summaryrefslogtreecommitdiffstats
path: root/drivers/firmware/arm_scmi/driver.c
blob: b406b3f78f4678142a5ac76c1c45f580d7ba7bd3 (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
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
// SPDX-License-Identifier: GPL-2.0
/*
 * System Control and Management Interface (SCMI) Message Protocol driver
 *
 * SCMI Message Protocol is used between the System Control Processor(SCP)
 * and the Application Processors(AP). The Message Handling Unit(MHU)
 * provides a mechanism for inter-processor communication between SCP's
 * Cortex M3 and AP.
 *
 * SCP offers control and management of the core/cluster power states,
 * various power domain DVFS including the core/cluster, certain system
 * clocks configuration, thermal sensors and many others.
 *
 * Copyright (C) 2018-2021 ARM Ltd.
 */

#include <linux/bitmap.h>
#include <linux/device.h>
#include <linux/export.h>
#include <linux/idr.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/ktime.h>
#include <linux/hashtable.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/of_address.h>
#include <linux/of_device.h>
#include <linux/processor.h>
#include <linux/refcount.h>
#include <linux/slab.h>

#include "common.h"
#include "notify.h"

#define CREATE_TRACE_POINTS
#include <trace/events/scmi.h>

enum scmi_error_codes {
	SCMI_SUCCESS = 0,	/* Success */
	SCMI_ERR_SUPPORT = -1,	/* Not supported */
	SCMI_ERR_PARAMS = -2,	/* Invalid Parameters */
	SCMI_ERR_ACCESS = -3,	/* Invalid access/permission denied */
	SCMI_ERR_ENTRY = -4,	/* Not found */
	SCMI_ERR_RANGE = -5,	/* Value out of range */
	SCMI_ERR_BUSY = -6,	/* Device busy */
	SCMI_ERR_COMMS = -7,	/* Communication Error */
	SCMI_ERR_GENERIC = -8,	/* Generic Error */
	SCMI_ERR_HARDWARE = -9,	/* Hardware Error */
	SCMI_ERR_PROTOCOL = -10,/* Protocol Error */
};

/* List of all SCMI devices active in system */
static LIST_HEAD(scmi_list);
/* Protection for the entire list */
static DEFINE_MUTEX(scmi_list_mutex);
/* Track the unique id for the transfers for debug & profiling purpose */
static atomic_t transfer_last_id;

static DEFINE_IDR(scmi_requested_devices);
static DEFINE_MUTEX(scmi_requested_devices_mtx);

struct scmi_requested_dev {
	const struct scmi_device_id *id_table;
	struct list_head node;
};

/**
 * struct scmi_xfers_info - Structure to manage transfer information
 *
 * @xfer_alloc_table: Bitmap table for allocated messages.
 *	Index of this bitmap table is also used for message
 *	sequence identifier.
 * @xfer_lock: Protection for message allocation
 * @max_msg: Maximum number of messages that can be pending
 * @free_xfers: A free list for available to use xfers. It is initialized with
 *		a number of xfers equal to the maximum allowed in-flight
 *		messages.
 * @pending_xfers: An hashtable, indexed by msg_hdr.seq, used to keep all the
 *		   currently in-flight messages.
 */
struct scmi_xfers_info {
	unsigned long *xfer_alloc_table;
	spinlock_t xfer_lock;
	int max_msg;
	struct hlist_head free_xfers;
	DECLARE_HASHTABLE(pending_xfers, SCMI_PENDING_XFERS_HT_ORDER_SZ);
};

/**
 * struct scmi_protocol_instance  - Describe an initialized protocol instance.
 * @handle: Reference to the SCMI handle associated to this protocol instance.
 * @proto: A reference to the protocol descriptor.
 * @gid: A reference for per-protocol devres management.
 * @users: A refcount to track effective users of this protocol.
 * @priv: Reference for optional protocol private data.
 * @ph: An embedded protocol handle that will be passed down to protocol
 *	initialization code to identify this instance.
 *
 * Each protocol is initialized independently once for each SCMI platform in
 * which is defined by DT and implemented by the SCMI server fw.
 */
struct scmi_protocol_instance {
	const struct scmi_handle	*handle;
	const struct scmi_protocol	*proto;
	void				*gid;
	refcount_t			users;
	void				*priv;
	struct scmi_protocol_handle	ph;
};

#define ph_to_pi(h)	container_of(h, struct scmi_protocol_instance, ph)

/**
 * struct scmi_info - Structure representing a SCMI instance
 *
 * @dev: Device pointer
 * @desc: SoC description for this instance
 * @version: SCMI revision information containing protocol version,
 *	implementation version and (sub-)vendor identification.
 * @handle: Instance of SCMI handle to send to clients
 * @tx_minfo: Universal Transmit Message management info
 * @rx_minfo: Universal Receive Message management info
 * @tx_idr: IDR object to map protocol id to Tx channel info pointer
 * @rx_idr: IDR object to map protocol id to Rx channel info pointer
 * @protocols: IDR for protocols' instance descriptors initialized for
 *	       this SCMI instance: populated on protocol's first attempted
 *	       usage.
 * @protocols_mtx: A mutex to protect protocols instances initialization.
 * @protocols_imp: List of protocols implemented, currently maximum of
 *	MAX_PROTOCOLS_IMP elements allocated by the base protocol
 * @active_protocols: IDR storing device_nodes for protocols actually defined
 *		      in the DT and confirmed as implemented by fw.
 * @notify_priv: Pointer to private data structure specific to notifications.
 * @node: List head
 * @users: Number of users of this instance
 */
struct scmi_info {
	struct device *dev;
	const struct scmi_desc *desc;
	struct scmi_revision_info version;
	struct scmi_handle handle;
	struct scmi_xfers_info tx_minfo;
	struct scmi_xfers_info rx_minfo;
	struct idr tx_idr;
	struct idr rx_idr;
	struct idr protocols;
	/* Ensure mutual exclusive access to protocols instance array */
	struct mutex protocols_mtx;
	u8 *protocols_imp;
	struct idr active_protocols;
	void *notify_priv;
	struct list_head node;
	int users;
};

#define handle_to_scmi_info(h)	container_of(h, struct scmi_info, handle)

static const int scmi_linux_errmap[] = {
	/* better than switch case as long as return value is continuous */
	0,			/* SCMI_SUCCESS */
	-EOPNOTSUPP,		/* SCMI_ERR_SUPPORT */
	-EINVAL,		/* SCMI_ERR_PARAM */
	-EACCES,		/* SCMI_ERR_ACCESS */
	-ENOENT,		/* SCMI_ERR_ENTRY */
	-ERANGE,		/* SCMI_ERR_RANGE */
	-EBUSY,			/* SCMI_ERR_BUSY */
	-ECOMM,			/* SCMI_ERR_COMMS */
	-EIO,			/* SCMI_ERR_GENERIC */
	-EREMOTEIO,		/* SCMI_ERR_HARDWARE */
	-EPROTO,		/* SCMI_ERR_PROTOCOL */
};

static inline int scmi_to_linux_errno(int errno)
{
	int err_idx = -errno;

	if (err_idx >= SCMI_SUCCESS && err_idx < ARRAY_SIZE(scmi_linux_errmap))
		return scmi_linux_errmap[err_idx];
	return -EIO;
}

void scmi_notification_instance_data_set(const struct scmi_handle *handle,
					 void *priv)
{
	struct scmi_info *info = handle_to_scmi_info(handle);

	info->notify_priv = priv;
	/* Ensure updated protocol private date are visible */
	smp_wmb();
}

void *scmi_notification_instance_data_get(const struct scmi_handle *handle)
{
	struct scmi_info *info = handle_to_scmi_info(handle);

	/* Ensure protocols_private_data has been updated */
	smp_rmb();
	return info->notify_priv;
}

