summaryrefslogtreecommitdiffstats
path: root/drivers/gpu/drm/drm_bridge.c
blob: e1cfba2ff583b27a00b0e9d1ac522bcceae27798 (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
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
/*
 * Copyright (c) 2014 Samsung Electronics Co., Ltd
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sub license,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the
 * next paragraph) shall be included in all copies or substantial portions
 * of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */

#include <linux/err.h>
#include <linux/media-bus-format.h>
#include <linux/module.h>
#include <linux/mutex.h>

#include <drm/drm_atomic_state_helper.h>
#include <drm/drm_bridge.h>
#include <drm/drm_debugfs.h>
#include <drm/drm_edid.h>
#include <drm/drm_encoder.h>
#include <drm/drm_file.h>
#include <drm/drm_of.h>
#include <drm/drm_print.h>

#include "drm_crtc_internal.h"

/**
 * DOC: overview
 *
 * &struct drm_bridge represents a device that hangs on to an encoder. These are
 * handy when a regular &drm_encoder entity isn't enough to represent the entire
 * encoder chain.
 *
 * A bridge is always attached to a single &drm_encoder at a time, but can be
 * either connected to it directly, or through a chain of bridges::
 *
 *     [ CRTC ---> ] Encoder ---> Bridge A ---> Bridge B
 *
 * Here, the output of the encoder feeds to bridge A, and that furthers feeds to
 * bridge B. Bridge chains can be arbitrarily long, and shall be fully linear:
 * Chaining multiple bridges to the output of a bridge, or the same bridge to
 * the output of different bridges, is not supported.
 *
 * &drm_bridge, like &drm_panel, aren't &drm_mode_object entities like planes,
 * CRTCs, encoders or connectors and hence are not visible to userspace. They
 * just provide additional hooks to get the desired output at the end of the
 * encoder chain.
 */

/**
 * DOC:	display driver integration
 *
 * Display drivers are responsible for linking encoders with the first bridge
 * in the chains. This is done by acquiring the appropriate bridge with
 * devm_drm_of_get_bridge(). Once acquired, the bridge shall be attached to the
 * encoder with a call to drm_bridge_attach().
 *
 * Bridges are responsible for linking themselves with the next bridge in the
 * chain, if any. This is done the same way as for encoders, with the call to
 * drm_bridge_attach() occurring in the &drm_bridge_funcs.attach operation.
 *
 * Once these links are created, the bridges can participate along with encoder
 * functions to perform mode validation and fixup (through
 * drm_bridge_chain_mode_valid() and drm_atomic_bridge_chain_check()), mode
 * setting (through drm_bridge_chain_mode_set()), enable (through
 * drm_atomic_bridge_chain_pre_enable() and drm_atomic_bridge_chain_enable())
 * and disable (through drm_atomic_bridge_chain_disable() and
 * drm_atomic_bridge_chain_post_disable()). Those functions call the
 * corresponding operations provided in &drm_bridge_funcs in sequence for all
 * bridges in the chain.
 *
 * For display drivers that use the atomic helpers
 * drm_atomic_helper_check_modeset(),
 * drm_atomic_helper_commit_modeset_enables() and
 * drm_atomic_helper_commit_modeset_disables() (either directly in hand-rolled
 * commit check and commit tail handlers, or through the higher-level
 * drm_atomic_helper_check() and drm_atomic_helper_commit_tail() or
 * drm_atomic_helper_commit_tail_rpm() helpers), this is done transparently and
 * requires no intervention from the driver. For other drivers, the relevant
 * DRM bridge chain functions shall be called manually.
 *
 * Bridges also participate in implementing the &drm_connector at the end of
 * the bridge chain. Display drivers may use the drm_bridge_connector_init()
 * helper to create the &drm_connector, or implement it manually on top of the
 * connector-related operations exposed by the bridge (see the overview
 * documentation of bridge operations for more details).
 */

/**
 * DOC: special care dsi
 *
 * The interaction between the bridges and other frameworks involved in
 * the probing of the upstream driver and the bridge driver can be
 * challenging. Indeed, there's multiple cases that needs to be
 * considered:
 *
 * - The upstream driver doesn't use the component framework and isn't a
 *   MIPI-DSI host. In this case, the bridge driver will probe at some
 *   point and the upstream driver should try to probe again by returning
 *   EPROBE_DEFER as long as the bridge driver hasn't probed.
 *
 * - The upstream driver doesn't use the component framework, but is a
 *   MIPI-DSI host. The bridge device uses the MIPI-DCS commands to be
 *   controlled. In this case, the bridge device is a child of the
 *   display device and when it will probe it's assured that the display
 *   device (and MIPI-DSI host) is present. The upstream driver will be
 *   assured that the bridge driver is connected between the
 *   &mipi_dsi_host_ops.attach and &mipi_dsi_host_ops.detach operations.
 *   Therefore, it must run mipi_dsi_host_register() in its probe
 *   function, and then run drm_bridge_attach() in its
 *   &mipi_dsi_host_ops.attach hook.
 *
 * - The upstream driver uses the component framework and is a MIPI-DSI
 *   host. The bridge device uses the MIPI-DCS commands to be
 *   controlled. This is the same situation than above, and can run
 *   mipi_dsi_host_register() in either its probe or bind hooks.
 *
 * - The upstream driver uses the component framework and is a MIPI-DSI
 *   host. The bridge device uses a separate bus (such as I2C) to be
 *   controlled. In this case, there's no correlation between the probe
 *   of the bridge and upstream drivers, so care must be taken to avoid
 *   an endless EPROBE_DEFER loop, with each driver waiting for the
 *   other to probe.
 *
 * The ideal pattern to cover the last item (and all the others in the
 * MIPI-DSI host driver case) is to split the operations like this:
 *
 * - The MIPI-DSI host driver must run mipi_dsi_host_register() in its
 *   probe hook. It will make sure that the MIPI-DSI host sticks around,
 *   and that the driver's bind can be called.
 *
 * - In its probe hook, the bridge driver must try to find its MIPI-DSI
 *   host, register as a MIPI-DSI device and attach the MIPI-DSI device
 *   to its host. The bridge driver is now functional.
 *
 * - In its &struct mipi_dsi_host_ops.attach hook, the MIPI-DSI host can
 *   now add its component. Its bind hook will now be called and since
 *   the bridge driver is attached and registered, we can now look for
 *   and attach it.
 *
 * At this point, we're now certain that both the upstream driver and
 * the bridge driver are functional and we can't have a deadlock-like
 * situation when probing.
 */

