text: // SPDX-License-Identifier: GPL-2.0-or-later
  /*
   * Watchdog timer for PowerPC Book-E systems
   *
   * Author: Matthew McClintock
   * Maintainer: Kumar Gala <galak@kernel.crashing.org>
   *
   * Copyright 2005, 2008, 2010-2011 Freescale Semiconductor Inc.
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/module.h>
  #include <linux/smp.h>
  #include <linux/watchdog.h>
  
  #include <asm/reg_booke.h>
  #include <asm/time.h>
  #include <asm/div64.h>
  
  /* If the kernel parameter wdt=1, the watchdog will be enabled at boot.
   * Also, the wdt_period sets the watchdog timer period timeout.
   * For E500 cpus the wdt_period sets which bit changing from 0->1 will
   * trigger a watchdog timeout. This watchdog timeout will occur 3 times, the
   * first time nothing will happen, the second time a watchdog exception will
   * occur, and the final time the board will reset.
   */
  
  
  #ifdef	CONFIG_PPC_FSL_BOOK3E
  #define WDTP(x)		((((x)&0x3)<<30)|(((x)&0x3c)<<15))
  #define WDTP_MASK	(WDTP(0x3f))
  #else
  #define WDTP(x)		(TCR_WP(x))
  #define WDTP_MASK	(TCR_WP_MASK)
  #endif
  
  static bool booke_wdt_enabled;
  module_param(booke_wdt_enabled, bool, 0);
  static int  booke_wdt_period = CONFIG_BOOKE_WDT_DEFAULT_TIMEOUT;
  module_param(booke_wdt_period, int, 0);
  static bool nowayout = WATCHDOG_NOWAYOUT;
  module_param(nowayout, bool, 0);
  MODULE_PARM_DESC(nowayout,
  		"Watchdog cannot be stopped once started (default="
  				__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  
  #ifdef CONFIG_PPC_FSL_BOOK3E
  
  /* For the specified period, determine the number of seconds
   * corresponding to the reset time.  There will be a watchdog
   * exception at approximately 3/5 of this time.
   *
   * The formula to calculate this is given by:
   * 2.5 * (2^(63-period+1)) / timebase_freq
   *
   * In order to simplify things, we assume that period is
   * at least 1.  This will still result in a very long timeout.
   */
  static unsigned long long period_to_sec(unsigned int period)
  {
  	unsigned long long tmp = 1ULL << (64 - period);
  	unsigned long tmp2 = ppc_tb_freq;
  
  	/* tmp may be a very large number and we don't want to overflow,
  	 * so divide the timebase freq instead of multiplying tmp
  	 */
  	tmp2 = tmp2 / 5 * 2;
  
  	do_div(tmp, tmp2);
  	return tmp;
  }
  
  /*
   * This procedure will find the highest period which will give a timeout
   * greater than the one required. e.g. for a bus speed of 66666666 and
   * and a parameter of 2 secs, then this procedure will return a value of 38.
   */
  static unsigned int sec_to_period(unsigned int secs)
  {
  	unsigned int period;
  	for (period = 63; period > 0; period--) {
  		if (period_to_sec(period) >= secs)
  			return period;
  	}
  	return 0;
  }
  
  #define MAX_WDT_TIMEOUT		period_to_sec(1)
  
  #else /* CONFIG_PPC_FSL_BOOK3E */
  
  static unsigned long long period_to_sec(unsigned int period)
  {
  	return period;
  }
  
  static unsigned int sec_to_period(unsigned int secs)
  {
  	return secs;
  }
  
  #define MAX_WDT_TIMEOUT		3	/* from Kconfig */
  
  #endif /* !CONFIG_PPC_FSL_BOOK3E */
  
  static void __booke_wdt_set(void *data)
  {
  	u32 val;
  	struct watchdog_device *wdog = data;
  
  	val = mfspr(SPRN_TCR);
  	val &= ~WDTP_MASK;
  	val |= WDTP(sec_to_period(wdog->timeout));
  
  	mtspr(SPRN_TCR, val);
  }
  
  static void booke_wdt_set(void *data)
  {
  	on_each_cpu(__booke_wdt_set, data, 0);
  }
  
  static void __booke_wdt_ping(void *data)
  {
  	mtspr(SPRN_TSR, TSR_ENW|TSR_WIS);
  }
  
  static int booke_wdt_ping(struct watchdog_device *wdog)
  {
  	on_each_cpu(__booke_wdt_ping, NULL, 0);
  
  	return 0;
  }
  
  static void __booke_wdt_enable(void *data)
  {
  	u32 val;
  	struct watchdog_device *wdog = data;
  
