summaryrefslogtreecommitdiffstats
path: root/drivers/firmware/arm_scmi/driver.c
blob: 3eb0382491cebbc973de870eda7fc43ec244eee2 (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
// 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 ARM Ltd.
 */

#include <linux/bitmap.h>
#include <linux/export.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/ktime.h>
#include <linux/mailbox_client.h>
#include <linux/module.h>
#include <linux/of_address.h>
#include <linux/of_device.h>
#include <linux/processor.h>
#include <linux/semaphore.h>
#include <linux/slab.h>

#include "common.h"

#define MSG_ID_MASK		GENMASK(7, 0)
#define MSG_XTRACT_ID(hdr)	FIELD_GET(MSG_ID_MASK, (hdr))
#define MSG_TYPE_MASK		GENMASK(9, 8)
#define MSG_XTRACT_TYPE(hdr)	FIELD_GET(MSG_TYPE_MASK, (hdr))
#define MSG_TYPE_COMMAND	0
#define MSG_TYPE_DELAYED_RESP	2
#define MSG_TYPE_NOTIFICATION	3
#define MSG_PROTOCOL_ID_MASK	GENMASK(17, 10)
#define MSG_XTRACT_PROT_ID(hdr)	FIELD_GET(MSG_PROTOCOL_ID_MASK, (hdr))
#define MSG_TOKEN_ID_MASK	GENMASK(27, 18)
#define MSG_XTRACT_TOKEN(hdr)	FIELD_GET(MSG_TOKEN_ID_MASK, (hdr))
#define MSG_TOKEN_MAX		(MSG_XTRACT_TOKEN(MSG_TOKEN_ID_MASK) + 1)

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 */
	SCMI_ERR_MAX
};

/* List of all SCMI devices active in system */
static LIST_HEAD(scmi_list);
/* Protection for the entire list */
static DEFINE_MUTEX(scmi_list_mutex);

/**
 * struct scmi_xfers_info - Structure to manage transfer information
 *
 * @xfer_block: Preallocated Message array
 * @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
 */
struct scmi_xfers_info {
	struct scmi_xfer *xfer_block;
	unsigned long *xfer_alloc_table;
	spinlock_t xfer_lock;
};

/**
 * struct scmi_desc - Description of SoC integration
 *
 * @max_rx_timeout_ms: Timeout for communication with SoC (in Milliseconds)
 * @max_msg: Maximum number of messages that can be pending
 *	simultaneously in the system
 * @max_msg_size: Maximum size of data per message that can be handled.
 */
struct scmi_desc {
	int max_rx_timeout_ms;
	int max_msg;
	int max_msg_size;
};

/**
 * struct scmi_chan_info - Structure representing a SCMI channel information
 *
 * @cl: Mailbox Client
 * @chan: Transmit/Receive mailbox channel
 * @payload: Transmit/Receive mailbox channel payload area
 * @dev: Reference to device in the SCMI hierarchy corresponding to this
 *	 channel
 * @handle: Pointer to SCMI entity handle
 */
struct scmi_chan_info {
	struct mbox_client cl;
	struct mbox_chan *chan;
	void __iomem *payload;
	struct device *dev;
	struct scmi_handle *handle;
};

/**
 * struct scmi_info - Structure representing a SCMI instance
 *
 * @dev: Device pointer
 * @desc: SoC description for this instance
 * @handle: Instance of SCMI handle to send to clients
 * @version: SCMI revision information containing protocol version,
 *	implementation version and (sub-)vendor identification.
 * @tx_minfo: Universal Transmit 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_imp: List of protocols implemented, currently maximum of
 *	MAX_PROTOCOLS_IMP elements allocated by the base protocol
 * @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 idr tx_idr;
	struct idr rx_idr;
	u8 *protocols_imp;
	struct list_head node;
	int users;
};

#define client_to_scmi_chan_info(c) container_of(c, struct scmi_chan_info, cl)
#define handle_to_scmi_info(h)	container_of(h, struct scmi_info, handle)

/*
 * SCMI specification requires all parameters, message headers, return
 * arguments or any protocol data to be expressed in little endian
 * format only.
 */
struct scmi_shared_mem {
	__le32 reserved;
	__le32 channel_status;
#define SCMI_SHMEM_CHAN_STAT_CHANNEL_ERROR	BIT(1)
#define SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE	BIT(0)
	__le32 reserved1[2];
	__le32 flags;
#define SCMI_SHMEM_FLAG_INTR_ENABLED	BIT(0)
	__le32 length;
	__le32 msg_header;
	u8 msg_payload[0];
};

