1 /* 2 * Watchdog timer for PowerPC Book-E systems 3 * 4 * Author: Matthew McClintock 5 * Maintainer: Kumar Gala <galak@kernel.crashing.org> 6 * 7 * Copyright 2005, 2008, 2010-2011 Freescale Semiconductor Inc. 8 * 9 * This program is free software; you can redistribute it and/or modify it 10 * under the terms of the GNU General Public License as published by the 11 * Free Software Foundation; either version 2 of the License, or (at your 12 * option) any later version. 13 */ 14 15 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 16 17 #include <linux/module.h> 18 #include <linux/fs.h> 19 #include <linux/smp.h> 20 #include <linux/miscdevice.h> 21 #include <linux/notifier.h> 22 #include <linux/watchdog.h> 23 #include <linux/uaccess.h> 24 25 #include <asm/reg_booke.h> 26 #include <asm/time.h> 27 #include <asm/div64.h> 28 29 /* If the kernel parameter wdt=1, the watchdog will be enabled at boot. 30 * Also, the wdt_period sets the watchdog timer period timeout. 31 * For E500 cpus the wdt_period sets which bit changing from 0->1 will 32 * trigger a watchog timeout. This watchdog timeout will occur 3 times, the 33 * first time nothing will happen, the second time a watchdog exception will 34 * occur, and the final time the board will reset. 35 */ 36 37 u32 booke_wdt_enabled; 38 u32 booke_wdt_period = CONFIG_BOOKE_WDT_DEFAULT_TIMEOUT; 39 40 #ifdef CONFIG_PPC_FSL_BOOK3E 41 #define WDTP(x) ((((x)&0x3)<<30)|(((x)&0x3c)<<15)) 42 #define WDTP_MASK (WDTP(0x3f)) 43 #else 44 #define WDTP(x) (TCR_WP(x)) 45 #define WDTP_MASK (TCR_WP_MASK) 46 #endif 47 48 static DEFINE_SPINLOCK(booke_wdt_lock); 49 50 /* For the specified period, determine the number of seconds 51 * corresponding to the reset time. There will be a watchdog 52 * exception at approximately 3/5 of this time. 53 * 54 * The formula to calculate this is given by: 55 * 2.5 * (2^(63-period+1)) / timebase_freq 56 * 57 * In order to simplify things, we assume that period is 58 * at least 1. This will still result in a very long timeout. 59 */ 60 static unsigned long long period_to_sec(unsigned int period) 61 { 62 unsigned long long tmp = 1ULL << (64 - period); 63 unsigned long tmp2 = ppc_tb_freq; 64 65 /* tmp may be a very large number and we don't want to overflow, 66 * so divide the timebase freq instead of multiplying tmp 67 */ 68 tmp2 = tmp2 / 5 * 2; 69 70 do_div(tmp, tmp2); 71 return tmp; 72 } 73 74 /* 75 * This procedure will find the highest period which will give a timeout 76 * greater than the one required. e.g. for a bus speed of 66666666 and 77 * and a parameter of 2 secs, then this procedure will return a value of 38. 78 */ 79 static unsigned int sec_to_period(unsigned int secs) 80 { 81 unsigned int period; 82 for (period = 63; period > 0; period--) { 83 if (period_to_sec(period) >= secs) 84 return period; 85 } 86 return 0; 87 } 88 89 static void __booke_wdt_set(void *data) 90 { 91 u32 val; 92 93 val = mfspr(SPRN_TCR); 94 val &= ~WDTP_MASK; 95 val |= WDTP(booke_wdt_period); 96 97 mtspr(SPRN_TCR, val); 98 } 99 100 static void booke_wdt_set(void) 101 { 102 on_each_cpu(__booke_wdt_set, NULL, 0); 103 } 104 105 static void __booke_wdt_ping(void *data) 106 { 107 mtspr(SPRN_TSR, TSR_ENW|TSR_WIS); 108 } 109 110 static void booke_wdt_ping(void) 111 { 112 on_each_cpu(__booke_wdt_ping, NULL, 0); 113 } 114 115 static void __booke_wdt_enable(void *data) 116 { 117 u32 val; 118 119 /* clear status before enabling watchdog */ 120 __booke_wdt_ping(NULL); 121 val = mfspr(SPRN_TCR); 122 val &= ~WDTP_MASK; 123 val |= (TCR_WIE|TCR_WRC(WRC_CHIP)|WDTP(booke_wdt_period)); 124 125 mtspr(SPRN_TCR, val); 126 } 127 128 /** 129 * booke_wdt_disable - disable the watchdog on the given CPU 130 * 131 * This function is called on each CPU. It disables the watchdog on that CPU. 132 * 133 * TCR[WRC] cannot be changed once it has been set to non-zero, but we can 134 * effectively disable the watchdog by setting its period to the maximum value. 135 */ 136 static void __booke_wdt_disable(void *data) 137 { 138 u32 val; 139 140 val = mfspr(SPRN_TCR); 141 val &= ~(TCR_WIE | WDTP_MASK); 142 mtspr(SPRN_TCR, val); 143 144 /* clear status to make sure nothing is pending */ 145 __booke_wdt_ping(NULL); 146 147 } 148 149 static ssize_t booke_wdt_write(struct file *file, const char __user *buf, 150 size_t count, loff_t *ppos) 151 { 152 booke_wdt_ping(); 153 return count; 154 } 155 156 static struct watchdog_info ident = { 157 .