/**
 * scmi_xfer_token_set  - Reserve and set new token for the xfer at hand
 *
 * @minfo: Pointer to Tx/Rx Message management info based on channel type
 * @xfer: The xfer to act upon
 *
 * Pick the next unused monotonically increasing token and set it into
 * xfer->hdr.seq: picking a monotonically increasing value avoids immediate
 * reuse of freshly completed or timed-out xfers, thus mitigating the risk
 * of incorrect association of a late and expired xfer with a live in-flight
 * transaction, both happening to re-use the same token identifier.
 *
 * Since platform is NOT required to answer our request in-order we should
 * account for a few rare but possible scenarios:
 *
 *  - exactly 'next_token' may be NOT available so pick xfer_id >= next_token
 *    using find_next_zero_bit() starting from candidate next_token bit
 *
 *  - all tokens ahead upto (MSG_TOKEN_ID_MASK - 1) are used in-flight but we
 *    are plenty of free tokens at start, so try a second pass using
 *    find_next_zero_bit() and starting from 0.
 *
 *  X = used in-flight
 *
 * Normal
 * ------
 *
 *		|- xfer_id picked
 *   -----------+----------------------------------------------------------
 *   | | |X|X|X| | | | | | ... ... ... ... ... ... ... ... ... ... ...|X|X|
 *   ----------------------------------------------------------------------
 *		^
 *		|- next_token
 *
 * Out-of-order pending at start
 * -----------------------------
 *
 *	  |- xfer_id picked, last_token fixed
 *   -----+----------------------------------------------------------------
 *   |X|X| | | | |X|X| ... ... ... ... ... ... ... ... ... ... ... ...|X| |
 *   ----------------------------------------------------------------------
 *    ^
 *    |- next_token
 *
 *
 * Out-of-order pending at end
 * ---------------------------
 *
 *	  |- xfer_id picked, last_token fixed
 *   -----+----------------------------------------------------------------
 *   |X|X| | | | |X|X| ... ... ... ... ... ... ... ... ... ... |X|X|X||X|X|
 *   ----------------------------------------------------------------------
 *								^
 *								|- next_token
 *
 * Context: Assumes to be called with @xfer_lock already acquired.
 *
 * Return: 0 on Success or error
 */
static int scmi_xfer_token_set(struct scmi_xfers_info *minfo,
			       struct scmi_xfer *xfer)
{
	unsigned long xfer_id, next_token;

	/*
	 * Pick a candidate monotonic token in range [0, MSG_TOKEN_MAX - 1]
	 * using the pre-allocated transfer_id as a base.
	 * Note that the global transfer_id is shared across all message types
	 * so there could be holes in the allocated set of monotonic sequence
	 * numbers, but that is going to limit the effectiveness of the
	 * mitigation only in very rare limit conditions.
	 */
	next_token = (xfer->transfer_id & (MSG_TOKEN_MAX - 1));

	/* Pick the next available xfer_id >= next_token */
	xfer_id = find_next_zero_bit(minfo->xfer_alloc_table,
				     MSG_TOKEN_MAX, next_token);
	if (xfer_id == MSG_TOKEN_MAX) {
		/*
		 * After heavily out-of-order responses, there are no free
		 * tokens ahead, but only at start of xfer_alloc_table so
		 * try again from the beginning.
		 */
		xfer_id = find_next_zero_bit(minfo->xfer_alloc_table,
					     MSG_TOKEN_MAX, 0);
		/*
		 * Something is wrong if we got here since there can be a
		 * maximum number of (MSG_TOKEN_MAX - 1) in-flight messages
		 * but we have not found any free token [0, MSG_TOKEN_MAX - 1].
		 */
		if (WARN_ON_ONCE(xfer_id == MSG_TOKEN_MAX))
			return -ENOMEM;
	}

	/* Update +/- last_token accordingly if we skipped some hole */
	if (xfer_id != next_token)
		atomic_add((int)(xfer_id - next_token), &transfer_last_id);

	/* Set in-flight */
	set_bit(xfer_id, minfo->xfer_alloc_table);
	xfer->hdr.seq = (u16)xfer_id;

	return 0;
}

/**
 * scmi_xfer_token_clear  - Release the token
 *
 * @minfo: Pointer to Tx/Rx Message management info based on channel type
 * @xfer: The xfer to act upon
 */
static inline void scmi_xfer_token_clear(struct scmi_xfers_info *minfo,
					 struct scmi_xfer *xfer)
{
	clear_bit(xfer->hdr.seq, minfo->xfer_alloc_table);
}

/**
 * scmi_xfer_get() - Allocate one message
 *
 * @handle: Pointer to SCMI entity handle
 * @minfo: Pointer to Tx/Rx Message management info based on channel type
 * @set_pending: If true a monotonic token is picked and the xfer is added to
 *		 the pending hash table.
 *
 * Helper function which is used by various message functions that are
 * exposed to clients of this driver for allocating a message traffic event.
 *
 * Picks an xfer from the free list @free_xfers (if any available) and, if
 * required, sets a monotonically increasing token and stores the inflight xfer
 * into the @pending_xfers hashtable for later retrieval.
 *
 * The successfully initialized xfer is refcounted.
 *
 * Context: Holds @xfer_lock while manipulating @xfer_alloc_table and
 *	    @free_xfers.
 *
 * Return: 0 if all went fine, else corresponding error.
 */
static struct scmi_xfer *scmi_xfer_get(const struct scmi_handle *handle,
				       struct scmi_xfers_info *minfo,
				       bool set_pending)
{
	int ret;
	unsigned long flags;
	struct scmi_xfer *xfer;

	spin_lock_irqsave(&minfo->xfer_lock, flags);
	if (hlist_empty(&minfo->free_xfers)) {
		spin_unlock_irqrestore(&minfo->xfer_lock, flags);
		return ERR_PTR(-ENOMEM);
	}

	/* grab an xfer from the free_list */
	xfer = hlist_entry(minfo->free_xfers.first, struct scmi_xfer, node);
	hlist_del_init(&xfer->node);

	/*
	 * Allocate transfer_id early so that can be used also as base for
	 * monotonic sequence number generation if needed.
	 */
	xfer->transfer_id = atomic_inc_return(&transfer_last_id);

	if (set_pending) {
		/* Pick and set monotonic token */
		ret = scmi_xfer_token_set(minfo, xfer);
		if (!ret) {
			hash_add(minfo->pending_xfers, &xfer->node,
				 xfer->hdr.seq);
			xfer->pending = true;
		} else {
			dev_err(handle->dev,
				"Failed to get monotonic token %d\n", ret);
			hlist_add_head(&xfer->node, &minfo->free_xfers);
			xfer = ERR_PTR(ret);
		}
	}

	if (!IS_ERR(xfer)) {
		refcount_set(&xfer->users, 1);
		atomic_set(&xfer->busy, SCMI_XFER_FREE);
	}
	spin_unlock_irqrestore(&minfo->xfer_lock, flags);

	return xfer;
}

/**
 * __scmi_xfer_put() - Release a message
 *
 * @minfo: Pointer to Tx/Rx Message management info based on channel type
 * @xfer: message that was reserved by scmi_xfer_get
 *
 * After refcount check, possibly release an xfer, clearing the token slot,
 * removing xfer from @pending_xfers and putting it back into free_xfers.
 *
 * This holds a spinlock to maintain integrity of internal data structures.
 */
static void
__scmi_xfer_put(struct scmi_xfers_info *minfo, struct scmi_xfer *xfer)
{
	unsigned long flags;

	spin_lock_irqsave(&minfo->xfer_lock, flags);
	if (refcount_dec_and_test(&xfer->users)) {
		if (xfer->pending) {
			scmi_xfer_token_clear(minfo, xfer);
			hash_del(&xfer->node);
			xfer->pending = false;
		}
		hlist_add_head(&xfer->node, &minfo->free_xfers);
	}
	spin_unlock_irqrestore(&minfo->xfer_lock, flags);
}

/**
 * scmi_xfer_lookup_unlocked  -  Helper to lookup an xfer_id
 *
 * @minfo: Pointer to Tx/Rx Message management info based on channel type
 * @xfer_id: Token ID to lookup in @pending_xfers
 *
 * Refcounting is untouched.
 *
 * Context: Assumes to be called with @xfer_lock already acquired.
 *
 * Return: A valid xfer on Success or error otherwise
 */
static struct scmi_xfer *
scmi_xfer_lookup_unlocked(struct scmi_xfers_info *minfo, u16 xfer_id)
{
	struct scmi_xfer *xfer = NULL;

	if (test_bit(xfer_id, minfo->xfer_alloc_table))
		xfer = XFER_FIND(minfo->pending_xfers, xfer_id);

	return xfer ?: ERR_PTR(-EINVAL);
}

/**
 * scmi_msg_response_validate  - Validate message type against state of related
 * xfer
 *
 * @cinfo: A reference to the channel descriptor.
 * @msg_type: Message type to check
 * @xfer: A reference to the xfer to validate against @msg_type
 *
 * This function checks if @msg_type is congruent with the current state of
 * a pending @xfer; if an asynchronous delayed response is received before the
 * related synchronous response (Out-of-Order Delayed Response) the missing
 * synchronous response is assumed to be OK and completed, carrying on with the
 * Delayed Response: this is done to address the case in which the underlying
 * SCMI transport can deliver such out-of-order responses.
 *
 * Context: Assumes to be called with xfer->lock already acquired.
 *
 * Return: 0 on Success, error otherwise
 */
static inline int scmi_msg_response_validate(struct scmi_chan_info *cinfo,
					     u8 msg_type,
					     struct scmi_xfer *xfer)
{
	/*
	 * Even if a response was indeed expected on this slot at this point,
	 * a buggy platform could wrongly reply feeding us an unexpected
	 * delayed response we're not prepared to handle: bail-out safely
	 * blaming firmware.
	 */
	if (msg_type == MSG_TYPE_DELAYED_RESP && !xfer->async_done) {
		dev_err(cinfo->dev,
			"Delayed Response for %d not expected! Buggy F/W ?\n",
			xfer->hdr.seq);
		return -EINVAL;
	}

