drivers/net/wireless/rt2x00/rt2x00link.c

   1 /*
   2         Copyright (C) 2004 - 2009 rt2x00 SourceForge Project
   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  * When no TX/RX percentage could be calculated due to lack of
  40  * frames on the air, we fallback to a percentage of 50%.
  41  * This will assure we will get at least get some decent value
  42  * when the link tuner starts.
  43  * The value will be dropped and overwritten with the correct (measured)
  44  * value anyway during the first run of the link tuner.
  45  */
  46 #define DEFAULT_PERCENTAGE      50
  47
  48 /*
  49  * Small helper macro for percentage calculation
  50  * This is a very simple macro with the only catch that it will
  51  * produce a default value in case no total value was provided.
  52  */
  53 #define PERCENTAGE(__value, __total) \
  54         ( (__total) ? (((__value) * 100) / (__total)) : (DEFAULT_PERCENTAGE) )
  55
  56 /*
  57  * Helper struct and macro to work with moving/walking averages.
  58  * When adding a value to the average value the following calculation
  59  * is needed:
  60  *
  61  *        avg_rssi = ((avg_rssi * 7) + rssi) / 8;
  62  *
  63  * The advantage of this approach is that we only need 1 variable
  64  * to store the average in (No need for a count and a total).
  65  * But more importantly, normal average values will over time
  66  * move less and less towards newly added values this results
  67  * that with link tuning, the device can have a very good RSSI
  68  * for a few minutes but when the device is moved away from the AP
  69  * the average will not decrease fast enough to compensate.
  70  * The walking average compensates this and will move towards
  71  * the new values correctly allowing a effective link tuning,
  72  * the speed of the average moving towards other values depends
  73  * on the value for the number of samples. The higher the number
  74  * of samples, the slower the average will move.
  75  * We use two variables to keep track of the average value to
  76  * compensate for the rounding errors. This can be a significant
  77  * error (>5dBm) if the factor is too low.
  78  */
  79 #define AVG_SAMPLES     8
  80 #define AVG_FACTOR      1000
  81 #define MOVING_AVERAGE(__avg, __val) \
  82 ({ \
  83         struct avg_val __new; \
  84         __new.avg_weight = \
  85             (__avg).avg_weight  ? \
  86                 ((((__avg).avg_weight * ((AVG_SAMPLES) - 1)) + \
  87                   ((__val) * (AVG_FACTOR))) / \
  88                  (AVG_SAMPLES) ) : \
  89                 ((__val) * (AVG_FACTOR)); \
  90         __new.avg = __new.avg_weight / (AVG_FACTOR); \
  91         __new; \
  92 })
  93
  94 /*
  95  * For calculating the Signal quality we have determined
  96  * the total number of success and failed RX and TX frames.
  97  * With the addition of the average RSSI value we can determine
  98  * the link quality using the following algorithm:
  99  *
 100  *         rssi_percentage = (avg_rssi * 100) / rssi_offset
 101  *         rx_percentage = (rx_success * 100) / rx_total
 102  *         tx_percentage = (tx_success * 100) / tx_total
 103  *         avg_signal = ((WEIGHT_RSSI * avg_rssi) +
 104  *                       (WEIGHT_TX * tx_percentage) +
 105  *                       (WEIGHT_RX * rx_percentage)) / 100
 106  *
 107  * This value should then be checked to not be greater then 100.
 108  * This means the values of WEIGHT_RSSI, WEIGHT_RX, WEIGHT_TX must
 109  * sum up to 100 as well.
 110  */
 111 #define WEIGHT_RSSI     20
 112 #define WEIGHT_RX       40
 113 #define WEIGHT_TX       40
 114
 115 static int rt2x00link_antenna_get_link_rssi(struct rt2x00_dev *rt2x00dev)
 116 {
 117         struct link_ant *ant = &rt2x00dev->link.ant;
 118
 119         if (ant->rssi_ant.avg && rt2x00dev->link.qual.rx_success)
 120                 return ant->rssi_ant.avg;
 121         return DEFAULT_RSSI;
 122 }
 123
 124 static int rt2x00link_antenna_get_rssi_history(struct rt2x00_dev *rt2x00dev)
 125 {
 126         struct link_ant *ant = &rt2x00dev->link.ant;
 127
 128         if (ant->rssi_history)
 129                 return ant->rssi_history;
 130         return DEFAULT_RSSI;
 131 }
 132
 133 static void rt2x00link_antenna_update_rssi_history(struct rt2x00_dev *rt2x00dev,
 134                                                    int rssi)
 135 {
 136         struct link_ant *ant = &rt2x00dev->link.ant;
 137         ant->rssi_history = rssi;
 138 }
 139
 140 static void rt2x00link_antenna_reset(struct rt2x00_dev *rt2x00dev)
 141 {
 142         rt2x00dev->link.ant.rssi_ant.avg = 0;
 143         rt2x00dev->link.ant.rssi_ant.avg_weight = 0;
 144 }
 145
 146 static void rt2x00lib_antenna_diversity_sample(struct rt2x00_dev *rt2x00dev)
 147 {
 148         struct link_ant *ant = &rt2x00dev->link.ant;
 149         struct antenna_setup new_ant;
 150         int other_antenna;
 151
 152         int sample_current = rt2x00link_antenna_get_link_rssi(rt2x00dev);
 153         int sample_other = rt2x00link_antenna_get_rssi_history(rt2x00dev);
 154
 155         memcpy(&new_ant, &ant->active, sizeof(new_ant));
 156
 157         /*
 158          * We are done sampling. Now we should evaluate the results.
