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
 192         /*
 193          * Determine if software diversity is enabled for
 194          * either the TX or RX antenna (or both).
 195          * Always perform this check since within the link
 196          * tuner interval the configuration might have changed.
 197          */
 198         ant->flags &= ~ANTENNA_RX_DIVERSITY;
 199         ant->flags &= ~ANTENNA_TX_DIVERSITY;
 200
 201         if (rt2x00dev->default_ant.rx == ANTENNA_SW_DIVERSITY)
 202                 ant->flags |= ANTENNA_RX_DIVERSITY;
 203         if (rt2x00dev->default_ant.tx == ANTENNA_SW_DIVERSITY)
 204                 ant->flags |= ANTENNA_TX_DIVERSITY;
 205
 206         if (!(ant->flags & ANTENNA_RX_DIVERSITY) &&
 207             !(ant->flags & ANTENNA_TX_DIVERSITY)) {
 208                 ant->flags = 0;
 209                 return true;
 210         }
 211
 212         /*
 213          * If we have only sampled the data over the last period
 214          * we should now harvest the data. Otherwise just evaluate
 215          * the data. The latter should only be performed once
 216          * every 2 seconds.
 217          */
 218         if (ant->flags & ANTENNA_MODE_SAMPLE) {
 219                 rt2x00lib_antenna_diversity_sample(rt2x00dev);
 220                 return true;
 221         } else if (rt2x00dev->link.count & 1) {
 222                 rt2x00lib_antenna_diversity_eval(rt2x00dev);
 223                 return true;
 224         }
 225
 226         return false;
 227 }
 228
 229 void rt2x00link_update_stats(struct rt2x00_dev *rt2x00dev,
 230                              struct sk_buff *skb,
 231                              struct rxdone_entry_desc *rxdesc)
 232 {
 233         struct link *link = &rt2x00dev->link;
 234         struct link_qual *qual = &rt2x00dev->link.qual;
 235         struct link_ant *ant = &rt2x00dev->link.ant;
 236         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 237
 238         /*
 239          * No need to update the stats for !=STA interfaces
 240          */
 241         if (!rt2x00dev->intf_sta_count)
 242                 return;
 243
 244         /*
 245          * Frame was received successfully since non-succesfull
 246          * frames would have been dropped by the hardware.
 247          */
 248         qual->rx_success++;
 249
 250         /*
 251          * We are only interested in quality statistics from
 252          * beacons which came from the BSS which we are
 253          * associated with.
 254          */
 255         if (!ieee80211_is_beacon(hdr->frame_control) ||
 256             !(rxdesc->dev_flags & RXDONE_MY_BSS))
 257                 return;
 258
 259         /*
 260          * Update global RSSI
 261          */
 262         link->avg_rssi = MOVING_AVERAGE(link->avg_rssi, rxdesc->rssi);
 263
 264         /*
 265          * Update antenna RSSI
 266          */
 267         ant->rssi_ant = MOVING_AVERAGE(ant->rssi_ant, rxdesc->rssi);
 268 }
 269
 270 void rt2x00link_start_tuner(struct rt2x00_dev *rt2x00dev)
 271 {
 272         struct link *link = &rt2x00dev->link;
 273
 274         /*
 275          * Link tuning should only be performed when
 276          * an active sta interface exists. AP interfaces
 277          * don't need link tuning and monitor mode interfaces
 278          * should never have to work with link tuners.
 279          */
 280         if (!rt2x00dev->intf_sta_count)
 281                 return;
 282
 283         /**
 284          * While scanning, link tuning is disabled. By default
 285          * the most sensitive settings will be used to make sure
 286          * that all beacons and probe responses will be received
 287          * during the scan.
 288          */
 289         if (test_bit(DEVICE_STATE_SCANNING, &rt2x00dev->flags))
 290                 return;
 291
 292         rt2x00link_reset_tuner(rt2x00dev, false);
 293
 294         if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
 295                 ieee80211_queue_delayed_work(rt2x00dev->hw,
 296                                              &link->work, LINK_TUNE_INTERVAL);
 297 }
 298
 299 void rt2x00link_stop_tuner(struct rt2x00_dev *rt2x00dev)
 300 {
 301         cancel_delayed_work_sync(&rt2x00dev->link.work);
 302 }
 303
 304 void rt2x00link_reset_tuner(struct rt2x00_dev *rt2x00dev, bool antenna)
 305 {
 306         struct link_qual *qual = &rt2x00dev->link.qual;
 307         u8 vgc_level = qual->vgc_level_reg;
 308
 309         if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
 310                 return;
 311
 312         /*
 313          * Reset link information.
 314          * Both the currently active vgc level as well as
 315          * the link tuner counter should be reset. Resetting
 316          * the counter is important for devices where the
 317          * device should only perform link tuning during the
 318          * first minute after being enabled.
 319          */
 320         rt2x00dev->link.count = 0;
 321         memset(qual, 0, sizeof(*qual));
 322
 323         /*
 324          * Restore the VGC level as stored in the registers,
 325          * the driver can use this to determine if the register
 326          * must be updated during reset or not.
