LXR linux/arch/sh/boards/mach-dreamcast/rtc.c

   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 */
  33static 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 */
  57static 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
  76void aica_time_init(void)
  77{
  78        rtc_sh_get_time = aica_rtc_gettimeofday;
  79        rtc_sh_set_time = aica_rtc_settimeofday;
  80}
  81
  82