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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * Watchdog timer for PowerPC Book-E systems4 *5 * Author: Matthew McClintock6 * 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 ": " fmt12 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 will24 * trigger a watchdog timeout. This watchdog timeout will occur 3 times, the25 * first time nothing will happen, the second time a watchdog exception will26 * occur, and the final time the board will reset.27 */28 29 30#ifdef CONFIG_PPC_E50031#define WDTP(x) ((((x)&0x3)<<30)|(((x)&0x3c)<<15))32#define WDTP_MASK (WDTP(0x3f))33#else34#define WDTP(x) (TCR_WP(x))35#define WDTP_MASK (TCR_WP_MASK)36#endif37 38static bool booke_wdt_enabled;39module_param(booke_wdt_enabled, bool, 0);40static int booke_wdt_period = CONFIG_BOOKE_WDT_DEFAULT_TIMEOUT;41module_param(booke_wdt_period, int, 0);42static bool nowayout = WATCHDOG_NOWAYOUT;43module_param(nowayout, bool, 0);44MODULE_PARM_DESC(nowayout,45 "Watchdog cannot be stopped once started (default="46 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");47 48#ifdef CONFIG_PPC_E50049 50/* For the specified period, determine the number of seconds51 * corresponding to the reset time. There will be a watchdog52 * 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_freq56 *57 * In order to simplify things, we assume that period is58 * at least 1. This will still result in a very long timeout.59 */60static 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 tmp67 */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 timeout76 * greater than the one required. e.g. for a bus speed of 66666666 and77 * a parameter of 2 secs, then this procedure will return a value of 38.78 */79static 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_E500 */92 93static unsigned long long period_to_sec(unsigned int period)94{95 return period;96}97 98static 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_E500 */106 107static 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 119static void booke_wdt_set(void *data)120{121 on_each_cpu(__booke_wdt_set, data, 0);122}123 124static void __booke_wdt_ping(void *data)125{126 mtspr(SPRN_TSR, TSR_ENW|TSR_WIS);127}128 129static int booke_wdt_ping(struct watchdog_device *wdog)130{131 on_each_cpu(__booke_wdt_ping, NULL, 0);132 133 return 0;134}135 136static 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 CPU152 *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 can156 * effectively disable the watchdog by setting its period to the maximum value.157 */158static 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 171static 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 179static 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 187static 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 196static struct watchdog_info booke_wdt_info __ro_after_init = {197 .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,198 .identity = "PowerPC Book-E Watchdog",199};200 201static 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 209static struct watchdog_device booke_wdt_dev = {210 .info = &booke_wdt_info,211 .ops = &booke_wdt_ops,212 .min_timeout = 1,213};214 215static void __exit booke_wdt_exit(void)216{217 watchdog_unregister_device(&booke_wdt_dev);218}219 220static 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 238module_init(booke_wdt_init);239module_exit(booke_wdt_exit);240 241MODULE_ALIAS("booke_wdt");242MODULE_DESCRIPTION("PowerPC Book-E watchdog driver");243MODULE_LICENSE("GPL");244