1 /* 2 * LTC2952 (PowerPath) driver 3 * 4 * Copyright (C) 2014, Xsens Technologies BV <info@xsens.com> 5 * Maintainer: René Moll <linux@r-moll.nl> 6 * 7 * This program is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU General Public License 9 * as published by the Free Software Foundation; either version 2 10 * of the License, or (at your option) any later version. 11 * 12 * This program is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 * GNU General Public License for more details. 16 * 17 * ---------------------------------------- 18 * - Description 19 * ---------------------------------------- 20 * 21 * This driver is to be used with an external PowerPath Controller (LTC2952). 22 * Its function is to determine when a external shut down is triggered 23 * and react by properly shutting down the system. 24 * 25 * This driver expects a device tree with a ltc2952 entry for pin mapping. 26 * 27 * ---------------------------------------- 28 * - GPIO 29 * ---------------------------------------- 30 * 31 * The following GPIOs are used: 32 * - trigger (input) 33 * A level change indicates the shut-down trigger. If it's state reverts 34 * within the time-out defined by trigger_delay, the shut down is not 35 * executed. If no pin is assigned to this input, the driver will start the 36 * watchdog toggle immediately. The chip will only power off the system if 37 * it is requested to do so through the kill line. 38 * 39 * - watchdog (output) 40 * Once a shut down is triggered, the driver will toggle this signal, 41 * with an internal (wde_interval) to stall the hardware shut down. 42 * 43 * - kill (output) 44 * The last action during shut down is triggering this signalling, such 45 * that the PowerPath Control will power down the hardware. 46 * 47 * ---------------------------------------- 48 * - Interrupts 49 * ---------------------------------------- 50 * 51 * The driver requires a non-shared, edge-triggered interrupt on the trigger 52 * GPIO. 53 * 54 */ 55 56 #include <linux/kernel.h> 57 #include <linux/init.h> 58 #include <linux/interrupt.h> 59 #include <linux/device.h> 60 #include <linux/platform_device.h> 61 #include <linux/ktime.h> 62 #include <linux/slab.h> 63 #include <linux/kmod.h> 64 #include <linux/module.h> 65 #include <linux/mod_devicetable.h> 66 #include <linux/gpio/consumer.h> 67 #include <linux/reboot.h> 68 69 struct ltc2952_poweroff { 70 struct hrtimer timer_trigger; 71 struct hrtimer timer_wde; 72 73 ktime_t trigger_delay; 74 ktime_t wde_interval; 75 76 struct device *dev; 77 78 struct gpio_desc *gpio_trigger; 79 struct gpio_desc *gpio_watchdog; 80 struct gpio_desc *gpio_kill; 81 82 bool kernel_panic; 83 struct notifier_block panic_notifier; 84 }; 85 86 #define to_ltc2952(p, m) container_of(p, struct ltc2952_poweroff, m) 87 88 /* 89 * This global variable is only needed for pm_power_off. We should 90 * remove it entirely once we don't need the global state anymore. 