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
spi_slave_time_complete(void * arg)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
spi_slave_time_submit(struct spi_slave_time_priv * priv)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(&priv->msg, &priv->xfer, 1);
76
77 priv->msg.complete = spi_slave_time_complete;
78 priv->msg.context = priv;
79
80 ret = spi_async(priv->spi, &priv->msg);
81 if (ret)
82 dev_err(&priv->spi->dev, "spi_async() failed %d\n", ret);
83
84 return ret;
85 }
86
spi_slave_time_probe(struct spi_device * spi)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(&spi->dev, sizeof(*priv), GFP_KERNEL);
93 if (!priv)
94 return -ENOMEM;
95
96 priv->spi = spi;
97 init_completion(&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, priv);
106 return 0;
107 }
108
spi_slave_time_remove(struct spi_device * spi)109 static int 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 return 0;
116 }
117
118 static struct spi_driver spi_slave_time_driver = {
119 .driver = {
120 .name = "spi-slave-time",
121 },
122 .probe = spi_slave_time_probe,
123 .remove = spi_slave_time_remove,
124 };
125 module_spi_driver(spi_slave_time_driver);
126
127 MODULE_AUTHOR("Geert Uytterhoeven <geert+renesas@glider.be>");
128 MODULE_DESCRIPTION("SPI slave reporting uptime at previous SPI message");
129 MODULE_LICENSE("GPL v2");
130