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/* Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
/* Watchdog driver */
#include "board.h"
#include "common.h"
#include "config.h"
#include "registers.h"
#include "gpio.h"
#include "hwtimer.h"
#include "task.h"
#include "timer.h"
#include "util.h"
#include "watchdog.h"
/* LSI oscillator frequency is typically 38 kHz
* but might vary from 28 to 56kHz.
* So let's pick 56kHz to ensure we reload
* early enough.
*/
#define LSI_CLOCK 56000
/* Prescaler divider = /256 */
#define IWDG_PRESCALER 6
#define IWDG_PRESCALER_DIV (1 << ((IWDG_PRESCALER) + 2))
/*
* We use the WWDG as an early warning for the real watchdog, which just
* resets. Since it has a very short period, we need to allow several cycles
* of this to make up one IWDG cycle. The WWDG's early warning kicks in
* half way through the cycle, with a maximum time of 65.54ms at 32 MHz.
*/
#define WATCHDOG_CYCLES_BEFORE_RESET \
(WATCHDOG_PERIOD_MS / (65540 * 32000 / CPU_CLOCK))
/* Keep a track of how many WWDG cycles we have had */
static unsigned int watchdog_count;
static void watchdog_reset_count(void)
{
watchdog_count = WATCHDOG_CYCLES_BEFORE_RESET;
}
void watchdog_reload(void)
{
/* Reload the watchdog */
STM32_IWDG_KR = 0xaaaa;
watchdog_reset_count();
#ifdef CONFIG_WATCHDOG_HELP
hwtimer_reset_watchdog();
#endif
}
int watchdog_init(void)
{
uint32_t watchdog_period;
/* set the time-out period */
watchdog_period = WATCHDOG_PERIOD_MS *
(LSI_CLOCK / IWDG_PRESCALER_DIV) / 1000;
/* Unlock watchdog registers */
STM32_IWDG_KR = 0x5555;
/* Set the prescaler between the LSI clock and the watchdog counter */
STM32_IWDG_PR = IWDG_PRESCALER & 7;
/* Set the reload value of the watchdog counter */
STM32_IWDG_RLR = watchdog_period & 0x7FF ;
/* Start the watchdog (and re-lock registers) */
STM32_IWDG_KR = 0xcccc;
watchdog_reset_count();
#ifdef CONFIG_WATCHDOG_HELP
/* Use a harder timer to warn about an impending watchdog reset */
hwtimer_setup_watchdog();
#endif
return EC_SUCCESS;
}
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