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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
76static 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
85static 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
94static 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
101static 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
107static 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
148static 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
188static 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 */
196 if (!(ant->flags & ANTENNA_RX_DIVERSITY) &&
197 !(ant->flags & ANTENNA_TX_DIVERSITY)) {
198 ant->flags = 0;
199 return true;
200 }
201
202 /*
203 * If we have only sampled the data over the last period
204 * we should now harvest the data. Otherwise just evaluate
205 * the data. The latter should only be performed once
206 * every 2 seconds.
207 */
208 if (ant->flags & ANTENNA_MODE_SAMPLE) {
209 rt2x00lib_antenna_diversity_sample(rt2x00dev);
210 return true;
211 } else if (rt2x00dev->link.count & 1) {
212 rt2x00lib_antenna_diversity_eval(rt2x00dev);
213 return true;
214 }
215
216 return false;
217}
218
219void rt2x00link_update_stats(struct rt2x00_dev *rt2x00dev,
220 struct sk_buff *skb,
221 struct rxdone_entry_desc *rxdesc)
222{
223 struct link *link = &rt2x00dev->link;
224 struct link_qual *qual = &rt2x00dev->link.qual;
225 struct link_ant *ant = &rt2x00dev->link.ant;
226 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
227
228 /*
229 * No need to update the stats for !=STA interfaces
230 */
231 if (!rt2x00dev->intf_sta_count)
232 return;
233
234 /*
235 * Frame was received successfully since non-succesfull
236 * frames would have been dropped by the hardware.
237 */
238 qual->rx_success++;
239
240 /*
241 * We are only interested in quality statistics from
242 * beacons which came from the BSS which we are
243 * associated with.
244 */
245 if (!ieee80211_is_beacon(hdr->frame_control) ||
246 !(rxdesc->dev_flags & RXDONE_MY_BSS))
247 return;
248
249 /*
250 * Update global RSSI
251 */
252 link->avg_rssi = MOVING_AVERAGE(link->avg_rssi, rxdesc->rssi);
253
254 /*
255 * Update antenna RSSI
256 */
257 ant->rssi_ant = MOVING_AVERAGE(ant->rssi_ant, rxdesc->rssi);
258}
259
260void rt2x00link_start_tuner(struct rt2x00_dev *rt2x00dev)
261{
262 struct link *link = &rt2x00dev->link;
263
264 /*
265 * Link tuning should only be performed when
266 * an active sta interface exists. AP interfaces
267 * don't need link tuning and monitor mode interfaces
268 * should never have to work with link tuners.
269 */
270 if (!rt2x00dev->intf_sta_count)
271 return;
272
273 /**
274 * While scanning, link tuning is disabled. By default
275 * the most sensitive settings will be used to make sure
276 * that all beacons and probe responses will be received
277 * during the scan.
278 */
279 if (test_bit(DEVICE_STATE_SCANNING, &rt2x00dev->flags))
280 return;
281
282 rt2x00link_reset_tuner(rt2x00dev, false);
283
284 if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
285 ieee80211_queue_delayed_work(rt2x00dev->hw,
286 &link->work, LINK_TUNE_INTERVAL);
287}
288
289void rt2x00link_stop_tuner(struct rt2x00_dev *rt2x00dev)
290{
291 cancel_delayed_work_sync(&rt2x00dev->link.work);
292}
293
294void rt2x00link_reset_tuner(struct rt2x00_dev *rt2x00dev, bool antenna)
295{
296 struct link_qual *qual = &rt2x00dev->link.qual;
297 u8 vgc_level = qual->vgc_level_reg;
298
299 if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
300 return;
301
302 /*
303 * Reset link information.
304 * Both the currently active vgc level as well as
305 * the link tuner counter should be reset. Resetting
306 * the counter is important for devices where the
307 * device should only perform link tuning during the
308 * first minute after being enabled.
309 */
310 rt2x00dev->link.count = 0;
311 memset(qual, 0, sizeof(*qual));
312
313 /*
314 * Restore the VGC level as stored in the registers,
315 * the driver can use this to determine if the register
316 * must be updated during reset or not.
317 */
318 qual->vgc_level_reg = vgc_level;
319
320 /*
321 * Reset the link tuner.
322 */
323 rt2x00dev->ops->lib->reset_tuner(rt2x00dev, qual);
324
325 if (antenna)
326 rt2x00link_antenna_reset(rt2x00dev);
327}
328
329static void rt2x00link_reset_qual(struct rt2x00_dev *rt2x00dev)
330{
331 struct link_qual *qual = &rt2x00dev->link.qual;
332
333 qual->rx_success = 0;
334 qual->rx_failed = 0;
335 qual->tx_success = 0;
336 qual->tx_failed = 0;
337}
338
339static void rt2x00link_tuner(struct work_struct *work)
340{
341 struct rt2x00_dev *rt2x00dev =
342 container_of(work, struct rt2x00_dev, link.work.work);
343 struct link *link = &rt2x00dev->link;
344 struct link_qual *qual = &rt2x00dev->link.qual;
345
346 /*
347 * When the radio is shutting down we should
348 * immediately cease all link tuning.
