 170          * When the difference exceeds the threshold we should
 171          * sample the rssi from the other antenna to make a valid
 172          * comparison between the 2 antennas.
 173          */
 174         if (abs(rssi_curr - rssi_old) < 5)
 175                 return;
 176
 177         ant->flags |= ANTENNA_MODE_SAMPLE;
 178
 179         if (ant->flags & ANTENNA_RX_DIVERSITY)
 180                 new_ant.rx = (new_ant.rx == ANTENNA_A) ? ANTENNA_B : ANTENNA_A;
 181
 182         if (ant->flags & ANTENNA_TX_DIVERSITY)
 183                 new_ant.tx = (new_ant.tx == ANTENNA_A) ? ANTENNA_B : ANTENNA_A;
 184
 185         rt2x00lib_config_antenna(rt2x00dev, new_ant);
 186 }
 187
 188 static bool rt2x00lib_antenna_diversity(struct rt2x00_dev *rt2x00dev)
 189 {
 190         struct link_ant *ant = &rt2x00dev->link.ant;
 191         unsigned int flags = ant->flags;
 192
 193         /*
 194          * Determine if software diversity is enabled for
 195          * either the TX or RX antenna (or both).
 196          * Always perform this check since within the link
 197          * tuner interval the configuration might have changed.
 198          */
 199         flags &= ~ANTENNA_RX_DIVERSITY;
 200         flags &= ~ANTENNA_TX_DIVERSITY;
 201
 202         if (rt2x00dev->default_ant.rx == ANTENNA_SW_DIVERSITY)
 203                 flags |= ANTENNA_RX_DIVERSITY;
 204         if (rt2x00dev->default_ant.tx == ANTENNA_SW_DIVERSITY)
 205                 flags |= ANTENNA_TX_DIVERSITY;
 206
 207         if (!(ant->flags & ANTENNA_RX_DIVERSITY) &&
 208             !(ant->flags & ANTENNA_TX_DIVERSITY)) {
 209                 ant->flags = 0;
 210                 return true;
 211         }
 212
 213         /* Update flags */
 214         ant->flags = flags;
 215
 216         /*
 217          * If we have only sampled the data over the last period
 218          * we should now harvest the data. Otherwise just evaluate
 219          * the data. The latter should only be performed once
 220          * every 2 seconds.
 221          */
 222         if (ant->flags & ANTENNA_MODE_SAMPLE) {
 223                 rt2x00lib_antenna_diversity_sample(rt2x00dev);
 224                 return true;
 225         } else if (rt2x00dev->link.count & 1) {
 226                 rt2x00lib_antenna_diversity_eval(rt2x00dev);
 227                 return true;
 228         }
 229
 230         return false;
 231 }
 232
 233 void rt2x00link_update_stats(struct rt2x00_dev *rt2x00dev,
 234                              struct sk_buff *skb,
 235                              struct rxdone_entry_desc *rxdesc)
 236 {
 237         struct link *link = &rt2x00dev->link;
 238         struct link_qual *qual = &rt2x00dev->link.qual;
 239         struct link_ant *ant = &rt2x00dev->link.ant;
 240         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 241
 242         /*
 243          * Frame was received successfully since non-succesfull
 244          * frames would have been dropped by the hardware.
 245          */
 246         qual->rx_success++;
 247
 248         /*
 249          * We are only interested in quality statistics from
 250          * beacons which came from the BSS which we are
 251          * associated with.
 252          */
 253         if (!ieee80211_is_beacon(hdr->frame_control) ||
 254             !(rxdesc->dev_flags & RXDONE_MY_BSS))
 255                 return;
 256
 257         /*
 258          * Update global RSSI
 259          */
 260         link->avg_rssi = MOVING_AVERAGE(link->avg_rssi, rxdesc->rssi);
 261
 262         /*
 263          * Update antenna RSSI
 264          */
 265         ant->rssi_ant = MOVING_AVERAGE(ant->rssi_ant, rxdesc->rssi);
 266 }
 267
 268 void rt2x00link_start_tuner(struct rt2x00_dev *rt2x00dev)
 269 {
 270         struct link *link = &rt2x00dev->link;
 271
 272         /*
 273          * Link tuning should only be performed when
 274          * an active sta or master interface exists.
 275          * Single monitor mode interfaces should never have
 276          * work with link tuners.