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING, 158 .identity = "PowerPC Book-E Watchdog", 159 }; 160 161 static long booke_wdt_ioctl(struct file *file, 162 unsigned int cmd, unsigned long arg) 163 { 164 u32 tmp = 0; 165 u32 __user *p = (u32 __user *)arg; 166 167 switch (cmd) { 168 case WDIOC_GETSUPPORT: 169 return copy_to_user(p, &ident, sizeof(ident)) ? -EFAULT : 0; 170 case WDIOC_GETSTATUS: 171 return put_user(0, p); 172 case WDIOC_GETBOOTSTATUS: 173 /* XXX: something is clearing TSR */ 174 tmp = mfspr(SPRN_TSR) & TSR_WRS(3); 175 /* returns CARDRESET if last reset was caused by the WDT */ 176 return put_user((tmp ? WDIOF_CARDRESET : 0), p); 177 case WDIOC_SETOPTIONS: 178 if (get_user(tmp, p)) 179 return -EFAULT; 180 if (tmp == WDIOS_ENABLECARD) { 181 booke_wdt_ping(); 182 break; 183 } else 184 return -EINVAL; 185 return 0; 186 case WDIOC_KEEPALIVE: 187 booke_wdt_ping(); 188 return 0; 189 case WDIOC_SETTIMEOUT: 190 if (get_user(tmp, p)) 191 return -EFAULT; 192 #ifdef CONFIG_PPC_FSL_BOOK3E 193 /* period of 1 gives the largest possible timeout */ 194 if (tmp > period_to_sec(1)) 195 return -EINVAL; 196 booke_wdt_period = sec_to_period(tmp); 197 #else 198 booke_wdt_period = tmp; 199 #endif 200 booke_wdt_set(); 201 /* Fall */ 202 case WDIOC_GETTIMEOUT: 203 #ifdef CONFIG_FSL_BOOKE 204 return put_user(period_to_sec(booke_wdt_period), p); 205 #else 206 return put_user(booke_wdt_period, p); 207 #endif 208 default: 209 return -ENOTTY; 210 } 211 212 return 0; 213 } 214 215 /* wdt_is_active stores whether or not the /dev/watchdog device is opened */ 216 static unsigned long wdt_is_active; 217 218 static int booke_wdt_open(struct inode *inode, struct file *file) 219 { 220 /* /dev/watchdog can only be opened once */ 221 if (test_and_set_bit(0, &wdt_is_active)) 222 return -EBUSY; 223 224 spin_lock(&booke_wdt_lock); 225 if (booke_wdt_enabled == 0) { 226 booke_wdt_enabled = 1; 227 on_each_cpu(__booke_wdt_enable, NULL, 0); 228 pr_debug("watchdog enabled (timeout = %llu sec)\n", 229 period_to_sec(booke_wdt_period)); 230 } 231 spin_unlock(&booke_wdt_lock); 232 233 return nonseekable_open(inode, file); 234 } 235 236 static int booke_wdt_release(struct inode *inode, struct file *file) 237 { 238 #ifndef CONFIG_WATCHDOG_NOWAYOUT 239 /* Normally, the watchdog is disabled when /dev/watchdog is closed, but 240 * if CONFIG_WATCHDOG_NOWAYOUT is defined, then it means that the 241 * watchdog should remain enabled. So we disable it only if 242 * CONFIG_WATCHDOG_NOWAYOUT is not defined. 243 */ 244 on_each_cpu(__booke_wdt_disable, NULL, 0); 245 booke_wdt_enabled = 0; 246 pr_debug("watchdog disabled\n"); 247 #endif 248 249 clear_bit(0, &wdt_is_active); 250 251 return 0; 252 } 253 254 static const struct file_operations booke_wdt_fops = { 255 .owner = THIS_MODULE, 256 .llseek = no_llseek, 257 .write = booke_wdt_write, 258 .unlocked_ioctl = booke_wdt_ioctl, 259 .open = booke_wdt_open, 260 .release = booke_wdt_release, 261 }; 262 263 static struct miscdevice booke_wdt_miscdev = { 264 .minor = WATCHDOG_MINOR, 265 .name = "watchdog", 266 .fops = &booke_wdt_fops, 267 }; 268 269 static void __exit booke_wdt_exit(void) 270 { 271 misc_deregister(&booke_wdt_miscdev); 272 } 273 274 static int __init booke_wdt_init(void) 275 { 276 int ret = 0; 277 278 pr_info("powerpc book-e watchdog driver loaded\n"); 279 ident.firmware_version = cur_cpu_spec->pvr_value; 280 281 ret = misc_register(&booke_wdt_miscdev); 282 if (ret) { 283 pr_err("cannot register device (minor=%u, ret=%i)\n", 284 WATCHDOG_MINOR, ret); 285 return ret; 286 } 287 288 spin_lock(&booke_wdt_lock); 289 if (booke_wdt_enabled == 1) { 290 pr_info("watchdog enabled (timeout = %llu sec)\n", 291 period_to_sec(booke_wdt_period)); 292 on_each_cpu(__booke_wdt_enable, NULL, 0); 293 } 294 spin_unlock(&booke_wdt_lock); 295 296 return ret; 297 } 298 299 module_init(booke_wdt_init); 300 module_exit(booke_wdt_exit); 301 302 MODULE_DESCRIPTION("PowerPC Book-E watchdog driver"); 303 MODULE_LICENSE("GPL"); 304