	switch (xfer->state) {
	case SCMI_XFER_SENT_OK:
		if (msg_type == MSG_TYPE_DELAYED_RESP) {
			/*
			 * Delayed Response expected but delivered earlier.
			 * Assume message RESPONSE was OK and skip state.
			 */
			xfer->hdr.status = SCMI_SUCCESS;
			xfer->state = SCMI_XFER_RESP_OK;
			complete(&xfer->done);
			dev_warn(cinfo->dev,
				 "Received valid OoO Delayed Response for %d\n",
				 xfer->hdr.seq);
		}
		break;
	case SCMI_XFER_RESP_OK:
		if (msg_type != MSG_TYPE_DELAYED_RESP)
			return -EINVAL;
		break;
	case SCMI_XFER_DRESP_OK:
		/* No further message expected once in SCMI_XFER_DRESP_OK */
		return -EINVAL;
	}

	return 0;
}

/**
 * scmi_xfer_state_update  - Update xfer state
 *
 * @xfer: A reference to the xfer to update
 * @msg_type: Type of message being processed.
 *
 * Note that this message is assumed to have been already successfully validated
 * by @scmi_msg_response_validate(), so here we just update the state.
 *
 * Context: Assumes to be called on an xfer exclusively acquired using the
 *	    busy flag.
 */
static inline void scmi_xfer_state_update(struct scmi_xfer *xfer, u8 msg_type)
{
	xfer->hdr.type = msg_type;

	/* Unknown command types were already discarded earlier */
	if (xfer->hdr.type == MSG_TYPE_COMMAND)
		xfer->state = SCMI_XFER_RESP_OK;
	else
		xfer->state = SCMI_XFER_DRESP_OK;
}

static bool scmi_xfer_acquired(struct scmi_xfer *xfer)
{
	int ret;

	ret = atomic_cmpxchg(&xfer->busy, SCMI_XFER_FREE, SCMI_XFER_BUSY);

	return ret == SCMI_XFER_FREE;
}

/**
 * scmi_xfer_command_acquire  -  Helper to lookup and acquire a command xfer
 *
 * @cinfo: A reference to the channel descriptor.
 * @msg_hdr: A message header to use as lookup key
 *
 * When a valid xfer is found for the sequence number embedded in the provided
 * msg_hdr, reference counting is properly updated and exclusive access to this
 * xfer is granted till released with @scmi_xfer_command_release.
 *
 * Return: A valid @xfer on Success or error otherwise.
 */
static inline struct scmi_xfer *
scmi_xfer_command_acquire(struct scmi_chan_info *cinfo, u32 msg_hdr)
{
	int ret;
	unsigned long flags;
	struct scmi_xfer *xfer;
	struct scmi_info *info = handle_to_scmi_info(cinfo->handle);
	struct scmi_xfers_info *minfo = &info->tx_minfo;
	u8 msg_type = MSG_XTRACT_TYPE(msg_hdr);
	u16 xfer_id = MSG_XTRACT_TOKEN(msg_hdr);

	/* Are we even expecting this? */
	spin_lock_irqsave(&minfo->xfer_lock, flags);
	xfer = scmi_xfer_lookup_unlocked(minfo, xfer_id);
	if (IS_ERR(xfer)) {
		dev_err(cinfo->dev,
			"Message for %d type %d is not expected!\n",
			xfer_id, msg_type);
		spin_unlock_irqrestore(&minfo->xfer_lock, flags);
		return xfer;
	}
	refcount_inc(&xfer->users);
	spin_unlock_irqrestore(&minfo->xfer_lock, flags);

	spin_lock_irqsave(&xfer->lock, flags);
	ret = scmi_msg_response_validate(cinfo, msg_type, xfer);
	/*
	 * If a pending xfer was found which was also in a congruent state with
	 * the received message, acquire exclusive access to it setting the busy
	 * flag.
	 * Spins only on the rare limit condition of concurrent reception of
	 * RESP and DRESP for the same xfer.
	 */
	if (!ret) {
		spin_until_cond(scmi_xfer_acquired(xfer));
		scmi_xfer_state_update(xfer, msg_type);
	}
	spin_unlock_irqrestore(&xfer->lock, flags);

	if (ret) {
		dev_err(cinfo->dev,
			"Invalid message type:%d for %d - HDR:0x%X  state:%d\n",
			msg_type, xfer_id, msg_hdr, xfer->state);
		/* On error the refcount incremented above has to be dropped */
		__scmi_xfer_put(minfo, xfer);
		xfer = ERR_PTR(-EINVAL);
	}

	return xfer;
}

static inline void scmi_xfer_command_release(struct scmi_info *info,
					     struct scmi_xfer *xfer)
{
	atomic_set(&xfer->busy, SCMI_XFER_FREE);
	__scmi_xfer_put(&info->tx_minfo, xfer);
}

static inline void scmi_clear_channel(struct scmi_info *info,
				      struct scmi_chan_info *cinfo)
{
	if (info->desc->ops->clear_channel)
		info->desc->ops->clear_channel(cinfo);
}

static void scmi_handle_notification(struct scmi_chan_info *cinfo,
				     u32 msg_hdr, void *priv)
{
	struct scmi_xfer *xfer;
	struct device *dev = cinfo->dev;
	struct scmi_info *info = handle_to_scmi_info(cinfo->handle);
	struct scmi_xfers_info *minfo = &info->rx_minfo;
	ktime_t ts;

	ts = ktime_get_boottime();
	xfer = scmi_xfer_get(cinfo->handle, minfo, false);
	if (IS_ERR(xfer)) {
		dev_err(dev, "failed to get free message slot (%ld)\n",
			PTR_ERR(xfer));
		scmi_clear_channel(info, cinfo);
		return;
	}

	unpack_scmi_header(msg_hdr, &xfer->hdr);
	if (priv)
		xfer->priv = priv;
	info->desc->ops->fetch_notification(cinfo, info->desc->max_msg_size,
					    xfer);
	scmi_notify(cinfo->handle, xfer->hdr.protocol_id,
		    xfer->hdr.id, xfer->rx.buf, xfer->rx.len, ts);

	trace_scmi_rx_done(xfer->transfer_id, xfer->hdr.id,
			   xfer->hdr.protocol_id, xfer->hdr.seq,
			   MSG_TYPE_NOTIFICATION);

	__scmi_xfer_put(minfo, xfer);

	scmi_clear_channel(info, cinfo);
}

static void scmi_handle_response(struct scmi_chan_info *cinfo,
				 u32 msg_hdr, void *priv)
{
	struct scmi_xfer *xfer;
	struct scmi_info *info = handle_to_scmi_info(cinfo->handle);

	xfer = scmi_xfer_command_acquire(cinfo, msg_hdr);
	if (IS_ERR(xfer)) {
		scmi_clear_channel(info, cinfo);
		return;
	}

	/* rx.len could be shrunk in the sync do_xfer, so reset to maxsz */
	if (xfer->hdr.type == MSG_TYPE_DELAYED_RESP)
		xfer->rx.len = info->desc->max_msg_size;

	if (priv)
		xfer->priv = priv;
	info->desc->ops->fetch_response(cinfo, xfer);

	trace_scmi_rx_done(xfer->transfer_id, xfer->hdr.id,
			   xfer->hdr.protocol_id, xfer->hdr.seq,
			   xfer->hdr.type);

	if (xfer->hdr.type == MSG_TYPE_DELAYED_RESP) {
		scmi_clear_channel(info, cinfo);
		complete(xfer->async_done);
	} else {
		complete(&xfer->done);
	}

	scmi_xfer_command_release(info, xfer);
}

/**
 * scmi_rx_callback() - callback for receiving messages
 *
 * @cinfo: SCMI channel info
 * @msg_hdr: Message header
 * @priv: Transport specific private data.
 *
 * Processes one received message to appropriate transfer information and
 * signals completion of the transfer.
 *
 * NOTE: This function will be invoked in IRQ context, hence should be
 * as optimal as possible.
 */
void scmi_rx_callback(struct scmi_chan_info *cinfo, u32 msg_hdr, void *priv)
{
	u8 msg_type = MSG_XTRACT_TYPE(msg_hdr);

	switch (msg_type) {
	case MSG_TYPE_NOTIFICATION:
		scmi_handle_notification(cinfo, msg_hdr, priv);
		break;
	case MSG_TYPE_COMMAND:
	case MSG_TYPE_DELAYED_RESP:
		scmi_handle_response(cinfo, msg_hdr, priv);
		break;
	default:
		WARN_ONCE(1, "received unknown msg_type:%d\n", msg_type);
		break;
	}
}

/**
 * xfer_put() - Release a transmit message
 *
 * @ph: Pointer to SCMI protocol handle
 * @xfer: message that was reserved by xfer_get_init
 */
static void xfer_put(const struct scmi_protocol_handle *ph,
		     struct scmi_xfer *xfer)
{
	const struct scmi_protocol_instance *pi = ph_to_pi(ph);
	struct scmi_info *info = handle_to_scmi_info(pi->handle);

