qmk_firmware/tmk_core/common/avr/suspend_avr.h

#ifndef SUSPEND_AVR_H
#define SUSPEND_AVR_H

#include <stdint.h>
#include <stdbool.h>
#include <avr/sleep.h>
#include <avr/wdt.h>
#include <avr/interrupt.h>

#ifndef __AVR_XMEGA__

#define wdt_intr_enable(value)   \
__asm__ __volatile__ (  \
    "in __tmp_reg__,__SREG__" "\n\t"    \
    "cli" "\n\t"    \
    "wdr" "\n\t"    \
    "sts %0,%1" "\n\t"  \
    "out __SREG__,__tmp_reg__" "\n\t"   \
    "sts %0,%2" "\n\t" \
    : /* no outputs */  \
    : "M" (_SFR_MEM_ADDR(_WD_CONTROL_REG)), \
    "r" (_BV(_WD_CHANGE_BIT) | _BV(WDE)), \
    "r" ((uint8_t) ((value & 0x08 ? _WD_PS3_MASK : 0x00) | \
        _BV(WDIE) | (value & 0x07)) ) \
    : "r0"  \
)

#endif

#endif