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)
{
	if (errno < SCMI_SUCCESS && errno > SCMI_ERR_MAX)
		return scmi_linux_errmap[-errno];
	return -EIO;
}

/**
 * scmi_dump_header_dbg() - Helper to dump a message header.
 *
 * @dev: Device pointer corresponding to the SCMI entity
 * @hdr: pointer to header.
 */
static inline void scmi_dump_header_dbg(struct device *dev,
					struct scmi_msg_hdr *hdr)
{
	dev_dbg(dev, "Message ID: %x Sequence ID: %x Protocol: %x\n",
		hdr->id, hdr->seq, hdr->protocol_id);
}

static void scmi_fetch_response(struct scmi_xfer *xfer,
				struct scmi_shared_mem __iomem *mem)
{
	xfer->hdr.status = ioread32(mem->msg_payload);
	/* Skip the length of header and status in payload area i.e 8 bytes */
	xfer->rx.len = min_t(size_t, xfer->rx.len, ioread32(&mem->length) - 8);

	/* Take a copy to the rx buffer.. */
	memcpy_fromio(xfer->rx.buf, mem->msg_payload + 4, xfer->rx.len);
}

/**
 * pack_scmi_header() - packs and returns 32-bit header
 *
 * @hdr: pointer to header containing all the information on message id,
 *	protocol id and sequence id.
 *
 * Return: 32-bit packed message header to be sent to the platform.
 */
static inline u32 pack_scmi_header(struct scmi_msg_hdr *hdr)
{
	return FIELD_PREP(MSG_ID_MASK, hdr->id) |
		FIELD_PREP(MSG_TOKEN_ID_MASK, hdr->seq) |
		FIELD_PREP(MSG_PROTOCOL_ID_MASK, hdr->protocol_id);
}

/**
 * unpack_scmi_header() - unpacks and records message and protocol id
 *
 * @msg_hdr: 32-bit packed message header sent from the platform
 * @hdr: pointer to header to fetch message and protocol id.
 */
static inline void unpack_scmi_header(u32 msg_hdr, struct scmi_msg_hdr *hdr)
{
	hdr->id = MSG_XTRACT_ID(msg_hdr);
	hdr->protocol_id = MSG_XTRACT_PROT_ID(msg_hdr);
}

/**
 * scmi_tx_prepare() - mailbox client callback to prepare for the transfer
 *
 * @cl: client pointer
 * @m: mailbox message
 *
 * This function prepares the shared memory which contains the header and the
 * payload.
 */
static void scmi_tx_prepare(struct mbox_client *cl, void *m)
{
	struct scmi_xfer *t = m;
	struct scmi_chan_info *cinfo = client_to_scmi_chan_info(cl);
	struct scmi_shared_mem __iomem *mem = cinfo->payload;

	/*
	 * Ideally channel must be free by now unless OS timeout last
	 * request and platform continued to process the same, wait
	 * until it releases the shared memory, otherwise we may endup
	 * overwriting its response with new message payload or vice-versa
	 */
	spin_until_cond(ioread32(&mem->channel_status) &
			SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE);
	/* Mark channel busy + clear error */
	iowrite32(0x0, &mem->channel_status);
	iowrite32(t->hdr.poll_completion ? 0 : SCMI_SHMEM_FLAG_INTR_ENABLED,
		  &mem->flags);
	iowrite32(sizeof(mem->msg_header) + t->tx.len, &mem->length);
	iowrite32(pack_scmi_header(&t->hdr), &mem->msg_header);
	if (t->tx.buf)
		memcpy_toio(mem->msg_payload, t->tx.buf, t->tx.len);
}

/**
 * scmi_xfer_get() - Allocate one message
 *
 * @handle: Pointer to SCMI entity handle
 * @minfo: Pointer to Tx/Rx Message management info based on channel type
 *
 * Helper function which is used by various message functions that are
 * exposed to clients of this driver for allocating a message traffic event.
 *
 * This function can sleep depending on pending requests already in the system
 * for the SCMI entity. Further, this also holds a spinlock to maintain
 * integrity of internal data structures.
 *
 * 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)
{
	u16 xfer_id;
	struct scmi_xfer *xfer;
	unsigned long flags, bit_pos;
	struct scmi_info *info = handle_to_scmi_info(handle);