	__scmi_xfer_put(&info->tx_minfo, xfer);
}

#define SCMI_MAX_POLL_TO_NS	(100 * NSEC_PER_USEC)

static bool scmi_xfer_done_no_timeout(struct scmi_chan_info *cinfo,
				      struct scmi_xfer *xfer, ktime_t stop)
{
	struct scmi_info *info = handle_to_scmi_info(cinfo->handle);

	/*
	 * Poll also on xfer->done so that polling can be forcibly terminated
	 * in case of out-of-order receptions of delayed responses
	 */
	return info->desc->ops->poll_done(cinfo, xfer) ||
	       try_wait_for_completion(&xfer->done) ||
	       ktime_after(ktime_get(), stop);
}

/**
 * do_xfer() - Do one transfer
 *
 * @ph: Pointer to SCMI protocol handle
 * @xfer: Transfer to initiate and wait for response
 *
 * Return: -ETIMEDOUT in case of no response, if transmit error,
 *	return corresponding error, else if all goes well,
 *	return 0.
 */
static int do_xfer(const struct scmi_protocol_handle *ph,
		   struct scmi_xfer *xfer)
{
	int ret;
	int timeout;
	const struct scmi_protocol_instance *pi = ph_to_pi(ph);
	struct scmi_info *info = handle_to_scmi_info(pi->handle);
	struct device *dev = info->dev;
	struct scmi_chan_info *cinfo;

	if (xfer->hdr.poll_completion && !info->desc->ops->poll_done) {
		dev_warn_once(dev,
			      "Polling mode is not supported by transport.\n");
		return -EINVAL;
	}

	/*
	 * Initialise protocol id now from protocol handle to avoid it being
	 * overridden by mistake (or malice) by the protocol code mangling with
	 * the scmi_xfer structure prior to this.
	 */
	xfer->hdr.protocol_id = pi->proto->id;
	reinit_completion(&xfer->done);

	cinfo = idr_find(&info->tx_idr, xfer->hdr.protocol_id);
	if (unlikely(!cinfo))
		return -EINVAL;

	trace_scmi_xfer_begin(xfer->transfer_id, xfer->hdr.id,
			      xfer->hdr.protocol_id, xfer->hdr.seq,
			      xfer->hdr.poll_completion);

	xfer->state = SCMI_XFER_SENT_OK;
	/*
	 * Even though spinlocking is not needed here since no race is possible
	 * on xfer->state due to the monotonically increasing tokens allocation,
	 * we must anyway ensure xfer->state initialization is not re-ordered
	 * after the .send_message() to be sure that on the RX path an early
	 * ISR calling scmi_rx_callback() cannot see an old stale xfer->state.
	 */
	smp_mb();

	ret = info->desc->ops->send_message(cinfo, xfer);
	if (ret < 0) {
		dev_dbg(dev, "Failed to send message %d\n", ret);
		return ret;
	}

	if (xfer->hdr.poll_completion) {
		ktime_t stop = ktime_add_ns(ktime_get(), SCMI_MAX_POLL_TO_NS);

		spin_until_cond(scmi_xfer_done_no_timeout(cinfo, xfer, stop));
		if (ktime_before(ktime_get(), stop)) {
			unsigned long flags;

			/*
			 * Do not fetch_response if an out-of-order delayed
			 * response is being processed.
			 */
			spin_lock_irqsave(&xfer->lock, flags);
			if (xfer->state == SCMI_XFER_SENT_OK) {
				info->desc->ops->fetch_response(cinfo, xfer);
				xfer->state = SCMI_XFER_RESP_OK;
			}
			spin_unlock_irqrestore(&xfer->lock, flags);
		} else {
			ret = -ETIMEDOUT;
		}
	} else {
		/* And we wait for the response. */
		timeout = msecs_to_jiffies(info->desc->max_rx_timeout_ms);
		if (!wait_for_completion_timeout(&xfer->done, timeout)) {
			dev_err(dev, "timed out in resp(caller: %pS)\n",
				(void *)_RET_IP_);
			ret = -ETIMEDOUT;
		}
	}

	if (!ret && xfer->hdr.status)
		ret = scmi_to_linux_errno(xfer->hdr.status);

	if (info->desc->ops->mark_txdone)
		info->desc->ops->mark_txdone(cinfo, ret);

	trace_scmi_xfer_end(xfer->transfer_id, xfer->hdr.id,
			    xfer->hdr.protocol_id, xfer->hdr.seq, ret);

	return ret;
}

static void reset_rx_to_maxsz(const struct scmi_protocol_handle *ph,
			      struct scmi_xfer *xfer)
{
	const struct scmi_protocol_instance *pi = ph_to_pi(ph);
	struct scmi_info *info = handle_to_scmi_info(pi->handle);

	xfer->rx.len = info->desc->max_msg_size;
}

#define SCMI_MAX_RESPONSE_TIMEOUT	(2 * MSEC_PER_SEC)

/**
 * do_xfer_with_response() - Do one transfer and wait until the delayed
 *	response is received
 *
 * @ph: Pointer to SCMI protocol handle
 * @xfer: Transfer to initiate and wait for response
 *
 * Return: -ETIMEDOUT in case of no delayed response, if transmit error,
 *	return corresponding error, else if all goes well, return 0.
 */
static int do_xfer_with_response(const struct scmi_protocol_handle *ph,
				 struct scmi_xfer *xfer)
{
	int ret, timeout = msecs_to_jiffies(SCMI_MAX_RESPONSE_TIMEOUT);
	DECLARE_COMPLETION_ONSTACK(async_response);

	xfer->async_done = &async_response;

	ret = do_xfer(ph, xfer);
	if (!ret) {
		if (!wait_for_completion_timeout(xfer->async_done, timeout))
			ret = -ETIMEDOUT;
		else if (xfer->hdr.status)
			ret = scmi_to_linux_errno(xfer->hdr.status);
	}

	xfer->async_done = NULL;
	return ret;
}

/**
 * xfer_get_init() - Allocate and initialise one message for transmit
 *
 * @ph: Pointer to SCMI protocol handle
 * @msg_id: Message identifier
 * @tx_size: transmit message size
 * @rx_size: receive message size
 * @p: pointer to the allocated and initialised message
 *
 * This function allocates the message using @scmi_xfer_get and
 * initialise the header.
 *
 * Return: 0 if all went fine with @p pointing to message, else
 *	corresponding error.
 */
static int xfer_get_init(const struct scmi_protocol_handle *ph,
			 u8 msg_id, size_t tx_size, size_t rx_size,
			 struct scmi_xfer **p)
{
	int ret;
	struct scmi_xfer *xfer;
	const struct scmi_protocol_instance *pi = ph_to_pi(ph);
	struct scmi_info *info = handle_to_scmi_info(pi->handle);
	struct scmi_xfers_info *minfo = &info->tx_minfo;
	struct device *dev = info->dev;

	/* Ensure we have sane transfer sizes */
	if (rx_size > info->desc->max_msg_size ||
	    tx_size > info->desc->max_msg_size)
		return -ERANGE;

	xfer = scmi_xfer_get(pi->handle, minfo, true);
	if (IS_ERR(xfer)) {
		ret = PTR_ERR(xfer);
		dev_err(dev, "failed to get free message slot(%d)\n", ret);
		return ret;
	}

	xfer->tx.len = tx_size;
	xfer->rx.len = rx_size ? : info->desc->max_msg_size;
	xfer->hdr.type = MSG_TYPE_COMMAND;
	xfer->hdr.id = msg_id;
	xfer->hdr.poll_completion = false;

	*p = xfer;

	return 0;
}

/**
 * version_get() - command to get the revision of the SCMI entity
 *
 * @ph: Pointer to SCMI protocol handle
 * @version: Holds returned version of protocol.
 *
 * Updates the SCMI information in the internal data structure.
 *
 * Return: 0 if all went fine, else return appropriate error.
 */
static int version_get(const struct scmi_protocol_handle *ph, u32 *version)
{
	int ret;
	__le32 *rev_info;
	struct scmi_xfer *t;

	ret = xfer_get_init(ph, PROTOCOL_VERSION, 0, sizeof(*version), &t);
	if (ret)
		return ret;

	ret = do_xfer(ph, t);
	if (!ret) {
		rev_info = t->rx.buf;
		*version = le32_to_cpu(*rev_info);
	}

	xfer_put(ph, t);
	return ret;
}

/**
 * scmi_set_protocol_priv  - Set protocol specific data at init time
 *
 * @ph: A reference to the protocol handle.
 * @priv: The private data to set.
 *
 * Return: 0 on Success
 */
static int scmi_set_protocol_priv(const struct scmi_protocol_handle *ph,
				  void *priv)
{
	struct scmi_protocol_instance *pi = ph_to_pi(ph);

	pi->priv = priv;

	return 0;
}

/**
 * scmi_get_protocol_priv  - Set protocol specific data at init time
 *
 * @ph: A reference to the protocol handle.
 *
 * Return: Protocol private data if any was set.
 */
static void *scmi_get_protocol_priv(const struct scmi_protocol_handle *ph)
{
	const struct scmi_protocol_instance *pi = ph_to_pi(ph);

	return pi->priv;
}

static const struct scmi_xfer_ops xfer_ops = {
	.version_get = version_get,
	.xfer_get_init = xfer_get_init,
	.reset_rx_to_maxsz = reset_rx_to_maxsz,
	.do_xfer = do_xfer,
	.do_xfer_with_response = do_xfer_with_response,
	.xfer_put = xfer_put,
};

