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 ARM 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/device.h> 25 #include <linux/err.h> 26 #include <linux/fs.h> 27 #include <linux/io.h> 28 #include <linux/kernel.h> 29 #include <linux/miscdevice.h> 30 #include <linux/module.h> 31 #include <linux/moduleparam.h> 32 #include <linux/of.h> 33 #include <linux/pm.h> 34 #include <linux/platform_device.h> 35 #include <linux/spinlock.h> 36 #include <linux/timer.h> 37 #include <linux/uaccess.h> 38 #include <linux/watchdog.h> 39 40 #define WDOG_CONTROL_REG_OFFSET 0x00 41 #define WDOG_CONTROL_REG_WDT_EN_MASK 0x01 42 #define WDOG_TIMEOUT_RANGE_REG_OFFSET 0x04 43 #define WDOG_CURRENT_COUNT_REG_OFFSET 0x08 44 #define WDOG_COUNTER_RESTART_REG_OFFSET 0x0c 45 #define WDOG_COUNTER_RESTART_KICK_VALUE 0x76 46 47 /* The maximum TOP (timeout period) value that can be set in the watchdog. */ 48 #define DW_WDT_MAX_TOP 15 49 50 static bool nowayout = WATCHDOG_NOWAYOUT; 51 module_param(nowayout, bool, 0); 52 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started " 53 "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")"); 54 55 #define WDT_TIMEOUT (HZ / 2) 56 57 static struct { 58 spinlock_t lock; 59 void __iomem *regs; 60 struct clk *clk; 61 unsigned long in_use; 62 unsigned long next_heartbeat; 63 struct timer_list timer; 64 int expect_close; 65 } dw_wdt; 66 67 static inline int dw_wdt_is_enabled(void) 68 { 69 return readl(dw_wdt.regs + WDOG_CONTROL_REG_OFFSET) & 70 WDOG_CONTROL_REG_WDT_EN_MASK; 71 } 72 73 static inline int dw_wdt_top_in_seconds(unsigned top) 74 { 75 /* 76 * There are 16 possible timeout values in 0..15 where the number of 77 * cycles is 2 ^ (16 + i) and the watchdog counts down. 78 */ 79 return (1 << (16 + top)) / clk_get_rate(dw_wdt.clk); 80 } 81 82 static int dw_wdt_get_top(void) 83 { 84 int top = readl(dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET) & 0xF; 85 86 return dw_wdt_top_in_seconds(top); 87 } 88 89 static inline void dw_wdt_set_next_heartbeat(void) 90 { 91 dw_wdt.next_heartbeat = jiffies + dw_wdt_get_top() * HZ; 92 } 93 94 static int dw_wdt_set_top(unsigned top_s) 95 { 96 int i, top_val = DW_WDT_MAX_TOP; 97 98 /* 99 * Iterate over the timeout values until we find the closest match. We 100 * always look for >=. 101 */ 102 for (i = 0; i <= DW_WDT_MAX_TOP; ++i) 103 if (dw_wdt_top_in_seconds(i) >= top_s) { 104 top_val = i; 105 break; 106 } 107 108 /* Set the new value in the watchdog. */ 109 writel(top_val, dw_wdt.regs + WDOG_TIMEOUT_RANGE_REG_OFFSET); 110 111 dw_wdt_set_next_heartbeat(); 112 113 return dw_wdt_top_in_seconds(top_val); 114 } 115 116 static void dw_wdt_keepalive(void) 117 { 118 writel(WDOG_COUNTER_RESTART_KICK_VALUE, dw_wdt.regs + 119 WDOG_COUNTER_RESTART_REG_OFFSET); 120 } 121 122 static void dw_wdt_ping(unsigned long data) 123 { 124 if (time_before(jiffies, dw_wdt.next_heartbeat) || 125 (!nowayout && !dw_wdt.in_use)) { 126 dw_wdt_keepalive(); 127 mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT); 128 } else 129 pr_crit("keepalive missed, machine will reset\n"); 130 } 131 132 static int dw_wdt_open(struct inode *inode, struct file *filp) 133 { 134 if (test_and_set_bit(0, &dw_wdt.in_use)) 135 return -EBUSY; 136 137 /* Make sure we don't get unloaded. */ 138 __module_get(THIS_MODULE); 139 140 spin_lock(&dw_wdt.lock); 141 if (!dw_wdt_is_enabled()) { 142 /* 143 * The watchdog is not currently enabled. Set the timeout to 144 * the maximum and then start it. 145 */ 146 dw_wdt_set_top(DW_WDT_MAX_TOP); 147 writel(WDOG_CONTROL_REG_WDT_EN_MASK, 148 dw_wdt.regs + WDOG_CONTROL_REG_OFFSET); 149 } 150 151 dw_wdt_set_next_heartbeat(); 152 153 spin_unlock(&dw_wdt.lock); 154 155 return nonseekable_open(inode, filp); 156 } 157 158 static ssize_t dw_wdt_write(struct file *filp, const char __user *buf, 159 size_t len, loff_t *offset) 160 { 161 if (!len) 162 return 0; 163 164 if (!nowayout) { 165 size_t i; 166 167 dw_wdt.expect_close = 0; 168 169 for (i = 0; i < len; ++i) { 170 char c; 171 172 if (get_user(c, buf + i)) 173 return -EFAULT; 174 175 if (c == 'V') { 176 dw_wdt.expect_close = 1; 177 break; 178 } 179 } 180 } 181 182 dw_wdt_set_next_heartbeat(); 183 mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT); 184 185 return len; 186 } 187 188 static u32 dw_wdt_time_left(void) 189 { 190 return readl(dw_wdt.regs + WDOG_CURRENT_COUNT_REG_OFFSET) / 191 clk_get_rate(dw_wdt.clk); 192 } 193 194 static const struct watchdog_info dw_wdt_ident = { 195 .