1 /* 2 * Copyright 2010-2011 Picochip Ltd., Jamie Iles 3 * http://www.picochip.com 4 * 5 * This program is free software; you can redistribute it and/or 6 * modify it under the terms of the GNU General Public License 7 * as published by the Free Software Foundation; either version 8 * 2 of the License, or (at your option) any later version. 9 * 10 * This file implements a driver for the Synopsys DesignWare watchdog device 11 * in the many subsystems. The watchdog has 16 different timeout periods 12 * and these are a function of the input clock frequency. 13 * 14 * The DesignWare watchdog cannot be stopped once it has been started so we 15 * use a software timer to implement a ping that will keep the watchdog alive. 16 * If we receive an expected close for the watchdog then we keep the timer 17 * running, otherwise the timer is stopped and the watchdog will expire. 18 */ 19 20 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 21 22 #include <linux/bitops.h> 23 #include <linux/clk.h> 24 #include <linux/delay.h> 25 #include <linux/device.h> 26 #include <linux/err.h> 27 #include <linux/fs.h> 28 #include <linux/io.h> 29 #include <linux/kernel.h> 30 #include <linux/miscdevice.h> 31 #include <linux/module.h> 32 #include <linux/moduleparam.h> 33 #include <linux/notifier.h> 34 #include <linux/of.h> 35 #include <linux/pm.h> 36 #include <linux/platform_device.h> 37 #include <linux/reboot.h> 38 #include <linux/spinlock.h> 39 #include <linux/timer.h> 40 #include <linux/uaccess.h> 41 #include <linux/watchdog.h> 42 43 #define WDOG_CONTROL_REG_OFFSET 0x00 44 #define WDOG_CONTROL_REG_WDT_EN_MASK 0x01 45 #define WDOG_TIMEOUT_RANGE_REG_OFFSET 0x04 46 #define WDOG_TIMEOUT_RANGE_TOPINIT_SHIFT 4 47 #define WDOG_CURRENT_COUNT_REG_OFFSET 0x08 48 #define WDOG_COUNTER_RESTART_REG_OFFSET 0x0c 49 #define WDOG_COUNTER_RESTART_KICK_VALUE 0x76 50 51 /* The maximum TOP (timeout period) value that can be set in the watchdog. */ 52 #define DW_WDT_MAX_TOP 15 53 54 #define DW_WDT_DEFAULT_SECONDS 30 55 56 static bool nowayout = WATCHDOG_NOWAYOUT; 57 module_param(nowayout, bool, 0); 58 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started " 59 "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")"); 60 61 #define WDT_TIMEOUT (HZ / 2) 62 63 static struct { 64 spinlock_t lock; 65 void __iomem *regs; 66 struct clk *clk; 67 unsigned long in_use; 68 unsigned long next_heartbeat; 69 struct timer_list timer; 70 int expect_close; 71 struct notifier_block restart_handler; 72 } dw_wdt; 73 74 static inline int dw_wdt_is_enabled(void) 75 { 76 return readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET) & 77 WDOG_CONTROL_REG_WDT_EN_MASK; 78 } 79 80 static inline int dw_wdt_top_in_seconds(unsigned top) 81 { 82 /* 83 * There are 16 possible timeout values in 0..15 where the number of 84 * cycles is 2 ^ (16 + i) and the watchdog counts down. 85 */ 86 return (1 << (16 + top)) / clk_get_rate(dw_wdt.clk); 87 } 88 89 static int dw_wdt_get_top(void) 90 { 91 int top = readl(dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET) & 0xF; 92 93 return dw_wdt_top_in_seconds(top); 94 } 95 96 static inline void dw_wdt_set_next_heartbeat(void) 97 { 98 dw_wdt.next_heartbeat = jiffies + dw_wdt_get_top() * HZ; 99 } 100 101 static void dw_wdt_keepalive(void) 102 { 103 writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs + 104 WDOG_COUNTER_RESTART_REG_OFFSET); 105 } 106 107 static int dw_wdt_set_top(unsigned top_s) 108 { 109 int i, top_val = DW_WDT_MAX_TOP; 110 111 /* 112 * Iterate over the timeout values until we find the closest match. We 113 * always look for >=. 