drivers/watchdog/booke_wdt.c

   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/smp.h>
  19 #include <linux/watchdog.h>
  20
  21 #include <asm/reg_booke.h>
  22 #include <asm/time.h>
  23 #include <asm/div64.h>
  24
  25 /* If the kernel parameter wdt=1, the watchdog will be enabled at boot.
  26  * Also, the wdt_period sets the watchdog timer period timeout.
  27  * For E500 cpus the wdt_period sets which bit changing from 0->1 will
  28  * trigger a watchog timeout. This watchdog timeout will occur 3 times, the
  29  * first time nothing will happen, the second time a watchdog exception will
  30  * occur, and the final time the board will reset.
  31  */
  32
  33 u32 booke_wdt_enabled;
  34 u32 booke_wdt_period = CONFIG_BOOKE_WDT_DEFAULT_TIMEOUT;
  35
  36 #ifdef  CONFIG_PPC_FSL_BOOK3E
  37 #define WDTP(x)         ((((x)&0x3)<<30)|(((x)&0x3c)<<15))
  38 #define WDTP_MASK       (WDTP(0x3f))
  39 #else
  40 #define WDTP(x)         (TCR_WP(x))
  41 #define WDTP_MASK       (TCR_WP_MASK)
  42 #endif
  43
  44 /* Checks wdt=x and wdt_period=xx command-line option */
  45 notrace int __init early_parse_wdt(char *p)
  46 {
  47         if (p && strncmp(p, "0", 1) != 0)
  48                 booke_wdt_enabled = 1;
  49
  50         return 0;
  51 }
  52 early_param("wdt", early_parse_wdt);
  53
  54 int __init early_parse_wdt_period(char *p)
  55 {
  56         unsigned long ret;
  57         if (p) {
  58                 if (!kstrtol(p, 0, &ret))
  59                         booke_wdt_period = ret;
  60         }
  61
  62         return 0;
  63 }
  64 early_param("wdt_period", early_parse_wdt_period);
  65
  66 #ifdef CONFIG_PPC_FSL_BOOK3E
  67
  68 /* For the specified period, determine the number of seconds
  69  * corresponding to the reset time.  There will be a watchdog
  70  * exception at approximately 3/5 of this time.
  71  *
  72  * The formula to calculate this is given by:
  73  * 2.5 * (2^(63-period+1)) / timebase_freq
  74  *
  75  * In order to simplify things, we assume that period is
  76  * at least 1.  This will still result in a very long timeout.
  77  */
  78 static unsigned long long period_to_sec(unsigned int period)
  79 {
  80         unsigned long long tmp = 1ULL << (64 - period);
  81         unsigned long tmp2 = ppc_tb_freq;
  82
  83         /* tmp may be a very large number and we don't want to overflow,
  84          * so divide the timebase freq instead of multiplying tmp
  85          */
  86         tmp2 = tmp2 / 5 * 2;
  87
  88         do_div(tmp, tmp2);
  89         return tmp;
  90 }
  91
  92 /*
  93  * This procedure will find the highest period which will give a timeout
  94  * greater than the one required. e.g. for a bus speed of 66666666 and
  95  * and a parameter of 2 secs, then this procedure will return a value of 38.
  96  */
  97 static unsigned int sec_to_period(unsigned int secs)
  98 {
  99         unsigned int period;
 100         for (period = 63; period > 0; period--) {
 101                 if (period_to_sec(period) >= secs)
 102                         return period;
 103         }
 104         return 0;
 105 }
 106
 107 #define MAX_WDT_TIMEOUT         period_to_sec(1)
 108
 109 #else /* CONFIG_PPC_FSL_BOOK3E */
 110
 111 static unsigned long long period_to_sec(unsigned int period)
 112 {
 113         return period;
 114 }
 115
 116 static unsigned int sec_to_period(unsigned int secs)
 117 {
 118         return secs;
 119 }
 120
 121 #define MAX_WDT_TIMEOUT         3       /* from Kconfig */
 122
 123 #endif /* !CONFIG_PPC_FSL_BOOK3E */
 124
 125 static void __booke_wdt_set(void *data)
 126 {
 127         u32 val;
 128         struct watchdog_device *wdog = data;
 129
 130         val = mfspr(SPRN_TCR);
 131         val &= ~WDTP_MASK;
 132         val |= WDTP(sec_to_period(wdog->timeout));
 133
 134         mtspr(SPRN_TCR, val);
 135 }
 136
 137 static void booke_wdt_set(void *data)
 138 {
 139         on_each_cpu(__booke_wdt_set, data, 0);
 140 }
 141
 142 static void __booke_wdt_ping(void *data)
 143 {
 144         mtspr(SPRN_TSR, TSR_ENW|TSR_WIS);
 145 }
 146
 147 static int booke_wdt_ping(struct watchdog_device *wdog)
 148 {
 149         on_each_cpu(__booke_wdt_ping, NULL, 0);
 150
 151         return 0;
 152 }
 153
 154 static void __booke_wdt_enable(void *data)
 155 {
 156         u32 val;
 157         struct watchdog_device *wdog = data;
 158
 159         /* clear status before enabling watchdog */
 160         __booke_wdt_ping(NULL);
 161         val = mfspr(SPRN_TCR);
 162         val &= ~WDTP_MASK;
 163         val |= (TCR_WIE|TCR_WRC(WRC_CHIP)|WDTP(sec_to_period(wdog->timeout)));
 164
 165         mtspr(SPRN_TCR, val);
 166 }
 167
 168 /**
 169  * booke_wdt_disable - disable the watchdog on the given CPU
 170  *
 171  * This function is called on each CPU.  It disables the watchdog on that CPU.