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | 196 WDIOF_MAGICCLOSE, 197 .identity = "Synopsys DesignWare Watchdog", 198 }; 199 200 static long dw_wdt_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) 201 { 202 unsigned long val; 203 int timeout; 204 205 switch (cmd) { 206 case WDIOC_GETSUPPORT: 207 return copy_to_user((void __user *)arg, &dw_wdt_ident, 208 sizeof(dw_wdt_ident)) ? -EFAULT : 0; 209 210 case WDIOC_GETSTATUS: 211 case WDIOC_GETBOOTSTATUS: 212 return put_user(0, (int __user *)arg); 213 214 case WDIOC_KEEPALIVE: 215 dw_wdt_set_next_heartbeat(); 216 return 0; 217 218 case WDIOC_SETTIMEOUT: 219 if (get_user(val, (int __user *)arg)) 220 return -EFAULT; 221 timeout = dw_wdt_set_top(val); 222 return put_user(timeout , (int __user *)arg); 223 224 case WDIOC_GETTIMEOUT: 225 return put_user(dw_wdt_get_top(), (int __user *)arg); 226 227 case WDIOC_GETTIMELEFT: 228 /* Get the time left until expiry. */ 229 if (get_user(val, (int __user *)arg)) 230 return -EFAULT; 231 return put_user(dw_wdt_time_left(), (int __user *)arg); 232 233 default: 234 return -ENOTTY; 235 } 236 } 237 238 static int dw_wdt_release(struct inode *inode, struct file *filp) 239 { 240 clear_bit(0, &dw_wdt.in_use); 241 242 if (!dw_wdt.expect_close) { 243 del_timer(&dw_wdt.timer); 244 245 if (!nowayout) 246 pr_crit("unexpected close, system will reboot soon\n"); 247 else 248 pr_crit("watchdog cannot be disabled, system will reboot soon\n"); 249 } 250 251 dw_wdt.expect_close = 0; 252 253 return 0; 254 } 255 256 #ifdef CONFIG_PM_SLEEP 257 static int dw_wdt_suspend(struct device *dev) 258 { 259 clk_disable_unprepare(dw_wdt.clk); 260 261 return 0; 262 } 263 264 static int dw_wdt_resume(struct device *dev) 265 { 266 int err = clk_prepare_enable(dw_wdt.clk); 267 268 if (err) 269 return err; 270 271 dw_wdt_keepalive(); 272 273 return 0; 274 } 275 #endif /* CONFIG_PM_SLEEP */ 276 277 static SIMPLE_DEV_PM_OPS(dw_wdt_pm_ops, dw_wdt_suspend, dw_wdt_resume); 278 279 static const struct file_operations wdt_fops = { 280 .owner = THIS_MODULE, 281 .llseek = no_llseek, 282 .open = dw_wdt_open, 283 .write = dw_wdt_write, 284 .unlocked_ioctl = dw_wdt_ioctl, 285 .release = dw_wdt_release 286 }; 287 288 static struct miscdevice dw_wdt_miscdev = { 289 .fops = &wdt_fops, 290 .name = "watchdog", 291 .minor = WATCHDOG_MINOR, 292 }; 293 294 static int dw_wdt_drv_probe(struct platform_device *pdev) 295 { 296 int ret; 297 struct resource *mem = platform_get_resource(pdev, IORESOURCE_MEM, 0); 298 299 if (!mem) 300 return -EINVAL; 301 302 dw_wdt.regs = devm_ioremap_resource(&pdev->dev, mem); 303 if (IS_ERR(dw_wdt.regs)) 304 return PTR_ERR(dw_wdt.regs); 305 306 dw_wdt.clk = devm_clk_get(&pdev->dev, NULL); 307 if (IS_ERR(dw_wdt.clk)) 308 return PTR_ERR(dw_wdt.clk); 309 310 ret = clk_prepare_enable(dw_wdt.clk); 311 if (ret) 312 return ret; 313 314 spin_lock_init(&dw_wdt.lock); 315 316 ret = misc_register(&dw_wdt_miscdev); 317 if (ret) 318 goto out_disable_clk; 319 320 dw_wdt_set_next_heartbeat(); 321 setup_timer(&dw_wdt.timer, dw_wdt_ping, 0); 322 mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT); 323 324 return 0; 325 326 out_disable_clk: 327 clk_disable_unprepare(dw_wdt.clk); 328 329 return ret; 330 } 331 332 static int dw_wdt_drv_remove(struct platform_device *pdev) 333 { 334 misc_deregister(&dw_wdt_miscdev); 335 336 clk_disable_unprepare(dw_wdt.clk); 337 338 return 0; 339 } 340 341 #ifdef CONFIG_OF 342 static const struct of_device_id dw_wdt_of_match[] = { 343 { .compatible = "snps,dw-wdt", }, 344 { /* sentinel */ } 345 }; 346 MODULE_DEVICE_TABLE(of, dw_wdt_of_match); 347 #endif 348 349 static struct platform_driver dw_wdt_driver = { 350 .probe = dw_wdt_drv_probe, 351 .remove = dw_wdt_drv_remove, 352 .driver = { 353 .name = "dw_wdt", 354 .owner = THIS_MODULE, 355 .of_match_table = of_match_ptr(dw_wdt_of_match), 356 .pm = &dw_wdt_pm_ops, 357 }, 358 }; 359 360 module_platform_driver(dw_wdt_driver); 361 362 MODULE_AUTHOR("Jamie Iles"); 363 MODULE_DESCRIPTION("Synopsys DesignWare Watchdog Driver"); 364 MODULE_LICENSE("GPL"); 365