 277          */
 278         if (!rt2x00dev->intf_ap_count && !rt2x00dev->intf_sta_count)
 279                 return;
 280
 281         rt2x00link_reset_tuner(rt2x00dev, false);
 282
 283         if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
 284                 ieee80211_queue_delayed_work(rt2x00dev->hw,
 285                                              &link->work, LINK_TUNE_INTERVAL);
 286 }
 287
 288 void rt2x00link_stop_tuner(struct rt2x00_dev *rt2x00dev)
 289 {
 290         cancel_delayed_work_sync(&rt2x00dev->link.work);
 291 }
 292
 293 void rt2x00link_reset_tuner(struct rt2x00_dev *rt2x00dev, bool antenna)
 294 {
 295         struct link_qual *qual = &rt2x00dev->link.qual;
 296
 297         if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
 298                 return;
 299
 300         /*
 301          * Reset link information.
 302          * Both the currently active vgc level as well as
 303          * the link tuner counter should be reset. Resetting
 304          * the counter is important for devices where the
 305          * device should only perform link tuning during the
 306          * first minute after being enabled.
 307          */
 308         rt2x00dev->link.count = 0;
 309         memset(qual, 0, sizeof(*qual));
 310
 311         /*
 312          * Reset the link tuner.
 313          */
 314         rt2x00dev->ops->lib->reset_tuner(rt2x00dev, qual);
 315
 316         if (antenna)
 317                 rt2x00link_antenna_reset(rt2x00dev);
 318 }
 319
 320 static void rt2x00link_reset_qual(struct rt2x00_dev *rt2x00dev)
 321 {
 322         struct link_qual *qual = &rt2x00dev->link.qual;
 323
 324         qual->rx_success = 0;
 325         qual->rx_failed = 0;
 326         qual->tx_success = 0;
 327         qual->tx_failed = 0;
 328 }
 329
 330 static void rt2x00link_tuner(struct work_struct *work)
 331 {
 332         struct rt2x00_dev *rt2x00dev =
 333             container_of(work, struct rt2x00_dev, link.work.work);
 334         struct link *link = &rt2x00dev->link;
 335         struct link_qual *qual = &rt2x00dev->link.qual;
 336
 337         /*
 338          * When the radio is shutting down we should
 339          * immediately cease all link tuning.
 340          */
 341         if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
 342                 return;
 343
 344         /*
 345          * Update statistics.
 346          */
 347         rt2x00dev->ops->lib->link_stats(rt2x00dev, qual);
 348         rt2x00dev->low_level_stats.dot11FCSErrorCount += qual->rx_failed;
 349
 350         /*
 351          * Update quality RSSI for link tuning,
 352          * when we have received some frames and we managed to
 353          * collect the RSSI data we could use this. Otherwise we
 354          * must fallback to the default RSSI value.
 355          */
 356         if (!link->avg_rssi.avg || !qual->rx_success)
 357                 qual->rssi = DEFAULT_RSSI;
 358         else
 359                 qual->rssi = link->avg_rssi.avg;
 360
 361         /*
 362          * Only perform the link tuning when Link tuning
 363          * has been enabled (This could have been disabled from the EEPROM).
 364          */
 365         if (!test_bit(CONFIG_DISABLE_LINK_TUNING, &rt2x00dev->flags))
 366                 rt2x00dev->ops->lib->link_tuner(rt2x00dev, qual, link->count);
 367
 368         /*
 369          * Send a signal to the led to update the led signal strength.
 370          */
 371         rt2x00leds_led_quality(rt2x00dev, qual->rssi);
 372
 373         /*
 374          * Evaluate antenna setup, make this the last step when
 375          * rt2x00lib_antenna_diversity made changes the quality
 376          * statistics will be reset.
 377          */
 378         if (rt2x00lib_antenna_diversity(rt2x00dev))
 379                 rt2x00link_reset_qual(rt2x00dev);
 380
 381         /*
 382          * Increase tuner counter, and reschedule the next link tuner run.
 383          */
 384         link->count++;
 385
 386         if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
 387                 ieee80211_queue_delayed_work(rt2x00dev->hw,
 388                                              &link->work, LINK_TUNE_INTERVAL);
 389 }
 390
 391 void rt2x00link_register(struct rt2x00_dev *rt2x00dev)
 392 {
 393         INIT_DELAYED_WORK(&rt2x00dev->link.work, rt2x00link_tuner);
 394 }