| 1 | /* MN10300 RTC management |
| 2 | * |
| 3 | * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved. |
| 4 | * Written by David Howells (dhowells@redhat.com) |
| 5 | * |
| 6 | * This program is free software; you can redistribute it and/or |
| 7 | * modify it under the terms of the GNU General Public Licence |
| 8 | * as published by the Free Software Foundation; either version |
| 9 | * 2 of the Licence, or (at your option) any later version. |
| 10 | */ |
| 11 | #include <linux/kernel.h> |
| 12 | #include <linux/module.h> |
| 13 | #include <linux/init.h> |
| 14 | #include <linux/mc146818rtc.h> |
| 15 | #include <linux/bcd.h> |
| 16 | #include <linux/timex.h> |
| 17 | #include <asm/rtc-regs.h> |
| 18 | #include <asm/rtc.h> |
| 19 | |
| 20 | DEFINE_SPINLOCK(rtc_lock); |
| 21 | EXPORT_SYMBOL(rtc_lock); |
| 22 | |
| 23 | /* |
| 24 | * Read the current RTC time |
| 25 | */ |
| 26 | void read_persistent_clock(struct timespec *ts) |
| 27 | { |
| 28 | struct rtc_time tm; |
| 29 | |
| 30 | get_rtc_time(&tm); |
| 31 | |
| 32 | ts->tv_nsec = 0; |
| 33 | ts->tv_sec = mktime(tm.tm_year, tm.tm_mon, tm.tm_mday, |
| 34 | tm.tm_hour, tm.tm_min, tm.tm_sec); |
| 35 | |
| 36 | /* if rtc is way off in the past, set something reasonable */ |
| 37 | if (ts->tv_sec < 0) |
| 38 | ts->tv_sec = mktime(2009, 1, 1, 12, 0, 0); |
| 39 | } |
| 40 | |
| 41 | /* |
| 42 | * In order to set the CMOS clock precisely, set_rtc_mmss has to be called 500 |
| 43 | * ms after the second nowtime has started, because when nowtime is written |
| 44 | * into the registers of the CMOS clock, it will jump to the next second |
| 45 | * precisely 500 ms later. Check the Motorola MC146818A or Dallas DS12887 data |
| 46 | * sheet for details. |
| 47 | * |
| 48 | * BUG: This routine does not handle hour overflow properly; it just |
| 49 | * sets the minutes. Usually you'll only notice that after reboot! |
| 50 | */ |
| 51 | static int set_rtc_mmss(unsigned long nowtime) |
| 52 | { |
| 53 | unsigned char save_control, save_freq_select; |
| 54 | int retval = 0; |
| 55 | int real_seconds, real_minutes, cmos_minutes; |
| 56 | |
| 57 | /* gets recalled with irq locally disabled */ |
| 58 | spin_lock(&rtc_lock); |
| 59 | save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being |
| 60 | * set */ |
| 61 | CMOS_WRITE(save_control | RTC_SET, RTC_CONTROL); |
| 62 | |
| 63 | save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset |
| 64 | * prescaler */ |
| 65 | CMOS_WRITE(save_freq_select | RTC_DIV_RESET2, RTC_FREQ_SELECT); |
| 66 | |
| 67 | cmos_minutes = CMOS_READ(RTC_MINUTES); |
| 68 | if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) |
| 69 | cmos_minutes = bcd2bin(cmos_minutes); |
| 70 | |
| 71 | /* |
| 72 | * since we're only adjusting minutes and seconds, |
| 73 | * don't interfere with hour overflow. This avoids |
| 74 | * messing with unknown time zones but requires your |
| 75 | * RTC not to be off by more than 15 minutes |
| 76 | */ |
| 77 | real_seconds = nowtime % 60; |
| 78 | real_minutes = nowtime / 60; |
| 79 | if (((abs(real_minutes - cmos_minutes) + 15) / 30) & 1) |
| 80 | /* correct for half hour time zone */ |
| 81 | real_minutes += 30; |
| 82 | real_minutes %= 60; |
| 83 | |
| 84 | if (abs(real_minutes - cmos_minutes) < 30) { |
| 85 | if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) { |
| 86 | real_seconds = bin2bcd(real_seconds); |
| 87 | real_minutes = bin2bcd(real_minutes); |
| 88 | } |
| 89 | CMOS_WRITE(real_seconds, RTC_SECONDS); |
| 90 | CMOS_WRITE(real_minutes, RTC_MINUTES); |
| 91 | } else { |
| 92 | printk_once(KERN_NOTICE |
| 93 | "set_rtc_mmss: can't update from %d to %d\n", |
| 94 | cmos_minutes, real_minutes); |
| 95 | retval = -1; |
| 96 | } |
| 97 | |
| 98 | /* The following flags have to be released exactly in this order, |
| 99 | * otherwise the DS12887 (popular MC146818A clone with integrated |
| 100 | * battery and quartz) will not reset the oscillator and will not |
| 101 | * update precisely 500 ms later. You won't find this mentioned in |
| 102 | * the Dallas Semiconductor data sheets, but who believes data |
| 103 | * sheets anyway ... -- Markus Kuhn |
| 104 | */ |
| 105 | CMOS_WRITE(save_control, RTC_CONTROL); |
| 106 | CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT); |
| 107 | spin_unlock(&rtc_lock); |
| 108 | |
| 109 | return retval; |
| 110 | } |
| 111 | |
| 112 | int update_persistent_clock(struct timespec now) |
| 113 | { |
| 114 | return set_rtc_mmss(now.tv_sec); |
| 115 | } |
| 116 | |
| 117 | /* |
| 118 | * calibrate the TSC clock against the RTC |
| 119 | */ |
| 120 | void __init calibrate_clock(void) |
| 121 | { |
| 122 | unsigned char status; |
| 123 | |
| 124 | /* make sure the RTC is running and is set to operate in 24hr mode */ |
| 125 | status = RTSRC; |
| 126 | RTCRB |= RTCRB_SET; |
| 127 | RTCRB |= RTCRB_TM_24HR; |
| 128 | RTCRB &= ~RTCRB_DM_BINARY; |
| 129 | RTCRA |= RTCRA_DVR; |
| 130 | RTCRA &= ~RTCRA_DVR; |
| 131 | RTCRB &= ~RTCRB_SET; |
| 132 | } |