91 */ 92 static struct ltc2952_poweroff *ltc2952_data; 93 94 /** 95 * ltc2952_poweroff_timer_wde - Timer callback 96 * Toggles the watchdog reset signal each wde_interval 97 * 98 * @timer: corresponding timer 99 * 100 * Returns HRTIMER_RESTART for an infinite loop which will only stop when the 101 * machine actually shuts down 102 */ 103 static enum hrtimer_restart ltc2952_poweroff_timer_wde(struct hrtimer *timer) 104 { 105 ktime_t now; 106 int state; 107 unsigned long overruns; 108 struct ltc2952_poweroff *data = to_ltc2952(timer, timer_wde); 109 110 if (data->kernel_panic) 111 return HRTIMER_NORESTART; 112 113 state = gpiod_get_value(data->gpio_watchdog); 114 gpiod_set_value(data->gpio_watchdog, !state); 115 116 now = hrtimer_cb_get_time(timer); 117 overruns = hrtimer_forward(timer, now, data->wde_interval); 118 119 return HRTIMER_RESTART; 120 } 121 122 static void ltc2952_poweroff_start_wde(struct ltc2952_poweroff *data) 123 { 124 hrtimer_start(&data->timer_wde, data->wde_interval, HRTIMER_MODE_REL); 125 } 126 127 static enum hrtimer_restart 128 ltc2952_poweroff_timer_trigger(struct hrtimer *timer) 129 { 130 struct ltc2952_poweroff *data = to_ltc2952(timer, timer_trigger); 131 132 ltc2952_poweroff_start_wde(data); 133 dev_info(data->dev, "executing shutdown\n"); 134 orderly_poweroff(true); 135 136 return HRTIMER_NORESTART; 137 } 138 139 /** 140 * ltc2952_poweroff_handler - Interrupt handler 141 * Triggered each time the trigger signal changes state and (de)activates a 142 * time-out (timer_trigger). Once the time-out is actually reached the shut 143 * down is executed. 144 * 145 * @irq: IRQ number 146 * @dev_id: pointer to the main data structure 147 */ 148 static irqreturn_t ltc2952_poweroff_handler(int irq, void *dev_id) 149 { 150 struct ltc2952_poweroff *data = dev_id; 151 152 if (data->kernel_panic || hrtimer_active(&data->timer_wde)) { 153 /* shutdown is already triggered, nothing to do any more */ 154 return IRQ_HANDLED; 155 } 156 157 if (gpiod_get_value(data->gpio_trigger)) { 158 hrtimer_start(&data->timer_trigger, data->trigger_delay, 159 HRTIMER_MODE_REL); 160 } else { 161 hrtimer_cancel(&data->timer_trigger); 162 } 163 return IRQ_HANDLED; 164 } 165 166 static void ltc2952_poweroff_kill(void) 167 { 168 gpiod_set_value(ltc2952_data->gpio_kill, 1); 169 } 170 171 static void ltc2952_poweroff_default(struct ltc2952_poweroff *data) 172 { 173 data->wde_interval = 300L * 1E6L; 174 data->trigger_delay = ktime_set(2, 500L*1E6L); 175 176 hrtimer_init(&data->timer_trigger, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 177 data->timer_trigger.function = ltc2952_poweroff_timer_trigger; 178 179 hrtimer_init(&data->timer_wde, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 180 data->timer_wde.function = ltc2952_poweroff_timer_wde; 181 } 182 183 static int ltc2952_poweroff_init(struct platform_device *pdev) 184 { 185 int ret; 186 struct ltc2952_poweroff *data = platform_get_drvdata(pdev); 187 188 ltc2952_poweroff_default(data); 189 190 data->gpio_watchdog = devm_gpiod_get(&pdev->dev, "watchdog", 191 GPIOD_OUT_LOW); 192 if (IS_ERR(data->gpio_watchdog)) { 193 ret = PTR_ERR(data->gpio_watchdog); 194 dev_err(&pdev->dev, "unable to claim gpio \"watchdog\"\n"); 195 return ret; 196 } 197 198 data->gpio_kill = devm_gpiod_get(&pdev->dev, "kill", GPIOD_OUT_LOW); 199 if (IS_ERR(data->gpio_kill)) { 200 ret = PTR_ERR(data->gpio_kill); 201 dev_err(&pdev->dev, "unable to claim gpio \"kill\"\n"); 202 return ret; 203 } 204 205 data->gpio_trigger = devm_gpiod_get_optional(&pdev->dev, "trigger", 206 GPIOD_IN); 207 if (IS_ERR(data->gpio_trigger)) { 208 /* 209 * It's not a problem if the trigger gpio isn't available, but 210 * it is worth a warning if its use was