 159          */
 160         ant->flags &= ~ANTENNA_MODE_SAMPLE;
 161
 162         /*
 163          * During the last period we have sampled the RSSI
 164          * from both antennas. It now is time to determine
 165          * which antenna demonstrated the best performance.
 166          * When we are already on the antenna with the best
 167          * performance, just create a good starting point
 168          * for the history and we are done.
 169          */
 170         if (sample_current >= sample_other) {
 171                 rt2x00link_antenna_update_rssi_history(rt2x00dev,
 172                         sample_current);
 173                 return;
 174         }
 175
 176         other_antenna = (ant->active.rx == ANTENNA_A) ? ANTENNA_B : ANTENNA_A;
 177
 178         if (ant->flags & ANTENNA_RX_DIVERSITY)
 179                 new_ant.rx = other_antenna;
 180
 181         if (ant->flags & ANTENNA_TX_DIVERSITY)
 182                 new_ant.tx = other_antenna;
 183
 184         rt2x00lib_config_antenna(rt2x00dev, new_ant);
 185 }
 186
 187 static void rt2x00lib_antenna_diversity_eval(struct rt2x00_dev *rt2x00dev)
 188 {
 189         struct link_ant *ant = &rt2x00dev->link.ant;
 190         struct antenna_setup new_ant;
 191         int rssi_curr;
 192         int rssi_old;
 193
 194         memcpy(&new_ant, &ant->active, sizeof(new_ant));
 195
 196         /*
 197          * Get current RSSI value along with the historical value,
 198          * after that update the history with the current value.
 199          */
 200         rssi_curr = rt2x00link_antenna_get_link_rssi(rt2x00dev);
 201         rssi_old = rt2x00link_antenna_get_rssi_history(rt2x00dev);
 202         rt2x00link_antenna_update_rssi_history(rt2x00dev, rssi_curr);
 203
 204         /*
 205          * Legacy driver indicates that we should swap antenna's
 206          * when the difference in RSSI is greater that 5. This
 207          * also should be done when the RSSI was actually better
 208          * then the previous sample.
 209          * When the difference exceeds the threshold we should
 210          * sample the rssi from the other antenna to make a valid
 211          * comparison between the 2 antennas.
 212          */
 213         if (abs(rssi_curr - rssi_old) < 5)
 214                 return;
 215
 216         ant->flags |= ANTENNA_MODE_SAMPLE;
 217
 218         if (ant->flags & ANTENNA_RX_DIVERSITY)
 219                 new_ant.rx = (new_ant.rx == ANTENNA_A) ? ANTENNA_B : ANTENNA_A;
 220
 221         if (ant->flags & ANTENNA_TX_DIVERSITY)
 222                 new_ant.tx = (new_ant.tx == ANTENNA_A) ? ANTENNA_B : ANTENNA_A;
 223
 224         rt2x00lib_config_antenna(rt2x00dev, new_ant);
 225 }
 226
 227 static bool rt2x00lib_antenna_diversity(struct rt2x00_dev *rt2x00dev)
 228 {
 229         struct link_ant *ant = &rt2x00dev->link.ant;
 230         unsigned int flags = ant->flags;
 231
 232         /*
 233          * Determine if software diversity is enabled for
 234          * either the TX or RX antenna (or both).
 235          * Always perform this check since within the link
 236          * tuner interval the configuration might have changed.