	/* Keep the locked section as small as possible */
	spin_lock_irqsave(&minfo->xfer_lock, flags);
	bit_pos = find_first_zero_bit(minfo->xfer_alloc_table,
				      info->desc->max_msg);
	if (bit_pos == info->desc->max_msg) {
		spin_unlock_irqrestore(&minfo->xfer_lock, flags);
		return ERR_PTR(-ENOMEM);
	}
	set_bit(bit_pos, minfo->xfer_alloc_table);
	spin_unlock_irqrestore(&minfo->xfer_lock, flags);

	xfer_id = bit_pos;

	xfer = &minfo->xfer_block[xfer_id];
	xfer->hdr.seq = xfer_id;
	reinit_completion(&xfer->done);

	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
 *
 * 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;

	/*
	 * Keep the locked section as small as possible
	 * NOTE: we might escape with smp_mb and no lock here..
	 * but just be conservative and symmetric.
	 */
	spin_lock_irqsave(&minfo->xfer_lock, flags);
	clear_bit(xfer->hdr.seq, minfo->xfer_alloc_table);
	spin_unlock_irqrestore(&minfo->xfer_lock, flags);
}

/**
 * scmi_rx_callback() - mailbox client callback for receive messages
 *
 * @cl: client pointer
 * @m: mailbox message
 *
 * 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.
 */
static void scmi_rx_callback(struct mbox_client *cl, void *m)
{
	u8 msg_type;
	u32 msg_hdr;
	u16 xfer_id;
	struct scmi_xfer *xfer;
	struct scmi_chan_info *cinfo = client_to_scmi_chan_info(cl);
	struct device *dev = cinfo->dev;
	struct scmi_info *info = handle_to_scmi_info(cinfo->handle);
	struct scmi_xfers_info *minfo = &info->tx_minfo;
	struct scmi_shared_mem __iomem *mem = cinfo->payload;

	msg_hdr = ioread32(&mem->msg_header);
	msg_type = MSG_XTRACT_TYPE(msg_hdr);
	xfer_id = MSG_XTRACT_TOKEN(msg_hdr);

	if (msg_type == MSG_TYPE_NOTIFICATION)
		return; /* Notifications not yet supported */

	/* Are we even expecting this? */
	if (!test_bit(xfer_id, minfo->xfer_alloc_table)) {
		dev_err(dev, "message for %d is not expected!\n", xfer_id);
		return;
	}

	xfer = &minfo->xfer_block[xfer_id];

	scmi_dump_header_dbg(dev, &xfer->hdr);

	scmi_fetch_response(xfer, mem);

	if (msg_type == MSG_TYPE_DELAYED_RESP)
		complete(xfer->async_done);
	else
		complete(&xfer->done);
}

/**
 * scmi_xfer_put() - Release a transmit message
 *
 * @handle: Pointer to SCMI entity handle
 * @xfer: message that was reserved by scmi_xfer_get
 */
void scmi_xfer_put(const struct scmi_handle *handle, struct scmi_xfer *xfer)
{
	struct scmi_info *info = handle_to_scmi_info(handle);

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

static bool
scmi_xfer_poll_done(const struct scmi_chan_info *cinfo, struct scmi_xfer *xfer)
{
	struct scmi_shared_mem __iomem *mem = cinfo->payload;
	u16 xfer_id = MSG_XTRACT_TOKEN(ioread32(&mem->msg_header));

	if (xfer->hdr.seq != xfer_id)
		return false;

	return ioread32(&mem->channel_status) &
		(SCMI_SHMEM_CHAN_STAT_CHANNEL_ERROR |
		SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE);
}

#define SCMI_MAX_POLL_TO_NS	(100 * NSEC_PER_USEC)

static bool scmi_xfer_done_no_timeout(const struct scmi_chan_info *cinfo,
				      struct scmi_xfer *xfer, ktime_t stop)
{
	ktime_t __cur = ktime_get();

	return scmi_xfer_poll_done(cinfo, xfer) || ktime_after(__cur, stop);
}

/**
 * scmi_do_xfer() - Do one transfer
 *
 * @handle: Pointer to SCMI entity 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.
 */
int scmi_do_xfer(const struct scmi_handle *handle, struct scmi_xfer *xfer)
{
	int ret;
	int timeout;
	struct scmi_info *info = handle_to_scmi_info(handle);
	struct device *dev = info->dev;
	struct scmi_chan_info *cinfo;