349 */
350 if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags) ||
351 test_bit(DEVICE_STATE_SCANNING, &rt2x00dev->flags))
352 return;
353
354 /*
355 * Update statistics.
356 */
357 rt2x00dev->ops->lib->link_stats(rt2x00dev, qual);
358 rt2x00dev->low_level_stats.dot11FCSErrorCount += qual->rx_failed;
359
360 /*
361 * Update quality RSSI for link tuning,
362 * when we have received some frames and we managed to
363 * collect the RSSI data we could use this. Otherwise we
364 * must fallback to the default RSSI value.
365 */
366 if (!link->avg_rssi.avg || !qual->rx_success)
367 qual->rssi = DEFAULT_RSSI;
368 else
369 qual->rssi = link->avg_rssi.avg;
370
371 /*
372 * Check if link tuning is supported by the hardware, some hardware
373 * do not support link tuning at all, while other devices can disable
374 * the feature from the EEPROM.
375 */
376 if (test_bit(CAPABILITY_LINK_TUNING, &rt2x00dev->cap_flags))
377 rt2x00dev->ops->lib->link_tuner(rt2x00dev, qual, link->count);
378
379 /*
380 * Send a signal to the led to update the led signal strength.
381 */
382 rt2x00leds_led_quality(rt2x00dev, qual->rssi);
383
384 /*
385 * Evaluate antenna setup, make this the last step when
386 * rt2x00lib_antenna_diversity made changes the quality
387 * statistics will be reset.
388 */
389 if (rt2x00lib_antenna_diversity(rt2x00dev))
390 rt2x00link_reset_qual(rt2x00dev);
391
392 /*
393 * Increase tuner counter, and reschedule the next link tuner run.
394 */
395 link->count++;
396
397 if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
398 ieee80211_queue_delayed_work(rt2x00dev->hw,
399 &link->work, LINK_TUNE_INTERVAL);
400}
401
402void rt2x00link_start_watchdog(struct rt2x00_dev *rt2x00dev)
403{
404 struct link *link = &rt2x00dev->link;
405
406 if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags) &&
407 rt2x00dev->ops->lib->watchdog)
408 ieee80211_queue_delayed_work(rt2x00dev->hw,
409 &link->watchdog_work,
410 WATCHDOG_INTERVAL);
411}
412
413void rt2x00link_stop_watchdog(struct rt2x00_dev *rt2x00dev)
414{
415 cancel_delayed_work_sync(&rt2x00dev->link.watchdog_work);
416}
417
418static void rt2x00link_watchdog(struct work_struct *work)
419{
420 struct rt2x00_dev *rt2x00dev =
421 container_of(work, struct rt2x00_dev, link.watchdog_work.work);
422 struct link *link = &rt2x00dev->link;
423
424 /*
425 * When the radio is shutting down we should
426 * immediately cease the watchdog monitoring.
427 */
428 if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
429 return;
430
431 rt2x00dev->ops->lib->watchdog(rt2x00dev);
432
433 if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
434 ieee80211_queue_delayed_work(rt2x00dev->hw,
435 &link->watchdog_work,
436 WATCHDOG_INTERVAL);
437}
438
439void rt2x00link_start_agc(struct rt2x00_dev *rt2x00dev)
440{
441 struct link *link = &rt2x00dev->link;
442
443 if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags) &&
444 rt2x00dev->ops->lib->gain_calibration)
445 ieee80211_queue_delayed_work(rt2x00dev->hw,
446 &link->agc_work,
447 AGC_INTERVAL);
448}
449
450void rt2x00link_stop_agc(struct rt2x00_dev *rt2x00dev)
451{
452 cancel_delayed_work_sync(&rt2x00dev->link.agc_work);
453}
454
455static void rt2x00link_agc(struct work_struct *work)
456{
457 struct rt2x00_dev *rt2x00dev =
458 container_of(work, struct rt2x00_dev, link.agc_work.work);
459 struct link *link = &rt2x00dev->link;
460
461 /*
462 * When the radio is shutting down we should
463 * immediately cease the watchdog monitoring.
464 */
465 if (!test_bit(DEVICE_STATE_ENABLED_RADIO, &rt2x00dev->flags))
466 return;
467
468 rt2x00dev->ops->lib->gain_calibration(rt2x00dev);
469
470 if (test_bit(DEVICE_STATE_PRESENT, &rt2x00dev->flags))
471 ieee80211_queue_delayed_work(rt2x00dev->hw,
472 &link->agc_work,
473 AGC_INTERVAL);
474}
475
476void rt2x00link_register(struct rt2x00_dev *rt2x00dev)
477{
478 INIT_DELAYED_WORK(&rt2x00dev->link.agc_work, rt2x00link_agc);
479 INIT_DELAYED_WORK(&rt2x00dev->link.watchdog_work, rt2x00link_watchdog);
480 INIT_DELAYED_WORK(&rt2x00dev->link.work, rt2x00link_tuner);
481}