/**
 * DOC: dsi bridge operations
 *
 * DSI host interfaces are expected to be implemented as bridges rather than
 * encoders, however there are a few aspects of their operation that need to
 * be defined in order to provide a consistent interface.
 *
 * A DSI host should keep the PHY powered down until the pre_enable operation is
 * called. All lanes are in an undefined idle state up to this point, and it
 * must not be assumed that it is LP-11.
 * pre_enable should initialise the PHY, set the data lanes to LP-11, and the
 * clock lane to either LP-11 or HS depending on the mode_flag
 * %MIPI_DSI_CLOCK_NON_CONTINUOUS.
 *
 * Ordinarily the downstream bridge DSI peripheral pre_enable will have been
 * called before the DSI host. If the DSI peripheral requires LP-11 and/or
 * the clock lane to be in HS mode prior to pre_enable, then it can set the
 * &pre_enable_prev_first flag to request the pre_enable (and
 * post_disable) order to be altered to enable the DSI host first.
 *
 * Either the CRTC being enabled, or the DSI host enable operation should switch
 * the host to actively transmitting video on the data lanes.
 *
 * The reverse also applies. The DSI host disable operation or stopping the CRTC
 * should stop transmitting video, and the data lanes should return to the LP-11
 * state. The DSI host &post_disable operation should disable the PHY.
 * If the &pre_enable_prev_first flag is set, then the DSI peripheral's
 * bridge &post_disable will be called before the DSI host's post_disable.
 *
 * Whilst it is valid to call &host_transfer prior to pre_enable or after
 * post_disable, the exact state of the lanes is undefined at this point. The
 * DSI host should initialise the interface, transmit the data, and then disable
 * the interface again.
 *
 * Ultra Low Power State (ULPS) is not explicitly supported by DRM. If
 * implemented, it therefore needs to be handled entirely within the DSI Host
 * driver.
 */

static DEFINE_MUTEX(bridge_lock);
static LIST_HEAD(bridge_list);

/**
 * drm_bridge_add - add the given bridge to the global bridge list
 *
 * @bridge: bridge control structure
 */
void drm_bridge_add(struct drm_bridge *bridge)
{
	mutex_init(&bridge->hpd_mutex);

	mutex_lock(&bridge_lock);
	list_add_tail(&bridge->list, &bridge_list);
	mutex_unlock(&bridge_lock);
}
EXPORT_SYMBOL(drm_bridge_add);

static void drm_bridge_remove_void(void *bridge)
{
	drm_bridge_remove(bridge);
}

/**
 * devm_drm_bridge_add - devm managed version of drm_bridge_add()
 *
 * @dev: device to tie the bridge lifetime to
 * @bridge: bridge control structure
 *
 * This is the managed version of drm_bridge_add() which automatically
 * calls drm_bridge_remove() when @dev is unbound.
 *
 * Return: 0 if no error or negative error code.
 */
int devm_drm_bridge_add(struct device *dev, struct drm_bridge *bridge)
{
	drm_bridge_add(bridge);
	return devm_add_action_or_reset(dev, drm_bridge_remove_void, bridge);
}
EXPORT_SYMBOL(devm_drm_bridge_add);

/**
 * drm_bridge_remove - remove the given bridge from the global bridge list
 *
 * @bridge: bridge control structure
 */
void drm_bridge_remove(struct drm_bridge *bridge)
{
	mutex_lock(&bridge_lock);
	list_del_init(&bridge->list);
	mutex_unlock(&bridge_lock);

	mutex_destroy(&bridge->hpd_mutex);
}
EXPORT_SYMBOL(drm_bridge_remove);

static struct drm_private_state *
drm_bridge_atomic_duplicate_priv_state(struct drm_private_obj *obj)
{
	struct drm_bridge *bridge = drm_priv_to_bridge(obj);
	struct drm_bridge_state *state;

	state = bridge->funcs->atomic_duplicate_state(bridge);
	return state ? &state->base : NULL;
}

static void
drm_bridge_atomic_destroy_priv_state(struct drm_private_obj *obj,
				     struct drm_private_state *s)
{
	struct drm_bridge_state *state = drm_priv_to_bridge_state(s);
	struct drm_bridge *bridge = drm_priv_to_bridge(obj);

	bridge->funcs->atomic_destroy_state(bridge, state);
}

static const struct drm_private_state_funcs drm_bridge_priv_state_funcs = {
	.atomic_duplicate_state = drm_bridge_atomic_duplicate_priv_state,
	.atomic_destroy_state = drm_bridge_atomic_destroy_priv_state,
};

/**
 * drm_bridge_attach - attach the bridge to an encoder's chain
 *
 * @encoder: DRM encoder
 * @bridge: bridge to attach
 * @previous: previous bridge in the chain (optional)
 * @flags: DRM_BRIDGE_ATTACH_* flags
 *
 * Called by a kms driver to link the bridge to an encoder's chain. The previous
 * argument specifies the previous bridge in the chain. If NULL, the bridge is
 * linked directly at the encoder's output. Otherwise it is linked at the
 * previous bridge's output.
 *
 * If non-NULL the previous bridge must be already attached by a call to this
 * function.
 *
 * Note that bridges attached to encoders are auto-detached during encoder
 * cleanup in drm_encoder_cleanup(), so drm_bridge_attach() should generally
 * *not* be balanced with a drm_bridge_detach() in driver code.
 *
 * RETURNS:
 * Zero on success, error code on failure
 */
int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
		      struct drm_bridge *previous,
		      enum drm_bridge_attach_flags flags)
{
	int ret;

	if (!encoder || !bridge)
		return -EINVAL;

	if (previous && (!previous->dev || previous->encoder != encoder))
		return -EINVAL;

	if (bridge->dev)
		return -EBUSY;

	bridge->dev = encoder->dev;
	bridge->encoder = encoder;

	if (previous)
		list_add(&bridge->chain_node, &previous->chain_node);
	else
		list_add(&bridge->chain_node, &encoder->bridge_chain);

	if (bridge->funcs->attach) {
		ret = bridge->funcs->attach(bridge, flags);
		if (ret < 0)
			goto err_reset_bridge;
	}

	if (bridge->funcs->atomic_reset) {
		struct drm_bridge_state *state;

		state = bridge->funcs->atomic_reset(bridge);
		if (IS_ERR(state)) {
			ret = PTR_ERR(state);
			goto err_detach_bridge;
		}

		drm_atomic_private_obj_init(bridge->dev, &bridge->base,
					    &state->base,
					    &drm_bridge_priv_state_funcs);
	}

	return 0;

err_detach_bridge:
	if (bridge->funcs->detach)
		bridge->funcs->detach(bridge);

err_reset_bridge:
	bridge->dev = NULL;
	bridge->encoder = NULL;
	list_del(&bridge->chain_node);

