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
38 struct 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
46 static
47 int spi_slave_system_control_submit(struct spi_slave_system_control_priv *priv);
48
spi_slave_system_control_complete(void * arg)49 static 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
91 terminate:
92 dev_info(&priv->spi->dev, "Terminating\n");
93 complete(&priv->finished);
94 }
95
96 static
spi_slave_system_control_submit(struct spi_slave_system_control_priv * priv)97 int 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
spi_slave_system_control_probe(struct spi_device * spi)113 static 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
spi_slave_system_control_remove(struct spi_device * spi)135 static 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
143 static 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 };
150 module_spi_driver(spi_slave_system_control_driver);
151
152 MODULE_AUTHOR("Geert Uytterhoeven <geert+renesas@glider.be>");
153 MODULE_DESCRIPTION("SPI slave handler controlling system state");
154 MODULE_LICENSE("GPL v2");
155