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 to work with moving/walking averages.
  50  * When adding a value to the average value the following calculation
  51  * is needed:
  52  *
  53  *        avg_rssi = ((avg_rssi * 7) + rssi) / 8;
  54  *
  55  * The advantage of this approach is that we only need 1 variable
  56  * to store the average in (No need for a count and a total).
  57  * But more importantly, normal average values will over time
  58  * move less and less towards newly added values this results
  59  * that with link tuning, the device can have a very good RSSI
  60  * for a few minutes but when the device is moved away from the AP
  61  * the average will not decrease fast enough to compensate.
  62  * The walking average compensates this and will move towards
  63  * the new values correctly allowing a effective link tuning.
  64  */
  65 #define MOVING_AVERAGE(__avg, __val, __samples) \
  66         ( (((__avg) * ((__samples) - 1)) + (__val)) / (__samples) )
  67
  68 /*
  69  * Small helper macro for percentage calculation
  70  * This is a very simple macro with the only catch that it will
  71  * produce a default value in case no total value was provided.
  72  */
  73 #define PERCENTAGE(__value, __total) \
  74         ( (__total) ? (((__value) * 100) / (__total)) : (DEFAULT_PERCENTAGE) )
  75
  76 /*
  77  * For calculating the Signal quality we have determined
  78  * the total number of success and failed RX and TX frames.
  79  * With the addition of the average RSSI value we can determine
  80  * the link quality using the following algorithm:
  81  *
  82  *         rssi_percentage = (avg_rssi * 100) / rssi_offset
  83  *         rx_percentage = (rx_success * 100) / rx_total
  84  *         tx_percentage = (tx_success * 100) / tx_total
  85  *         avg_signal = ((WEIGHT_RSSI * avg_rssi) +
  86  *                       (WEIGHT_TX * tx_percentage) +
  87  *                       (WEIGHT_RX * rx_percentage)) / 100
  88  *
  89  * This value should then be checked to not be greater then 100.
  90  * This means the values of WEIGHT_RSSI, WEIGHT_RX, WEIGHT_TX must
  91  * sum up to 100 as well.
  92  */
  93 #define WEIGHT_RSSI     20
  94 #define WEIGHT_RX       40
  95 #define WEIGHT_TX       40
  96
  97 static int rt2x00link_antenna_get_link_rssi(struct rt2x00_dev *rt2x00dev)
  98 {
  99         struct link_ant *ant = &rt2x00dev->link.ant;
 100
 101         if (ant->rssi_ant && rt2x00dev->link.qual.rx_success)
 102                 return ant->rssi_ant;
 103         return DEFAULT_RSSI;
 104 }
 105
 106 static int rt2x00link_antenna_get_rssi_history(struct rt2x00_dev *rt2x00dev,
 107                                                enum antenna antenna)
 108 {
 109         struct link_ant *ant = &rt2x00dev->link.ant;
 110
 111         if (ant->rssi_history[antenna - ANTENNA_A])
 112                 return ant->rssi_history[antenna - ANTENNA_A];
 113         return DEFAULT_RSSI;
 114 }
 115 /* Small wrapper for rt2x00link_antenna_get_rssi_history() */
 116 #define rt2x00link_antenna_get_rssi_rx_history(__dev) \
 117         rt2x00link_antenna_get_rssi_history((__dev), \
 118                                             (__dev)->link.ant.active.rx)
 119 #define rt2x00link_antenna_get_rssi_tx_history(__dev) \
 120         rt2x00link_antenna_get_rssi_history((__dev), \
 121                                             (__dev)->link.ant.active.tx)
 122
 123 static void rt2x00link_antenna_update_rssi_history(struct rt2x00_dev *rt2x00dev,
 124                                                    enum antenna antenna,
 125                                                    int rssi)
 126 {
 127         struct link_ant *ant = &rt2x00dev->link.ant;
 128         ant->rssi_history[ant->active.rx - ANTENNA_A] = rssi;
 129 }
 130 /* Small wrapper for rt2x00link_antenna_get_rssi_history() */
 131 #define rt2x00link_antenna_update_rssi_rx_history(__dev, __rssi) \
 132         rt2x00link_antenna_update_rssi_history((__dev), \
 133                                                (__dev)->link.ant.active.rx, \
 134                                                (__rssi))
 135 #define rt2x00link_antenna_update_rssi_tx_history(__dev, __rssi) \
 136         rt2x00link_antenna_update_rssi_history((__dev), \
 137                                                (__dev)->link.ant.active.tx, \
 138                                                (__rssi))
 139
 140 static void rt2x00link_antenna_reset(struct rt2x00_dev *rt2x00dev)
 141 {
 142         rt2x00dev->link.ant.rssi_ant = 0;
 143 }
 144
 145 static void rt2x00lib_antenna_diversity_sample(struct rt2x00_dev *rt2x00dev)
 146 {
 147         struct link_ant *ant = &rt2x00dev->link.ant;
 148         struct antenna_setup new_ant;
 149         int sample_a = rt2x00link_antenna_get_rssi_history(rt2x00dev, ANTENNA_A);
 150         int sample_b = rt2x00link_antenna_get_rssi_history(rt2x00dev, ANTENNA_B);
 151
 152         memcpy(&new_ant, &ant->active, sizeof(new_ant));
 153
 154         /*
 155          * We are done sampling. Now we should evaluate the results.
