summaryrefslogtreecommitdiff
path: root/drivers/hwtracing/stm/core.c
blob: 2712e699ba08cf2d30415eef43287b36cdc5ec75 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
// SPDX-License-Identifier: GPL-2.0
/*
 * System Trace Module (STM) infrastructure
 * Copyright (c) 2014, Intel Corporation.
 *
 * STM class implements generic infrastructure for  System Trace Module devices
 * as defined in MIPI STPv2 specification.
 */

#include <linux/pm_runtime.h>
#include <linux/uaccess.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/compat.h>
#include <linux/kdev_t.h>
#include <linux/srcu.h>
#include <linux/slab.h>
#include <linux/stm.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/vmalloc.h>
#include "stm.h"

#include <uapi/linux/stm.h>

static unsigned int stm_core_up;

/*
 * The SRCU here makes sure that STM device doesn't disappear from under a
 * stm_source_write() caller, which may want to have as little overhead as
 * possible.
 */
static struct srcu_struct stm_source_srcu;

static ssize_t masters_show(struct device *dev,
			    struct device_attribute *attr,
			    char *buf)
{
	struct stm_device *stm = to_stm_device(dev);
	int ret;

	ret = sprintf(buf, "%u %u\n", stm->data->sw_start, stm->data->sw_end);

	return ret;
}

static DEVICE_ATTR_RO(masters);

static ssize_t channels_show(struct device *dev,
			     struct device_attribute *attr,
			     char *buf)
{
	struct stm_device *stm = to_stm_device(dev);
	int ret;

	ret = sprintf(buf, "%u\n", stm->data->sw_nchannels);

	return ret;
}

static DEVICE_ATTR_RO(channels);

static ssize_t hw_override_show(struct device *dev,
				struct device_attribute *attr,
				char *buf)
{
	struct stm_device *stm = to_stm_device(dev);
	int ret;

	ret = sprintf(buf, "%u\n", stm->data->hw_override);

	return ret;
}

static DEVICE_ATTR_RO(hw_override);

static struct attribute *stm_attrs[] = {
	&dev_attr_masters.attr,
	&dev_attr_channels.attr,
	&dev_attr_hw_override.attr,
	NULL,
};

ATTRIBUTE_GROUPS(stm);

static struct class stm_class = {
	.name		= "stm",
	.dev_groups	= stm_groups,
};

/**
 * stm_find_device() - find stm device by name
 * @buf:	character buffer containing the name
 *
 * This is called when either policy gets assigned to an stm device or an
 * stm_source device gets linked to an stm device.
 *
 * This grabs device's reference (get_device()) and module reference, both
 * of which the calling path needs to make sure to drop with stm_put_device().
 *
 * Return:	stm device pointer or null if lookup failed.
 */
struct stm_device *stm_find_device(const char *buf)
{
	struct stm_device *stm;
	struct device *dev;

	if (!stm_core_up)
		return NULL;

	dev = class_find_device_by_name(&stm_class, buf);
	if (!dev)
		return NULL;

	stm = to_stm_device(dev);
	if (!try_module_get(stm->owner)) {
		/* matches class_find_device() above */
		put_device(dev);
		return NULL;
	}

	return stm;
}

/**
 * stm_put_device() - drop references on the stm device
 * @stm:	stm device, previously acquired by stm_find_device()
 *
 * This drops the module reference and device reference taken by
 * stm_find_device() or stm_char_open().
 */
void stm_put_device(struct stm_device *stm)
{
	module_put(stm->owner);
	put_device(&stm->dev);
}

/*
 * Internally we only care about software-writable masters here, that is the
 * ones in the range [stm_data->sw_start..stm_data..sw_end], however we need
 * original master numbers to be visible externally, since they are the ones
 * that will appear in the STP stream. Thus, the internal bookkeeping uses
 * $master - stm_data->sw_start to reference master descriptors and such.
 */

#define __stm_master(_s, _m)				\
	((_s)->masters[(_m) - (_s)->data->sw_start])

static inline struct stp_master *
stm_master(struct stm_device *stm, unsigned int idx)
{
	if (idx < stm->data->sw_start || idx > stm->data->sw_end)
		return NULL;

	return __stm_master(stm, idx);
}

static int stp_master_alloc(struct stm_device *stm, unsigned int idx)
{
	struct stp_master *master;

	master = kzalloc(struct_size(master, chan_map,
				     BITS_TO_LONGS(stm->data->sw_nchannels)),
			 GFP_ATOMIC);
	if (!master)
		return -ENOMEM;

	master->nr_free = stm->data->sw_nchannels;
	__stm_master(stm, idx) = master;

	return 0;
}

static void stp_master_free(struct stm_device *stm, unsigned int idx)
{
	struct stp_master *master = stm_master(stm, idx);

	if (!master)
		return;

