1/*
2 * SPI slave handler controlling system state
3 *
4 * This SPI slave handler allows remote control of system reboot, power off,
5 * halt, and suspend.
6 *
7 * Copyright (C) 2016-2017 Glider bvba
8 *
9 * This file is subject to the terms and conditions of the GNU General Public
10 * License.  See the file "COPYING" in the main directory of this archive
11 * for more details.
12 *
13 * Usage (assuming /dev/spidev2.0 corresponds to the SPI master on the remote
14 * system):
15 *
16 *   # reboot='\x7c\x50'
17 *   # poweroff='\x71\x3f'
18 *   # halt='\x38\x76'
19 *   # suspend='\x1b\x1b'
20 *   # spidev_test -D /dev/spidev2.0 -p $suspend # or $reboot, $poweroff, $halt
21 */
22
23#include <linux/completion.h>
24#include <linux/module.h>
25#include <linux/reboot.h>
26#include <linux/suspend.h>
27#include <linux/spi/spi.h>
28
29/*
30 * The numbers are chosen to display something human-readable on two 7-segment
31 * displays connected to two 74HC595 shift registers
32 */
33#define CMD_REBOOT	0x7c50	/* rb */
34#define CMD_POWEROFF	0x713f	/* OF */
35#define CMD_HALT	0x3876	/* HL */
36#define CMD_SUSPEND	0x1b1b	/* ZZ */
37
38struct spi_slave_system_control_priv {
39	struct spi_device *spi;
40	struct completion finished;
41	struct spi_transfer xfer;
42	struct spi_message msg;
43	__be16 cmd;
44};
45
46static
47int spi_slave_system_control_submit(struct spi_slave_system_control_priv *priv);
48
49static void spi_slave_system_control_complete(void *arg)
50{
51	struct spi_slave_system_control_priv *priv = arg;
52	u16 cmd;
53	int ret;
54
55	if (priv->msg.status)
56		goto terminate;
57
58	cmd = be16_to_cpu(priv->cmd);
59	switch (cmd) {
60	case CMD_REBOOT:
61		dev_info(&priv->spi->dev, "Rebooting system...\n");
62		kernel_restart(NULL);
63		break;
64
65	case CMD_POWEROFF:
66		dev_info(&priv->spi->dev, "Powering off system...\n");
67		kernel_power_off();
68		break;
69
70	case CMD_HALT:
71		dev_info(&priv->spi->dev, "Halting system...\n");
72		kernel_halt();
73		break;
74
75	case CMD_SUSPEND:
76		dev_info(&priv->spi->dev, "Suspending system...\n");
77		pm_suspend(PM_SUSPEND_MEM);
78		break;
79
80	default:
81		dev_warn(&priv->spi->dev, "Unknown command 0x%x\n", cmd);
82		break;
83	}
84
85	ret = spi_slave_system_control_submit(priv);
86	if (ret)
87		goto terminate;
88
89	return;
90
91terminate:
92	dev_info(&priv->spi->dev, "Terminating\n");
93	complete(&priv->finished);
94}
95
96static
97int spi_slave_system_control_submit(struct spi_slave_system_control_priv *priv)
98{
99	int ret;
100
101	spi_message_init_with_transfers(&priv->msg, &priv->xfer, 1);
102
103	priv->msg.complete = spi_slave_system_control_complete;
104	priv->msg.context = priv;
105
106	ret = spi_async(priv->spi, &priv->msg);
107	if (ret)
108		dev_err(&priv->spi->dev, "spi_async() failed %d\n", ret);
109
110	return ret;
111}
112
113static int spi_slave_system_control_probe(struct spi_device *spi)
114{
115	struct spi_slave_system_control_priv *priv;
116	int ret;
117
118	priv = devm_kzalloc(&spi->dev, sizeof(*priv), GFP_KERNEL);
119	if (!priv)
120		return -ENOMEM;
121
122	priv->spi = spi;
123	init_completion(&priv->finished);
124	priv->xfer.rx_buf = &priv->cmd;
125	priv->xfer.len = sizeof(priv->cmd);
126
127	ret = spi_slave_system_control_submit(priv);
128	if (ret)
129		return ret;
130
131	spi_set_drvdata(spi, priv);
132	return 0;
133}
134
135static void spi_slave_system_control_remove(struct spi_device *spi)
136{
137	struct spi_slave_system_control_priv *priv = spi_get_drvdata(spi);
138
139	spi_slave_abort(spi);
140	wait_for_completion(&priv->finished);
141}
142
143static struct spi_driver spi_slave_system_control_driver = {
144	.driver = {
145		.name	= "spi-slave-system-control",
146	},
147	.probe		= spi_slave_system_control_probe,
148	.remove		= spi_slave_system_control_remove,
149};
150module_spi_driver(spi_slave_system_control_driver);
151
152MODULE_AUTHOR("Geert Uytterhoeven <geert+renesas@glider.be>");
153MODULE_DESCRIPTION("SPI slave handler controlling system state");
154MODULE_LICENSE("GPL v2");
155