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/timer.h> 39 #include <linux/uaccess.h> 40 #include <linux/watchdog.h> 41 42 #define WDOG_CONTROL_REG_OFFSET 0x00 43 #define WDOG_CONTROL_REG_WDT_EN_MASK 0x01 44 #define WDOG_TIMEOUT_RANGE_REG_OFFSET 0x04 45 #define WDOG_TIMEOUT_RANGE_TOPINIT_SHIFT 4 46 #define WDOG_CURRENT_COUNT_REG_OFFSET 0x08 47 #define WDOG_COUNTER_RESTART_REG_OFFSET 0x0c 48 #define WDOG_COUNTER_RESTART_KICK_VALUE 0x76 49 50 /* The maximum TOP (timeout period) value that can be set in the watchdog. */ 51 #define DW_WDT_MAX_TOP 15 52 53 #define DW_WDT_DEFAULT_SECONDS 30 54 55 static bool nowayout = WATCHDOG_NOWAYOUT; 56 module_param(nowayout, bool, 0); 57 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started " 58 "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")"); 59 60 #define WDT_TIMEOUT (HZ / 2) 61 62 static struct { 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 void dw_wdt_keepalive(void) 100 { 101 writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs + 102 WDOG_COUNTER_RESTART_REG_OFFSET); 103 } 104 105 static int dw_wdt_set_top(unsigned top_s) 106 { 107 int i, top_val = DW_WDT_MAX_TOP; 108 109 /* 110 * Iterate over the timeout values until we find the closest match. We 111 * always look for >=. 112 */ 113 for (i = 0; i <= DW_WDT_MAX_TOP; ++i) 114 if (dw_wdt_top_in_seconds(i) >= top_s) { 115 top_val = i; 116 break; 117 } 118 119 /* 120 * Set the new value in the watchdog. Some versions of dw_wdt 121 * have have TOPINIT in the TIMEOUT_RANGE register (as per 122 * CP_WDT_DUAL_TOP in WDT_COMP_PARAMS_1). On those we 123 * effectively get a pat of the watchdog right here. 124 */ 125 writel(top_val | top_val << WDOG_TIMEOUT_RANGE_TOPINIT_SHIFT, 126 dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET); 127 128 /* 129 * Add an explicit pat to handle versions of the watchdog that 130 * don't have TOPINIT. This won't hurt on versions that have 131 * it. 132 */ 133 dw_wdt_keepalive(); 134 135 dw_wdt_set_next_heartbeat(); 136 137 return dw_wdt_top_in_seconds(top_val); 138 } 139 140 static int dw_wdt_restart_handle(struct notifier_block *this, 141 unsigned long mode, void *cmd) 142 { 143 u32 val; 144 145 writel(0, dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET); 146 val = readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET); 147 if (val & WDOG_CONTROL_REG_WDT_EN_MASK) 148 writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs + 149 WDOG_COUNTER_RESTART_REG_OFFSET); 150 else 151 writel(WDOG_CONTROL_REG_WDT_EN_MASK, 152 dw_wdt.regs + WDOG_CONTROL_REG_OFFSET); 153 154 /* wait for reset to assert... */ 155 mdelay(500); 156 157 return NOTIFY_DONE; 158 } 159 160 static void dw_wdt_ping(unsigned long data) 161 { 162 if (time_before(jiffies, dw_wdt.next_heartbeat) || 163 (!nowayout && !dw_wdt.in_use)) { 164 dw_wdt_keepalive(); 165 mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT); 166 } else 167 pr_crit("keepalive missed, machine will reset\n"); 168 } 169 170 static int dw_wdt_open(struct inode *inode, struct file *filp) 171 { 172 if (test_and_set_bit(0, &dw_wdt.in_use)) 173 return -EBUSY; 174 175 /* Make sure we don't get unloaded. */ 176 __module_get(THIS_MODULE); 177 178 if (!dw_wdt_is_enabled()) { 179 /* 180 * The watchdog is not currently enabled. Set the timeout to 181 * something reasonable and then start it. 182 */ 183 dw_wdt_set_top(DW_WDT_DEFAULT_SECONDS); 184 writel(WDOG_CONTROL_REG_WDT_EN_MASK, 185 dw_wdt.regs + WDOG_CONTROL_REG_OFFSET); 186 } 187 188 dw_wdt_set_next_heartbeat(); 189 190 return nonseekable_open(inode, filp); 191 } 192 193 static ssize_t dw_wdt_write(struct file *filp, const char __user *buf, 194 size_t len, loff_t *offset) 195 { 196 if (!len) 197 return 0; 198 199 if (!nowayout) { 200 size_t i; 201 202 dw_wdt.expect_close = 0; 203 204 for (i = 0; i < len; ++i) { 205 char c; 206 207 if (get_user(c, buf + i)) 208 return -EFAULT; 209 210 if (c == 'V') { 211 dw_wdt.expect_close = 1; 212 break; 213 } 214 } 215 } 216 217 dw_wdt_set_next_heartbeat(); 218 dw_wdt_keepalive(); 219 mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT); 220 221 return len; 222 } 223 224 static u32 dw_wdt_time_left(void) 225 { 226 return readl(dw_wdt.regs + WDOG_CURRENT_COUNT_REG_OFFSET) / 227 clk_get_rate(dw_wdt.clk); 228 } 229 230 static const struct watchdog_info dw_wdt_ident = { 231 .