	__stm_master(stm, idx) = NULL;
	kfree(master);
}

static void stm_output_claim(struct stm_device *stm, struct stm_output *output)
{
	struct stp_master *master = stm_master(stm, output->master);

	lockdep_assert_held(&stm->mc_lock);
	lockdep_assert_held(&output->lock);

	if (WARN_ON_ONCE(master->nr_free < output->nr_chans))
		return;

	bitmap_allocate_region(&master->chan_map[0], output->channel,
			       ilog2(output->nr_chans));

	master->nr_free -= output->nr_chans;
}

static void
stm_output_disclaim(struct stm_device *stm, struct stm_output *output)
{
	struct stp_master *master = stm_master(stm, output->master);

	lockdep_assert_held(&stm->mc_lock);
	lockdep_assert_held(&output->lock);

	bitmap_release_region(&master->chan_map[0], output->channel,
			      ilog2(output->nr_chans));

	master->nr_free += output->nr_chans;
	output->nr_chans = 0;
}

/*
 * This is like bitmap_find_free_region(), except it can ignore @start bits
 * at the beginning.
 */
static int find_free_channels(unsigned long *bitmap, unsigned int start,
			      unsigned int end, unsigned int width)
{
	unsigned int pos;
	int i;

	for (pos = start; pos < end + 1; pos = ALIGN(pos, width)) {
		pos = find_next_zero_bit(bitmap, end + 1, pos);
		if (pos + width > end + 1)
			break;

		if (pos & (width - 1))
			continue;

		for (i = 1; i < width && !test_bit(pos + i, bitmap); i++)
			;
		if (i == width)
			return pos;

		/* step over [pos..pos+i) to continue search */
		pos += i;
	}

	return -1;
}

static int
stm_find_master_chan(struct stm_device *stm, unsigned int width,
		     unsigned int *mstart, unsigned int mend,
		     unsigned int *cstart, unsigned int cend)
{
	struct stp_master *master;
	unsigned int midx;
	int pos, err;

	for (midx = *mstart; midx <= mend; midx++) {
		if (!stm_master(stm, midx)) {
			err = stp_master_alloc(stm, midx);
			if (err)
				return err;
		}

		master = stm_master(stm, midx);

		if (!master->nr_free)
			continue;

		pos = find_free_channels(master->chan_map, *cstart, cend,
					 width);
		if (pos < 0)
			continue;

		*mstart = midx;
		*cstart = pos;
		return 0;
	}

	return -ENOSPC;
}

static int stm_output_assign(struct stm_device *stm, unsigned int width,
			     struct stp_policy_node *policy_node,
			     struct stm_output *output)
{
	unsigned int midx, cidx, mend, cend;
	int ret = -EINVAL;

	if (width > stm->data->sw_nchannels)
		return -EINVAL;

	/* We no longer accept policy_node==NULL here */
	if (WARN_ON_ONCE(!policy_node))
		return -EINVAL;

	/*
	 * Also, the caller holds reference to policy_node, so it won't
	 * disappear on us.
	 */
	stp_policy_node_get_ranges(policy_node, &midx, &mend, &cidx, &cend);

	spin_lock(&stm->mc_lock);
	spin_lock(&output->lock);
	/* output is already assigned -- shouldn't happen */
	if (WARN_ON_ONCE(output->nr_chans))
		goto unlock;

	ret = stm_find_master_chan(stm, width, &midx, mend, &cidx, cend);
	if (ret < 0)
		goto unlock;

	output->master = midx;
	output->channel = cidx;
	output->nr_chans = width;
	if (stm->pdrv->output_open) {
		void *priv = stp_policy_node_priv(policy_node);

		if (WARN_ON_ONCE(!priv))
			goto unlock;

		/* configfs subsys mutex is held by the caller */
		ret = stm->pdrv->output_open(priv, output);
		if (ret)
			goto unlock;
	}

	stm_output_claim(stm, output);
	dev_dbg(&stm->dev, "assigned %u:%u (+%u)\n", midx, cidx, width);

	ret = 0;
unlock:
	if (ret)
		output->nr_chans = 0;

	spin_unlock(&output->lock);
	spin_unlock(&stm->mc_lock);

	return ret;
}

static void stm_output_free(struct stm_device *stm, struct stm_output *output)
{
	spin_lock(&stm->mc_lock);
	spin_lock(&output->lock);
	if (output->nr_chans)
		stm_output_disclaim(stm, output);
	if (stm->pdrv && stm->pdrv->output_close)
		stm->pdrv->output_close(output);
	spin_unlock(&output->lock);
	spin_unlock(&stm->mc_lock);
}