#ifdef CONFIG_OF
	DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
		  bridge->of_node, encoder->name, ret);
#else
	DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
		  encoder->name, ret);
#endif

	return ret;
}
EXPORT_SYMBOL(drm_bridge_attach);

void drm_bridge_detach(struct drm_bridge *bridge)
{
	if (WARN_ON(!bridge))
		return;

	if (WARN_ON(!bridge->dev))
		return;

	if (bridge->funcs->atomic_reset)
		drm_atomic_private_obj_fini(&bridge->base);

	if (bridge->funcs->detach)
		bridge->funcs->detach(bridge);

	list_del(&bridge->chain_node);
	bridge->dev = NULL;
}

/**
 * DOC: bridge operations
 *
 * Bridge drivers expose operations through the &drm_bridge_funcs structure.
 * The DRM internals (atomic and CRTC helpers) use the helpers defined in
 * drm_bridge.c to call bridge operations. Those operations are divided in
 * three big categories to support different parts of the bridge usage.
 *
 * - The encoder-related operations support control of the bridges in the
 *   chain, and are roughly counterparts to the &drm_encoder_helper_funcs
 *   operations. They are used by the legacy CRTC and the atomic modeset
 *   helpers to perform mode validation, fixup and setting, and enable and
 *   disable the bridge automatically.
 *
 *   The enable and disable operations are split in
 *   &drm_bridge_funcs.pre_enable, &drm_bridge_funcs.enable,
 *   &drm_bridge_funcs.disable and &drm_bridge_funcs.post_disable to provide
 *   finer-grained control.
 *
 *   Bridge drivers may implement the legacy version of those operations, or
 *   the atomic version (prefixed with atomic\_), in which case they shall also
 *   implement the atomic state bookkeeping operations
 *   (&drm_bridge_funcs.atomic_duplicate_state,
 *   &drm_bridge_funcs.atomic_destroy_state and &drm_bridge_funcs.reset).
 *   Mixing atomic and non-atomic versions of the operations is not supported.
 *
 * - The bus format negotiation operations
 *   &drm_bridge_funcs.atomic_get_output_bus_fmts and
 *   &drm_bridge_funcs.atomic_get_input_bus_fmts allow bridge drivers to
 *   negotiate the formats transmitted between bridges in the chain when
 *   multiple formats are supported. Negotiation for formats is performed
 *   transparently for display drivers by the atomic modeset helpers. Only
 *   atomic versions of those operations exist, bridge drivers that need to
 *   implement them shall thus also implement the atomic version of the
 *   encoder-related operations. This feature is not supported by the legacy
 *   CRTC helpers.
 *
 * - The connector-related operations support implementing a &drm_connector
 *   based on a chain of bridges. DRM bridges traditionally create a
 *   &drm_connector for bridges meant to be used at the end of the chain. This
 *   puts additional burden on bridge drivers, especially for bridges that may
 *   be used in the middle of a chain or at the end of it. Furthermore, it
 *   requires all operations of the &drm_connector to be handled by a single
 *   bridge, which doesn't always match the hardware architecture.
 *
 *   To simplify bridge drivers and make the connector implementation more
 *   flexible, a new model allows bridges to unconditionally skip creation of
 *   &drm_connector and instead expose &drm_bridge_funcs operations to support
 *   an externally-implemented &drm_connector. Those operations are
 *   &drm_bridge_funcs.detect, &drm_bridge_funcs.get_modes,
 *   &drm_bridge_funcs.get_edid, &drm_bridge_funcs.hpd_notify,
 *   &drm_bridge_funcs.hpd_enable and &drm_bridge_funcs.hpd_disable. When
 *   implemented, display drivers shall create a &drm_connector instance for
 *   each chain of bridges, and implement those connector instances based on
 *   the bridge connector operations.
 *
 *   Bridge drivers shall implement the connector-related operations for all
 *   the features that the bridge hardware support. For instance, if a bridge
 *   supports reading EDID, the &drm_bridge_funcs.get_edid shall be
 *   implemented. This however doesn't mean that the DDC lines are wired to the
 *   bridge on a particular platform, as they could also be connected to an I2C
 *   controller of the SoC. Support for the connector-related operations on the
 *   running platform is reported through the &drm_bridge.ops flags. Bridge
 *   drivers shall detect which operations they can support on the platform
 *   (usually this information is provided by ACPI or DT), and set the
 *   &drm_bridge.ops flags for all supported operations. A flag shall only be
 *   set if the corresponding &drm_bridge_funcs operation is implemented, but
 *   an implemented operation doesn't necessarily imply that the corresponding
 *   flag will be set. Display drivers shall use the &drm_bridge.ops flags to
 *   decide which bridge to delegate a connector operation to. This mechanism
 *   allows providing a single static const &drm_bridge_funcs instance in
 *   bridge drivers, improving security by storing function pointers in
 *   read-only memory.
 *
 *   In order to ease transition, bridge drivers may support both the old and
 *   new models by making connector creation optional and implementing the
 *   connected-related bridge operations. Connector creation is then controlled
 *   by the flags argument to the drm_bridge_attach() function. Display drivers
 *   that support the new model and create connectors themselves shall set the
 *   %DRM_BRIDGE_ATTACH_NO_CONNECTOR flag, and bridge drivers shall then skip
 *   connector creation. For intermediate bridges in the chain, the flag shall
 *   be passed to the drm_bridge_attach() call for the downstream bridge.
 *   Bridge drivers that implement the new model only shall return an error
 *   from their &drm_bridge_funcs.attach handler when the
 *   %DRM_BRIDGE_ATTACH_NO_CONNECTOR flag is not set. New display drivers
 *   should use the new model, and convert the bridge drivers they use if
 *   needed, in order to gradually transition to the new model.
 */