 327          */
 328         qual->vgc_level_reg = vgc_level;
 329
 330         /*
 331          * Reset the link tuner.
 332          */
 333         rt2x00dev->ops->lib->reset_tuner(rt2x00dev, qual);
 334
 335         if (antenna)
 336                 rt2x00link_antenna_reset(rt2x00dev);
 337 }
 338
 339 static void rt2x00link_reset_qual(struct rt2x00_dev *rt2x00dev)
 340 {
 341         struct link_qual *qual = &rt2x00dev->link.qual;
 342
 343         qual->rx_success = 0;
 344         qual->rx_failed = 0;
 345         qual->tx_success = 0;
 346         qual->tx_failed = 0;
 347 }
 348
 349 static void rt2x00link_tuner(struct work_struct *work)
 350 {
 351         struct rt2x00_dev *rt2x00dev =
 352             container_of(work, struct rt2x00_dev, link.work.work);
 353         struct link *link = &rt2x00dev->link;
 354         struct link_qual *qual = &rt2x00dev->link.qual;
 355
 356         /*
 357          * When the radio is shutting down we should
 358          * immediately cease all link tuning.
 359          */
 360         if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags) ||
 361             test_bit(DEVICE_STATE_SCANNING, &rt2x00dev->flags))
 362                 return;
 363
 364         /*
 365          * Update statistics.
 366          */
 367         rt2x00dev->ops->lib->link_stats(rt2x00dev, qual);
 368         rt2x00dev->low_level_stats.dot11FCSErrorCount += qual->rx_failed;
 369
 370         /*
 371          * Update quality RSSI for link tuning,
 372          * when we have received some frames and we managed to
 373          * collect the RSSI data we could use this. Otherwise we
 374          * must fallback to the default RSSI value.
 375          */
 376         if (!link->avg_rssi.avg || !qual->rx_success)
 377                 qual->rssi = DEFAULT_RSSI;
 378         else
 379                 qual->rssi = link->avg_rssi.avg;
 380
 381         /*
 382          * Check if link tuning is supported by the hardware, some hardware
 383          * do not support link tuning at all, while other devices can disable
 384          * the feature from the EEPROM.
 385          */
 386         if (test_bit(DRIVER_SUPPORT_LINK_TUNING, &rt2x00dev->flags))
 387                 rt2x00dev->ops->lib->link_tuner(rt2x00dev, qual, link->count);
 388
 389         /*
 390          * Send a signal to the led to update the led signal strength.
 391          */
 392         rt2x00leds_led_quality(rt2x00dev, qual->rssi);
 393
 394         /*
 395          * Evaluate antenna setup, make this the last step when
 396          * rt2x00lib_antenna_diversity made changes the quality
 397          * statistics will be reset.
 398          */
 399         if (rt2x00lib_antenna_diversity(rt2x00dev))
 400                 rt2x00link_reset_qual(rt2x00dev);
 401
 402         /*
 403          * Increase tuner counter, and reschedule the next link tuner run.
 404          */
 405         link->count++;
 406
 407         if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
 408                 ieee80211_queue_delayed_work(rt2x00dev->hw,
 409                                              &link->work, LINK_TUNE_INTERVAL);
 410 }
 411
 412 void rt2x00link_start_watchdog(struct rt2x00_dev *rt2x00dev)
 413 {
 414         struct link *link = &rt2x00dev->link;
 415
 416         if (!test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags) ||
 417             !test_bit(DRIVER_SUPPORT_WATCHDOG, &rt2x00dev->flags))
 418                 return;
 419
 420         ieee80211_queue_delayed_work(rt2x00dev->hw,
 421                                      &link->watchdog_work, WATCHDOG_INTERVAL);
 422 }
 423
 424 void rt2x00link_stop_watchdog(struct rt2x00_dev *rt2x00dev)
 425 {
 426         cancel_delayed_work_sync(&rt2x00dev->link.watchdog_work);
 427 }
 428
 429 static void rt2x00link_watchdog(struct work_struct *work)
 430 {
 431         struct rt2x00_dev *rt2x00dev =
 432             container_of(work, struct rt2x00_dev, link.watchdog_work.work);
 433         struct link *link = &rt2x00dev->link;
 434
 435         /*
 436          * When the radio is shutting down we should
 437          * immediately cease the watchdog monitoring.
 438          */
 439         if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
 440                 return;
 441
 442         rt2x00dev->ops->lib->watchdog(rt2x00dev);
 443
 444         if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
 445                 ieee80211_queue_delayed_work(rt2x00dev->hw,
 446                                              &link->watchdog_work,
 447                                              WATCHDOG_INTERVAL);
 448 }
 449
 450 void rt2x00link_register(struct rt2x00_dev *rt2x00dev)
 451 {
 452         INIT_DELAYED_WORK(&rt2x00dev->link.watchdog_work, rt2x00link_watchdog);
 453         INIT_DELAYED_WORK(&rt2x00dev->link.work, rt2x00link_tuner);
 454 }