static void stm_output_init(struct stm_output *output)
{
	spin_lock_init(&output->lock);
}

static int major_match(struct device *dev, const void *data)
{
	unsigned int major = *(unsigned int *)data;

	return MAJOR(dev->devt) == major;
}

/*
 * Framing protocol management
 * Modules can implement STM protocol drivers and (un-)register them
 * with the STM class framework.
 */
static struct list_head stm_pdrv_head;
static struct mutex stm_pdrv_mutex;

struct stm_pdrv_entry {
	struct list_head			entry;
	const struct stm_protocol_driver	*pdrv;
	const struct config_item_type		*node_type;
};

static const struct stm_pdrv_entry *
__stm_lookup_protocol(const char *name)
{
	struct stm_pdrv_entry *pe;

	/*
	 * If no name is given (NULL or ""), fall back to "p_basic".
	 */
	if (!name || !*name)
		name = "p_basic";

	list_for_each_entry(pe, &stm_pdrv_head, entry) {
		if (!strcmp(name, pe->pdrv->name))
			return pe;
	}

	return NULL;
}

int stm_register_protocol(const struct stm_protocol_driver *pdrv)
{
	struct stm_pdrv_entry *pe = NULL;
	int ret = -ENOMEM;

	mutex_lock(&stm_pdrv_mutex);

	if (__stm_lookup_protocol(pdrv->name)) {
		ret = -EEXIST;
		goto unlock;
	}

	pe = kzalloc(sizeof(*pe), GFP_KERNEL);
	if (!pe)
		goto unlock;

	if (pdrv->policy_attr) {
		pe->node_type = get_policy_node_type(pdrv->policy_attr);
		if (!pe->node_type)
			goto unlock;
	}

	list_add_tail(&pe->entry, &stm_pdrv_head);
	pe->pdrv = pdrv;

	ret = 0;
unlock:
	mutex_unlock(&stm_pdrv_mutex);

	if (ret)
		kfree(pe);

	return ret;
}
EXPORT_SYMBOL_GPL(stm_register_protocol);

void stm_unregister_protocol(const struct stm_protocol_driver *pdrv)
{
	struct stm_pdrv_entry *pe, *iter;

	mutex_lock(&stm_pdrv_mutex);

	list_for_each_entry_safe(pe, iter, &stm_pdrv_head, entry) {
		if (pe->pdrv == pdrv) {
			list_del(&pe->entry);

			if (pe->node_type) {
				kfree(pe->node_type->ct_attrs);
				kfree(pe->node_type);
			}
			kfree(pe);
			break;
		}
	}

	mutex_unlock(&stm_pdrv_mutex);
}
EXPORT_SYMBOL_GPL(stm_unregister_protocol);

static bool stm_get_protocol(const struct stm_protocol_driver *pdrv)
{
	return try_module_get(pdrv->owner);
}

void stm_put_protocol(const struct stm_protocol_driver *pdrv)
{
	module_put(pdrv->owner);
}

int stm_lookup_protocol(const char *name,
			const struct stm_protocol_driver **pdrv,
			const struct config_item_type **node_type)
{
	const struct stm_pdrv_entry *pe;

	mutex_lock(&stm_pdrv_mutex);

	pe = __stm_lookup_protocol(name);
	if (pe && pe->pdrv && stm_get_protocol(pe->pdrv)) {
		*pdrv = pe->pdrv;
		*node_type = pe->node_type;
	}

	mutex_unlock(&stm_pdrv_mutex);

	return pe ? 0 : -ENOENT;
}

static int stm_char_open(struct inode *inode, struct file *file)
{
	struct stm_file *stmf;
	struct device *dev;
	unsigned int major = imajor(inode);
	int err = -ENOMEM;

	dev = class_find_device(&stm_class, NULL, &major, major_match);
	if (!dev)
		return -ENODEV;

	stmf = kzalloc(sizeof(*stmf), GFP_KERNEL);
	if (!stmf)
		goto err_put_device;

	err = -ENODEV;
	stm_output_init(&stmf->output);
	stmf->stm = to_stm_device(dev);

	if (!try_module_get(stmf->stm->owner))
		goto err_free;

	file->private_data = stmf;

	return nonseekable_open(inode, file);

err_free:
	kfree(stmf);
err_put_device:
	/* matches class_find_device() above */
	put_device(dev);

	return err;
}

static int stm_char_release(struct inode *inode, struct file *file)
{
	struct stm_file *stmf = file->private_data;
	struct stm_device *stm = stmf->stm;

	if (stm->data->unlink)
		stm->data->unlink(stm->data, stmf->output.master,
				  stmf->output.channel);

	stm_output_free(stm, &stmf->output);

