1// SPDX-License-Identifier: GPL-2.0
2/*
3 * For transport using shared mem structure.
4 *
5 * Copyright (C) 2019 ARM Ltd.
6 */
7
8#include <linux/io.h>
9#include <linux/processor.h>
10#include <linux/types.h>
11
12#include "common.h"
13
14/*
15 * SCMI specification requires all parameters, message headers, return
16 * arguments or any protocol data to be expressed in little endian
17 * format only.
18 */
19struct scmi_shared_mem {
20	__le32 reserved;
21	__le32 channel_status;
22#define SCMI_SHMEM_CHAN_STAT_CHANNEL_ERROR	BIT(1)
23#define SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE	BIT(0)
24	__le32 reserved1[2];
25	__le32 flags;
26#define SCMI_SHMEM_FLAG_INTR_ENABLED	BIT(0)
27	__le32 length;
28	__le32 msg_header;
29	u8 msg_payload[];
30};
31
32void shmem_tx_prepare(struct scmi_shared_mem __iomem *shmem,
33		      struct scmi_xfer *xfer)
34{
35	/*
36	 * Ideally channel must be free by now unless OS timeout last
37	 * request and platform continued to process the same, wait
38	 * until it releases the shared memory, otherwise we may endup
39	 * overwriting its response with new message payload or vice-versa
40	 */
41	spin_until_cond(ioread32(&shmem->channel_status) &
42			SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE);
43	/* Mark channel busy + clear error */
44	iowrite32(0x0, &shmem->channel_status);
45	iowrite32(xfer->hdr.poll_completion ? 0 : SCMI_SHMEM_FLAG_INTR_ENABLED,
46		  &shmem->flags);
47	iowrite32(sizeof(shmem->msg_header) + xfer->tx.len, &shmem->length);
48	iowrite32(pack_scmi_header(&xfer->hdr), &shmem->msg_header);
49	if (xfer->tx.buf)
50		memcpy_toio(shmem->msg_payload, xfer->tx.buf, xfer->tx.len);
51}
52
53u32 shmem_read_header(struct scmi_shared_mem __iomem *shmem)
54{
55	return ioread32(&shmem->msg_header);
56}
57
58void shmem_fetch_response(struct scmi_shared_mem __iomem *shmem,
59			  struct scmi_xfer *xfer)
60{
61	size_t len = ioread32(&shmem->length);
62
63	xfer->hdr.status = ioread32(shmem->msg_payload);
64	/* Skip the length of header and status in shmem area i.e 8 bytes */
65	xfer->rx.len = min_t(size_t, xfer->rx.len, len > 8 ? len - 8 : 0);
66
67	/* Take a copy to the rx buffer.. */
68	memcpy_fromio(xfer->rx.buf, shmem->msg_payload + 4, xfer->rx.len);
69}
70
71void shmem_fetch_notification(struct scmi_shared_mem __iomem *shmem,
72			      size_t max_len, struct scmi_xfer *xfer)
73{
74	size_t len = ioread32(&shmem->length);
75
76	/* Skip only the length of header in shmem area i.e 4 bytes */
77	xfer->rx.len = min_t(size_t, max_len, len > 4 ? len - 4 : 0);
78
79	/* Take a copy to the rx buffer.. */
80	memcpy_fromio(xfer->rx.buf, shmem->msg_payload, xfer->rx.len);
81}
82
83void shmem_clear_channel(struct scmi_shared_mem __iomem *shmem)
84{
85	iowrite32(SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE, &shmem->channel_status);
86}
87
88bool shmem_poll_done(struct scmi_shared_mem __iomem *shmem,
89		     struct scmi_xfer *xfer)
90{
91	u16 xfer_id;
92
93	xfer_id = MSG_XTRACT_TOKEN(ioread32(&shmem->msg_header));
94
95	if (xfer->hdr.seq != xfer_id)
96		return false;
97
98	return ioread32(&shmem->channel_status) &
99		(SCMI_SHMEM_CHAN_STAT_CHANNEL_ERROR |
100		 SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE);
101}
102