/**
 * scmi_revision_area_get  - Retrieve version memory area.
 *
 * @ph: A reference to the protocol handle.
 *
 * A helper to grab the version memory area reference during SCMI Base protocol
 * initialization.
 *
 * Return: A reference to the version memory area associated to the SCMI
 *	   instance underlying this protocol handle.
 */
struct scmi_revision_info *
scmi_revision_area_get(const struct scmi_protocol_handle *ph)
{
	const struct scmi_protocol_instance *pi = ph_to_pi(ph);

	return pi->handle->version;
}

/**
 * scmi_alloc_init_protocol_instance  - Allocate and initialize a protocol
 * instance descriptor.
 * @info: The reference to the related SCMI instance.
 * @proto: The protocol descriptor.
 *
 * Allocate a new protocol instance descriptor, using the provided @proto
 * description, against the specified SCMI instance @info, and initialize it;
 * all resources management is handled via a dedicated per-protocol devres
 * group.
 *
 * Context: Assumes to be called with @protocols_mtx already acquired.
 * Return: A reference to a freshly allocated and initialized protocol instance
 *	   or ERR_PTR on failure. On failure the @proto reference is at first
 *	   put using @scmi_protocol_put() before releasing all the devres group.
 */
static struct scmi_protocol_instance *
scmi_alloc_init_protocol_instance(struct scmi_info *info,
				  const struct scmi_protocol *proto)
{
	int ret = -ENOMEM;
	void *gid;
	struct scmi_protocol_instance *pi;
	const struct scmi_handle *handle = &info->handle;

	/* Protocol specific devres group */
	gid = devres_open_group(handle->dev, NULL, GFP_KERNEL);
	if (!gid) {
		scmi_protocol_put(proto->id);
		goto out;
	}

	pi = devm_kzalloc(handle->dev, sizeof(*pi), GFP_KERNEL);
	if (!pi)
		goto clean;

	pi->gid = gid;
	pi->proto = proto;
	pi->handle = handle;
	pi->ph.dev = handle->dev;
	pi->ph.xops = &xfer_ops;
	pi->ph.set_priv = scmi_set_protocol_priv;
	pi->ph.get_priv = scmi_get_protocol_priv;
	refcount_set(&pi->users, 1);
	/* proto->init is assured NON NULL by scmi_protocol_register */
	ret = pi->proto->instance_init(&pi->ph);
	if (ret)
		goto clean;

	ret = idr_alloc(&info->protocols, pi, proto->id, proto->id + 1,
			GFP_KERNEL);
	if (ret != proto->id)
		goto clean;

	/*
	 * Warn but ignore events registration errors since we do not want
	 * to skip whole protocols if their notifications are messed up.
	 */
	if (pi->proto->events) {
		ret = scmi_register_protocol_events(handle, pi->proto->id,
						    &pi->ph,
						    pi->proto->events);
		if (ret)
			dev_warn(handle->dev,
				 "Protocol:%X - Events Registration Failed - err:%d\n",
				 pi->proto->id, ret);
	}

	devres_close_group(handle->dev, pi->gid);
	dev_dbg(handle->dev, "Initialized protocol: 0x%X\n", pi->proto->id);

	return pi;

clean:
	/* Take care to put the protocol module's owner before releasing all */
	scmi_protocol_put(proto->id);
	devres_release_group(handle->dev, gid);
out:
	return ERR_PTR(ret);
}

/**
 * scmi_get_protocol_instance  - Protocol initialization helper.
 * @handle: A reference to the SCMI platform instance.
 * @protocol_id: The protocol being requested.
 *
 * In case the required protocol has never been requested before for this
 * instance, allocate and initialize all the needed structures while handling
 * resource allocation with a dedicated per-protocol devres subgroup.
 *
 * Return: A reference to an initialized protocol instance or error on failure:
 *	   in particular returns -EPROBE_DEFER when the desired protocol could
 *	   NOT be found.
 */
static struct scmi_protocol_instance * __must_check
scmi_get_protocol_instance(const struct scmi_handle *handle, u8 protocol_id)
{
	struct scmi_protocol_instance *pi;
	struct scmi_info *info = handle_to_scmi_info(handle);

	mutex_lock(&info->protocols_mtx);
	pi = idr_find(&info->protocols, protocol_id);

	if (pi) {
		refcount_inc(&pi->users);
	} else {
		const struct scmi_protocol *proto;

		/* Fails if protocol not registered on bus */
		proto = scmi_protocol_get(protocol_id);
		if (proto)
			pi = scmi_alloc_init_protocol_instance(info, proto);
		else
			pi = ERR_PTR(-EPROBE_DEFER);
	}
	mutex_unlock(&info->protocols_mtx);

	return pi;
}

/**
 * scmi_protocol_acquire  - Protocol acquire
 * @handle: A reference to the SCMI platform instance.
 * @protocol_id: The protocol being requested.
 *
 * Register a new user for the requested protocol on the specified SCMI
 * platform instance, possibly triggering its initialization on first user.
 *
 * Return: 0 if protocol was acquired successfully.
 */
int scmi_protocol_acquire(const struct scmi_handle *handle, u8 protocol_id)
{
	return PTR_ERR_OR_ZERO(scmi_get_protocol_instance(handle, protocol_id));
}

/**
 * scmi_protocol_release  - Protocol de-initialization helper.
 * @handle: A reference to the SCMI platform instance.
 * @protocol_id: The protocol being requested.
 *
 * Remove one user for the specified protocol and triggers de-initialization
 * and resources de-allocation once the last user has gone.
 */
void scmi_protocol_release(const struct scmi_handle *handle, u8 protocol_id)
{
	struct scmi_info *info = handle_to_scmi_info(handle);
	struct scmi_protocol_instance *pi;

	mutex_lock(&info->protocols_mtx);
	pi = idr_find(&info->protocols, protocol_id);
	if (WARN_ON(!pi))
		goto out;

	if (refcount_dec_and_test(&pi->users)) {
		void *gid = pi->gid;

		if (pi->proto->events)
			scmi_deregister_protocol_events(handle, protocol_id);

		if (pi->proto->instance_deinit)
			pi->proto->instance_deinit(&pi->ph);

		idr_remove(&info->protocols, protocol_id);

		scmi_protocol_put(protocol_id);

		devres_release_group(handle->dev, gid);
		dev_dbg(handle->dev, "De-Initialized protocol: 0x%X\n",
			protocol_id);
	}

out:
	mutex_unlock(&info->protocols_mtx);
}

void scmi_setup_protocol_implemented(const struct scmi_protocol_handle *ph,
				     u8 *prot_imp)
{
	const struct scmi_protocol_instance *pi = ph_to_pi(ph);
	struct scmi_info *info = handle_to_scmi_info(pi->handle);

	info->protocols_imp = prot_imp;
}

static bool
scmi_is_protocol_implemented(const struct scmi_handle *handle, u8 prot_id)
{
	int i;
	struct scmi_info *info = handle_to_scmi_info(handle);

	if (!info->protocols_imp)
		return false;

	for (i = 0; i < MAX_PROTOCOLS_IMP; i++)
		if (info->protocols_imp[i] == prot_id)
			return true;
	return false;
}

struct scmi_protocol_devres {
	const struct scmi_handle *handle;
	u8 protocol_id;
};

static void scmi_devm_release_protocol(struct device *dev, void *res)
{
	struct scmi_protocol_devres *dres = res;

	scmi_protocol_release(dres->handle, dres->protocol_id);
}

/**
 * scmi_devm_protocol_get  - Devres managed get protocol operations and handle
 * @sdev: A reference to an scmi_device whose embedded struct device is to
 *	  be used for devres accounting.
 * @protocol_id: The protocol being requested.
 * @ph: A pointer reference used to pass back the associated protocol handle.
 *
 * Get hold of a protocol accounting for its usage, eventually triggering its
 * initialization, and returning the protocol specific operations and related
 * protocol handle which will be used as first argument in most of the
 * protocols operations methods.
 * Being a devres based managed method, protocol hold will be automatically
 * released, and possibly de-initialized on last user, once the SCMI driver
 * owning the scmi_device is unbound from it.
 *
 * Return: A reference to the requested protocol operations or error.
 *	   Must be checked for errors by caller.
 */
static const void __must_check *
scmi_devm_protocol_get(struct scmi_device *sdev, u8 protocol_id,
		       struct scmi_protocol_handle **ph)
{
	struct scmi_protocol_instance *pi;
	struct scmi_protocol_devres *dres;
	struct scmi_handle *handle = sdev->handle;

	if (!ph)
		return ERR_PTR(-EINVAL);

	dres = devres_alloc(scmi_devm_release_protocol,
			    sizeof(*dres), GFP_KERNEL);
	if (!dres)
		return ERR_PTR(-ENOMEM);

	pi = scmi_get_protocol_instance(handle, protocol_id);
	if (IS_ERR(pi)) {
		devres_free(dres);
		return pi;
	}

	dres->handle = handle;
	dres->protocol_id = protocol_id;
	devres_add(&sdev->dev, dres);