	/*
	 * matches the stm_char_open()'s
	 * class_find_device() + try_module_get()
	 */
	stm_put_device(stm);
	kfree(stmf);

	return 0;
}

static int
stm_assign_first_policy(struct stm_device *stm, struct stm_output *output,
			char **ids, unsigned int width)
{
	struct stp_policy_node *pn;
	int err, n;

	/*
	 * On success, stp_policy_node_lookup() will return holding the
	 * configfs subsystem mutex, which is then released in
	 * stp_policy_node_put(). This allows the pdrv->output_open() in
	 * stm_output_assign() to serialize against the attribute accessors.
	 */
	for (n = 0, pn = NULL; ids[n] && !pn; n++)
		pn = stp_policy_node_lookup(stm, ids[n]);

	if (!pn)
		return -EINVAL;

	err = stm_output_assign(stm, width, pn, output);

	stp_policy_node_put(pn);

	return err;
}

/**
 * stm_data_write() - send the given payload as data packets
 * @data:	stm driver's data
 * @m:		STP master
 * @c:		STP channel
 * @ts_first:	timestamp the first packet
 * @buf:	data payload buffer
 * @count:	data payload size
 */
ssize_t notrace stm_data_write(struct stm_data *data, unsigned int m,
			       unsigned int c, bool ts_first, const void *buf,
			       size_t count)
{
	unsigned int flags = ts_first ? STP_PACKET_TIMESTAMPED : 0;
	ssize_t sz;
	size_t pos;

	for (pos = 0, sz = 0; pos < count; pos += sz) {
		sz = min_t(unsigned int, count - pos, 8);
		sz = data->packet(data, m, c, STP_PACKET_DATA, flags, sz,
				  &((u8 *)buf)[pos]);
		if (sz <= 0)
			break;

		if (ts_first) {
			flags = 0;
			ts_first = false;
		}
	}

	return sz < 0 ? sz : pos;
}
EXPORT_SYMBOL_GPL(stm_data_write);

static ssize_t notrace
stm_write(struct stm_device *stm, struct stm_output *output,
	  unsigned int chan, const char *buf, size_t count)
{
	int err;

	/* stm->pdrv is serialized against policy_mutex */
	if (!stm->pdrv)
		return -ENODEV;

	err = stm->pdrv->write(stm->data, output, chan, buf, count);
	if (err < 0)
		return err;

	return err;
}

static ssize_t stm_char_write(struct file *file, const char __user *buf,
			      size_t count, loff_t *ppos)
{
	struct stm_file *stmf = file->private_data;
	struct stm_device *stm = stmf->stm;
	char *kbuf;
	int err;

	if (count + 1 > PAGE_SIZE)
		count = PAGE_SIZE - 1;

	/*
	 * If no m/c have been assigned to this writer up to this
	 * point, try to use the task name and "default" policy entries.
	 */
	if (!stmf->output.nr_chans) {
		char comm[sizeof(current->comm)];
		char *ids[] = { comm, "default", NULL };

		get_task_comm(comm, current);

		err = stm_assign_first_policy(stmf->stm, &stmf->output, ids, 1);
		/*
		 * EBUSY means that somebody else just assigned this
		 * output, which is just fine for write()
		 */
		if (err)
			return err;
	}

	kbuf = kmalloc(count + 1, GFP_KERNEL);
	if (!kbuf)
		return -ENOMEM;

	err = copy_from_user(kbuf, buf, count);
	if (err) {
		kfree(kbuf);
		return -EFAULT;
	}

	pm_runtime_get_sync(&stm->dev);

	count = stm_write(stm, &stmf->output, 0, kbuf, count);

	pm_runtime_mark_last_busy(&stm->dev);
	pm_runtime_put_autosuspend(&stm->dev);
	kfree(kbuf);

	return count;
}

static void stm_mmap_open(struct vm_area_struct *vma)
{
	struct stm_file *stmf = vma->vm_file->private_data;
	struct stm_device *stm = stmf->stm;

	pm_runtime_get(&stm->dev);
}

static void stm_mmap_close(struct vm_area_struct *vma)
{
	struct stm_file *stmf = vma->vm_file->private_data;
	struct stm_device *stm = stmf->stm;

	pm_runtime_mark_last_busy(&stm->dev);
	pm_runtime_put_autosuspend(&stm->dev);
}

static const struct vm_operations_struct stm_mmap_vmops = {
	.open	= stm_mmap_open,
	.close	= stm_mmap_close,
};