 156          */
 157         ant->flags &= ~ANTENNA_MODE_SAMPLE;
 158
 159         /*
 160          * During the last period we have sampled the RSSI
 161          * from both antennas. It now is time to determine
 162          * which antenna demonstrated the best performance.
 163          * When we are already on the antenna with the best
 164          * performance, then there really is nothing for us
 165          * left to do.
 166          */
 167         if (sample_a == sample_b)
 168                 return;
 169
 170         if (ant->flags & ANTENNA_RX_DIVERSITY)
 171                 new_ant.rx = (sample_a > sample_b) ? ANTENNA_A : ANTENNA_B;
 172
 173         if (ant->flags & ANTENNA_TX_DIVERSITY)
 174                 new_ant.tx = (sample_a > sample_b) ? ANTENNA_A : ANTENNA_B;
 175
 176         rt2x00lib_config_antenna(rt2x00dev, new_ant);
 177 }
 178
 179 static void rt2x00lib_antenna_diversity_eval(struct rt2x00_dev *rt2x00dev)
 180 {
 181         struct link_ant *ant = &rt2x00dev->link.ant;
 182         struct antenna_setup new_ant;
 183         int rssi_curr;
 184         int rssi_old;
 185
 186         memcpy(&new_ant, &ant->active, sizeof(new_ant));
 187
 188         /*
 189          * Get current RSSI value along with the historical value,
 190          * after that update the history with the current value.
 191          */
 192         rssi_curr = rt2x00link_antenna_get_link_rssi(rt2x00dev);
 193         rssi_old = rt2x00link_antenna_get_rssi_rx_history(rt2x00dev);
 194         rt2x00link_antenna_update_rssi_rx_history(rt2x00dev, rssi_curr);
 195
 196         /*
 197          * Legacy driver indicates that we should swap antenna's
 198          * when the difference in RSSI is greater that 5. This
 199          * also should be done when the RSSI was actually better
 200          * then the previous sample.
 201          * When the difference exceeds the threshold we should
 202          * sample the rssi from the other antenna to make a valid
 203          * comparison between the 2 antennas.
 204          */
 205         if (abs(rssi_curr - rssi_old) < 5)
 206                 return;
 207
 208         ant->flags |= ANTENNA_MODE_SAMPLE;
 209
 210         if (ant->flags & ANTENNA_RX_DIVERSITY)
 211                 new_ant.rx = (new_ant.rx == ANTENNA_A) ? ANTENNA_B : ANTENNA_A;
 212
 213         if (ant->flags & ANTENNA_TX_DIVERSITY)
 214                 new_ant.tx = (new_ant.tx == ANTENNA_A) ? ANTENNA_B : ANTENNA_A;
 215
 216         rt2x00lib_config_antenna(rt2x00dev, new_ant);
 217 }
 218
 219 static void rt2x00lib_antenna_diversity(struct rt2x00_dev *rt2x00dev)
 220 {
 221         struct link_ant *ant = &rt2x00dev->link.ant;
 222
 223         /*
 224          * Determine if software diversity is enabled for
 225          * either the TX or RX antenna (or both).
 226          * Always perform this check since within the link
 227          * tuner interval the configuration might have changed.