	*ph = &pi->ph;

	return pi->proto->ops;
}

static int scmi_devm_protocol_match(struct device *dev, void *res, void *data)
{
	struct scmi_protocol_devres *dres = res;

	if (WARN_ON(!dres || !data))
		return 0;

	return dres->protocol_id == *((u8 *)data);
}

/**
 * scmi_devm_protocol_put  - Devres managed put protocol operations and handle
 * @sdev: A reference to an scmi_device whose embedded struct device is to
 *	  be used for devres accounting.
 * @protocol_id: The protocol being requested.
 *
 * Explicitly release a protocol hold previously obtained calling the above
 * @scmi_devm_protocol_get.
 */
static void scmi_devm_protocol_put(struct scmi_device *sdev, u8 protocol_id)
{
	int ret;

	ret = devres_release(&sdev->dev, scmi_devm_release_protocol,
			     scmi_devm_protocol_match, &protocol_id);
	WARN_ON(ret);
}

static inline
struct scmi_handle *scmi_handle_get_from_info_unlocked(struct scmi_info *info)
{
	info->users++;
	return &info->handle;
}

/**
 * scmi_handle_get() - Get the SCMI handle for a device
 *
 * @dev: pointer to device for which we want SCMI handle
 *
 * NOTE: The function does not track individual clients of the framework
 * and is expected to be maintained by caller of SCMI protocol library.
 * scmi_handle_put must be balanced with successful scmi_handle_get
 *
 * Return: pointer to handle if successful, NULL on error
 */
struct scmi_handle *scmi_handle_get(struct device *dev)
{
	struct list_head *p;
	struct scmi_info *info;
	struct scmi_handle *handle = NULL;

	mutex_lock(&scmi_list_mutex);
	list_for_each(p, &scmi_list) {
		info = list_entry(p, struct scmi_info, node);
		if (dev->parent == info->dev) {
			handle = scmi_handle_get_from_info_unlocked(info);
			break;
		}
	}
	mutex_unlock(&scmi_list_mutex);

	return handle;
}

/**
 * scmi_handle_put() - Release the handle acquired by scmi_handle_get
 *
 * @handle: handle acquired by scmi_handle_get
 *
 * NOTE: The function does not track individual clients of the framework
 * and is expected to be maintained by caller of SCMI protocol library.
 * scmi_handle_put must be balanced with successful scmi_handle_get
 *
 * Return: 0 is successfully released
 *	if null was passed, it returns -EINVAL;
 */
int scmi_handle_put(const struct scmi_handle *handle)
{
	struct scmi_info *info;

	if (!handle)
		return -EINVAL;

	info = handle_to_scmi_info(handle);
	mutex_lock(&scmi_list_mutex);
	if (!WARN_ON(!info->users))
		info->users--;
	mutex_unlock(&scmi_list_mutex);

	return 0;
}

static int __scmi_xfer_info_init(struct scmi_info *sinfo,
				 struct scmi_xfers_info *info)
{
	int i;
	struct scmi_xfer *xfer;
	struct device *dev = sinfo->dev;
	const struct scmi_desc *desc = sinfo->desc;

	/* Pre-allocated messages, no more than what hdr.seq can support */
	if (WARN_ON(!info->max_msg || info->max_msg > MSG_TOKEN_MAX)) {
		dev_err(dev,
			"Invalid maximum messages %d, not in range [1 - %lu]\n",
			info->max_msg, MSG_TOKEN_MAX);
		return -EINVAL;
	}

	hash_init(info->pending_xfers);

	/* Allocate a bitmask sized to hold MSG_TOKEN_MAX tokens */
	info->xfer_alloc_table = devm_kcalloc(dev, BITS_TO_LONGS(MSG_TOKEN_MAX),
					      sizeof(long), GFP_KERNEL);
	if (!info->xfer_alloc_table)
		return -ENOMEM;

	/*
	 * Preallocate a number of xfers equal to max inflight messages,
	 * pre-initialize the buffer pointer to pre-allocated buffers and
	 * attach all of them to the free list
	 */
	INIT_HLIST_HEAD(&info->free_xfers);
	for (i = 0; i < info->max_msg; i++) {
		xfer = devm_kzalloc(dev, sizeof(*xfer), GFP_KERNEL);
		if (!xfer)
			return -ENOMEM;

		xfer->rx.buf = devm_kcalloc(dev, sizeof(u8), desc->max_msg_size,
					    GFP_KERNEL);
		if (!xfer->rx.buf)
			return -ENOMEM;

		xfer->tx.buf = xfer->rx.buf;
		init_completion(&xfer->done);
		spin_lock_init(&xfer->lock);

		/* Add initialized xfer to the free list */
		hlist_add_head(&xfer->node, &info->free_xfers);
	}

	spin_lock_init(&info->xfer_lock);

	return 0;
}

static int scmi_channels_max_msg_configure(struct scmi_info *sinfo)
{
	const struct scmi_desc *desc = sinfo->desc;

	if (!desc->ops->get_max_msg) {
		sinfo->tx_minfo.max_msg = desc->max_msg;
		sinfo->rx_minfo.max_msg = desc->max_msg;
	} else {
		struct scmi_chan_info *base_cinfo;

		base_cinfo = idr_find(&sinfo->tx_idr, SCMI_PROTOCOL_BASE);
		if (!base_cinfo)
			return -EINVAL;
		sinfo->tx_minfo.max_msg = desc->ops->get_max_msg(base_cinfo);

		/* RX channel is optional so can be skipped */
		base_cinfo = idr_find(&sinfo->rx_idr, SCMI_PROTOCOL_BASE);
		if (base_cinfo)
			sinfo->rx_minfo.max_msg =
				desc->ops->get_max_msg(base_cinfo);
	}

	return 0;
}

static int scmi_xfer_info_init(struct scmi_info *sinfo)
{
	int ret;

	ret = scmi_channels_max_msg_configure(sinfo);
	if (ret)
		return ret;

	ret = __scmi_xfer_info_init(sinfo, &sinfo->tx_minfo);
	if (!ret && idr_find(&sinfo->rx_idr, SCMI_PROTOCOL_BASE))
		ret = __scmi_xfer_info_init(sinfo, &sinfo->rx_minfo);

	return ret;
}

static int scmi_chan_setup(struct scmi_info *info, struct device *dev,
			   int prot_id, bool tx)
{
	int ret, idx;
	struct scmi_chan_info *cinfo;
	struct idr *idr;

	/* Transmit channel is first entry i.e. index 0 */
	idx = tx ? 0 : 1;
	idr = tx ? &info->tx_idr : &info->rx_idr;

	/* check if already allocated, used for multiple device per protocol */
	cinfo = idr_find(idr, prot_id);
	if (cinfo)
		return 0;

	if (!info->desc->ops->chan_available(dev, idx)) {
		cinfo = idr_find(idr, SCMI_PROTOCOL_BASE);
		if (unlikely(!cinfo)) /* Possible only if platform has no Rx */
			return -EINVAL;
		goto idr_alloc;
	}

	cinfo = devm_kzalloc(info->dev, sizeof(*cinfo), GFP_KERNEL);
	if (!cinfo)
		return -ENOMEM;

	cinfo->dev = dev;

	ret = info->desc->ops->chan_setup(cinfo, info->dev, tx);
	if (ret)
		return ret;

idr_alloc:
	ret = idr_alloc(idr, cinfo, prot_id, prot_id + 1, GFP_KERNEL);
	if (ret != prot_id) {
		dev_err(dev, "unable to allocate SCMI idr slot err %d\n", ret);
		return ret;
	}

	cinfo->handle = &info->handle;
	return 0;
}

static inline int
scmi_txrx_setup(struct scmi_info *info, struct device *dev, int prot_id)
{
	int ret = scmi_chan_setup(info, dev, prot_id, true);

	if (!ret) /* Rx is optional, hence no error check */
		scmi_chan_setup(info, dev, prot_id, false);

	return ret;
}

/**
 * scmi_get_protocol_device  - Helper to get/create an SCMI device.
 *
 * @np: A device node representing a valid active protocols for the referred
 * SCMI instance.
 * @info: The referred SCMI instance for which we are getting/creating this
 * device.
 * @prot_id: The protocol ID.
 * @name: The device name.
 *
 * Referring to the specific SCMI instance identified by @info, this helper
 * takes care to return a properly initialized device matching the requested
 * @proto_id and @name: if device was still not existent it is created as a
 * child of the specified SCMI instance @info and its transport properly
 * initialized as usual.
 *
 * Return: A properly initialized scmi device, NULL otherwise.
 */
static inline struct scmi_device *
scmi_get_protocol_device(struct device_node *np, struct scmi_info *info,
			 int prot_id, const char *name)
{
	struct scmi_device *sdev;

