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 static bool nowayout = WATCHDOG_NOWAYOUT; 55 module_param(nowayout, bool, 0); 56 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started " 57 "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")"); 58 59 #define WDT_TIMEOUT (HZ / 2) 60 61 static struct { 62 spinlock_t lock; 63 void __iomem *regs; 64 struct clk *clk; 65 unsigned long in_use; 66 unsigned long next_heartbeat; 67 struct timer_list timer; 68 int expect_close; 69 struct notifier_block restart_handler; 70 } dw_wdt; 71 72 static inline int dw_wdt_is_enabled(void) 73 { 74 return readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET) & 75 WDOG_CONTROL_REG_WDT_EN_MASK; 76 } 77 78 static inline int dw_wdt_top_in_seconds(unsigned top) 79 { 80 /* 81 * There are 16 possible timeout values in 0..15 where the number of 82 * cycles is 2 ^ (16 + i) and the watchdog counts down. 83 */ 84 return (1 << (16 + top)) / clk_get_rate(dw_wdt.clk); 85 } 86 87 static int dw_wdt_get_top(void) 88 { 89 int top = readl(dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET) & 0xF; 90 91 return dw_wdt_top_in_seconds(top); 92 } 93 94 static inline void dw_wdt_set_next_heartbeat(void) 95 { 96 dw_wdt.next_heartbeat = jiffies + dw_wdt_get_top() * HZ; 97 } 98 99 static int dw_wdt_set_top(unsigned top_s) 100 { 101 int i, top_val = DW_WDT_MAX_TOP; 102 103 /* 104 * Iterate over the timeout values until we find the closest match. We 105 * always look for >=. 106 */ 107 for (i = 0; i <= DW_WDT_MAX_TOP; ++i) 108 if (dw_wdt_top_in_seconds(i) >= top_s) { 109 top_val = i; 110 break; 111 } 112 113 /* Set the new value in the watchdog. */ 114 writel(top_val | top_val << WDOG_TIMEOUT_RANGE_TOPINIT_SHIFT, 115 dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET); 116 117 dw_wdt_set_next_heartbeat(); 118 119 return dw_wdt_top_in_seconds(top_val); 120 } 121 122 static void dw_wdt_keepalive(void) 123 { 124 writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs + 125 WDOG_COUNTER_RESTART_REG_OFFSET); 126 } 127 128 static int dw_wdt_restart_handle(struct notifier_block *this, 129 unsigned long mode, void *cmd) 130 { 131 u32 val; 132 133 writel(0, dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET); 134 val = readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET); 135 if (val & WDOG_CONTROL_REG_WDT_EN_MASK) 136 writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs + 137 WDOG_COUNTER_RESTART_REG_OFFSET); 138 else 139 writel(WDOG_CONTROL_REG_WDT_EN_MASK, 140 dw_wdt.regs + WDOG_CONTROL_REG_OFFSET); 141 142 /* wait for reset to assert... */ 143 mdelay(500); 144 145 return NOTIFY_DONE; 146 } 147 148 static void dw_wdt_ping(unsigned long data) 149 { 150 if (time_before(jiffies, dw_wdt.next_heartbeat) || 151 (!nowayout && !dw_wdt.in_use)) { 152 dw_wdt_keepalive(); 153 mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT); 154 } else 155 pr_crit("keepalive missed, machine will reset\n"); 156 } 157 158 static int dw_wdt_open(struct inode *inode, struct file *filp) 159 { 160 if (test_and_set_bit(0, &dw_wdt.in_use)) 161 return -EBUSY; 162 163 /* Make sure we don't get unloaded. */ 164 __module_get(THIS_MODULE); 165 166 spin_lock(&dw_wdt.lock); 167 if (!dw_wdt_is_enabled()) { 168 /* 169 * The watchdog is not currently enabled. Set the timeout to 170 * the maximum and then start it. 171 */ 172 dw_wdt_set_top(DW_WDT_MAX_TOP); 173 writel(WDOG_CONTROL_REG_WDT_EN_MASK, 174 dw_wdt.regs + WDOG_CONTROL_REG_OFFSET); 175 } 176 177 dw_wdt_set_next_heartbeat(); 178 179 spin_unlock(&dw_wdt.lock); 180 181 return nonseekable_open(inode, filp); 182 } 183 184 static ssize_t dw_wdt_write(struct file *filp, const char __user *buf, 185 size_t len, loff_t *offset) 186 { 187 if (!len) 188 return 0; 189 190 if (!nowayout) { 191 size_t i; 192 193 dw_wdt.expect_close = 0; 194 195 for (i = 0; i < len; ++i) { 196 char c; 197 198 if (get_user(c, buf + i)) 199 return -EFAULT; 200 201 if (c == 'V') { 202 dw_wdt.expect_close = 1; 203 break; 204 } 205 } 206 } 207 208 dw_wdt_set_next_heartbeat(); 209 mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT); 210 211 return len; 212 } 213 214 static u32 dw_wdt_time_left(void) 215 { 216 return readl(dw_wdt.regs + WDOG_CURRENT_COUNT_REG_OFFSET) / 217 clk_get_rate(dw_wdt.clk); 218 } 219 220 static const struct watchdog_info dw_wdt_ident = { 221 .