defined in the device 211 * tree. 212 */ 213 dev_err(&pdev->dev, "unable to claim gpio \"trigger\"\n"); 214 data->gpio_trigger = NULL; 215 } 216 217 if (devm_request_irq(&pdev->dev, gpiod_to_irq(data->gpio_trigger), 218 ltc2952_poweroff_handler, 219 (IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING), 220 "ltc2952-poweroff", 221 data)) { 222 /* 223 * Some things may have happened: 224 * - No trigger input was defined 225 * - Claiming the GPIO failed 226 * - We could not map to an IRQ 227 * - We couldn't register an interrupt handler 228 * 229 * None of these really are problems, but all of them 230 * disqualify the push button from controlling the power. 231 * 232 * It is therefore important to note that if the ltc2952 233 * detects a button press for long enough, it will still start 234 * its own powerdown window and cut the power on us if we don't 235 * start the watchdog trigger. 236 */ 237 if (data->gpio_trigger) { 238 dev_warn(&pdev->dev, 239 "unable to configure the trigger interrupt\n"); 240 devm_gpiod_put(&pdev->dev, data->gpio_trigger); 241 data->gpio_trigger = NULL; 242 } 243 dev_info(&pdev->dev, 244 "power down trigger input will not be used\n"); 245 ltc2952_poweroff_start_wde(data); 246 } 247 248 return 0; 249 } 250 251 static int ltc2952_poweroff_notify_panic(struct notifier_block *nb, 252 unsigned long code, void *unused) 253 { 254 struct ltc2952_poweroff *data = to_ltc2952(nb, panic_notifier); 255 256 data->kernel_panic = true; 257 return NOTIFY_DONE; 258 } 259 260 static int ltc2952_poweroff_probe(struct platform_device *pdev) 261 { 262 int ret; 263 struct ltc2952_poweroff *data; 264 265 if (pm_power_off) { 266 dev_err(&pdev->dev, "pm_power_off already registered"); 267 return -EBUSY; 268 } 269 270 data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL); 271 if (!data) 272 return -ENOMEM; 273 274 data->dev = &pdev->dev; 275 platform_set_drvdata(pdev, data); 276 277 ret = ltc2952_poweroff_init(pdev); 278 if (ret) 279 return ret; 280 281 /* TODO: remove ltc2952_data */ 282 ltc2952_data = data; 283 pm_power_off = ltc2952_poweroff_kill; 284 285 data->panic_notifier.notifier_call = ltc2952_poweroff_notify_panic; 286 atomic_notifier_chain_register(&panic_notifier_list, 287 &data->panic_notifier); 288 dev_info(&pdev->dev, "probe successful\n"); 289 290 return 0; 291 } 292 293 static int ltc2952_poweroff_remove(struct platform_device *pdev) 294 { 295 struct ltc2952_poweroff *data = platform_get_drvdata(pdev); 296 297 pm_power_off = NULL; 298 hrtimer_cancel(&data->timer_trigger); 299 hrtimer_cancel(&data->timer_wde); 300 atomic_notifier_chain_unregister(&panic_notifier_list, 301 &data->panic_notifier); 302 return 0; 303 } 304 305 static const struct of_device_id of_ltc2952_poweroff_match[] = { 306 { .compatible = "lltc,ltc2952"}, 307 {}, 308 }; 309 MODULE_DEVICE_TABLE(of, of_ltc2952_poweroff_match); 310 311 static struct platform_driver ltc2952_poweroff_driver = { 312 .probe = ltc2952_poweroff_probe, 313 .remove = ltc2952_poweroff_remove, 314 .driver = { 315 .name = "ltc2952-poweroff", 316 .of_match_table = of_ltc2952_poweroff_match, 317 }, 318 }; 319 320 module_platform_driver(ltc2952_poweroff_driver); 321 322 MODULE_AUTHOR("René Moll <rene.moll@xsens.com>"); 323 MODULE_DESCRIPTION("LTC PowerPath power-off driver"); 324 MODULE_LICENSE("GPL v2"); 325