1 | /* |
2 | * SPI slave handler reporting uptime at reception of previous SPI message |
3 | * |
4 | * This SPI slave handler sends the time of reception of the last SPI message |
5 | * as two 32-bit unsigned integers in binary format and in network byte order, |
6 | * representing the number of seconds and fractional seconds (in microseconds) |
7 | * since boot up. |
8 | * |
9 | * Copyright (C) 2016-2017 Glider bvba |
10 | * |
11 | * This file is subject to the terms and conditions of the GNU General Public |
12 | * License. See the file "COPYING" in the main directory of this archive |
13 | * for more details. |
14 | * |
15 | * Usage (assuming /dev/spidev2.0 corresponds to the SPI master on the remote |
16 | * system): |
17 | * |
18 | * # spidev_test -D /dev/spidev2.0 -p dummy-8B |
19 | * spi mode: 0x0 |
20 | * bits per word: 8 |
21 | * max speed: 500000 Hz (500 KHz) |
22 | * RX | 00 00 04 6D 00 09 5B BB ... |
23 | * ^^^^^ ^^^^^^^^ |
24 | * seconds microseconds |
25 | */ |
26 | |
27 | #include <linux/completion.h> |
28 | #include <linux/module.h> |
29 | #include <linux/sched/clock.h> |
30 | #include <linux/spi/spi.h> |
31 | |
32 | |
33 | struct spi_slave_time_priv { |
34 | struct spi_device *spi; |
35 | struct completion finished; |
36 | struct spi_transfer xfer; |
37 | struct spi_message msg; |
38 | __be32 buf[2]; |
39 | }; |
40 | |
41 | static int spi_slave_time_submit(struct spi_slave_time_priv *priv); |
42 | |
43 | static void spi_slave_time_complete(void *arg) |
44 | { |
45 | struct spi_slave_time_priv *priv = arg; |
46 | int ret; |
47 | |
48 | ret = priv->msg.status; |
49 | if (ret) |
50 | goto terminate; |
51 | |
52 | ret = spi_slave_time_submit(priv); |
53 | if (ret) |
54 | goto terminate; |
55 | |
56 | return; |
57 | |
58 | terminate: |
59 | dev_info(&priv->spi->dev, "Terminating\n" ); |
60 | complete(&priv->finished); |
61 | } |
62 | |
63 | static int spi_slave_time_submit(struct spi_slave_time_priv *priv) |
64 | { |
65 | u32 rem_us; |
66 | int ret; |
67 | u64 ts; |
68 | |
69 | ts = local_clock(); |
70 | rem_us = do_div(ts, 1000000000) / 1000; |
71 | |
72 | priv->buf[0] = cpu_to_be32(ts); |
73 | priv->buf[1] = cpu_to_be32(rem_us); |
74 | |
75 | spi_message_init_with_transfers(m: &priv->msg, xfers: &priv->xfer, num_xfers: 1); |
76 | |
77 | priv->msg.complete = spi_slave_time_complete; |
78 | priv->msg.context = priv; |
79 | |
80 | ret = spi_async(spi: priv->spi, message: &priv->msg); |
81 | if (ret) |
82 | dev_err(&priv->spi->dev, "spi_async() failed %d\n" , ret); |
83 | |
84 | return ret; |
85 | } |
86 | |
87 | static int spi_slave_time_probe(struct spi_device *spi) |
88 | { |
89 | struct spi_slave_time_priv *priv; |
90 | int ret; |
91 | |
92 | priv = devm_kzalloc(dev: &spi->dev, size: sizeof(*priv), GFP_KERNEL); |
93 | if (!priv) |
94 | return -ENOMEM; |
95 | |
96 | priv->spi = spi; |
97 | init_completion(x: &priv->finished); |
98 | priv->xfer.tx_buf = priv->buf; |
99 | priv->xfer.len = sizeof(priv->buf); |
100 | |
101 | ret = spi_slave_time_submit(priv); |
102 | if (ret) |
103 | return ret; |
104 | |
105 | spi_set_drvdata(spi, data: priv); |
106 | return 0; |
107 | } |
108 | |
109 | static void spi_slave_time_remove(struct spi_device *spi) |
110 | { |
111 | struct spi_slave_time_priv *priv = spi_get_drvdata(spi); |
112 | |
113 | spi_slave_abort(spi); |
114 | wait_for_completion(&priv->finished); |
115 | } |
116 | |
117 | static struct spi_driver spi_slave_time_driver = { |
118 | .driver = { |
119 | .name = "spi-slave-time" , |
120 | }, |
121 | .probe = spi_slave_time_probe, |
122 | .remove = spi_slave_time_remove, |
123 | }; |
124 | module_spi_driver(spi_slave_time_driver); |
125 | |
126 | MODULE_AUTHOR("Geert Uytterhoeven <geert+renesas@glider.be>" ); |
127 | MODULE_DESCRIPTION("SPI slave reporting uptime at previous SPI message" ); |
128 | MODULE_LICENSE("GPL v2" ); |
129 | |