rtc-aica.c

linux-2.4.29操作系统的源码

/* arch/sh/kernel/rtc-aica.c
 *
 * Dreamcast AICA RTC routines.
 *
 * Copyright (c) 2001 M. R. Brown <[e-mail]>
 *
 * Released under the terms of the GNU GPL v2.0.
 *
 */

#include <linux/time.h>

#include <asm/io.h>

/* The AICA RTC has an Epoch of 1/1/1950, so we must subtract 20 years (in
   seconds to get the standard Unix Epoch when getting the time, and add 20
   years when setting the time. */
#define TWENTY_YEARS ((20 * 365LU + 5) * 86400)

/* The AICA RTC is represented by a 32-bit seconds counter stored in 2 16-bit
   registers.*/
#define AICA_RTC_SECS_H		0xa0710000
#define AICA_RTC_SECS_L		0xa0710004

/**
 * aica_rtc_gettimeofday - Get the time from the AICA RTC
 * @tv: pointer to resulting timeval
 *
 * Grabs the current RTC seconds counter and adjusts it to the Unix Epoch.
 */
void aica_rtc_gettimeofday(struct timeval *tv) {
	unsigned long val1, val2;

	do {
		val1 = ((ctrl_inl(AICA_RTC_SECS_H) & 0xffff) << 16) |
			(ctrl_inl(AICA_RTC_SECS_L) & 0xffff);

		val2 = ((ctrl_inl(AICA_RTC_SECS_H) & 0xffff) << 16) |
			(ctrl_inl(AICA_RTC_SECS_L) & 0xffff);
	} while (val1 != val2);

	tv->tv_sec = val1 - TWENTY_YEARS;

	/* Can't get microseconds with just a seconds counter. */
	tv->tv_usec = 0;
}

/**
 * aica_rtc_settimeofday - Set the AICA RTC to the current time
 * @tv: contains the timeval to set
 *
 * Adjusts the given @tv to the AICA Epoch and sets the RTC seconds counter.
 */
int aica_rtc_settimeofday(const struct timeval *tv) {
	unsigned long val1, val2;
	unsigned long secs = tv->tv_sec + TWENTY_YEARS;

	do {
		ctrl_outl((secs & 0xffff0000) >> 16, AICA_RTC_SECS_H);
		ctrl_outl((secs & 0xffff), AICA_RTC_SECS_L);

		val1 = ((ctrl_inl(AICA_RTC_SECS_H) & 0xffff) << 16) |
			(ctrl_inl(AICA_RTC_SECS_L) & 0xffff);

		val2 = ((ctrl_inl(AICA_RTC_SECS_H) & 0xffff) << 16) |
			(ctrl_inl(AICA_RTC_SECS_L) & 0xffff);
	} while (val1 != val2);

	return 0;
}