	/* Already created for this parent SCMI instance ? */
	sdev = scmi_child_dev_find(info->dev, prot_id, name);
	if (sdev)
		return sdev;

	pr_debug("Creating SCMI device (%s) for protocol %x\n", name, prot_id);

	sdev = scmi_device_create(np, info->dev, prot_id, name);
	if (!sdev) {
		dev_err(info->dev, "failed to create %d protocol device\n",
			prot_id);
		return NULL;
	}

	if (scmi_txrx_setup(info, &sdev->dev, prot_id)) {
		dev_err(&sdev->dev, "failed to setup transport\n");
		scmi_device_destroy(sdev);
		return NULL;
	}

	return sdev;
}

static inline void
scmi_create_protocol_device(struct device_node *np, struct scmi_info *info,
			    int prot_id, const char *name)
{
	struct scmi_device *sdev;

	sdev = scmi_get_protocol_device(np, info, prot_id, name);
	if (!sdev)
		return;

	/* setup handle now as the transport is ready */
	scmi_set_handle(sdev);
}

/**
 * scmi_create_protocol_devices  - Create devices for all pending requests for
 * this SCMI instance.
 *
 * @np: The device node describing the protocol
 * @info: The SCMI instance descriptor
 * @prot_id: The protocol ID
 *
 * All devices previously requested for this instance (if any) are found and
 * created by scanning the proper @&scmi_requested_devices entry.
 */
static void scmi_create_protocol_devices(struct device_node *np,
					 struct scmi_info *info, int prot_id)
{
	struct list_head *phead;

	mutex_lock(&scmi_requested_devices_mtx);
	phead = idr_find(&scmi_requested_devices, prot_id);
	if (phead) {
		struct scmi_requested_dev *rdev;

		list_for_each_entry(rdev, phead, node)
			scmi_create_protocol_device(np, info, prot_id,
						    rdev->id_table->name);
	}
	mutex_unlock(&scmi_requested_devices_mtx);
}

/**
 * scmi_protocol_device_request  - Helper to request a device
 *
 * @id_table: A protocol/name pair descriptor for the device to be created.
 *
 * This helper let an SCMI driver request specific devices identified by the
 * @id_table to be created for each active SCMI instance.
 *
 * The requested device name MUST NOT be already existent for any protocol;
 * at first the freshly requested @id_table is annotated in the IDR table
 * @scmi_requested_devices, then a matching device is created for each already
 * active SCMI instance. (if any)
 *
 * This way the requested device is created straight-away for all the already
 * initialized(probed) SCMI instances (handles) and it remains also annotated
 * as pending creation if the requesting SCMI driver was loaded before some
 * SCMI instance and related transports were available: when such late instance
 * is probed, its probe will take care to scan the list of pending requested
 * devices and create those on its own (see @scmi_create_protocol_devices and
 * its enclosing loop)
 *
 * Return: 0 on Success
 */
int scmi_protocol_device_request(const struct scmi_device_id *id_table)
{
	int ret = 0;
	unsigned int id = 0;
	struct list_head *head, *phead = NULL;
	struct scmi_requested_dev *rdev;
	struct scmi_info *info;

	pr_debug("Requesting SCMI device (%s) for protocol %x\n",
		 id_table->name, id_table->protocol_id);

	/*
	 * Search for the matching protocol rdev list and then search
	 * of any existent equally named device...fails if any duplicate found.
	 */
	mutex_lock(&scmi_requested_devices_mtx);
	idr_for_each_entry(&scmi_requested_devices, head, id) {
		if (!phead) {
			/* A list found registered in the IDR is never empty */
			rdev = list_first_entry(head, struct scmi_requested_dev,
						node);
			if (rdev->id_table->protocol_id ==
			    id_table->protocol_id)
				phead = head;
		}
		list_for_each_entry(rdev, head, node) {
			if (!strcmp(rdev->id_table->name, id_table->name)) {
				pr_err("Ignoring duplicate request [%d] %s\n",
				       rdev->id_table->protocol_id,
				       rdev->id_table->name);
				ret = -EINVAL;
				goto out;
			}
		}
	}

	/*
	 * No duplicate found for requested id_table, so let's create a new
	 * requested device entry for this new valid request.
	 */
	rdev = kzalloc(sizeof(*rdev), GFP_KERNEL);
	if (!rdev) {
		ret = -ENOMEM;
		goto out;
	}
	rdev->id_table = id_table;

	/*
	 * Append the new requested device table descriptor to the head of the
	 * related protocol list, eventually creating such head if not already
	 * there.
	 */
	if (!phead) {
		phead = kzalloc(sizeof(*phead), GFP_KERNEL);
		if (!phead) {
			kfree(rdev);
			ret = -ENOMEM;
			goto out;
		}
		INIT_LIST_HEAD(phead);

		ret = idr_alloc(&scmi_requested_devices, (void *)phead,
				id_table->protocol_id,
				id_table->protocol_id + 1, GFP_KERNEL);
		if (ret != id_table->protocol_id) {
			pr_err("Failed to save SCMI device - ret:%d\n", ret);
			kfree(rdev);
			kfree(phead);
			ret = -EINVAL;
			goto out;
		}
		ret = 0;
	}
	list_add(&rdev->node, phead);

	/*
	 * Now effectively create and initialize the requested device for every
	 * already initialized SCMI instance which has registered the requested
	 * protocol as a valid active one: i.e. defined in DT and supported by
	 * current platform FW.
	 */
	mutex_lock(&scmi_list_mutex);
	list_for_each_entry(info, &scmi_list, node) {
		struct device_node *child;

		child = idr_find(&info->active_protocols,
				 id_table->protocol_id);
		if (child) {
			struct scmi_device *sdev;

			sdev = scmi_get_protocol_device(child, info,
							id_table->protocol_id,
							id_table->name);
			/* Set handle if not already set: device existed */
			if (sdev && !sdev->handle)
				sdev->handle =
					scmi_handle_get_from_info_unlocked(info);
		} else {
			dev_err(info->dev,
				"Failed. SCMI protocol %d not active.\n",
				id_table->protocol_id);
		}
	}
	mutex_unlock(&scmi_list_mutex);

out:
	mutex_unlock(&scmi_requested_devices_mtx);

	return ret;
}

/**
 * scmi_protocol_device_unrequest  - Helper to unrequest a device
 *
 * @id_table: A protocol/name pair descriptor for the device to be unrequested.
 *
 * An helper to let an SCMI driver release its request about devices; note that
 * devices are created and initialized once the first SCMI driver request them
 * but they destroyed only on SCMI core unloading/unbinding.
 *
 * The current SCMI transport layer uses such devices as internal references and
 * as such they could be shared as same transport between multiple drivers so
 * that cannot be safely destroyed till the whole SCMI stack is removed.
 * (unless adding further burden of refcounting.)
 */
void scmi_protocol_device_unrequest(const struct scmi_device_id *id_table)
{
	struct list_head *phead;

	pr_debug("Unrequesting SCMI device (%s) for protocol %x\n",
		 id_table->name, id_table->protocol_id);

	mutex_lock(&scmi_requested_devices_mtx);
	phead = idr_find(&scmi_requested_devices, id_table->protocol_id);
	if (phead) {
		struct scmi_requested_dev *victim, *tmp;

		list_for_each_entry_safe(victim, tmp, phead, node) {
			if (!strcmp(victim->id_table->name, id_table->name)) {
				list_del(&victim->node);
				kfree(victim);
				break;
			}
		}

		if (list_empty(phead)) {
			idr_remove(&scmi_requested_devices,
				   id_table->protocol_id);
			kfree(phead);
		}
	}
	mutex_unlock(&scmi_requested_devices_mtx);
}

static int scmi_cleanup_txrx_channels(struct scmi_info *info)
{
	int ret;
	struct idr *idr = &info->tx_idr;

	ret = idr_for_each(idr, info->desc->ops->chan_free, idr);
	idr_destroy(&info->tx_idr);

	idr = &info->rx_idr;
	ret = idr_for_each(idr, info->desc->ops->chan_free, idr);
	idr_destroy(&info->rx_idr);

	return ret;
}

static int scmi_probe(struct platform_device *pdev)
{
	int ret;
	struct scmi_handle *handle;
	const struct scmi_desc *desc;
	struct scmi_info *info;
	struct device *dev = &pdev->dev;
	struct device_node *child, *np = dev->of_node;

	desc = of_device_get_match_data(dev);
	if (!desc)
		return -EINVAL;

	info = devm_kzalloc(dev, sizeof(*info), GFP_KERNEL);
	if (!info)
		return -ENOMEM;

	info->dev = dev;
	info->desc = desc;
	INIT_LIST_HEAD(&info->node);
	idr_init(&info->protocols);
	mutex_init(&info->protocols_mtx);
	idr_init(&info->active_protocols);

	platform_set_drvdata(pdev, info);
	idr_init(&info->tx_idr);
	idr_init(&info->rx_idr);

	handle = &info->handle;
	handle->dev = info->dev;
	handle->version = &info->version;
	handle->devm_protocol_get = scmi_devm_protocol_get;
	handle->devm_protocol_put = scmi_devm_protocol_put;

	if (desc->ops->link_supplier) {
		ret = desc->ops->link_supplier(dev);
		if (ret)
			return ret;
	}

	ret = scmi_txrx_setup(info, dev, SCMI_PROTOCOL_BASE);
	if (ret)
		return ret;

	ret = scmi_xfer_info_init(info);
	if (ret)
		goto clear_txrx_setup;

	if (scmi_notification_init(handle))
		dev_err(dev, "SCMI Notifications NOT available.\n");

