u-boot/drivers/rtc/at91sam9_rtt.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * (C) Copyright 2010
 * Reinhard Meyer, reinhard.meyer@emk-elektronik.de
 */

/*
 * Date & Time support for the internal Real-time Timer
 * of AT91SAM9260 and compatibles.
 * Compatible with the LinuX rtc driver workaround:
 * The RTT cannot be written to, but only reset.
 * The actual time is the sum of RTT and one of
 * the four GPBR registers.
 *
 * The at91sam9260 has 4 GPBR (0-3).
 * For their typical use see at91_gpbr.h !
 *
 * make sure u-boot and kernel use the same GPBR !
 */

#include <common.h>
#include <command.h>
#include <rtc.h>
#include <asm/io.h>
#include <linux/errno.h>
#include <asm/arch/hardware.h>
#include <asm/arch/at91_rtt.h>
#include <asm/arch/at91_gpbr.h>

int rtc_get (struct rtc_time *tmp)
{
	at91_rtt_t *rtt = (at91_rtt_t *) ATMEL_BASE_RTT;
	at91_gpbr_t *gpbr = (at91_gpbr_t *) ATMEL_BASE_GPBR;
	ulong tim;
	ulong tim2;
	ulong off;

	do {
		tim = readl(&rtt->vr);
		tim2 = readl(&rtt->vr);
	} while (tim!=tim2);
	off = readl(&gpbr->reg[AT91_GPBR_INDEX_TIMEOFF]);
	/* off==0 means time is invalid, but we ignore that */
	rtc_to_tm(tim+off, tmp);
	return 0;
}

int rtc_set (struct rtc_time *tmp)
{
	at91_rtt_t *rtt = (at91_rtt_t *) ATMEL_BASE_RTT;
	at91_gpbr_t *gpbr = (at91_gpbr_t *) ATMEL_BASE_GPBR;
	ulong tim;

	tim = rtc_mktime(tmp);

	/* clear alarm, set prescaler to 32768, clear counter */
	writel(32768+AT91_RTT_RTTRST, &rtt->mr);
	writel(~0, &rtt->ar);
	writel(tim, &gpbr->reg[AT91_GPBR_INDEX_TIMEOFF]);
	/* wait for counter clear to happen, takes less than a 1/32768th second */
	while (readl(&rtt->vr) != 0)
		;
	return 0;
}

void rtc_reset (void)
{
	at91_rtt_t *rtt = (at91_rtt_t *) ATMEL_BASE_RTT;
	at91_gpbr_t *gpbr = (at91_gpbr_t *) ATMEL_BASE_GPBR;

	/* clear alarm, set prescaler to 32768, clear counter */
	writel(32768+AT91_RTT_RTTRST, &rtt->mr);
	writel(~0, &rtt->ar);
	writel(0, &gpbr->reg[AT91_GPBR_INDEX_TIMEOFF]);
	/* wait for counter clear to happen, takes less than a 1/32768th second */
	while (readl(&rtt->vr) != 0)
		;
}