 172  *
 173  * TCR[WRC] cannot be changed once it has been set to non-zero, but we can
 174  * effectively disable the watchdog by setting its period to the maximum value.
 175  */
 176 static void __booke_wdt_disable(void *data)
 177 {
 178         u32 val;
 179
 180         val = mfspr(SPRN_TCR);
 181         val &= ~(TCR_WIE | WDTP_MASK);
 182         mtspr(SPRN_TCR, val);
 183
 184         /* clear status to make sure nothing is pending */
 185         __booke_wdt_ping(NULL);
 186
 187 }
 188
 189 static int booke_wdt_start(struct watchdog_device *wdog)
 190 {
 191         on_each_cpu(__booke_wdt_enable, wdog, 0);
 192         pr_debug("watchdog enabled (timeout = %u sec)\n", wdog->timeout);
 193
 194         return 0;
 195 }
 196
 197 static int booke_wdt_stop(struct watchdog_device *wdog)
 198 {
 199         on_each_cpu(__booke_wdt_disable, NULL, 0);
 200         pr_debug("watchdog disabled\n");
 201
 202         return 0;
 203 }
 204
 205 static int booke_wdt_set_timeout(struct watchdog_device *wdt_dev,
 206                                  unsigned int timeout)
 207 {
 208         if (timeout > MAX_WDT_TIMEOUT)
 209                 return -EINVAL;
 210         wdt_dev->timeout = timeout;
 211         booke_wdt_set(wdt_dev);
 212
 213         return 0;
 214 }
 215
 216 static struct watchdog_info booke_wdt_info = {
 217         .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
 218         .identity = "PowerPC Book-E Watchdog",
 219 };
 220
 221 static struct watchdog_ops booke_wdt_ops = {
 222         .owner = THIS_MODULE,
 223         .start = booke_wdt_start,
 224         .stop = booke_wdt_stop,
 225         .ping = booke_wdt_ping,
 226         .set_timeout = booke_wdt_set_timeout,
 227 };
 228
 229 static struct watchdog_device booke_wdt_dev = {
 230         .info = &booke_wdt_info,
 231         .ops = &booke_wdt_ops,
 232         .min_timeout = 1,
 233         .max_timeout = 0xFFFF
 234 };
 235
 236 static void __exit booke_wdt_exit(void)
 237 {
 238         watchdog_unregister_device(&booke_wdt_dev);
 239 }
 240
 241 static int __init booke_wdt_init(void)
 242 {
 243         int ret = 0;
 244         bool nowayout = WATCHDOG_NOWAYOUT;
 245
 246         pr_info("powerpc book-e watchdog driver loaded\n");
 247         booke_wdt_info.firmware_version = cur_cpu_spec->pvr_value;
 248         booke_wdt_set_timeout(&booke_wdt_dev,
 249                               period_to_sec(booke_wdt_period));
 250         watchdog_set_nowayout(&booke_wdt_dev, nowayout);
 251         if (booke_wdt_enabled)
 252                 booke_wdt_start(&booke_wdt_dev);
 253
 254         ret = watchdog_register_device(&booke_wdt_dev);
 255
 256         return ret;
 257 }
 258
 259 module_init(booke_wdt_init);
 260 module_exit(booke_wdt_exit);
 261
 262 MODULE_DESCRIPTION("PowerPC Book-E watchdog driver");
 263 MODULE_LICENSE("GPL");