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 
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
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 
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 
135 static int 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 	return 0;
142 }
143 
144 static struct spi_driver spi_slave_system_control_driver = {
145 	.driver = {
146 		.name	= "spi-slave-system-control",
147 	},
148 	.probe		= spi_slave_system_control_probe,
149 	.remove		= spi_slave_system_control_remove,
150 };
151 module_spi_driver(spi_slave_system_control_driver);
152 
153 MODULE_AUTHOR("Geert Uytterhoeven <geert+renesas@glider.be>");
154 MODULE_DESCRIPTION("SPI slave handler controlling system state");
155 MODULE_LICENSE("GPL v2");
156