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

	ret = mbox_send_message(cinfo->chan, xfer);
	if (ret < 0) {
		dev_dbg(dev, "mbox send fail %d\n", ret);
		return ret;
	}

	/* mbox_send_message returns non-negative value on success, so reset */
	ret = 0;

	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))
			scmi_fetch_response(xfer, cinfo->payload);
		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, "mbox 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);

	/*
	 * NOTE: we might prefer not to need the mailbox ticker to manage the
	 * transfer queueing since the protocol layer queues things by itself.
	 * Unfortunately, we have to kick the mailbox framework after we have
	 * received our message.
	 */
	mbox_client_txdone(cinfo->chan, ret);

	return ret;
}

#define SCMI_MAX_RESPONSE_TIMEOUT	(2 * MSEC_PER_SEC)

/**
 * scmi_do_xfer_with_response() - Do one transfer and wait until the delayed
 *	response is received
 *
 * @handle: Pointer to SCMI entity 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.
 */
int scmi_do_xfer_with_response(const struct scmi_handle *handle,
			       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 = scmi_do_xfer(handle, xfer);
	if (!ret && !wait_for_completion_timeout(xfer->async_done, timeout))
		ret = -ETIMEDOUT;

	xfer->async_done = NULL;
	return ret;
}

/**
 * scmi_xfer_get_init() - Allocate and initialise one message for transmit
 *
 * @handle: Pointer to SCMI entity handle
 * @msg_id: Message identifier
 * @prot_id: Protocol identifier for the message
 * @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.
 */
int scmi_xfer_get_init(const struct scmi_handle *handle, u8 msg_id, u8 prot_id,
		       size_t tx_size, size_t rx_size, struct scmi_xfer **p)
{
	int ret;
	struct scmi_xfer *xfer;
	struct scmi_info *info = handle_to_scmi_info(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(handle, minfo);
	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.id = msg_id;
	xfer->hdr.protocol_id = prot_id;
	xfer->hdr.poll_completion = false;

	*p = xfer;

	return 0;
}

/**
 * scmi_version_get() - command to get the revision of the SCMI entity
 *
 * @handle: Pointer to SCMI entity handle
 * @protocol: Protocol identifier for the message
 * @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.
 */
int scmi_version_get(const struct scmi_handle *handle, u8 protocol,
		     u32 *version)
{
	int ret;
	__le32 *rev_info;
	struct scmi_xfer *t;

	ret = scmi_xfer_get_init(handle, PROTOCOL_VERSION, protocol, 0,
				 sizeof(*version), &t);
	if (ret)
		return ret;

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

	scmi_xfer_put(handle, t);
	return ret;
}

void scmi_setup_protocol_implemented(const struct scmi_handle *handle,
				     u8 *prot_imp)
{
	struct scmi_info *info = handle_to_scmi_info(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;
}

/**
 * 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 = &info->handle;
			info->users++;
			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)
{
	int i;
	struct scmi_xfer *xfer;
	struct device *dev = sinfo->dev;
	const struct scmi_desc *desc = sinfo->desc;
	struct scmi_xfers_info *info = &sinfo->tx_minfo;

	/* Pre-allocated messages, no more than what hdr.seq can support */
	if (WARN_ON(desc->max_msg >= MSG_TOKEN_MAX)) {
		dev_err(dev, "Maximum message of %d exceeds supported %ld\n",
			desc->max_msg, MSG_TOKEN_MAX);
		return -EINVAL;
	}

	info->xfer_block = devm_kcalloc(dev, desc->max_msg,
					sizeof(*info->xfer_block), GFP_KERNEL);
	if (!info->xfer_block)
		return -ENOMEM;

	info->xfer_alloc_table = devm_kcalloc(dev, BITS_TO_LONGS(desc->max_msg),
					      sizeof(long), GFP_KERNEL);
	if (!info->xfer_alloc_table)
		return -ENOMEM;