	/*
	 * Trigger SCMI Base protocol initialization.
	 * It's mandatory and won't be ever released/deinit until the
	 * SCMI stack is shutdown/unloaded as a whole.
	 */
	ret = scmi_protocol_acquire(handle, SCMI_PROTOCOL_BASE);
	if (ret) {
		dev_err(dev, "unable to communicate with SCMI\n");
		goto notification_exit;
	}

	mutex_lock(&scmi_list_mutex);
	list_add_tail(&info->node, &scmi_list);
	mutex_unlock(&scmi_list_mutex);

	for_each_available_child_of_node(np, child) {
		u32 prot_id;

		if (of_property_read_u32(child, "reg", &prot_id))
			continue;

		if (!FIELD_FIT(MSG_PROTOCOL_ID_MASK, prot_id))
			dev_err(dev, "Out of range protocol %d\n", prot_id);

		if (!scmi_is_protocol_implemented(handle, prot_id)) {
			dev_err(dev, "SCMI protocol %d not implemented\n",
				prot_id);
			continue;
		}

		/*
		 * Save this valid DT protocol descriptor amongst
		 * @active_protocols for this SCMI instance/
		 */
		ret = idr_alloc(&info->active_protocols, child,
				prot_id, prot_id + 1, GFP_KERNEL);
		if (ret != prot_id) {
			dev_err(dev, "SCMI protocol %d already activated. Skip\n",
				prot_id);
			continue;
		}

		of_node_get(child);
		scmi_create_protocol_devices(child, info, prot_id);
	}

	return 0;

notification_exit:
	scmi_notification_exit(&info->handle);
clear_txrx_setup:
	scmi_cleanup_txrx_channels(info);
	return ret;
}

void scmi_free_channel(struct scmi_chan_info *cinfo, struct idr *idr, int id)
{
	idr_remove(idr, id);
}

static int scmi_remove(struct platform_device *pdev)
{
	int ret = 0, id;
	struct scmi_info *info = platform_get_drvdata(pdev);
	struct device_node *child;

	mutex_lock(&scmi_list_mutex);
	if (info->users)
		ret = -EBUSY;
	else
		list_del(&info->node);
	mutex_unlock(&scmi_list_mutex);

	if (ret)
		return ret;

	scmi_notification_exit(&info->handle);

	mutex_lock(&info->protocols_mtx);
	idr_destroy(&info->protocols);
	mutex_unlock(&info->protocols_mtx);

	idr_for_each_entry(&info->active_protocols, child, id)
		of_node_put(child);
	idr_destroy(&info->active_protocols);

	/* Safe to free channels since no more users */
	return scmi_cleanup_txrx_channels(info);
}

static ssize_t protocol_version_show(struct device *dev,
				     struct device_attribute *attr, char *buf)
{
	struct scmi_info *info = dev_get_drvdata(dev);

	return sprintf(buf, "%u.%u\n", info->version.major_ver,
		       info->version.minor_ver);
}
static DEVICE_ATTR_RO(protocol_version);

static ssize_t firmware_version_show(struct device *dev,
				     struct device_attribute *attr, char *buf)
{
	struct scmi_info *info = dev_get_drvdata(dev);

	return sprintf(buf, "0x%x\n", info->version.impl_ver);
}
static DEVICE_ATTR_RO(firmware_version);

static ssize_t vendor_id_show(struct device *dev,
			      struct device_attribute *attr, char *buf)
{
	struct scmi_info *info = dev_get_drvdata(dev);

	return sprintf(buf, "%s\n", info->version.vendor_id);
}
static DEVICE_ATTR_RO(vendor_id);

static ssize_t sub_vendor_id_show(struct device *dev,
				  struct device_attribute *attr, char *buf)
{
	struct scmi_info *info = dev_get_drvdata(dev);

	return sprintf(buf, "%s\n", info->version.sub_vendor_id);
}
static DEVICE_ATTR_RO(sub_vendor_id);

static struct attribute *versions_attrs[] = {
	&dev_attr_firmware_version.attr,
	&dev_attr_protocol_version.attr,
	&dev_attr_vendor_id.attr,
	&dev_attr_sub_vendor_id.attr,
	NULL,
};
ATTRIBUTE_GROUPS(versions);

/* Each compatible listed below must have descriptor associated with it */
static const struct of_device_id scmi_of_match[] = {
#ifdef CONFIG_ARM_SCMI_TRANSPORT_MAILBOX
	{ .compatible = "arm,scmi", .data = &scmi_mailbox_desc },
#endif
#ifdef CONFIG_ARM_SCMI_TRANSPORT_SMC
	{ .compatible = "arm,scmi-smc", .data = &scmi_smc_desc},
#endif
#ifdef CONFIG_ARM_SCMI_TRANSPORT_VIRTIO
	{ .compatible = "arm,scmi-virtio", .data = &scmi_virtio_desc},
#endif
	{ /* Sentinel */ },
};

MODULE_DEVICE_TABLE(of, scmi_of_match);

static struct platform_driver scmi_driver = {
	.driver = {
		   .name = "arm-scmi",
		   .of_match_table = scmi_of_match,
		   .dev_groups = versions_groups,
		   },
	.probe = scmi_probe,
	.remove = scmi_remove,
};

/**
 * __scmi_transports_setup  - Common helper to call transport-specific
 * .init/.exit code if provided.
 *
 * @init: A flag to distinguish between init and exit.
 *
 * Note that, if provided, we invoke .init/.exit functions for all the
 * transports currently compiled in.
 *
 * Return: 0 on Success.
 */
static inline int __scmi_transports_setup(bool init)
{
	int ret = 0;
	const struct of_device_id *trans;

	for (trans = scmi_of_match; trans->data; trans++) {
		const struct scmi_desc *tdesc = trans->data;

		if ((init && !tdesc->transport_init) ||
		    (!init && !tdesc->transport_exit))
			continue;

		if (init)
			ret = tdesc->transport_init();
		else
			tdesc->transport_exit();

		if (ret) {
			pr_err("SCMI transport %s FAILED initialization!\n",
			       trans->compatible);
			break;
		}
	}

	return ret;
}

static int __init scmi_transports_init(void)
{
	return __scmi_transports_setup(true);
}

static void __exit scmi_transports_exit(void)
{
	__scmi_transports_setup(false);
}

static int __init scmi_driver_init(void)
{
	int ret;

	/* Bail out if no SCMI transport was configured */
	if (WARN_ON(!IS_ENABLED(CONFIG_ARM_SCMI_HAVE_TRANSPORT)))
		return -EINVAL;

	scmi_bus_init();

	/* Initialize any compiled-in transport which provided an init/exit */
	ret = scmi_transports_init();
	if (ret)
		return ret;

	scmi_base_register();

	scmi_clock_register();
	scmi_perf_register();
	scmi_power_register();
	scmi_reset_register();
	scmi_sensors_register();
	scmi_voltage_register();
	scmi_system_register();

	return platform_driver_register(&scmi_driver);
}
subsys_initcall(scmi_driver_init);

static void __exit scmi_driver_exit(void)
{
	scmi_base_unregister();

	scmi_clock_unregister();
	scmi_perf_unregister();
	scmi_power_unregister();
	scmi_reset_unregister();
	scmi_sensors_unregister();
	scmi_voltage_unregister();
	scmi_system_unregister();

	scmi_bus_exit();

	scmi_transports_exit();

	platform_driver_unregister(&scmi_driver);
}
module_exit(scmi_driver_exit);

MODULE_ALIAS("platform: arm-scmi");
MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
MODULE_DESCRIPTION("ARM SCMI protocol driver");
MODULE_LICENSE("GPL v2");