static int stm_char_mmap(struct file *file, struct vm_area_struct *vma)
{
	struct stm_file *stmf = file->private_data;
	struct stm_device *stm = stmf->stm;
	unsigned long size, phys;

	if (!stm->data->mmio_addr)
		return -EOPNOTSUPP;

	if (vma->vm_pgoff)
		return -EINVAL;

	size = vma->vm_end - vma->vm_start;

	if (stmf->output.nr_chans * stm->data->sw_mmiosz != size)
		return -EINVAL;

	phys = stm->data->mmio_addr(stm->data, stmf->output.master,
				    stmf->output.channel,
				    stmf->output.nr_chans);

	if (!phys)
		return -EINVAL;

	pm_runtime_get_sync(&stm->dev);

	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
	vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
	vma->vm_ops = &stm_mmap_vmops;
	vm_iomap_memory(vma, phys, size);

	return 0;
}

static int stm_char_policy_set_ioctl(struct stm_file *stmf, void __user *arg)
{
	struct stm_device *stm = stmf->stm;
	struct stp_policy_id *id;
	char *ids[] = { NULL, NULL };
	int ret = -EINVAL, wlimit = 1;
	u32 size;

	if (stmf->output.nr_chans)
		return -EBUSY;

	if (copy_from_user(&size, arg, sizeof(size)))
		return -EFAULT;

	if (size < sizeof(*id) || size >= PATH_MAX + sizeof(*id))
		return -EINVAL;

	/*
	 * size + 1 to make sure the .id string at the bottom is terminated,
	 * which is also why memdup_user() is not useful here
	 */
	id = kzalloc(size + 1, GFP_KERNEL);
	if (!id)
		return -ENOMEM;

	if (copy_from_user(id, arg, size)) {
		ret = -EFAULT;
		goto err_free;
	}

	if (id->__reserved_0 || id->__reserved_1)
		goto err_free;

	if (stm->data->sw_mmiosz)
		wlimit = PAGE_SIZE / stm->data->sw_mmiosz;

	if (id->width < 1 || id->width > wlimit)
		goto err_free;

	ids[0] = id->id;
	ret = stm_assign_first_policy(stmf->stm, &stmf->output, ids,
				      id->width);
	if (ret)
		goto err_free;

	if (stm->data->link)
		ret = stm->data->link(stm->data, stmf->output.master,
				      stmf->output.channel);

	if (ret)
		stm_output_free(stmf->stm, &stmf->output);

err_free:
	kfree(id);

	return ret;
}

static int stm_char_policy_get_ioctl(struct stm_file *stmf, void __user *arg)
{
	struct stp_policy_id id = {
		.size		= sizeof(id),
		.master		= stmf->output.master,
		.channel	= stmf->output.channel,
		.width		= stmf->output.nr_chans,
		.__reserved_0	= 0,
		.__reserved_1	= 0,
	};

	return copy_to_user(arg, &id, id.size) ? -EFAULT : 0;
}

static long
stm_char_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
	struct stm_file *stmf = file->private_data;
	struct stm_data *stm_data = stmf->stm->data;
	int err = -ENOTTY;
	u64 options;

	switch (cmd) {
	case STP_POLICY_ID_SET:
		err = stm_char_policy_set_ioctl(stmf, (void __user *)arg);
		if (err)
			return err;

		return stm_char_policy_get_ioctl(stmf, (void __user *)arg);

	case STP_POLICY_ID_GET:
		return stm_char_policy_get_ioctl(stmf, (void __user *)arg);

	case STP_SET_OPTIONS:
		if (copy_from_user(&options, (u64 __user *)arg, sizeof(u64)))
			return -EFAULT;

		if (stm_data->set_options)
			err = stm_data->set_options(stm_data,
						    stmf->output.master,
						    stmf->output.channel,
						    stmf->output.nr_chans,
						    options);

		break;
	default:
		break;
	}

	return err;
}

static const struct file_operations stm_fops = {
	.open		= stm_char_open,
	.release	= stm_char_release,
	.write		= stm_char_write,
	.mmap		= stm_char_mmap,
	.unlocked_ioctl	= stm_char_ioctl,
	.compat_ioctl	= compat_ptr_ioctl,
	.llseek		= no_llseek,
};

static void stm_device_release(struct device *dev)
{
	struct stm_device *stm = to_stm_device(dev);

	vfree(stm);
}

int stm_register_device(struct device *parent, struct stm_data *stm_data,
			struct module *owner)
{
	struct stm_device *stm;
	unsigned int nmasters;
	int err = -ENOMEM;

	if (!stm_core_up)
		return -EPROBE_DEFER;

	if (!stm_data->packet || !stm_data->sw_nchannels)
		return -EINVAL;