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | 232 WDIOF_MAGICCLOSE, 233 .identity = "Synopsys DesignWare Watchdog", 234 }; 235 236 static long dw_wdt_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) 237 { 238 unsigned long val; 239 int timeout; 240 241 switch (cmd) { 242 case WDIOC_GETSUPPORT: 243 return copy_to_user((void __user *)arg, &dw_wdt_ident, 244 sizeof(dw_wdt_ident)) ? -EFAULT : 0; 245 246 case WDIOC_GETSTATUS: 247 case WDIOC_GETBOOTSTATUS: 248 return put_user(0, (int __user *)arg); 249 250 case WDIOC_KEEPALIVE: 251 dw_wdt_set_next_heartbeat(); 252 return 0; 253 254 case WDIOC_SETTIMEOUT: 255 if (get_user(val, (int __user *)arg)) 256 return -EFAULT; 257 timeout = dw_wdt_set_top(val); 258 return put_user(timeout , (int __user *)arg); 259 260 case WDIOC_GETTIMEOUT: 261 return put_user(dw_wdt_get_top(), (int __user *)arg); 262 263 case WDIOC_GETTIMELEFT: 264 /* Get the time left until expiry. */ 265 if (get_user(val, (int __user *)arg)) 266 return -EFAULT; 267 return put_user(dw_wdt_time_left(), (int __user *)arg); 268 269 default: 270 return -ENOTTY; 271 } 272 } 273 274 static int dw_wdt_release(struct inode *inode, struct file *filp) 275 { 276 clear_bit(0, &dw_wdt.in_use); 277 278 if (!dw_wdt.expect_close) { 279 del_timer(&dw_wdt.timer); 280 281 if (!nowayout) 282 pr_crit("unexpected close, system will reboot soon\n"); 283 else 284 pr_crit("watchdog cannot be disabled, system will reboot soon\n"); 285 } 286 287 dw_wdt.expect_close = 0; 288 289 return 0; 290 } 291 292 #ifdef CONFIG_PM_SLEEP 293 static int dw_wdt_suspend(struct device *dev) 294 { 295 clk_disable_unprepare(dw_wdt.clk); 296 297 return 0; 298 } 299 300 static int dw_wdt_resume(struct device *dev) 301 { 302 int err = clk_prepare_enable(dw_wdt.clk); 303 304 if (err) 305 return err; 306 307 dw_wdt_keepalive(); 308 309 return 0; 310 } 311 #endif /* CONFIG_PM_SLEEP */ 312 313 static SIMPLE_DEV_PM_OPS(dw_wdt_pm_ops, dw_wdt_suspend, dw_wdt_resume); 314 315 static const struct file_operations wdt_fops = { 316 .owner = THIS_MODULE, 317 .llseek = no_llseek, 318 .open = dw_wdt_open, 319 .write = dw_wdt_write, 320 .unlocked_ioctl = dw_wdt_ioctl, 321 .release = dw_wdt_release 322 }; 323 324 static struct miscdevice dw_wdt_miscdev = { 325 .fops = &wdt_fops, 326 .name = "watchdog", 327 .minor = WATCHDOG_MINOR, 328 }; 329 330 static int dw_wdt_drv_probe(struct platform_device *pdev) 331 { 332 int ret; 333 struct resource *mem = platform_get_resource(pdev, IORESOURCE_MEM, 0); 334 335 dw_wdt.regs = devm_ioremap_resource(&pdev->dev, mem); 336 if (IS_ERR(dw_wdt.regs)) 337 return PTR_ERR(dw_wdt.regs); 338 339 dw_wdt.clk = devm_clk_get(&pdev->dev, NULL); 340 if (IS_ERR(dw_wdt.clk)) 341 return PTR_ERR(dw_wdt.clk); 342 343 ret = clk_prepare_enable(dw_wdt.clk); 344 if (ret) 345 return ret; 346 347 ret = misc_register(&dw_wdt_miscdev); 348 if (ret) 349 goto out_disable_clk; 350 351 dw_wdt.restart_handler.notifier_call = dw_wdt_restart_handle; 352 dw_wdt.restart_handler.priority = 128; 353 ret = register_restart_handler(&dw_wdt.restart_handler); 354 if (ret) 355 pr_warn("cannot register restart handler\n"); 356 357 dw_wdt_set_next_heartbeat(); 358 setup_timer(&dw_wdt.timer, dw_wdt_ping, 0); 359 mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT); 360 361 return 0; 362 363 out_disable_clk: 364 clk_disable_unprepare(dw_wdt.clk); 365 366 return ret; 367 } 368 369 static int dw_wdt_drv_remove(struct platform_device *pdev) 370 { 371 unregister_restart_handler(&dw_wdt.restart_handler); 372 373 misc_deregister(&dw_wdt_miscdev); 374 375 clk_disable_unprepare(dw_wdt.clk); 376 377 return 0; 378 } 379 380 #ifdef CONFIG_OF 381 static const struct of_device_id dw_wdt_of_match[] = { 382 { .compatible = "snps,dw-wdt", }, 383 { /* sentinel */ } 384 }; 385 MODULE_DEVICE_TABLE(of, dw_wdt_of_match); 386 #endif 387 388 static struct platform_driver dw_wdt_driver = { 389 .probe = dw_wdt_drv_probe, 390 .remove = dw_wdt_drv_remove, 391 .driver = { 392 .name = "dw_wdt", 393 .of_match_table = of_match_ptr(dw_wdt_of_match), 394 .pm = &dw_wdt_pm_ops, 395 }, 396 }; 397 398 module_platform_driver(dw_wdt_driver); 399 400 MODULE_AUTHOR("Jamie Iles"); 401 MODULE_DESCRIPTION("Synopsys DesignWare Watchdog Driver"); 402 MODULE_LICENSE("GPL"); 403