	/* Pre-initialize the buffer pointer to pre-allocated buffers */
	for (i = 0, xfer = info->xfer_block; i < desc->max_msg; i++, xfer++) {
		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(&info->xfer_lock);

	return 0;
}

static int scmi_mailbox_check(struct device_node *np, int idx)
{
	return of_parse_phandle_with_args(np, "mboxes", "#mbox-cells",
					  idx, NULL);
}

static int scmi_mbox_chan_setup(struct scmi_info *info, struct device *dev,
				int prot_id, bool tx)
{
	int ret, idx;
	struct resource res;
	resource_size_t size;
	struct device_node *shmem, *np = dev->of_node;
	struct scmi_chan_info *cinfo;
	struct mbox_client *cl;
	struct idr *idr;
	const char *desc = tx ? "Tx" : "Rx";

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

	if (scmi_mailbox_check(np, 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;

	cl = &cinfo->cl;
	cl->dev = dev;
	cl->rx_callback = scmi_rx_callback;
	cl->tx_prepare = tx ? scmi_tx_prepare : NULL;
	cl->tx_block = false;
	cl->knows_txdone = tx;

	shmem = of_parse_phandle(np, "shmem", idx);
	ret = of_address_to_resource(shmem, 0, &res);
	of_node_put(shmem);
	if (ret) {
		dev_err(dev, "failed to get SCMI %s payload memory\n", desc);
		return ret;
	}

	size = resource_size(&res);
	cinfo->payload = devm_ioremap(info->dev, res.start, size);
	if (!cinfo->payload) {
		dev_err(dev, "failed to ioremap SCMI %s payload\n", desc);
		return -EADDRNOTAVAIL;
	}

	cinfo->chan = mbox_request_channel(cl, idx);
	if (IS_ERR(cinfo->chan)) {
		ret = PTR_ERR(cinfo->chan);
		if (ret != -EPROBE_DEFER)
			dev_err(dev, "failed to request SCMI %s mailbox\n",
				desc);
		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_mbox_txrx_setup(struct scmi_info *info, struct device *dev, int prot_id)
{
	int ret = scmi_mbox_chan_setup(info, dev, prot_id, true);

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

	return ret;
}

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

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

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

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

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;

	/* Only mailbox method supported, check for the presence of one */
	if (scmi_mailbox_check(np, 0)) {
		dev_err(dev, "no mailbox found in %pOF\n", np);
		return -EINVAL;
	}

	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);

	ret = scmi_xfer_info_init(info);
	if (ret)
		return ret;

	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;

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

	ret = scmi_base_protocol_init(handle);
	if (ret) {
		dev_err(dev, "unable to communicate with SCMI(%d)\n", ret);
		return ret;
	}

	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;
		}

		scmi_create_protocol_device(child, info, prot_id);
	}

	return 0;
}

static int scmi_mbox_free_channel(int id, void *p, void *data)
{
	struct scmi_chan_info *cinfo = p;
	struct idr *idr = data;

	if (!IS_ERR_OR_NULL(cinfo->chan)) {
		mbox_free_channel(cinfo->chan);
		cinfo->chan = NULL;
	}

	idr_remove(idr, id);

	return 0;
}

static int scmi_remove(struct platform_device *pdev)
{
	int ret = 0;
	struct scmi_info *info = platform_get_drvdata(pdev);
	struct idr *idr = &info->tx_idr;

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

	if (ret)
		return ret;

	/* Safe to free channels since no more users */
	ret = idr_for_each(idr, scmi_mbox_free_channel, idr);
	idr_destroy(&info->tx_idr);

	idr = &info->rx_idr;
	ret = idr_for_each(idr, scmi_mbox_free_channel, idr);
	idr_destroy(&info->rx_idr);

	return ret;
}

static const struct scmi_desc scmi_generic_desc = {
	.max_rx_timeout_ms = 30,	/* We may increase this if required */
	.max_msg = 20,		/* Limited by MBOX_TX_QUEUE_LEN */
	.max_msg_size = 128,
};

/* Each compatible listed below must have descriptor associated with it */
static const struct of_device_id scmi_of_match[] = {
	{ .compatible = "arm,scmi", .data = &scmi_generic_desc },
	{ /* Sentinel */ },
};

MODULE_DEVICE_TABLE(of, scmi_of_match);

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

module_platform_driver(scmi_driver);

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