2 * arch/sh/boards/dreamcast/rtc.c
4 * Dreamcast AICA RTC routines.
6 * Copyright (c) 2001, 2002 M. R. Brown <mrbrown@0xd6.org>
7 * Copyright (c) 2002 Paul Mundt <lethal@chaoticdreams.org>
9 * Released under the terms of the GNU GPL v2.0.
13 #include <linux/time.h>
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)
22 /* The AICA RTC is represented by a 32-bit seconds counter stored in 2 16-bit
24 #define AICA_RTC_SECS_H 0xa0710000
25 #define AICA_RTC_SECS_L 0xa0710004
28 * aica_rtc_gettimeofday - Get the time from the AICA RTC
29 * @ts: pointer to resulting timespec
31 * Grabs the current RTC seconds counter and adjusts it to the Unix Epoch.
33 static void aica_rtc_gettimeofday(struct timespec
*ts
)
35 unsigned long val1
, val2
;
38 val1
= ((__raw_readl(AICA_RTC_SECS_H
) & 0xffff) << 16) |
39 (__raw_readl(AICA_RTC_SECS_L
) & 0xffff);
41 val2
= ((__raw_readl(AICA_RTC_SECS_H
) & 0xffff) << 16) |
42 (__raw_readl(AICA_RTC_SECS_L
) & 0xffff);
43 } while (val1
!= val2
);
45 ts
->tv_sec
= val1
- TWENTY_YEARS
;
47 /* Can't get nanoseconds with just a seconds counter. */
52 * aica_rtc_settimeofday - Set the AICA RTC to the current time
53 * @secs: contains the time_t to set
55 * Adjusts the given @tv to the AICA Epoch and sets the RTC seconds counter.
57 static int aica_rtc_settimeofday(const time_t secs
)
59 unsigned long val1
, val2
;
60 unsigned long adj
= secs
+ TWENTY_YEARS
;
63 __raw_writel((adj
& 0xffff0000) >> 16, AICA_RTC_SECS_H
);
64 __raw_writel((adj
& 0xffff), AICA_RTC_SECS_L
);
66 val1
= ((__raw_readl(AICA_RTC_SECS_H
) & 0xffff) << 16) |
67 (__raw_readl(AICA_RTC_SECS_L
) & 0xffff);
69 val2
= ((__raw_readl(AICA_RTC_SECS_H
) & 0xffff) << 16) |
70 (__raw_readl(AICA_RTC_SECS_L
) & 0xffff);
71 } while (val1
!= val2
);
76 void aica_time_init(void)
78 rtc_sh_get_time
= aica_rtc_gettimeofday
;
79 rtc_sh_set_time
= aica_rtc_settimeofday
;