  	/* clear status before enabling watchdog */
  	__booke_wdt_ping(NULL);
  	val = mfspr(SPRN_TCR);
  	val &= ~WDTP_MASK;
  	val |= (TCR_WIE|TCR_WRC(WRC_CHIP)|WDTP(sec_to_period(wdog->timeout)));
  
  	mtspr(SPRN_TCR, val);
  }
  
  /**
   * booke_wdt_disable - disable the watchdog on the given CPU
   *
   * This function is called on each CPU.  It disables the watchdog on that CPU.
   *
   * TCR[WRC] cannot be changed once it has been set to non-zero, but we can
   * effectively disable the watchdog by setting its period to the maximum value.
   */
  static void __booke_wdt_disable(void *data)
  {
  	u32 val;
  
  	val = mfspr(SPRN_TCR);
  	val &= ~(TCR_WIE | WDTP_MASK);
  	mtspr(SPRN_TCR, val);
  
  	/* clear status to make sure nothing is pending */
  	__booke_wdt_ping(NULL);
  
  }
  
  static int booke_wdt_start(struct watchdog_device *wdog)
  {
  	on_each_cpu(__booke_wdt_enable, wdog, 0);
  	pr_debug("watchdog enabled (timeout = %u sec)\n", wdog->timeout);
  
  	return 0;
  }
  
  static int booke_wdt_stop(struct watchdog_device *wdog)
  {
  	on_each_cpu(__booke_wdt_disable, NULL, 0);
  	pr_debug("watchdog disabled\n");
  
  	return 0;
  }
  
  static int booke_wdt_set_timeout(struct watchdog_device *wdt_dev,
  				 unsigned int timeout)
  {
  	wdt_dev->timeout = timeout;
  	booke_wdt_set(wdt_dev);
  
  	return 0;
  }
  
  static struct watchdog_info booke_wdt_info __ro_after_init = {
  	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
  	.identity = "PowerPC Book-E Watchdog",
  };
  
  static const struct watchdog_ops booke_wdt_ops = {
  	.owner = THIS_MODULE,
  	.start = booke_wdt_start,
  	.stop = booke_wdt_stop,
  	.ping = booke_wdt_ping,
  	.set_timeout = booke_wdt_set_timeout,
  };
  
  static struct watchdog_device booke_wdt_dev = {
  	.info = &booke_wdt_info,
  	.ops = &booke_wdt_ops,
  	.min_timeout = 1,
  };
  
  static void __exit booke_wdt_exit(void)
  {
  	watchdog_unregister_device(&booke_wdt_dev);
  }
  
  static int __init booke_wdt_init(void)
  {
  	int ret = 0;
  
  	pr_info("powerpc book-e watchdog driver loaded\n");
  	booke_wdt_info.firmware_version = cur_cpu_spec->pvr_value;
  	booke_wdt_set_timeout(&booke_wdt_dev,
  			      period_to_sec(booke_wdt_period));
  	watchdog_set_nowayout(&booke_wdt_dev, nowayout);
  	booke_wdt_dev.max_timeout = MAX_WDT_TIMEOUT;
  	if (booke_wdt_enabled)
  		booke_wdt_start(&booke_wdt_dev);
  
  	ret = watchdog_register_device(&booke_wdt_dev);
  
  	return ret;
  }
  
  module_init(booke_wdt_init);
  module_exit(booke_wdt_exit);
  
  MODULE_ALIAS("booke_wdt");
  MODULE_DESCRIPTION("PowerPC Book-E watchdog driver");
  MODULE_LICENSE("GPL");
  