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
rt2x00link_antenna_get_link_rssi(struct rt2x00_dev * rt2x00dev)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
rt2x00link_antenna_get_rssi_history(struct rt2x00_dev * rt2x00dev)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
rt2x00link_antenna_update_rssi_history(struct rt2x00_dev * rt2x00dev,int rssi)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
rt2x00link_antenna_reset(struct rt2x00_dev * rt2x00dev)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
rt2x00lib_antenna_diversity_sample(struct rt2x00_dev * rt2x00dev)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
rt2x00lib_antenna_diversity_eval(struct rt2x00_dev * rt2x00dev)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
rt2x00lib_antenna_diversity(struct rt2x00_dev * rt2x00dev)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
rt2x00link_update_stats(struct rt2x00_dev * rt2x00dev,struct sk_buff * skb,struct rxdone_entry_desc * rxdesc)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
rt2x00link_start_tuner(struct rt2x00_dev * rt2x00dev)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
rt2x00link_stop_tuner(struct rt2x00_dev * rt2x00dev)299 void rt2x00link_stop_tuner(struct rt2x00_dev *rt2x00dev)
300 {
301 cancel_delayed_work_sync(&rt2x00dev->link.work);
302 }
303
rt2x00link_reset_tuner(struct rt2x00_dev * rt2x00dev,bool antenna)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
rt2x00link_reset_qual(struct rt2x00_dev * rt2x00dev)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
rt2x00link_tuner(struct work_struct * work)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
rt2x00link_start_watchdog(struct rt2x00_dev * rt2x00dev)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
rt2x00link_stop_watchdog(struct rt2x00_dev * rt2x00dev)424 void rt2x00link_stop_watchdog(struct rt2x00_dev *rt2x00dev)
425 {
426 cancel_delayed_work_sync(&rt2x00dev->link.watchdog_work);
427 }
428
rt2x00link_watchdog(struct work_struct * work)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
rt2x00link_register(struct rt2x00_dev * rt2x00dev)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 }
455