	nmasters = stm_data->sw_end - stm_data->sw_start + 1;
	stm = vzalloc(sizeof(*stm) + nmasters * sizeof(void *));
	if (!stm)
		return -ENOMEM;

	stm->major = register_chrdev(0, stm_data->name, &stm_fops);
	if (stm->major < 0)
		goto err_free;

	device_initialize(&stm->dev);
	stm->dev.devt = MKDEV(stm->major, 0);
	stm->dev.class = &stm_class;
	stm->dev.parent = parent;
	stm->dev.release = stm_device_release;

	mutex_init(&stm->link_mutex);
	spin_lock_init(&stm->link_lock);
	INIT_LIST_HEAD(&stm->link_list);

	/* initialize the object before it is accessible via sysfs */
	spin_lock_init(&stm->mc_lock);
	mutex_init(&stm->policy_mutex);
	stm->sw_nmasters = nmasters;
	stm->owner = owner;
	stm->data = stm_data;
	stm_data->stm = stm;

	err = kobject_set_name(&stm->dev.kobj, "%s", stm_data->name);
	if (err)
		goto err_device;

	err = device_add(&stm->dev);
	if (err)
		goto err_device;

	/*
	 * Use delayed autosuspend to avoid bouncing back and forth
	 * on recurring character device writes, with the initial
	 * delay time of 2 seconds.
	 */
	pm_runtime_no_callbacks(&stm->dev);
	pm_runtime_use_autosuspend(&stm->dev);
	pm_runtime_set_autosuspend_delay(&stm->dev, 2000);
	pm_runtime_set_suspended(&stm->dev);
	pm_runtime_enable(&stm->dev);

	return 0;

err_device:
	unregister_chrdev(stm->major, stm_data->name);

	/* matches device_initialize() above */
	put_device(&stm->dev);
err_free:
	vfree(stm);

	return err;
}
EXPORT_SYMBOL_GPL(stm_register_device);

static int __stm_source_link_drop(struct stm_source_device *src,
				  struct stm_device *stm);

void stm_unregister_device(struct stm_data *stm_data)
{
	struct stm_device *stm = stm_data->stm;
	struct stm_source_device *src, *iter;
	int i, ret;

	pm_runtime_dont_use_autosuspend(&stm->dev);
	pm_runtime_disable(&stm->dev);

	mutex_lock(&stm->link_mutex);
	list_for_each_entry_safe(src, iter, &stm->link_list, link_entry) {
		ret = __stm_source_link_drop(src, stm);
		/*
		 * src <-> stm link must not change under the same
		 * stm::link_mutex, so complain loudly if it has;
		 * also in this situation ret!=0 means this src is
		 * not connected to this stm and it should be otherwise
		 * safe to proceed with the tear-down of stm.
		 */
		WARN_ON_ONCE(ret);
	}
	mutex_unlock(&stm->link_mutex);

	synchronize_srcu(&stm_source_srcu);

	unregister_chrdev(stm->major, stm_data->name);

	mutex_lock(&stm->policy_mutex);
	if (stm->policy)
		stp_policy_unbind(stm->policy);
	mutex_unlock(&stm->policy_mutex);

	for (i = stm->data->sw_start; i <= stm->data->sw_end; i++)
		stp_master_free(stm, i);

	device_unregister(&stm->dev);
	stm_data->stm = NULL;
}
EXPORT_SYMBOL_GPL(stm_unregister_device);

/*
 * stm::link_list access serialization uses a spinlock and a mutex; holding
 * either of them guarantees that the list is stable; modification requires
 * holding both of them.
 *
 * Lock ordering is as follows:
 *   stm::link_mutex
 *     stm::link_lock
 *       src::link_lock
 */

/**
 * stm_source_link_add() - connect an stm_source device to an stm device
 * @src:	stm_source device
 * @stm:	stm device
 *
 * This function establishes a link from stm_source to an stm device so that
 * the former can send out trace data to the latter.
 *
 * Return:	0 on success, -errno otherwise.
 */
static int stm_source_link_add(struct stm_source_device *src,
			       struct stm_device *stm)
{
	char *ids[] = { NULL, "default", NULL };
	int err = -ENOMEM;

	mutex_lock(&stm->link_mutex);
	spin_lock(&stm->link_lock);
	spin_lock(&src->link_lock);

	/* src->link is dereferenced under stm_source_srcu but not the list */
	rcu_assign_pointer(src->link, stm);
	list_add_tail(&src->link_entry, &stm->link_list);

	spin_unlock(&src->link_lock);
	spin_unlock(&stm->link_lock);
	mutex_unlock(&stm->link_mutex);

	ids[0] = kstrdup(src->data->name, GFP_KERNEL);
	if (!ids[0])
		goto fail_detach;

	err = stm_assign_first_policy(stm, &src->output, ids,
				      src->data->nr_chans);
	kfree(ids[0]);

	if (err)
		goto fail_detach;

