arch/sh/boards/dreamcast/rtc.c

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