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 64 case CMD_POWEROFF: 65 dev_info(&priv->spi->dev, "Powering off system...\n"); 66 kernel_power_off(); 67 break; 68 69 case CMD_HALT: 70 dev_info(&priv->spi->dev, "Halting system...\n"); 71 kernel_halt(); 72 break; 73 74 case CMD_SUSPEND: 75 dev_info(&priv->spi->dev, "Suspending system...\n"); 76 pm_suspend(PM_SUSPEND_MEM); 77 break; 78 79 default: 80 dev_warn(&priv->spi->dev, "Unknown command 0x%x\n", cmd); 81 break; 82 } 83 84 ret = spi_slave_system_control_submit(priv); 85 if (ret) 86 goto terminate; 87 88 return; 89 90 terminate: 91 dev_info(&priv->spi->dev, "Terminating\n"); 92 complete(&priv->finished); 93 } 94 95 static 96 int spi_slave_system_control_submit(struct spi_slave_system_control_priv *priv) 97 { 98 int ret; 99 100 spi_message_init_with_transfers(&priv->msg, &priv->xfer, 1); 101 102 priv->msg.complete = spi_slave_system_control_complete; 103 priv->msg.context = priv; 104 105 ret = spi_async(priv->spi, &priv->msg); 106 if (ret) 107 dev_err(&priv->spi->dev, "spi_async() failed %d\n", ret); 108 109 return ret; 110 } 111 112 static int spi_slave_system_control_probe(struct spi_device *spi) 113 { 114 struct spi_slave_system_control_priv *priv; 115 int ret; 116 117 priv = devm_kzalloc(&spi->dev, sizeof(*priv), GFP_KERNEL); 118 if (!priv) 119 return -ENOMEM; 120 121 priv->spi = spi; 122 init_completion(&priv->finished); 123 priv->xfer.rx_buf = &priv->cmd; 124 priv->xfer.len = sizeof(priv->cmd); 125 126 ret = spi_slave_system_control_submit(priv); 127 if (ret) 128 return ret; 129 130 spi_set_drvdata(spi, priv); 131 return 0; 132 } 133 134 static int spi_slave_system_control_remove(struct spi_device *spi) 135 { 136 struct spi_slave_system_control_priv *priv = spi_get_drvdata(spi); 137 138 spi_slave_abort(spi); 139 wait_for_completion(&priv->finished); 140 return 0; 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