	/* this is to notify the STM device that a new link has been made */
	if (stm->data->link)
		err = stm->data->link(stm->data, src->output.master,
				      src->output.channel);

	if (err)
		goto fail_free_output;

	/* this is to let the source carry out all necessary preparations */
	if (src->data->link)
		src->data->link(src->data);

	return 0;

fail_free_output:
	stm_output_free(stm, &src->output);

fail_detach:
	mutex_lock(&stm->link_mutex);
	spin_lock(&stm->link_lock);
	spin_lock(&src->link_lock);

	rcu_assign_pointer(src->link, NULL);
	list_del_init(&src->link_entry);

	spin_unlock(&src->link_lock);
	spin_unlock(&stm->link_lock);
	mutex_unlock(&stm->link_mutex);

	return err;
}

/**
 * __stm_source_link_drop() - detach stm_source from an stm device
 * @src:	stm_source device
 * @stm:	stm device
 *
 * If @stm is @src::link, disconnect them from one another and put the
 * reference on the @stm device.
 *
 * Caller must hold stm::link_mutex.
 */
static int __stm_source_link_drop(struct stm_source_device *src,
				  struct stm_device *stm)
{
	struct stm_device *link;
	int ret = 0;

	lockdep_assert_held(&stm->link_mutex);

	/* for stm::link_list modification, we hold both mutex and spinlock */
	spin_lock(&stm->link_lock);
	spin_lock(&src->link_lock);
	link = srcu_dereference_check(src->link, &stm_source_srcu, 1);

	/*
	 * The linked device may have changed since we last looked, because
	 * we weren't holding the src::link_lock back then; if this is the
	 * case, tell the caller to retry.
	 */
	if (link != stm) {
		ret = -EAGAIN;
		goto unlock;
	}

	stm_output_free(link, &src->output);
	list_del_init(&src->link_entry);
	pm_runtime_mark_last_busy(&link->dev);
	pm_runtime_put_autosuspend(&link->dev);
	/* matches stm_find_device() from stm_source_link_store() */
	stm_put_device(link);
	rcu_assign_pointer(src->link, NULL);

unlock:
	spin_unlock(&src->link_lock);
	spin_unlock(&stm->link_lock);

	/*
	 * Call the unlink callbacks for both source and stm, when we know
	 * that we have actually performed the unlinking.
	 */
	if (!ret) {
		if (src->data->unlink)
			src->data->unlink(src->data);

		if (stm->data->unlink)
			stm->data->unlink(stm->data, src->output.master,
					  src->output.channel);
	}

	return ret;
}

/**
 * stm_source_link_drop() - detach stm_source from its stm device
 * @src:	stm_source device
 *
 * Unlinking means disconnecting from source's STM device; after this
 * writes will be unsuccessful until it is linked to a new STM device.
 *
 * This will happen on "stm_source_link" sysfs attribute write to undo
 * the existing link (if any), or on linked STM device's de-registration.
 */
static void stm_source_link_drop(struct stm_source_device *src)
{
	struct stm_device *stm;
	int idx, ret;

retry:
	idx = srcu_read_lock(&stm_source_srcu);
	/*
	 * The stm device will be valid for the duration of this
	 * read section, but the link may change before we grab
	 * the src::link_lock in __stm_source_link_drop().
	 */
	stm = srcu_dereference(src->link, &stm_source_srcu);

	ret = 0;
	if (stm) {
		mutex_lock(&stm->link_mutex);
		ret = __stm_source_link_drop(src, stm);
		mutex_unlock(&stm->link_mutex);
	}

	srcu_read_unlock(&stm_source_srcu, idx);

	/* if it did change, retry */
	if (ret == -EAGAIN)
		goto retry;
}

static ssize_t stm_source_link_show(struct device *dev,
				    struct device_attribute *attr,
				    char *buf)
{
	struct stm_source_device *src = to_stm_source_device(dev);
	struct stm_device *stm;
	int idx, ret;

	idx = srcu_read_lock(&stm_source_srcu);
	stm = srcu_dereference(src->link, &stm_source_srcu);
	ret = sprintf(buf, "%s\n",
		      stm ? dev_name(&stm->dev) : "<none>");
	srcu_read_unlock(&stm_source_srcu, idx);