/**
 * drm_bridge_chain_mode_fixup - fixup proposed mode for all bridges in the
 *				 encoder chain
 * @bridge: bridge control structure
 * @mode: desired mode to be set for the bridge
 * @adjusted_mode: updated mode that works for this bridge
 *
 * Calls &drm_bridge_funcs.mode_fixup for all the bridges in the
 * encoder chain, starting from the first bridge to the last.
 *
 * Note: the bridge passed should be the one closest to the encoder
 *
 * RETURNS:
 * true on success, false on failure
 */
bool drm_bridge_chain_mode_fixup(struct drm_bridge *bridge,
				 const struct drm_display_mode *mode,
				 struct drm_display_mode *adjusted_mode)
{
	struct drm_encoder *encoder;

	if (!bridge)
		return true;

	encoder = bridge->encoder;
	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
		if (!bridge->funcs->mode_fixup)
			continue;

		if (!bridge->funcs->mode_fixup(bridge, mode, adjusted_mode))
			return false;
	}

	return true;
}
EXPORT_SYMBOL(drm_bridge_chain_mode_fixup);

/**
 * drm_bridge_chain_mode_valid - validate the mode against all bridges in the
 *				 encoder chain.
 * @bridge: bridge control structure
 * @info: display info against which the mode shall be validated
 * @mode: desired mode to be validated
 *
 * Calls &drm_bridge_funcs.mode_valid for all the bridges in the encoder
 * chain, starting from the first bridge to the last. If at least one bridge
 * does not accept the mode the function returns the error code.
 *
 * Note: the bridge passed should be the one closest to the encoder.
 *
 * RETURNS:
 * MODE_OK on success, drm_mode_status Enum error code on failure
 */
enum drm_mode_status
drm_bridge_chain_mode_valid(struct drm_bridge *bridge,
			    const struct drm_display_info *info,
			    const struct drm_display_mode *mode)
{
	struct drm_encoder *encoder;

	if (!bridge)
		return MODE_OK;

	encoder = bridge->encoder;
	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
		enum drm_mode_status ret;

		if (!bridge->funcs->mode_valid)
			continue;

		ret = bridge->funcs->mode_valid(bridge, info, mode);
		if (ret != MODE_OK)
			return ret;
	}

	return MODE_OK;
}
EXPORT_SYMBOL(drm_bridge_chain_mode_valid);

/**
 * drm_bridge_chain_mode_set - set proposed mode for all bridges in the
 *			       encoder chain
 * @bridge: bridge control structure
 * @mode: desired mode to be set for the encoder chain
 * @adjusted_mode: updated mode that works for this encoder chain
 *
 * Calls &drm_bridge_funcs.mode_set op for all the bridges in the
 * encoder chain, starting from the first bridge to the last.
 *
 * Note: the bridge passed should be the one closest to the encoder
 */
void drm_bridge_chain_mode_set(struct drm_bridge *bridge,
			       const struct drm_display_mode *mode,
			       const struct drm_display_mode *adjusted_mode)
{
	struct drm_encoder *encoder;

	if (!bridge)
		return;

	encoder = bridge->encoder;
	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
		if (bridge->funcs->mode_set)
			bridge->funcs->mode_set(bridge, mode, adjusted_mode);
	}
}
EXPORT_SYMBOL(drm_bridge_chain_mode_set);

/**
 * drm_atomic_bridge_chain_disable - disables all bridges in the encoder chain
 * @bridge: bridge control structure
 * @old_state: old atomic state
 *
 * Calls &drm_bridge_funcs.atomic_disable (falls back on
 * &drm_bridge_funcs.disable) op for all the bridges in the encoder chain,
 * starting from the last bridge to the first. These are called before calling
 * &drm_encoder_helper_funcs.atomic_disable
 *
 * Note: the bridge passed should be the one closest to the encoder
 */
void drm_atomic_bridge_chain_disable(struct drm_bridge *bridge,
				     struct drm_atomic_state *old_state)
{
	struct drm_encoder *encoder;
	struct drm_bridge *iter;

	if (!bridge)
		return;

	encoder = bridge->encoder;
	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
		if (iter->funcs->atomic_disable) {
			struct drm_bridge_state *old_bridge_state;

			old_bridge_state =
				drm_atomic_get_old_bridge_state(old_state,
								iter);
			if (WARN_ON(!old_bridge_state))
				return;

			iter->funcs->atomic_disable(iter, old_bridge_state);
		} else if (iter->funcs->disable) {
			iter->funcs->disable(iter);
		}

		if (iter == bridge)
			break;
	}
}
EXPORT_SYMBOL(drm_atomic_bridge_chain_disable);

static void drm_atomic_bridge_call_post_disable(struct drm_bridge *bridge,
						struct drm_atomic_state *old_state)
{
	if (old_state && bridge->funcs->atomic_post_disable) {
		struct drm_bridge_state *old_bridge_state;

		old_bridge_state =
			drm_atomic_get_old_bridge_state(old_state,
							bridge);
		if (WARN_ON(!old_bridge_state))
			return;

		bridge->funcs->atomic_post_disable(bridge,
						   old_bridge_state);
	} else if (bridge->funcs->post_disable) {
		bridge->funcs->post_disable(bridge);
	}
}

/**
 * drm_atomic_bridge_chain_post_disable - cleans up after disabling all bridges
 *					  in the encoder chain
 * @bridge: bridge control structure
 * @old_state: old atomic state
 *
 * Calls &drm_bridge_funcs.atomic_post_disable (falls back on
 * &drm_bridge_funcs.post_disable) op for all the bridges in the encoder chain,
 * starting from the first bridge to the last. These are called after completing
 * &drm_encoder_helper_funcs.atomic_disable
 *
 * If a bridge sets @pre_enable_prev_first, then the @post_disable for that
 * bridge will be called before the previous one to reverse the @pre_enable
 * calling direction.
 *
 * Note: the bridge passed should be the one closest to the encoder
 */
void drm_atomic_bridge_chain_post_disable(struct drm_bridge *bridge,
					  struct drm_atomic_state *old_state)
{
	struct drm_encoder *encoder;
	struct drm_bridge *next, *limit;

	if (!bridge)
		return;

	encoder = bridge->encoder;

	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
		limit = NULL;

		if (!list_is_last(&bridge->chain_node, &encoder->bridge_chain)) {
			next = list_next_entry(bridge, chain_node);

			if (next->pre_enable_prev_first) {
				/* next bridge had requested that prev
				 * was enabled first, so disabled last
				 */
				limit = next;

				/* Find the next bridge that has NOT requested
				 * prev to be enabled first / disabled last
				 */
				list_for_each_entry_from(next, &encoder->bridge_chain,
							 chain_node) {
					if (next->pre_enable_prev_first) {
						next = list_prev_entry(next, chain_node);
						limit = next;
						break;
					}
				}

