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// SPDX-License-Identifier: GPL-2.0
/*
* arch/sh/boards/dreamcast/rtc.c
*
* Dreamcast AICA RTC routines.
*
* Copyright (c) 2001, 2002 M. R. Brown <mrbrown@0xd6.org>
* Copyright (c) 2002 Paul Mundt <lethal@chaoticdreams.org>
*/
#include <linux/time.h>
#include <linux/rtc.h>
#include <linux/io.h>
#include <linux/platform_device.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
* @dev: the RTC device (ignored)
* @tm: pointer to resulting RTC time structure
*
* Grabs the current RTC seconds counter and adjusts it to the Unix Epoch.
*/
static int aica_rtc_gettimeofday(struct device *dev, struct rtc_time *tm)
{
unsigned long val1, val2;
time64_t t;
do {
val1 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
(__raw_readl(AICA_RTC_SECS_L) & 0xffff);
val2 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
(__raw_readl(AICA_RTC_SECS_L) & 0xffff);
} while (val1 != val2);
/* normalize to 1970..2106 time range */
t = (u32)(val1 - TWENTY_YEARS);
rtc_time64_to_tm(t, tm);
return 0;
}
/**
* aica_rtc_settimeofday - Set the AICA RTC to the current time
* @dev: the RTC device (ignored)
* @tm: pointer to new RTC time structure
*
* Adjusts the given @tv to the AICA Epoch and sets the RTC seconds counter.
*/
static int aica_rtc_settimeofday(struct device *dev, struct rtc_time *tm)
{
unsigned long val1, val2;
time64_t secs = rtc_tm_to_time64(tm);
u32 adj = secs + TWENTY_YEARS;
do {
__raw_writel((adj & 0xffff0000) >> 16, AICA_RTC_SECS_H);
__raw_writel((adj & 0xffff), AICA_RTC_SECS_L);
val1 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
(__raw_readl(AICA_RTC_SECS_L) & 0xffff);
val2 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
(__raw_readl(AICA_RTC_SECS_L) & 0xffff);
} while (val1 != val2);
return 0;
}
static const struct rtc_class_ops rtc_generic_ops = {
.read_time = aica_rtc_gettimeofday,
.set_time = aica_rtc_settimeofday,
};
static int __init aica_time_init(void)
{
struct platform_device *pdev;
pdev = platform_device_register_data(NULL, "rtc-generic", -1,
&rtc_generic_ops,
sizeof(rtc_generic_ops));
return PTR_ERR_OR_ZERO(pdev);
}
arch_initcall(aica_time_init);
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