 237          */
 238         flags &= ~ANTENNA_RX_DIVERSITY;
 239         flags &= ~ANTENNA_TX_DIVERSITY;
 240
 241         if (rt2x00dev->default_ant.rx == ANTENNA_SW_DIVERSITY)
 242                 flags |= ANTENNA_RX_DIVERSITY;
 243         if (rt2x00dev->default_ant.tx == ANTENNA_SW_DIVERSITY)
 244                 flags |= ANTENNA_TX_DIVERSITY;
 245
 246         if (!(ant->flags & ANTENNA_RX_DIVERSITY) &&
 247             !(ant->flags & ANTENNA_TX_DIVERSITY)) {
 248                 ant->flags = 0;
 249                 return true;
 250         }
 251
 252         /* Update flags */
 253         ant->flags = flags;
 254
 255         /*
 256          * If we have only sampled the data over the last period
 257          * we should now harvest the data. Otherwise just evaluate
 258          * the data. The latter should only be performed once
 259          * every 2 seconds.
 260          */
 261         if (ant->flags & ANTENNA_MODE_SAMPLE) {
 262                 rt2x00lib_antenna_diversity_sample(rt2x00dev);
 263                 return true;
 264         } else if (rt2x00dev->link.count & 1) {
 265                 rt2x00lib_antenna_diversity_eval(rt2x00dev);
 266                 return true;
 267         }
 268
 269         return false;
 270 }
 271
 272 void rt2x00link_update_stats(struct rt2x00_dev *rt2x00dev,
 273                              struct sk_buff *skb,
 274                              struct rxdone_entry_desc *rxdesc)
 275 {
 276         struct link *link = &rt2x00dev->link;
 277         struct link_qual *qual = &rt2x00dev->link.qual;
 278         struct link_ant *ant = &rt2x00dev->link.ant;
 279         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 280
 281         /*
 282          * Frame was received successfully since non-succesfull
 283          * frames would have been dropped by the hardware.
 284          */
 285         qual->rx_success++;
 286
 287         /*
 288          * We are only interested in quality statistics from
 289          * beacons which came from the BSS which we are
 290          * associated with.
 291          */
 292         if (!ieee80211_is_beacon(hdr->frame_control) ||
 293             !(rxdesc->dev_flags & RXDONE_MY_BSS))
 294                 return;
 295
 296         /*
 297          * Update global RSSI
 298          */
 299         link->avg_rssi = MOVING_AVERAGE(link->avg_rssi, rxdesc->rssi);
 300
 301         /*
 302          * Update antenna RSSI
 303          */
 304         ant->rssi_ant = MOVING_AVERAGE(ant->rssi_ant, rxdesc->rssi);
 305 }
 306
 307 static void rt2x00link_precalculate_signal(struct rt2x00_dev *rt2x00dev)
 308 {
 309         struct link *link = &rt2x00dev->link;
 310         struct link_qual *qual = &rt2x00dev->link.qual;
 311
 312         link->rx_percentage =
 313             PERCENTAGE(qual->rx_success, qual->rx_failed + qual->rx_success);
 314         link->tx_percentage =
 315             PERCENTAGE(qual->tx_success, qual->tx_failed + qual->tx_success);
 316 }
 317
 318 int rt2x00link_calculate_signal(struct rt2x00_dev *rt2x00dev, int rssi)
 319 {
 320         struct link *link = &rt2x00dev->link;
 321         int rssi_percentage = 0;
 322         int signal;
 323
 324         /*
 325          * We need a positive value for the RSSI.
 326          */
 327         if (rssi < 0)
 328                 rssi += rt2x00dev->rssi_offset;
 329
 330         /*
 331          * Calculate the different percentages,
 332          * which will be used for the signal.
 333          */
 334         rssi_percentage = PERCENTAGE(rssi, rt2x00dev->rssi_offset);
 335
 336         /*
 337          * Add the individual percentages and use the WEIGHT
 338          * defines to calculate the current link signal.
 339          */
 340         signal = ((WEIGHT_RSSI * rssi_percentage) +
 341                   (WEIGHT_TX * link->tx_percentage) +
 342                   (WEIGHT_RX * link->rx_percentage)) / 100;
 343
 344         return max_t(int, signal, 100);
 345 }
 346
 347 void rt2x00link_start_tuner(struct rt2x00_dev *rt2x00dev)
 348 {
 349         struct link *link = &rt2x00dev->link;
 350
 351         /*
 352          * Link tuning should only be performed when
 353          * an active sta or master interface exists.
 354          * Single monitor mode interfaces should never have
 355          * work with link tuners.