				/* Call these bridges in reverse order */
				list_for_each_entry_from_reverse(next, &encoder->bridge_chain,
								 chain_node) {
					if (next == bridge)
						break;

					drm_atomic_bridge_call_post_disable(next,
									    old_state);
				}
			}
		}

		drm_atomic_bridge_call_post_disable(bridge, old_state);

		if (limit)
			/* Jump all bridges that we have already post_disabled */
			bridge = limit;
	}
}
EXPORT_SYMBOL(drm_atomic_bridge_chain_post_disable);

static void drm_atomic_bridge_call_pre_enable(struct drm_bridge *bridge,
					      struct drm_atomic_state *old_state)
{
	if (old_state && bridge->funcs->atomic_pre_enable) {
		struct drm_bridge_state *old_bridge_state;

		old_bridge_state =
			drm_atomic_get_old_bridge_state(old_state,
							bridge);
		if (WARN_ON(!old_bridge_state))
			return;

		bridge->funcs->atomic_pre_enable(bridge, old_bridge_state);
	} else if (bridge->funcs->pre_enable) {
		bridge->funcs->pre_enable(bridge);
	}
}

/**
 * drm_atomic_bridge_chain_pre_enable - prepares for enabling all bridges in
 *					the encoder chain
 * @bridge: bridge control structure
 * @old_state: old atomic state
 *
 * Calls &drm_bridge_funcs.atomic_pre_enable (falls back on
 * &drm_bridge_funcs.pre_enable) op for all the bridges in the encoder chain,
 * starting from the last bridge to the first. These are called before calling
 * &drm_encoder_helper_funcs.atomic_enable
 *
 * If a bridge sets @pre_enable_prev_first, then the pre_enable for the
 * prev bridge will be called before pre_enable of this bridge.
 *
 * Note: the bridge passed should be the one closest to the encoder
 */
void drm_atomic_bridge_chain_pre_enable(struct drm_bridge *bridge,
					struct drm_atomic_state *old_state)
{
	struct drm_encoder *encoder;
	struct drm_bridge *iter, *next, *limit;

	if (!bridge)
		return;

	encoder = bridge->encoder;

	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
		if (iter->pre_enable_prev_first) {
			next = iter;
			limit = bridge;
			list_for_each_entry_from_reverse(next,
							 &encoder->bridge_chain,
							 chain_node) {
				if (next == bridge)
					break;

				if (!next->pre_enable_prev_first) {
					/* Found first bridge that does NOT
					 * request prev to be enabled first
					 */
					limit = list_prev_entry(next, chain_node);
					break;
				}
			}

			list_for_each_entry_from(next, &encoder->bridge_chain, chain_node) {
				/* Call requested prev bridge pre_enable
				 * in order.
				 */
				if (next == iter)
					/* At the first bridge to request prev
					 * bridges called first.
					 */
					break;

				drm_atomic_bridge_call_pre_enable(next, old_state);
			}
		}

		drm_atomic_bridge_call_pre_enable(iter, old_state);

		if (iter->pre_enable_prev_first)
			/* Jump all bridges that we have already pre_enabled */
			iter = limit;

		if (iter == bridge)
			break;
	}
}
EXPORT_SYMBOL(drm_atomic_bridge_chain_pre_enable);

/**
 * drm_atomic_bridge_chain_enable - enables all bridges in the encoder chain
 * @bridge: bridge control structure
 * @old_state: old atomic state
 *
 * Calls &drm_bridge_funcs.atomic_enable (falls back on
 * &drm_bridge_funcs.enable) op for all the bridges in the encoder chain,
 * starting from the first bridge to the last. These are called after completing
 * &drm_encoder_helper_funcs.atomic_enable
 *
 * Note: the bridge passed should be the one closest to the encoder
 */
void drm_atomic_bridge_chain_enable(struct drm_bridge *bridge,
				    struct drm_atomic_state *old_state)
{
	struct drm_encoder *encoder;

	if (!bridge)
		return;

	encoder = bridge->encoder;
	list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
		if (bridge->funcs->atomic_enable) {
			struct drm_bridge_state *old_bridge_state;

			old_bridge_state =
				drm_atomic_get_old_bridge_state(old_state,
								bridge);
			if (WARN_ON(!old_bridge_state))
				return;

			bridge->funcs->atomic_enable(bridge, old_bridge_state);
		} else if (bridge->funcs->enable) {
			bridge->funcs->enable(bridge);
		}
	}
}
EXPORT_SYMBOL(drm_atomic_bridge_chain_enable);

static int drm_atomic_bridge_check(struct drm_bridge *bridge,
				   struct drm_crtc_state *crtc_state,
				   struct drm_connector_state *conn_state)
{
	if (bridge->funcs->atomic_check) {
		struct drm_bridge_state *bridge_state;
		int ret;

		bridge_state = drm_atomic_get_new_bridge_state(crtc_state->state,
							       bridge);
		if (WARN_ON(!bridge_state))
			return -EINVAL;

		ret = bridge->funcs->atomic_check(bridge, bridge_state,
						  crtc_state, conn_state);
		if (ret)
			return ret;
	} else if (bridge->funcs->mode_fixup) {
		if (!bridge->funcs->mode_fixup(bridge, &crtc_state->mode,
					       &crtc_state->adjusted_mode))
			return -EINVAL;
	}

	return 0;
}

static int select_bus_fmt_recursive(struct drm_bridge *first_bridge,
				    struct drm_bridge *cur_bridge,
				    struct drm_crtc_state *crtc_state,
				    struct drm_connector_state *conn_state,
				    u32 out_bus_fmt)
{
	unsigned int i, num_in_bus_fmts = 0;
	struct drm_bridge_state *cur_state;
	struct drm_bridge *prev_bridge;
	u32 *in_bus_fmts;
	int ret;

	prev_bridge = drm_bridge_get_prev_bridge(cur_bridge);
	cur_state = drm_atomic_get_new_bridge_state(crtc_state->state,
						    cur_bridge);

	/*
	 * If bus format negotiation is not supported by this bridge, let's
	 * pass MEDIA_BUS_FMT_FIXED to the previous bridge in the chain and
	 * hope that it can handle this situation gracefully (by providing
	 * appropriate default values).
	 */
	if (!cur_bridge->funcs->atomic_get_input_bus_fmts) {
		if (cur_bridge != first_bridge) {
			ret = select_bus_fmt_recursive(first_bridge,
						       prev_bridge, crtc_state,
						       conn_state,
						       MEDIA_BUS_FMT_FIXED);
			if (ret)
				return ret;
		}