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | 222 WDIOF_MAGICCLOSE, 223 .identity = "Synopsys DesignWare Watchdog", 224 }; 225 226 static long dw_wdt_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) 227 { 228 unsigned long val; 229 int timeout; 230 231 switch (cmd) { 232 case WDIOC_GETSUPPORT: 233 return copy_to_user((void __user *)arg, &dw_wdt_ident, 234 sizeof(dw_wdt_ident)) ? -EFAULT : 0; 235 236 case WDIOC_GETSTATUS: 237 case WDIOC_GETBOOTSTATUS: 238 return put_user(0, (int __user *)arg); 239 240 case WDIOC_KEEPALIVE: 241 dw_wdt_set_next_heartbeat(); 242 return 0; 243 244 case WDIOC_SETTIMEOUT: 245 if (get_user(val, (int __user *)arg)) 246 return -EFAULT; 247 timeout = dw_wdt_set_top(val); 248 return put_user(timeout , (int __user *)arg); 249 250 case WDIOC_GETTIMEOUT: 251 return put_user(dw_wdt_get_top(), (int __user *)arg); 252 253 case WDIOC_GETTIMELEFT: 254 /* Get the time left until expiry. */ 255 if (get_user(val, (int __user *)arg)) 256 return -EFAULT; 257 return put_user(dw_wdt_time_left(), (int __user *)arg); 258 259 default: 260 return -ENOTTY; 261 } 262 } 263 264 static int dw_wdt_release(struct inode *inode, struct file *filp) 265 { 266 clear_bit(0, &dw_wdt.in_use); 267 268 if (!dw_wdt.expect_close) { 269 del_timer(&dw_wdt.timer); 270 271 if (!nowayout) 272 pr_crit("unexpected close, system will reboot soon\n"); 273 else 274 pr_crit("watchdog cannot be disabled, system will reboot soon\n"); 275 } 276 277 dw_wdt.expect_close = 0; 278 279 return 0; 280 } 281 282 #ifdef CONFIG_PM_SLEEP 283 static int dw_wdt_suspend(struct device *dev) 284 { 285 clk_disable_unprepare(dw_wdt.clk); 286 287 return 0; 288 } 289 290 static int dw_wdt_resume(struct device *dev) 291 { 292 int err = clk_prepare_enable(dw_wdt.clk); 293 294 if (err) 295 return err; 296 297 dw_wdt_keepalive(); 298 299 return 0; 300 } 301 #endif /* CONFIG_PM_SLEEP */ 302 303 static SIMPLE_DEV_PM_OPS(dw_wdt_pm_ops, dw_wdt_suspend, dw_wdt_resume); 304 305 static const struct file_operations wdt_fops = { 306 .owner = THIS_MODULE, 307 .llseek = no_llseek, 308 .open = dw_wdt_open, 309 .write = dw_wdt_write, 310 .unlocked_ioctl = dw_wdt_ioctl, 311 .release = dw_wdt_release 312 }; 313 314 static struct miscdevice dw_wdt_miscdev = { 315 .fops = &wdt_fops, 316 .name = "watchdog", 317 .minor = WATCHDOG_MINOR, 318 }; 319 320 static int dw_wdt_drv_probe(struct platform_device *pdev) 321 { 322 int ret; 323 struct resource *mem = platform_get_resource(pdev, IORESOURCE_MEM, 0); 324 325 dw_wdt.regs = devm_ioremap_resource(&pdev->dev, mem); 326 if (IS_ERR(dw_wdt.regs)) 327 return PTR_ERR(dw_wdt.regs); 328 329 dw_wdt.clk = devm_clk_get(&pdev->dev, NULL); 330 if (IS_ERR(dw_wdt.clk)) 331 return PTR_ERR(dw_wdt.clk); 332 333 ret = clk_prepare_enable(dw_wdt.clk); 334 if (ret) 335 return ret; 336 337 spin_lock_init(&dw_wdt.lock); 338 339 ret = misc_register(&dw_wdt_miscdev); 340 if (ret) 341 goto out_disable_clk; 342 343 dw_wdt.restart_handler.notifier_call = dw_wdt_restart_handle; 344 dw_wdt.restart_handler.priority = 128; 345 ret = register_restart_handler(&dw_wdt.restart_handler); 346 if (ret) 347 pr_warn("cannot register restart handler\n"); 348 349 dw_wdt_set_next_heartbeat(); 350 setup_timer(&dw_wdt.timer, dw_wdt_ping, 0); 351 mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT); 352 353 return 0; 354 355 out_disable_clk: 356 clk_disable_unprepare(dw_wdt.clk); 357 358 return ret; 359 } 360 361 static int dw_wdt_drv_remove(struct platform_device *pdev) 362 { 363 unregister_restart_handler(&dw_wdt.restart_handler); 364 365 misc_deregister(&dw_wdt_miscdev); 366 367 clk_disable_unprepare(dw_wdt.clk); 368 369 return 0; 370 } 371 372 #ifdef CONFIG_OF 373 static const struct of_device_id dw_wdt_of_match[] = { 374 { .compatible = "snps,dw-wdt", }, 375 { /* sentinel */ } 376 }; 377 MODULE_DEVICE_TABLE(of, dw_wdt_of_match); 378 #endif 379 380 static struct platform_driver dw_wdt_driver = { 381 .probe = dw_wdt_drv_probe, 382 .remove = dw_wdt_drv_remove, 383 .driver = { 384 .name = "dw_wdt", 385 .of_match_table = of_match_ptr(dw_wdt_of_match), 386 .pm = &dw_wdt_pm_ops, 387 }, 388 }; 389 390 module_platform_driver(dw_wdt_driver); 391 392 MODULE_AUTHOR("Jamie Iles"); 393 MODULE_DESCRIPTION("Synopsys DesignWare Watchdog Driver"); 394 MODULE_LICENSE("GPL"); 395