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 */
22 struct 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
shmem_tx_prepare(struct scmi_shared_mem __iomem * shmem,struct scmi_xfer * xfer,struct scmi_chan_info * cinfo)35 void 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
shmem_read_header(struct scmi_shared_mem __iomem * shmem)76 u32 shmem_read_header(struct scmi_shared_mem __iomem *shmem)
77 {
78 return ioread32(&shmem->msg_header);
79 }
80
shmem_fetch_response(struct scmi_shared_mem __iomem * shmem,struct scmi_xfer * xfer)81 void 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
shmem_fetch_notification(struct scmi_shared_mem __iomem * shmem,size_t max_len,struct scmi_xfer * xfer)94 void 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
shmem_clear_channel(struct scmi_shared_mem __iomem * shmem)106 void shmem_clear_channel(struct scmi_shared_mem __iomem *shmem)
107 {
108 iowrite32(SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE, &shmem->channel_status);
109 }
110
shmem_poll_done(struct scmi_shared_mem __iomem * shmem,struct scmi_xfer * xfer)111 bool 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