1/*
2 * arch/sh/boards/dreamcast/rtc.c
3 *
4 * Dreamcast AICA RTC routines.
5 *
6 * Copyright (c) 2001, 2002 M. R. Brown <mrbrown@0xd6.org>
7 * Copyright (c) 2002 Paul Mundt <lethal@chaoticdreams.org>
8 *
9 * Released under the terms of the GNU GPL v2.0.
10 *
11 */
12
13#include <linux/time.h>
14#include <asm/rtc.h>
15#include <asm/io.h>
16
17/* The AICA RTC has an Epoch of 1/1/1950, so we must subtract 20 years (in
18   seconds) to get the standard Unix Epoch when getting the time, and add
19   20 years when setting the time. */
20#define TWENTY_YEARS ((20 * 365LU + 5) * 86400)
21
22/* The AICA RTC is represented by a 32-bit seconds counter stored in 2 16-bit
23   registers.*/
24#define AICA_RTC_SECS_H		0xa0710000
25#define AICA_RTC_SECS_L		0xa0710004
26
27/**
28 * aica_rtc_gettimeofday - Get the time from the AICA RTC
29 * @ts: pointer to resulting timespec
30 *
31 * Grabs the current RTC seconds counter and adjusts it to the Unix Epoch.
32 */
33void aica_rtc_gettimeofday(struct timespec *ts)
34{
35	unsigned long val1, val2;
36
37	do {
38		val1 = ((ctrl_inl(AICA_RTC_SECS_H) & 0xffff) << 16) |
39			(ctrl_inl(AICA_RTC_SECS_L) & 0xffff);
40
41		val2 = ((ctrl_inl(AICA_RTC_SECS_H) & 0xffff) << 16) |
42			(ctrl_inl(AICA_RTC_SECS_L) & 0xffff);
43	} while (val1 != val2);
44
45	ts->tv_sec = val1 - TWENTY_YEARS;
46
47	/* Can't get nanoseconds with just a seconds counter. */
48	ts->tv_nsec = 0;
49}
50
51/**
52 * aica_rtc_settimeofday - Set the AICA RTC to the current time
53 * @secs: contains the time_t to set
54 *
55 * Adjusts the given @tv to the AICA Epoch and sets the RTC seconds counter.
56 */
57int aica_rtc_settimeofday(const time_t secs)
58{
59	unsigned long val1, val2;
60	unsigned long adj = secs + TWENTY_YEARS;
61
62	do {
63		ctrl_outl((adj & 0xffff0000) >> 16, AICA_RTC_SECS_H);
64		ctrl_outl((adj & 0xffff), AICA_RTC_SECS_L);
65
66		val1 = ((ctrl_inl(AICA_RTC_SECS_H) & 0xffff) << 16) |
67			(ctrl_inl(AICA_RTC_SECS_L) & 0xffff);
68
69		val2 = ((ctrl_inl(AICA_RTC_SECS_H) & 0xffff) << 16) |
70			(ctrl_inl(AICA_RTC_SECS_L) & 0xffff);
71	} while (val1 != val2);
72
73	return 0;
74}
75
76void aica_time_init(void)
77{
78	rtc_sh_get_time = aica_rtc_gettimeofday;
79	rtc_sh_set_time = aica_rtc_settimeofday;
80}
81