xref: /openbmc/linux/drivers/spi/spi-slave-time.c (revision a0386bba)
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 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