		/*
		 * Driver does not implement the atomic state hooks, but that's
		 * fine, as long as it does not access the bridge state.
		 */
		if (cur_state) {
			cur_state->input_bus_cfg.format = MEDIA_BUS_FMT_FIXED;
			cur_state->output_bus_cfg.format = out_bus_fmt;
		}

		return 0;
	}

	/*
	 * If the driver implements ->atomic_get_input_bus_fmts() it
	 * should also implement the atomic state hooks.
	 */
	if (WARN_ON(!cur_state))
		return -EINVAL;

	in_bus_fmts = cur_bridge->funcs->atomic_get_input_bus_fmts(cur_bridge,
							cur_state,
							crtc_state,
							conn_state,
							out_bus_fmt,
							&num_in_bus_fmts);
	if (!num_in_bus_fmts)
		return -ENOTSUPP;
	else if (!in_bus_fmts)
		return -ENOMEM;

	if (first_bridge == cur_bridge) {
		cur_state->input_bus_cfg.format = in_bus_fmts[0];
		cur_state->output_bus_cfg.format = out_bus_fmt;
		kfree(in_bus_fmts);
		return 0;
	}

	for (i = 0; i < num_in_bus_fmts; i++) {
		ret = select_bus_fmt_recursive(first_bridge, prev_bridge,
					       crtc_state, conn_state,
					       in_bus_fmts[i]);
		if (ret != -ENOTSUPP)
			break;
	}

	if (!ret) {
		cur_state->input_bus_cfg.format = in_bus_fmts[i];
		cur_state->output_bus_cfg.format = out_bus_fmt;
	}

	kfree(in_bus_fmts);
	return ret;
}

/*
 * This function is called by &drm_atomic_bridge_chain_check() just before
 * calling &drm_bridge_funcs.atomic_check() on all elements of the chain.
 * It performs bus format negotiation between bridge elements. The negotiation
 * happens in reverse order, starting from the last element in the chain up to
 * @bridge.
 *
 * Negotiation starts by retrieving supported output bus formats on the last
 * bridge element and testing them one by one. The test is recursive, meaning
 * that for each tested output format, the whole chain will be walked backward,
 * and each element will have to choose an input bus format that can be
 * transcoded to the requested output format. When a bridge element does not
 * support transcoding into a specific output format -ENOTSUPP is returned and
 * the next bridge element will have to try a different format. If none of the
 * combinations worked, -ENOTSUPP is returned and the atomic modeset will fail.
 *
 * This implementation is relying on
 * &drm_bridge_funcs.atomic_get_output_bus_fmts() and
 * &drm_bridge_funcs.atomic_get_input_bus_fmts() to gather supported
 * input/output formats.
 *
 * When &drm_bridge_funcs.atomic_get_output_bus_fmts() is not implemented by
 * the last element of the chain, &drm_atomic_bridge_chain_select_bus_fmts()
 * tries a single format: &drm_connector.display_info.bus_formats[0] if
 * available, MEDIA_BUS_FMT_FIXED otherwise.
 *
 * When &drm_bridge_funcs.atomic_get_input_bus_fmts() is not implemented,
 * &drm_atomic_bridge_chain_select_bus_fmts() skips the negotiation on the
 * bridge element that lacks this hook and asks the previous element in the
 * chain to try MEDIA_BUS_FMT_FIXED. It's up to bridge drivers to decide what
 * to do in that case (fail if they want to enforce bus format negotiation, or
 * provide a reasonable default if they need to support pipelines where not
 * all elements support bus format negotiation).
 */
static int
drm_atomic_bridge_chain_select_bus_fmts(struct drm_bridge *bridge,
					struct drm_crtc_state *crtc_state,
					struct drm_connector_state *conn_state)
{
	struct drm_connector *conn = conn_state->connector;
	struct drm_encoder *encoder = bridge->encoder;
	struct drm_bridge_state *last_bridge_state;
	unsigned int i, num_out_bus_fmts = 0;
	struct drm_bridge *last_bridge;
	u32 *out_bus_fmts;
	int ret = 0;

	last_bridge = list_last_entry(&encoder->bridge_chain,
				      struct drm_bridge, chain_node);
	last_bridge_state = drm_atomic_get_new_bridge_state(crtc_state->state,
							    last_bridge);

	if (last_bridge->funcs->atomic_get_output_bus_fmts) {
		const struct drm_bridge_funcs *funcs = last_bridge->funcs;

		/*
		 * If the driver implements ->atomic_get_output_bus_fmts() it
		 * should also implement the atomic state hooks.
		 */
		if (WARN_ON(!last_bridge_state))
			return -EINVAL;

		out_bus_fmts = funcs->atomic_get_output_bus_fmts(last_bridge,
							last_bridge_state,
							crtc_state,
							conn_state,
							&num_out_bus_fmts);
		if (!num_out_bus_fmts)
			return -ENOTSUPP;
		else if (!out_bus_fmts)
			return -ENOMEM;
	} else {
		num_out_bus_fmts = 1;
		out_bus_fmts = kmalloc(sizeof(*out_bus_fmts), GFP_KERNEL);
		if (!out_bus_fmts)
			return -ENOMEM;

		if (conn->display_info.num_bus_formats &&
		    conn->display_info.bus_formats)
			out_bus_fmts[0] = conn->display_info.bus_formats[0];
		else
			out_bus_fmts[0] = MEDIA_BUS_FMT_FIXED;
	}

	for (i = 0; i < num_out_bus_fmts; i++) {
		ret = select_bus_fmt_recursive(bridge, last_bridge, crtc_state,
					       conn_state, out_bus_fmts[i]);
		if (ret != -ENOTSUPP)
			break;
	}

	kfree(out_bus_fmts);

	return ret;
}

static void
drm_atomic_bridge_propagate_bus_flags(struct drm_bridge *bridge,
				      struct drm_connector *conn,
				      struct drm_atomic_state *state)
{
	struct drm_bridge_state *bridge_state, *next_bridge_state;
	struct drm_bridge *next_bridge;
	u32 output_flags = 0;

	bridge_state = drm_atomic_get_new_bridge_state(state, bridge);