 356          */
 357         if (!rt2x00dev->intf_ap_count && !rt2x00dev->intf_sta_count)
 358                 return;
 359
 360         link->rx_percentage = DEFAULT_PERCENTAGE;
 361         link->tx_percentage = DEFAULT_PERCENTAGE;
 362
 363         rt2x00link_reset_tuner(rt2x00dev, false);
 364
 365         if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
 366                 ieee80211_queue_delayed_work(rt2x00dev->hw,
 367                                              &link->work, LINK_TUNE_INTERVAL);
 368 }
 369
 370 void rt2x00link_stop_tuner(struct rt2x00_dev *rt2x00dev)
 371 {
 372         cancel_delayed_work_sync(&rt2x00dev->link.work);
 373 }
 374
 375 void rt2x00link_reset_tuner(struct rt2x00_dev *rt2x00dev, bool antenna)
 376 {
 377         struct link_qual *qual = &rt2x00dev->link.qual;
 378
 379         if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
 380                 return;
 381
 382         /*
 383          * Reset link information.
 384          * Both the currently active vgc level as well as
 385          * the link tuner counter should be reset. Resetting
 386          * the counter is important for devices where the
 387          * device should only perform link tuning during the
 388          * first minute after being enabled.
 389          */
 390         rt2x00dev->link.count = 0;
 391         memset(qual, 0, sizeof(*qual));
 392
 393         /*
 394          * Reset the link tuner.
 395          */
 396         rt2x00dev->ops->lib->reset_tuner(rt2x00dev, qual);
 397
 398         if (antenna)
 399                 rt2x00link_antenna_reset(rt2x00dev);
 400 }
 401
 402 static void rt2x00link_reset_qual(struct rt2x00_dev *rt2x00dev)
 403 {
 404         struct link_qual *qual = &rt2x00dev->link.qual;
 405
 406         qual->rx_success = 0;
 407         qual->rx_failed = 0;
 408         qual->tx_success = 0;
 409         qual->tx_failed = 0;
 410 }
 411
 412 static void rt2x00link_tuner(struct work_struct *work)
 413 {
 414         struct rt2x00_dev *rt2x00dev =
 415             container_of(work, struct rt2x00_dev, link.work.work);
 416         struct link *link = &rt2x00dev->link;
 417         struct link_qual *qual = &rt2x00dev->link.qual;
 418
 419         /*
 420          * When the radio is shutting down we should
 421          * immediately cease all link tuning.
 422          */
 423         if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
 424                 return;
 425
 426         /*
 427          * Update statistics.
 428          */
 429         rt2x00dev->ops->lib->link_stats(rt2x00dev, qual);
 430         rt2x00dev->low_level_stats.dot11FCSErrorCount += qual->rx_failed;
 431
 432         /*
 433          * Update quality RSSI for link tuning,
 434          * when we have received some frames and we managed to
 435          * collect the RSSI data we could use this. Otherwise we
 436          * must fallback to the default RSSI value.
 437          */
 438         if (!link->avg_rssi.avg || !qual->rx_success)
 439                 qual->rssi = DEFAULT_RSSI;
 440         else
 441                 qual->rssi = link->avg_rssi.avg;
 442
 443         /*
 444          * Only perform the link tuning when Link tuning
 445          * has been enabled (This could have been disabled from the EEPROM).
 446          */
 447         if (!test_bit(CONFIG_DISABLE_LINK_TUNING, &rt2x00dev->flags))
 448                 rt2x00dev->ops->lib->link_tuner(rt2x00dev, qual, link->count);
 449
 450         /*
 451          * Precalculate a portion of the link signal which is
 452          * in based on the tx/rx success/failure counters.
 453          */
 454         rt2x00link_precalculate_signal(rt2x00dev);
 455
 456         /*
 457          * Send a signal to the led to update the led signal strength.
 458          */
 459         rt2x00leds_led_quality(rt2x00dev, qual->rssi);
 460
 461         /*
 462          * Evaluate antenna setup, make this the last step when
 463          * rt2x00lib_antenna_diversity made changes the quality
 464          * statistics will be reset.
 465          */
 466         if (rt2x00lib_antenna_diversity(rt2x00dev))
 467                 rt2x00link_reset_qual(rt2x00dev);
 468
 469         /*
 470          * Increase tuner counter, and reschedule the next link tuner run.
 471          */
 472         link->count++;
 473
 474         if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
 475                 ieee80211_queue_delayed_work(rt2x00dev->hw,
 476                                              &link->work, LINK_TUNE_INTERVAL);
 477 }
 478
 479 void rt2x00link_register(struct rt2x00_dev *rt2x00dev)
 480 {
 481         INIT_DELAYED_WORK(&rt2x00dev->link.work, rt2x00link_tuner);
 482 }