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

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * arch/sh/boards/dreamcast/rtc.c
   4 *
   5 * Dreamcast AICA RTC routines.
   6 *
   7 * Copyright (c) 2001, 2002 M. R. Brown <mrbrown@0xd6.org>
   8 * Copyright (c) 2002 Paul Mundt <lethal@chaoticdreams.org>
   9 */
  10
  11#include <linux/time.h>
  12#include <linux/rtc.h>
  13#include <linux/io.h>
  14#include <linux/platform_device.h>
  15
  16/* The AICA RTC has an Epoch of 1/1/1950, so we must subtract 20 years (in
  17   seconds) to get the standard Unix Epoch when getting the time, and add
  18   20 years when setting the time. */
  19#define TWENTY_YEARS ((20 * 365LU + 5) * 86400)
  20
  21/* The AICA RTC is represented by a 32-bit seconds counter stored in 2 16-bit
  22   registers.*/
  23#define AICA_RTC_SECS_H         0xa0710000
  24#define AICA_RTC_SECS_L         0xa0710004
  25
  26/**
  27 * aica_rtc_gettimeofday - Get the time from the AICA RTC
  28 * @dev: the RTC device (ignored)
  29 * @tm: pointer to resulting RTC time structure
  30 *
  31 * Grabs the current RTC seconds counter and adjusts it to the Unix Epoch.
  32 */
  33static int aica_rtc_gettimeofday(struct device *dev, struct rtc_time *tm)
  34{
  35        unsigned long val1, val2;
  36        time64_t t;
  37
  38        do {
  39                val1 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
  40                        (__raw_readl(AICA_RTC_SECS_L) & 0xffff);
  41
  42                val2 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
  43                        (__raw_readl(AICA_RTC_SECS_L) & 0xffff);
  44        } while (val1 != val2);
  45
  46        /* normalize to 1970..2106 time range */
  47        t = (u32)(val1 - TWENTY_YEARS);
  48
  49        rtc_time64_to_tm(t, tm);
  50
  51        return 0;
  52}
  53
  54/**
  55 * aica_rtc_settimeofday - Set the AICA RTC to the current time
  56 * @dev: the RTC device (ignored)
  57 * @tm: pointer to new RTC time structure
  58 *
  59 * Adjusts the given @tv to the AICA Epoch and sets the RTC seconds counter.
  60 */
  61static int aica_rtc_settimeofday(struct device *dev, struct rtc_time *tm)
  62{
  63        unsigned long val1, val2;
  64        time64_t secs = rtc_tm_to_time64(tm);
  65        u32 adj = secs + TWENTY_YEARS;
  66
  67        do {
  68                __raw_writel((adj & 0xffff0000) >> 16, AICA_RTC_SECS_H);
  69                __raw_writel((adj & 0xffff), AICA_RTC_SECS_L);
  70
  71                val1 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
  72                        (__raw_readl(AICA_RTC_SECS_L) & 0xffff);
  73
  74                val2 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
  75                        (__raw_readl(AICA_RTC_SECS_L) & 0xffff);
  76        } while (val1 != val2);
  77
  78        return 0;
  79}
  80
  81static const struct rtc_class_ops rtc_generic_ops = {
  82        .read_time = aica_rtc_gettimeofday,
  83        .set_time = aica_rtc_settimeofday,
  84};
  85
  86static int __init aica_time_init(void)
  87{
  88        struct platform_device *pdev;
  89
  90        pdev = platform_device_register_data(NULL, "rtc-generic", -1,
  91                                             &rtc_generic_ops,
  92                                             sizeof(rtc_generic_ops));
  93
  94        return PTR_ERR_OR_ZERO(pdev);
  95}
  96arch_initcall(aica_time_init);
  97