	/* No bridge state attached to this bridge => nothing to propagate. */
	if (!bridge_state)
		return;

	next_bridge = drm_bridge_get_next_bridge(bridge);

	/*
	 * Let's try to apply the most common case here, that is, propagate
	 * display_info flags for the last bridge, and propagate the input
	 * flags of the next bridge element to the output end of the current
	 * bridge when the bridge is not the last one.
	 * There are exceptions to this rule, like when signal inversion is
	 * happening at the board level, but that's something drivers can deal
	 * with from their &drm_bridge_funcs.atomic_check() implementation by
	 * simply overriding the flags value we've set here.
	 */
	if (!next_bridge) {
		output_flags = conn->display_info.bus_flags;
	} else {
		next_bridge_state = drm_atomic_get_new_bridge_state(state,
								next_bridge);
		/*
		 * No bridge state attached to the next bridge, just leave the
		 * flags to 0.
		 */
		if (next_bridge_state)
			output_flags = next_bridge_state->input_bus_cfg.flags;
	}

	bridge_state->output_bus_cfg.flags = output_flags;

	/*
	 * Propagate the output flags to the input end of the bridge. Again, it's
	 * not necessarily what all bridges want, but that's what most of them
	 * do, and by doing that by default we avoid forcing drivers to
	 * duplicate the "dummy propagation" logic.
	 */
	bridge_state->input_bus_cfg.flags = output_flags;
}

/**
 * drm_atomic_bridge_chain_check() - Do an atomic check on the bridge chain
 * @bridge: bridge control structure
 * @crtc_state: new CRTC state
 * @conn_state: new connector state
 *
 * First trigger a bus format negotiation before calling
 * &drm_bridge_funcs.atomic_check() (falls back on
 * &drm_bridge_funcs.mode_fixup()) op for all the bridges in the encoder chain,
 * starting from the last bridge to the first. These are called before calling
 * &drm_encoder_helper_funcs.atomic_check()
 *
 * RETURNS:
 * 0 on success, a negative error code on failure
 */
int drm_atomic_bridge_chain_check(struct drm_bridge *bridge,
				  struct drm_crtc_state *crtc_state,
				  struct drm_connector_state *conn_state)
{
	struct drm_connector *conn = conn_state->connector;
	struct drm_encoder *encoder;
	struct drm_bridge *iter;
	int ret;

	if (!bridge)
		return 0;

	ret = drm_atomic_bridge_chain_select_bus_fmts(bridge, crtc_state,
						      conn_state);
	if (ret)
		return ret;

	encoder = bridge->encoder;
	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
		int ret;

		/*
		 * Bus flags are propagated by default. If a bridge needs to
		 * tweak the input bus flags for any reason, it should happen
		 * in its &drm_bridge_funcs.atomic_check() implementation such
		 * that preceding bridges in the chain can propagate the new
		 * bus flags.
		 */
		drm_atomic_bridge_propagate_bus_flags(iter, conn,
						      crtc_state->state);

		ret = drm_atomic_bridge_check(iter, crtc_state, conn_state);
		if (ret)
			return ret;

		if (iter == bridge)
			break;
	}

	return 0;
}
EXPORT_SYMBOL(drm_atomic_bridge_chain_check);

/**
 * drm_bridge_detect - check if anything is attached to the bridge output
 * @bridge: bridge control structure
 *
 * If the bridge supports output detection, as reported by the
 * DRM_BRIDGE_OP_DETECT bridge ops flag, call &drm_bridge_funcs.detect for the
 * bridge and return the connection status. Otherwise return
 * connector_status_unknown.
 *
 * RETURNS:
 * The detection status on success, or connector_status_unknown if the bridge
 * doesn't support output detection.
 */
enum drm_connector_status drm_bridge_detect(struct drm_bridge *bridge)
{
	if (!(bridge->ops & DRM_BRIDGE_OP_DETECT))
		return connector_status_unknown;

	return bridge->funcs->detect(bridge);
}
EXPORT_SYMBOL_GPL(drm_bridge_detect);

/**
 * drm_bridge_get_modes - fill all modes currently valid for the sink into the
 * @connector
 * @bridge: bridge control structure
 * @connector: the connector to fill with modes
 *
 * If the bridge supports output modes retrieval, as reported by the
 * DRM_BRIDGE_OP_MODES bridge ops flag, call &drm_bridge_funcs.get_modes to
 * fill the connector with all valid modes and return the number of modes
 * added. Otherwise return 0.
 *
 * RETURNS:
 * The number of modes added to the connector.
 */
int drm_bridge_get_modes(struct drm_bridge *bridge,
			 struct drm_connector *connector)
{
	if (!(bridge->ops & DRM_BRIDGE_OP_MODES))
		return 0;

	return bridge->funcs->get_modes(bridge, connector);
}
EXPORT_SYMBOL_GPL(drm_bridge_get_modes);

/**
 * drm_bridge_edid_read - read the EDID data of the connected display
 * @bridge: bridge control structure
 * @connector: the connector to read EDID for
 *
 * If the bridge supports output EDID retrieval, as reported by the
 * DRM_BRIDGE_OP_EDID bridge ops flag, call &drm_bridge_funcs.edid_read to get
 * the EDID and return it. Otherwise return NULL.
 *
 * If &drm_bridge_funcs.edid_read is not set, fall back to using
 * drm_bridge_get_edid() and wrapping it in struct drm_edid.
 *
 * RETURNS:
 * The retrieved EDID on success, or NULL otherwise.
 */
const struct drm_edid *drm_bridge_edid_read(struct drm_bridge *bridge,
					    struct drm_connector *connector)
{
	if (!(bridge->ops & DRM_BRIDGE_OP_EDID))
		return NULL;

	/* Transitional: Fall back to ->get_edid. */
	if (!bridge->funcs->edid_read) {
		const struct drm_edid *drm_edid;
		struct edid *edid;

		edid = drm_bridge_get_edid(bridge, connector);
		if (!edid)
			return NULL;

		drm_edid = drm_edid_alloc(edid, (edid->extensions + 1) * EDID_LENGTH);

		kfree(edid);

		return drm_edid;
	}

	return bridge->funcs->edid_read(bridge, connector);
}
EXPORT_SYMBOL_GPL(drm_bridge_edid_read);