 228          */
 229         ant->flags &= ~ANTENNA_RX_DIVERSITY;
 230         ant->flags &= ~ANTENNA_TX_DIVERSITY;
 231
 232         if (rt2x00dev->default_ant.rx == ANTENNA_SW_DIVERSITY)
 233                 ant->flags |= ANTENNA_RX_DIVERSITY;
 234         if (rt2x00dev->default_ant.tx == ANTENNA_SW_DIVERSITY)
 235                 ant->flags |= ANTENNA_TX_DIVERSITY;
 236
 237         if (!(ant->flags & ANTENNA_RX_DIVERSITY) &&
 238             !(ant->flags & ANTENNA_TX_DIVERSITY)) {
 239                 ant->flags = 0;
 240                 return;
 241         }
 242
 243         /*
 244          * If we have only sampled the data over the last period
 245          * we should now harvest the data. Otherwise just evaluate
 246          * the data. The latter should only be performed once
 247          * every 2 seconds.
 248          */
 249         if (ant->flags & ANTENNA_MODE_SAMPLE)
 250                 rt2x00lib_antenna_diversity_sample(rt2x00dev);
 251         else if (rt2x00dev->link.count & 1)
 252                 rt2x00lib_antenna_diversity_eval(rt2x00dev);
 253 }
 254
 255 void rt2x00link_update_stats(struct rt2x00_dev *rt2x00dev,
 256                              struct sk_buff *skb,
 257                              struct rxdone_entry_desc *rxdesc)
 258 {
 259         struct link *link = &rt2x00dev->link;
 260         struct link_qual *qual = &rt2x00dev->link.qual;
 261         struct link_ant *ant = &rt2x00dev->link.ant;
 262         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 263         int avg_rssi = rxdesc->rssi;
 264         int ant_rssi = rxdesc->rssi;
 265
 266         /*
 267          * Frame was received successfully since non-succesfull
 268          * frames would have been dropped by the hardware.
 269          */
 270         qual->rx_success++;
 271
 272         /*
 273          * We are only interested in quality statistics from
 274          * beacons which came from the BSS which we are
 275          * associated with.
 276          */
 277         if (!ieee80211_is_beacon(hdr->frame_control) ||
 278             !(rxdesc->dev_flags & RXDONE_MY_BSS))
 279                 return;
 280
 281         /*
 282          * Update global RSSI
 283          */
 284         if (link->avg_rssi)
 285                 avg_rssi = MOVING_AVERAGE(link->avg_rssi, rxdesc->rssi, 8);
 286         link->avg_rssi = avg_rssi;
 287
 288         /*
 289          * Update antenna RSSI
 290          */
 291         if (ant->rssi_ant)
 292                 ant_rssi = MOVING_AVERAGE(ant->rssi_ant, rxdesc->rssi, 8);
 293         ant->rssi_ant = ant_rssi;
 294 }
 295
 296 static void rt2x00link_precalculate_signal(struct rt2x00_dev *rt2x00dev)
 297 {
 298         struct link *link = &rt2x00dev->link;
 299         struct link_qual *qual = &rt2x00dev->link.qual;
 300
 301         link->rx_percentage =
 302             PERCENTAGE(qual->rx_success, qual->rx_failed + qual->rx_success);
 303         link->tx_percentage =
 304             PERCENTAGE(qual->tx_success, qual->tx_failed + qual->tx_success);
 305 }
 306
 307 int rt2x00link_calculate_signal(struct rt2x00_dev *rt2x00dev, int rssi)
 308 {
 309         struct link *link = &rt2x00dev->link;
 310         int rssi_percentage = 0;
 311         int signal;
 312
 313         /*
 314          * We need a positive value for the RSSI.
 315          */
 316         if (rssi < 0)
 317                 rssi += rt2x00dev->rssi_offset;
 318
 319         /*
 320          * Calculate the different percentages,
 321          * which will be used for the signal.
 322          */
 323         rssi_percentage = PERCENTAGE(rssi, rt2x00dev->rssi_offset);
 324
 325         /*
 326          * Add the individual percentages and use the WEIGHT
 327          * defines to calculate the current link signal.
 328          */
 329         signal = ((WEIGHT_RSSI * rssi_percentage) +
 330                   (WEIGHT_TX * link->tx_percentage) +
 331                   (WEIGHT_RX * link->rx_percentage)) / 100;
 332
 333         return max_t(int, signal, 100);
 334 }
 335
 336 void rt2x00link_start_tuner(struct rt2x00_dev *rt2x00dev)
 337 {
 338         struct link *link = &rt2x00dev->link;
 339
 340         /*
 341          * Link tuning should only be performed when
 342          * an active sta or master interface exists.
 343          * Single monitor mode interfaces should never have
 344          * work with link tuners.
