diff options
Diffstat (limited to 'arch/mn10300/kernel/rtc.c')
| -rw-r--r-- | arch/mn10300/kernel/rtc.c | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/arch/mn10300/kernel/rtc.c b/arch/mn10300/kernel/rtc.c new file mode 100644 index 00000000..48d7058b --- /dev/null +++ b/arch/mn10300/kernel/rtc.c @@ -0,0 +1,132 @@ +/* MN10300 RTC management + * + * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public Licence + * as published by the Free Software Foundation; either version + * 2 of the Licence, or (at your option) any later version. + */ +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/init.h> +#include <linux/mc146818rtc.h> +#include <linux/bcd.h> +#include <linux/timex.h> +#include <asm/rtc-regs.h> +#include <asm/rtc.h> + +DEFINE_SPINLOCK(rtc_lock); +EXPORT_SYMBOL(rtc_lock); + +/* + * Read the current RTC time + */ +void read_persistent_clock(struct timespec *ts) +{ + struct rtc_time tm; + + get_rtc_time(&tm); + + ts->tv_nsec = 0; + ts->tv_sec = mktime(tm.tm_year, tm.tm_mon, tm.tm_mday, + tm.tm_hour, tm.tm_min, tm.tm_sec); + + /* if rtc is way off in the past, set something reasonable */ + if (ts->tv_sec < 0) + ts->tv_sec = mktime(2009, 1, 1, 12, 0, 0); +} + +/* + * In order to set the CMOS clock precisely, set_rtc_mmss has to be called 500 + * ms after the second nowtime has started, because when nowtime is written + * into the registers of the CMOS clock, it will jump to the next second + * precisely 500 ms later. Check the Motorola MC146818A or Dallas DS12887 data + * sheet for details. + * + * BUG: This routine does not handle hour overflow properly; it just + * sets the minutes. Usually you'll only notice that after reboot! + */ +static int set_rtc_mmss(unsigned long nowtime) +{ + unsigned char save_control, save_freq_select; + int retval = 0; + int real_seconds, real_minutes, cmos_minutes; + + /* gets recalled with irq locally disabled */ + spin_lock(&rtc_lock); + save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being + * set */ + CMOS_WRITE(save_control | RTC_SET, RTC_CONTROL); + + save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset + * prescaler */ + CMOS_WRITE(save_freq_select | RTC_DIV_RESET2, RTC_FREQ_SELECT); + + cmos_minutes = CMOS_READ(RTC_MINUTES); + if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) + cmos_minutes = bcd2bin(cmos_minutes); + + /* + * since we're only adjusting minutes and seconds, + * don't interfere with hour overflow. This avoids + * messing with unknown time zones but requires your + * RTC not to be off by more than 15 minutes + */ + real_seconds = nowtime % 60; + real_minutes = nowtime / 60; + if (((abs(real_minutes - cmos_minutes) + 15) / 30) & 1) + /* correct for half hour time zone */ + real_minutes += 30; + real_minutes %= 60; + + if (abs(real_minutes - cmos_minutes) < 30) { + if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) { + real_seconds = bin2bcd(real_seconds); + real_minutes = bin2bcd(real_minutes); + } + CMOS_WRITE(real_seconds, RTC_SECONDS); + CMOS_WRITE(real_minutes, RTC_MINUTES); + } else { + printk_once(KERN_NOTICE + "set_rtc_mmss: can't update from %d to %d\n", + cmos_minutes, real_minutes); + retval = -1; + } + + /* The following flags have to be released exactly in this order, + * otherwise the DS12887 (popular MC146818A clone with integrated + * battery and quartz) will not reset the oscillator and will not + * update precisely 500 ms later. You won't find this mentioned in + * the Dallas Semiconductor data sheets, but who believes data + * sheets anyway ... -- Markus Kuhn + */ + CMOS_WRITE(save_control, RTC_CONTROL); + CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT); + spin_unlock(&rtc_lock); + + return retval; +} + +int update_persistent_clock(struct timespec now) +{ + return set_rtc_mmss(now.tv_sec); +} + +/* + * calibrate the TSC clock against the RTC + */ +void __init calibrate_clock(void) +{ + unsigned char status; + + /* make sure the RTC is running and is set to operate in 24hr mode */ + status = RTSRC; + RTCRB |= RTCRB_SET; + RTCRB |= RTCRB_TM_24HR; + RTCRB &= ~RTCRB_DM_BINARY; + RTCRA |= RTCRA_DVR; + RTCRA &= ~RTCRA_DVR; + RTCRB &= ~RTCRB_SET; +} |