114 */ 115 for (i = 0; i <= DW_WDT_MAX_TOP; ++i) 116 if (dw_wdt_top_in_seconds(i) >= top_s) { 117 top_val = i; 118 break; 119 } 120 121 /* 122 * Set the new value in the watchdog. Some versions of dw_wdt 123 * have have TOPINIT in the TIMEOUT_RANGE register (as per 124 * CP_WDT_DUAL_TOP in WDT_COMP_PARAMS_1). On those we 125 * effectively get a pat of the watchdog right here. 126 */ 127 writel(top_val | top_val << WDOG_TIMEOUT_RANGE_TOPINIT_SHIFT, 128 dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET); 129 130 /* 131 * Add an explicit pat to handle versions of the watchdog that 132 * don't have TOPINIT. This won't hurt on versions that have 133 * it. 134 */ 135 dw_wdt_keepalive(); 136 137 dw_wdt_set_next_heartbeat(); 138 139 return dw_wdt_top_in_seconds(top_val); 140 } 141 142 static int dw_wdt_restart_handle(struct notifier_block *this, 143 unsigned long mode, void *cmd) 144 { 145 u32 val; 146 147 writel(0, dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET); 148 val = readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET); 149 if (val & WDOG_CONTROL_REG_WDT_EN_MASK) 150 writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs + 151 WDOG_COUNTER_RESTART_REG_OFFSET); 152 else 153 writel(WDOG_CONTROL_REG_WDT_EN_MASK, 154 dw_wdt.regs + WDOG_CONTROL_REG_OFFSET); 155 156 /* wait for reset to assert... */ 157 mdelay(500); 158 159 return NOTIFY_DONE; 160 } 161 162 static void dw_wdt_ping(unsigned long data) 163 { 164 if (time_before(jiffies, dw_wdt.next_heartbeat) || 165 (!nowayout && !dw_wdt.in_use)) { 166 dw_wdt_keepalive(); 167 mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT); 168 } else 169 pr_crit("keepalive missed, machine will reset\n"); 170 } 171 172 static int dw_wdt_open(struct inode *inode, struct file *filp) 173 { 174 if (test_and_set_bit(0, &dw_wdt.in_use)) 175 return -EBUSY; 176 177 /* Make sure we don't get unloaded. */ 178 __module_get(THIS_MODULE); 179 180 spin_lock(&dw_wdt.lock); 181 if (!dw_wdt_is_enabled()) { 182 /* 183 * The watchdog is not currently enabled. Set the timeout to 184 * something reasonable and then start it. 185 */ 186 dw_wdt_set_top(DW_WDT_DEFAULT_SECONDS); 187 writel(WDOG_CONTROL_REG_WDT_EN_MASK, 188 dw_wdt.regs + WDOG_CONTROL_REG_OFFSET); 189 } 190 191 dw_wdt_set_next_heartbeat(); 192 193 spin_unlock(&dw_wdt.lock); 194 195 return nonseekable_open(inode, filp); 196 } 197 198 static ssize_t dw_wdt_write(struct file *filp, const char __user *buf, 199 size_t len, loff_t *offset) 200 { 201 if (!len) 202 return 0; 203 204 if (!nowayout) { 205 size_t i; 206 207 dw_wdt.expect_close = 0; 208 209 for (i = 0; i < len; ++i) { 210 char c; 211 212 if (get_user(c, buf + i)) 213 return -EFAULT; 214 215 if (c == 'V') { 216 dw_wdt.expect_close = 1; 217 break; 218 } 219 } 220 } 221 222 dw_wdt_set_next_heartbeat(); 223 mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT); 224 225 return len; 226 } 227 228 static u32 dw_wdt_time_left(void) 229 { 230 return readl(dw_wdt.regs + WDOG_CURRENT_COUNT_REG_OFFSET) / 231 clk_get_rate(dw_wdt.clk); 232 } 233 234 static const struct watchdog_info dw_wdt_ident = { 235 .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | 236 WDIOF_MAGICCLOSE, 237 .identity = "Synopsys DesignWare Watchdog", 238 }; 239 240 static long dw_wdt_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) 241 { 242 unsigned long val; 243 int timeout; 244 245 switch (cmd) { 246 case WDIOC_GETSUPPORT: 247 return copy_to_user((void __user *)arg, &dw_wdt_ident, 248 sizeof(dw_wdt_ident)) ? -EFAULT : 0; 249 250 case WDIOC_GETSTATUS: 251 case WDIOC_GETBOOTSTATUS: 252 return put_user(0, (int __user *)arg); 253 254 case WDIOC_KEEPALIVE: 255 dw_wdt_set_next_heartbeat(); 256 return 0; 257 258 case WDIOC_SETTIMEOUT: 259 if (get_user(val, (int __user *)arg)) 260 return -EFAULT; 261 timeout = dw_wdt_set_top(val); 262 return put_user(timeout , (int __user *)arg); 263 264 case WDIOC_GETTIMEOUT: 265 return put_user(dw_wdt_get_top(), (int __user *)arg); 266 267 case WDIOC_GETTIMELEFT: 268 /* Get the time left until expiry. */ 269 if (get_user(val, (int __user *)arg)) 270 return -EFAULT; 271 return put_user(dw_wdt_time_left(), (int __user *)arg); 272 273 default: 274 return -ENOTTY; 275 } 276 } 277 278 static int dw_wdt_release(struct inode *inode, struct file *filp) 279 { 280 clear_bit(0, &dw_wdt.in_use); 281 282 if (!dw_wdt.expect_close) { 283 del_timer(&dw_wdt.timer); 284 285 if (!nowayout) 286 pr_crit("unexpected close, system will reboot soon\n"); 287 else 288 pr_crit("watchdog cannot be disabled, system will reboot soon\n"); 289 } 290 291 dw_wdt.expect_close = 0; 292 293 return 0; 294 } 295 296 #ifdef CONFIG_PM_SLEEP 297 static int dw_wdt_suspend(struct device *dev) 298 { 299 clk_disable_unprepare(dw_wdt.clk); 300 301 return 0; 302 } 303 304 static int dw_wdt_resume(struct device *dev) 305 { 306 int err = clk_prepare_enable(dw_wdt.clk); 307 308 if (err) 309 return err; 310 311 dw_wdt_keepalive(); 312 313 return 0; 314 } 315 #endif /* CONFIG_PM_SLEEP */ 316 317 static SIMPLE_DEV_PM_OPS(dw_wdt_pm_ops, dw_wdt_suspend, dw_wdt_resume); 318 319 static const struct file_operations wdt_fops = { 320 .owner = THIS_MODULE, 321 .llseek = no_llseek, 322 .open = dw_wdt_open, 323 .write = dw_wdt_write, 324 .unlocked_ioctl = dw_wdt_ioctl, 325 .release = dw_wdt_release 326 }; 327 328 static struct miscdevice dw_wdt_miscdev = { 329 .fops = &wdt_fops, 330 .name = "watchdog", 331 .minor = WATCHDOG_MINOR, 332 }; 333 334 static int dw_wdt_drv_probe(struct platform_device *pdev) 335 { 336 int ret; 337 struct resource *mem = platform_get_resource(pdev, IORESOURCE_MEM, 0); 338 339 dw_wdt.regs = devm_ioremap_resource(&pdev->dev, mem); 340 if (IS_ERR(dw_wdt.regs)) 341 return PTR_ERR(dw_wdt.regs); 342 343 dw_wdt.clk = devm_clk_get(&pdev->dev, NULL); 344 if (IS_ERR(dw_wdt.clk)) 345 return PTR_ERR(dw_wdt.clk); 346 347 ret = clk_prepare_enable(dw_wdt.clk); 348 if (ret) 349 return ret; 350 351 spin_lock_init(&dw_wdt.lock); 352 353 ret = misc_register(&dw_wdt_miscdev); 354 if (ret) 355 goto out_disable_clk; 356 357 dw_wdt.restart_handler.notifier_call = dw_wdt_restart_handle; 358 dw_wdt.restart_handler.priority = 128; 359 ret = register_restart_handler(&dw_wdt.restart_handler); 360 if (ret) 361 pr_warn("cannot register restart handler\n"); 362 363 dw_wdt_set_next_heartbeat(); 364 setup_timer(&dw_wdt.timer, dw_wdt_ping, 0); 365 mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT); 366 367 return 0; 368 369 out_disable_clk: 370 clk_disable_unprepare(dw_wdt.clk); 371 372 return ret; 373 } 374 375 static int dw_wdt_drv_remove(struct platform_device *pdev) 376 { 377 unregister_restart_handler(&dw_wdt.restart_handler); 378 379 misc_deregister(&dw_wdt_miscdev); 380 381 clk_disable_unprepare(dw_wdt.clk); 382 383 return 0; 384 } 385 386 #ifdef CONFIG_OF 387 static const struct of_device_id dw_wdt_of_match[] = { 388 { .compatible = "snps,dw-wdt", }, 389 { /* sentinel */ } 390 }; 391 MODULE_DEVICE_TABLE(of, dw_wdt_of_match); 392 #endif 393 394 static struct platform_driver dw_wdt_driver = { 395 .probe = dw_wdt_drv_probe, 396 .remove = dw_wdt_drv_remove, 397 .driver = { 398 .name = "dw_wdt", 399 .of_match_table = of_match_ptr(dw_wdt_of_match), 400 .pm = &dw_wdt_pm_ops, 401 }, 402 }; 403 404 module_platform_driver(dw_wdt_driver); 405 406 MODULE_AUTHOR("Jamie Iles"); 407 MODULE_DESCRIPTION("Synopsys DesignWare Watchdog Driver"); 408 MODULE_LICENSE("GPL"); 409