drivers/watchdog/booke_wdt.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Watchdog timer for PowerPC Book-E systems
   4  *
   5  * Author: Matthew McClintock
   6  * Maintainer: Kumar Gala <galak@kernel.crashing.org>
   7  *
   8  * Copyright 2005, 2008, 2010-2011 Freescale Semiconductor Inc.
   9  */
  10
  11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  12
  13 #include <linux/module.h>
  14 #include <linux/smp.h>
  15 #include <linux/watchdog.h>
  16
  17 #include <asm/reg_booke.h>
  18 #include <asm/time.h>
  19 #include <asm/div64.h>
  20
  21 /* If the kernel parameter wdt=1, the watchdog will be enabled at boot.
  22  * Also, the wdt_period sets the watchdog timer period timeout.
  23  * For E500 cpus the wdt_period sets which bit changing from 0->1 will
  24  * trigger a watchdog timeout. This watchdog timeout will occur 3 times, the
  25  * first time nothing will happen, the second time a watchdog exception will
  26  * occur, and the final time the board will reset.
  27  */
  28
  29
  30 #ifdef  CONFIG_PPC_FSL_BOOK3E
  31 #define WDTP(x)         ((((x)&0x3)<<30)|(((x)&0x3c)<<15))
  32 #define WDTP_MASK       (WDTP(0x3f))
  33 #else
  34 #define WDTP(x)         (TCR_WP(x))
  35 #define WDTP_MASK       (TCR_WP_MASK)
  36 #endif
  37
  38 static bool booke_wdt_enabled;
  39 module_param(booke_wdt_enabled, bool, 0);
  40 static int  booke_wdt_period = CONFIG_BOOKE_WDT_DEFAULT_TIMEOUT;
  41 module_param(booke_wdt_period, int, 0);
  42 static bool nowayout = WATCHDOG_NOWAYOUT;
  43 module_param(nowayout, bool, 0);
  44 MODULE_PARM_DESC(nowayout,
  45                 "Watchdog cannot be stopped once started (default="
  46                                 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  47
  48 #ifdef CONFIG_PPC_FSL_BOOK3E
  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 #define MAX_WDT_TIMEOUT         period_to_sec(1)
  90
  91 #else /* CONFIG_PPC_FSL_BOOK3E */
  92
  93 static unsigned long long period_to_sec(unsigned int period)
  94 {
  95         return period;
  96 }
  97
  98 static unsigned int sec_to_period(unsigned int secs)
  99 {
 100         return secs;
 101 }
 102
 103 #define MAX_WDT_TIMEOUT         3       /* from Kconfig */
 104
 105 #endif /* !CONFIG_PPC_FSL_BOOK3E */
 106
 107 static void __booke_wdt_set(void *data)
 108 {
 109         u32 val;
 110         struct watchdog_device *wdog = data;
 111
 112         val = mfspr(SPRN_TCR);
 113         val &= ~WDTP_MASK;
 114         val |= WDTP(sec_to_period(wdog->timeout));
 115
 116         mtspr(SPRN_TCR, val);
 117 }
 118
 119 static void booke_wdt_set(void *data)
 120 {
 121         on_each_cpu(__booke_wdt_set, data, 0);
 122 }
 123
 124 static void __booke_wdt_ping(void *data)
 125 {
 126         mtspr(SPRN_TSR, TSR_ENW|TSR_WIS);
 127 }
 128
 129 static int booke_wdt_ping(struct watchdog_device *wdog)
 130 {
 131         on_each_cpu(__booke_wdt_ping, NULL, 0);
 132
 133         return 0;
 134 }
 135
 136 static void __booke_wdt_enable(void *data)
 137 {
 138         u32 val;
 139         struct watchdog_device *wdog = data;
 140
 141         /* clear status before enabling watchdog */
 142         __booke_wdt_ping(NULL);
 143         val = mfspr(SPRN_TCR);
 144         val &= ~WDTP_MASK;
 145         val |= (TCR_WIE|TCR_WRC(WRC_CHIP)|WDTP(sec_to_period(wdog->timeout)));
 146
 147         mtspr(SPRN_TCR, val);
 148 }
 149
 150 /**
 151  * booke_wdt_disable - disable the watchdog on the given CPU
 152  *
 153  * This function is called on each CPU.  It disables the watchdog on that CPU.
 154  *
 155  * TCR[WRC] cannot be changed once it has been set to non-zero, but we can
 156  * effectively disable the watchdog by setting its period to the maximum value.
 157  */
 158 static void __booke_wdt_disable(void *data)
 159 {
 160         u32 val;
 161
 162         val = mfspr(SPRN_TCR);
 163         val &= ~(TCR_WIE | WDTP_MASK);
 164         mtspr(SPRN_TCR, val);
 165
 166         /* clear status to make sure nothing is pending */
 167         __booke_wdt_ping(NULL);
 168
 169 }
 170
 171 static int booke_wdt_start(struct watchdog_device *wdog)
 172 {
 173         on_each_cpu(__booke_wdt_enable, wdog, 0);
 174         pr_debug("watchdog enabled (timeout = %u sec)\n", wdog->timeout);
 175
 176         return 0;
 177 }
 178
 179 static int booke_wdt_stop(struct watchdog_device *wdog)
 180 {
 181         on_each_cpu(__booke_wdt_disable, NULL, 0);
 182         pr_debug("watchdog disabled\n");
 183
 184         return 0;
 185 }
 186
 187 static int booke_wdt_set_timeout(struct watchdog_device *wdt_dev,
 188                                  unsigned int timeout)
 189 {
 190         wdt_dev->timeout = timeout;
 191         booke_wdt_set(wdt_dev);
 192
 193         return 0;
 194 }
 195
 196 static struct watchdog_info booke_wdt_info __ro_after_init = {
 197         .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
 198         .identity = "PowerPC Book-E Watchdog",
 199 };
 200
 201 static const struct watchdog_ops booke_wdt_ops = {
 202         .owner = THIS_MODULE,
 203         .start = booke_wdt_start,
 204         .stop = booke_wdt_stop,
 205         .ping = booke_wdt_ping,
 206         .set_timeout = booke_wdt_set_timeout,
 207 };
 208
 209 static struct watchdog_device booke_wdt_dev = {
 210         .info = &booke_wdt_info,
 211         .ops = &booke_wdt_ops,
 212         .min_timeout = 1,
 213 };
 214
 215 static void __exit booke_wdt_exit(void)
 216 {
 217         watchdog_unregister_device(&booke_wdt_dev);
 218 }
 219
 220 static int __init booke_wdt_init(void)
 221 {
 222         int ret = 0;
 223
 224         pr_info("powerpc book-e watchdog driver loaded\n");
 225         booke_wdt_info.firmware_version = cur_cpu_spec->pvr_value;
 226         booke_wdt_set_timeout(&booke_wdt_dev,
 227                               period_to_sec(booke_wdt_period));
 228         watchdog_set_nowayout(&booke_wdt_dev, nowayout);
 229         booke_wdt_dev.max_timeout = MAX_WDT_TIMEOUT;
 230         if (booke_wdt_enabled)
 231                 booke_wdt_start(&booke_wdt_dev);
 232
 233         ret = watchdog_register_device(&booke_wdt_dev);
 234
 235         return ret;
 236 }
 237
 238 module_init(booke_wdt_init);
 239 module_exit(booke_wdt_exit);
 240
 241 MODULE_ALIAS("booke_wdt");
 242 MODULE_DESCRIPTION("PowerPC Book-E watchdog driver");
 243 MODULE_LICENSE("GPL");