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  */
aica_rtc_gettimeofday(struct timespec * ts)33 static void aica_rtc_gettimeofday(struct timespec *ts)
34 {
35 	unsigned long val1, val2;
36 
37 	do {
38 		val1 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
39 			(__raw_readl(AICA_RTC_SECS_L) & 0xffff);
40 
41 		val2 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
42 			(__raw_readl(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  */
aica_rtc_settimeofday(const time_t secs)57 static int aica_rtc_settimeofday(const time_t secs)
58 {
59 	unsigned long val1, val2;
60 	unsigned long adj = secs + TWENTY_YEARS;
61 
62 	do {
63 		__raw_writel((adj & 0xffff0000) >> 16, AICA_RTC_SECS_H);
64 		__raw_writel((adj & 0xffff), AICA_RTC_SECS_L);
65 
66 		val1 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
67 			(__raw_readl(AICA_RTC_SECS_L) & 0xffff);
68 
69 		val2 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
70 			(__raw_readl(AICA_RTC_SECS_L) & 0xffff);
71 	} while (val1 != val2);
72 
73 	return 0;
74 }
75 
aica_time_init(void)76 void aica_time_init(void)
77 {
78 	rtc_sh_get_time = aica_rtc_gettimeofday;
79 	rtc_sh_set_time = aica_rtc_settimeofday;
80 }
81 
82