/**
 * drm_bridge_get_edid - get the EDID data of the connected display
 * @bridge: bridge control structure
 * @connector: the connector to read EDID for
 *
 * If the bridge supports output EDID retrieval, as reported by the
 * DRM_BRIDGE_OP_EDID bridge ops flag, call &drm_bridge_funcs.get_edid to
 * get the EDID and return it. Otherwise return NULL.
 *
 * Deprecated. Prefer using drm_bridge_edid_read().
 *
 * RETURNS:
 * The retrieved EDID on success, or NULL otherwise.
 */
struct edid *drm_bridge_get_edid(struct drm_bridge *bridge,
				 struct drm_connector *connector)
{
	if (!(bridge->ops & DRM_BRIDGE_OP_EDID))
		return NULL;

	return bridge->funcs->get_edid(bridge, connector);
}
EXPORT_SYMBOL_GPL(drm_bridge_get_edid);

/**
 * drm_bridge_hpd_enable - enable hot plug detection for the bridge
 * @bridge: bridge control structure
 * @cb: hot-plug detection callback
 * @data: data to be passed to the hot-plug detection callback
 *
 * Call &drm_bridge_funcs.hpd_enable if implemented and register the given @cb
 * and @data as hot plug notification callback. From now on the @cb will be
 * called with @data when an output status change is detected by the bridge,
 * until hot plug notification gets disabled with drm_bridge_hpd_disable().
 *
 * Hot plug detection is supported only if the DRM_BRIDGE_OP_HPD flag is set in
 * bridge->ops. This function shall not be called when the flag is not set.
 *
 * Only one hot plug detection callback can be registered at a time, it is an
 * error to call this function when hot plug detection is already enabled for
 * the bridge.
 */
void drm_bridge_hpd_enable(struct drm_bridge *bridge,
			   void (*cb)(void *data,
				      enum drm_connector_status status),
			   void *data)
{
	if (!(bridge->ops & DRM_BRIDGE_OP_HPD))
		return;

	mutex_lock(&bridge->hpd_mutex);

	if (WARN(bridge->hpd_cb, "Hot plug detection already enabled\n"))
		goto unlock;

	bridge->hpd_cb = cb;
	bridge->hpd_data = data;

	if (bridge->funcs->hpd_enable)
		bridge->funcs->hpd_enable(bridge);

unlock:
	mutex_unlock(&bridge->hpd_mutex);
}
EXPORT_SYMBOL_GPL(drm_bridge_hpd_enable);

/**
 * drm_bridge_hpd_disable - disable hot plug detection for the bridge
 * @bridge: bridge control structure
 *
 * Call &drm_bridge_funcs.hpd_disable if implemented and unregister the hot
 * plug detection callback previously registered with drm_bridge_hpd_enable().
 * Once this function returns the callback will not be called by the bridge
 * when an output status change occurs.
 *
 * Hot plug detection is supported only if the DRM_BRIDGE_OP_HPD flag is set in
 * bridge->ops. This function shall not be called when the flag is not set.
 */
void drm_bridge_hpd_disable(struct drm_bridge *bridge)
{
	if (!(bridge->ops & DRM_BRIDGE_OP_HPD))
		return;

	mutex_lock(&bridge->hpd_mutex);
	if (bridge->funcs->hpd_disable)
		bridge->funcs->hpd_disable(bridge);

	bridge->hpd_cb = NULL;
	bridge->hpd_data = NULL;
	mutex_unlock(&bridge->hpd_mutex);
}
EXPORT_SYMBOL_GPL(drm_bridge_hpd_disable);

/**
 * drm_bridge_hpd_notify - notify hot plug detection events
 * @bridge: bridge control structure
 * @status: output connection status
 *
 * Bridge drivers shall call this function to report hot plug events when they
 * detect a change in the output status, when hot plug detection has been
 * enabled by drm_bridge_hpd_enable().
 *
 * This function shall be called in a context that can sleep.
 */
void drm_bridge_hpd_notify(struct drm_bridge *bridge,
			   enum drm_connector_status status)
{
	mutex_lock(&bridge->hpd_mutex);
	if (bridge->hpd_cb)
		bridge->hpd_cb(bridge->hpd_data, status);
	mutex_unlock(&bridge->hpd_mutex);
}
EXPORT_SYMBOL_GPL(drm_bridge_hpd_notify);

#ifdef CONFIG_OF
/**
 * of_drm_find_bridge - find the bridge corresponding to the device node in
 *			the global bridge list
 *
 * @np: device node
 *
 * RETURNS:
 * drm_bridge control struct on success, NULL on failure
 */
struct drm_bridge *of_drm_find_bridge(struct device_node *np)
{
	struct drm_bridge *bridge;

	mutex_lock(&bridge_lock);

	list_for_each_entry(bridge, &bridge_list, list) {
		if (bridge->of_node == np) {
			mutex_unlock(&bridge_lock);
			return bridge;
		}
	}

	mutex_unlock(&bridge_lock);
	return NULL;
}
EXPORT_SYMBOL(of_drm_find_bridge);
#endif

#ifdef CONFIG_DEBUG_FS
static int drm_bridge_chains_info(struct seq_file *m, void *data)
{
	struct drm_debugfs_entry *entry = m->private;
	struct drm_device *dev = entry->dev;
	struct drm_printer p = drm_seq_file_printer(m);
	struct drm_mode_config *config = &dev->mode_config;
	struct drm_encoder *encoder;
	unsigned int bridge_idx = 0;

	list_for_each_entry(encoder, &config->encoder_list, head) {
		struct drm_bridge *bridge;

		drm_printf(&p, "encoder[%u]\n", encoder->base.id);

		drm_for_each_bridge_in_chain(encoder, bridge) {
			drm_printf(&p, "\tbridge[%u] type: %u, ops: %#x",
				   bridge_idx, bridge->type, bridge->ops);

#ifdef CONFIG_OF
			if (bridge->of_node)
				drm_printf(&p, ", OF: %pOFfc", bridge->of_node);
#endif

			drm_printf(&p, "\n");

			bridge_idx++;
		}
	}

	return 0;
}

static const struct drm_debugfs_info drm_bridge_debugfs_list[] = {
	{ "bridge_chains", drm_bridge_chains_info, 0 },
};

void drm_bridge_debugfs_init(struct drm_device *dev)
{
	drm_debugfs_add_files(dev, drm_bridge_debugfs_list,
			      ARRAY_SIZE(drm_bridge_debugfs_list));
}
#endif

MODULE_AUTHOR("Ajay Kumar <ajaykumar.rs@samsung.com>");
MODULE_DESCRIPTION("DRM bridge infrastructure");
MODULE_LICENSE("GPL and additional rights");