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/ktime.h>
9#include <linux/io.h>
10#include <linux/processor.h>
11#include <linux/types.h>
12
13#include <asm-generic/bug.h>
14
15#include "common.h"
16
17/*
18 * SCMI specification requires all parameters, message headers, return
19 * arguments or any protocol data to be expressed in little endian
20 * format only.
21 */
22struct scmi_shared_mem {
23	__le32 reserved;
24	__le32 channel_status;
25#define SCMI_SHMEM_CHAN_STAT_CHANNEL_ERROR	BIT(1)
26#define SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE	BIT(0)
27	__le32 reserved1[2];
28	__le32 flags;
29#define SCMI_SHMEM_FLAG_INTR_ENABLED	BIT(0)
30	__le32 length;
31	__le32 msg_header;
32	u8 msg_payload[];
33};
34
35void shmem_tx_prepare(struct scmi_shared_mem __iomem *shmem,
36		      struct scmi_xfer *xfer, struct scmi_chan_info *cinfo)
37{
38	ktime_t stop;
39
40	/*
41	 * Ideally channel must be free by now unless OS timeout last
42	 * request and platform continued to process the same, wait
43	 * until it releases the shared memory, otherwise we may endup
44	 * overwriting its response with new message payload or vice-versa.
45	 * Giving up anyway after twice the expected channel timeout so as
46	 * not to bail-out on intermittent issues where the platform is
47	 * occasionally a bit slower to answer.
48	 *
49	 * Note that after a timeout is detected we bail-out and carry on but
50	 * the transport functionality is probably permanently compromised:
51	 * this is just to ease debugging and avoid complete hangs on boot
52	 * due to a misbehaving SCMI firmware.
53	 */
54	stop = ktime_add_ms(ktime_get(), 2 * cinfo->rx_timeout_ms);
55	spin_until_cond((ioread32(&shmem->channel_status) &
56			 SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE) ||
57			 ktime_after(ktime_get(), stop));
58	if (!(ioread32(&shmem->channel_status) &
59	      SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE)) {
60		WARN_ON_ONCE(1);
61		dev_err(cinfo->dev,
62			"Timeout waiting for a free TX channel !\n");
63		return;
64	}
65
66	/* Mark channel busy + clear error */
67	iowrite32(0x0, &shmem->channel_status);
68	iowrite32(xfer->hdr.poll_completion ? 0 : SCMI_SHMEM_FLAG_INTR_ENABLED,
69		  &shmem->flags);
70	iowrite32(sizeof(shmem->msg_header) + xfer->tx.len, &shmem->length);
71	iowrite32(pack_scmi_header(&xfer->hdr), &shmem->msg_header);
72	if (xfer->tx.buf)
73		memcpy_toio(shmem->msg_payload, xfer->tx.buf, xfer->tx.len);
74}
75
76u32 shmem_read_header(struct scmi_shared_mem __iomem *shmem)
77{
78	return ioread32(&shmem->msg_header);
79}
80
81void shmem_fetch_response(struct scmi_shared_mem __iomem *shmem,
82			  struct scmi_xfer *xfer)
83{
84	size_t len = ioread32(&shmem->length);
85
86	xfer->hdr.status = ioread32(shmem->msg_payload);
87	/* Skip the length of header and status in shmem area i.e 8 bytes */
88	xfer->rx.len = min_t(size_t, xfer->rx.len, len > 8 ? len - 8 : 0);
89
90	/* Take a copy to the rx buffer.. */
91	memcpy_fromio(xfer->rx.buf, shmem->msg_payload + 4, xfer->rx.len);
92}
93
94void shmem_fetch_notification(struct scmi_shared_mem __iomem *shmem,
95			      size_t max_len, struct scmi_xfer *xfer)
96{
97	size_t len = ioread32(&shmem->length);
98
99	/* Skip only the length of header in shmem area i.e 4 bytes */
100	xfer->rx.len = min_t(size_t, max_len, len > 4 ? len - 4 : 0);
101
102	/* Take a copy to the rx buffer.. */
103	memcpy_fromio(xfer->rx.buf, shmem->msg_payload, xfer->rx.len);
104}
105
106void shmem_clear_channel(struct scmi_shared_mem __iomem *shmem)
107{
108	iowrite32(SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE, &shmem->channel_status);
109}
110
111bool shmem_poll_done(struct scmi_shared_mem __iomem *shmem,
112		     struct scmi_xfer *xfer)
113{
114	u16 xfer_id;
115
116	xfer_id = MSG_XTRACT_TOKEN(ioread32(&shmem->msg_header));
117
118	if (xfer->hdr.seq != xfer_id)
119		return false;
120
121	return ioread32(&shmem->channel_status) &
122		(SCMI_SHMEM_CHAN_STAT_CHANNEL_ERROR |
123		 SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE);
124}
125
126bool shmem_channel_free(struct scmi_shared_mem __iomem *shmem)
127{
128	return (ioread32(&shmem->channel_status) &
129			SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE);
130}
131