	return ret;
}

static ssize_t stm_source_link_store(struct device *dev,
				     struct device_attribute *attr,
				     const char *buf, size_t count)
{
	struct stm_source_device *src = to_stm_source_device(dev);
	struct stm_device *link;
	int err;

	stm_source_link_drop(src);

	link = stm_find_device(buf);
	if (!link)
		return -EINVAL;

	pm_runtime_get(&link->dev);

	err = stm_source_link_add(src, link);
	if (err) {
		pm_runtime_put_autosuspend(&link->dev);
		/* matches the stm_find_device() above */
		stm_put_device(link);
	}

	return err ? : count;
}

static DEVICE_ATTR_RW(stm_source_link);

static struct attribute *stm_source_attrs[] = {
	&dev_attr_stm_source_link.attr,
	NULL,
};

ATTRIBUTE_GROUPS(stm_source);

static struct class stm_source_class = {
	.name		= "stm_source",
	.dev_groups	= stm_source_groups,
};

static void stm_source_device_release(struct device *dev)
{
	struct stm_source_device *src = to_stm_source_device(dev);

	kfree(src);
}

/**
 * stm_source_register_device() - register an stm_source device
 * @parent:	parent device
 * @data:	device description structure
 *
 * This will create a device of stm_source class that can write
 * data to an stm device once linked.
 *
 * Return:	0 on success, -errno otherwise.
 */
int stm_source_register_device(struct device *parent,
			       struct stm_source_data *data)
{
	struct stm_source_device *src;
	int err;

	if (!stm_core_up)
		return -EPROBE_DEFER;

	src = kzalloc(sizeof(*src), GFP_KERNEL);
	if (!src)
		return -ENOMEM;

	device_initialize(&src->dev);
	src->dev.class = &stm_source_class;
	src->dev.parent = parent;
	src->dev.release = stm_source_device_release;

	err = kobject_set_name(&src->dev.kobj, "%s", data->name);
	if (err)
		goto err;

	pm_runtime_no_callbacks(&src->dev);
	pm_runtime_forbid(&src->dev);

	err = device_add(&src->dev);
	if (err)
		goto err;

	stm_output_init(&src->output);
	spin_lock_init(&src->link_lock);
	INIT_LIST_HEAD(&src->link_entry);
	src->data = data;
	data->src = src;

	return 0;

err:
	put_device(&src->dev);

	return err;
}
EXPORT_SYMBOL_GPL(stm_source_register_device);

/**
 * stm_source_unregister_device() - unregister an stm_source device
 * @data:	device description that was used to register the device
 *
 * This will remove a previously created stm_source device from the system.
 */
void stm_source_unregister_device(struct stm_source_data *data)
{
	struct stm_source_device *src = data->src;

	stm_source_link_drop(src);

	device_unregister(&src->dev);
}
EXPORT_SYMBOL_GPL(stm_source_unregister_device);

int notrace stm_source_write(struct stm_source_data *data,
			     unsigned int chan,
			     const char *buf, size_t count)
{
	struct stm_source_device *src = data->src;
	struct stm_device *stm;
	int idx;

	if (!src->output.nr_chans)
		return -ENODEV;

	if (chan >= src->output.nr_chans)
		return -EINVAL;

	idx = srcu_read_lock(&stm_source_srcu);

	stm = srcu_dereference(src->link, &stm_source_srcu);
	if (stm)
		count = stm_write(stm, &src->output, chan, buf, count);
	else
		count = -ENODEV;

	srcu_read_unlock(&stm_source_srcu, idx);

	return count;
}
EXPORT_SYMBOL_GPL(stm_source_write);

static int __init stm_core_init(void)
{
	int err;

	err = class_register(&stm_class);
	if (err)
		return err;

	err = class_register(&stm_source_class);
	if (err)
		goto err_stm;

	err = stp_configfs_init();
	if (err)
		goto err_src;

	init_srcu_struct(&stm_source_srcu);
	INIT_LIST_HEAD(&stm_pdrv_head);
	mutex_init(&stm_pdrv_mutex);

	/*
	 * So as to not confuse existing users with a requirement
	 * to load yet another module, do it here.
	 */
	if (IS_ENABLED(CONFIG_STM_PROTO_BASIC))
		(void)request_module_nowait("stm_p_basic");
	stm_core_up++;

	return 0;

err_src:
	class_unregister(&stm_source_class);
err_stm:
	class_unregister(&stm_class);

	return err;
}

module_init(stm_core_init);

static void __exit stm_core_exit(void)
{
	cleanup_srcu_struct(&stm_source_srcu);
	class_unregister(&stm_source_class);
	class_unregister(&stm_class);
	stp_configfs_exit();
}

module_exit(stm_core_exit);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("System Trace Module device class");
MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");