 345          */
 346         if (!rt2x00dev->intf_ap_count && !rt2x00dev->intf_sta_count)
 347                 return;
 348
 349         link->rx_percentage = DEFAULT_PERCENTAGE;
 350         link->tx_percentage = DEFAULT_PERCENTAGE;
 351
 352         rt2x00link_reset_tuner(rt2x00dev, false);
 353
 354         ieee80211_queue_delayed_work(rt2x00dev->hw,
 355                                      &link->work, LINK_TUNE_INTERVAL);
 356 }
 357
 358 void rt2x00link_stop_tuner(struct rt2x00_dev *rt2x00dev)
 359 {
 360         cancel_delayed_work_sync(&rt2x00dev->link.work);
 361 }
 362
 363 void rt2x00link_reset_tuner(struct rt2x00_dev *rt2x00dev, bool antenna)
 364 {
 365         struct link_qual *qual = &rt2x00dev->link.qual;
 366
 367         if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
 368                 return;
 369
 370         /*
 371          * Reset link information.
 372          * Both the currently active vgc level as well as
 373          * the link tuner counter should be reset. Resetting
 374          * the counter is important for devices where the
 375          * device should only perform link tuning during the
 376          * first minute after being enabled.
 377          */
 378         rt2x00dev->link.count = 0;
 379         memset(qual, 0, sizeof(*qual));
 380
 381         /*
 382          * Reset the link tuner.
 383          */
 384         rt2x00dev->ops->lib->reset_tuner(rt2x00dev, qual);
 385
 386         if (antenna)
 387                 rt2x00link_antenna_reset(rt2x00dev);
 388 }
 389
 390 static void rt2x00link_reset_qual(struct rt2x00_dev *rt2x00dev)
 391 {
 392         struct link_qual *qual = &rt2x00dev->link.qual;
 393
 394         qual->rx_success = 0;
 395         qual->rx_failed = 0;
 396         qual->tx_success = 0;
 397         qual->tx_failed = 0;
 398 }
 399
 400 static void rt2x00link_tuner(struct work_struct *work)
 401 {
 402         struct rt2x00_dev *rt2x00dev =
 403             container_of(work, struct rt2x00_dev, link.work.work);
 404         struct link *link = &rt2x00dev->link;
 405         struct link_qual *qual = &rt2x00dev->link.qual;
 406
 407         /*
 408          * When the radio is shutting down we should
 409          * immediately cease all link tuning.
 410          */
 411         if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
 412                 return;
 413
 414         /*
 415          * Update statistics.
 416          */
 417         rt2x00dev->ops->lib->link_stats(rt2x00dev, qual);
 418         rt2x00dev->low_level_stats.dot11FCSErrorCount += qual->rx_failed;
 419
 420         /*
 421          * Update quality RSSI for link tuning,
 422          * when we have received some frames and we managed to
 423          * collect the RSSI data we could use this. Otherwise we
 424          * must fallback to the default RSSI value.
 425          */
 426         if (!link->avg_rssi || !qual->rx_success)
 427                 qual->rssi = DEFAULT_RSSI;
 428         else
 429                 qual->rssi = link->avg_rssi;
 430
 431         /*
 432          * Only perform the link tuning when Link tuning
 433          * has been enabled (This could have been disabled from the EEPROM).
 434          */
 435         if (!test_bit(CONFIG_DISABLE_LINK_TUNING, &rt2x00dev->flags))
 436                 rt2x00dev->ops->lib->link_tuner(rt2x00dev, qual, link->count);
 437
 438         /*
 439          * Precalculate a portion of the link signal which is
 440          * in based on the tx/rx success/failure counters.
 441          */
 442         rt2x00link_precalculate_signal(rt2x00dev);
 443
 444         /*
 445          * Send a signal to the led to update the led signal strength.
 446          */
 447         rt2x00leds_led_quality(rt2x00dev, link->avg_rssi);
 448
 449         /*
 450          * Evaluate antenna setup, make this the last step since this could
 451          * possibly reset some statistics.
 452          */
 453         rt2x00lib_antenna_diversity(rt2x00dev);
 454
 455         /*
 456          * Reset the quality counters which recounted during each period.
 457          */
 458         rt2x00link_reset_qual(rt2x00dev);
 459
 460         /*
 461          * Increase tuner counter, and reschedule the next link tuner run.
 462          */
 463         link->count++;
 464         ieee80211_queue_delayed_work(rt2x00dev->hw,
 465                                      &link->work, LINK_TUNE_INTERVAL);
 466 }
 467
 468 void rt2x00link_register(struct rt2x00_dev *rt2x00dev)
 469 {
 470         INIT_DELAYED_WORK(&rt2x00dev->link.work, rt2x00link_tuner);
 471 }