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time.c

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/*!     \file drivers/time/time.c
 *      \brief Real time clock driver.
 *      \author Andrea Righi <drizzt@inwind.it>
 *      \date Last update: 2003-11-01
 *      \note Copyright (&copy;) 2003 Andrea Righi
 */

#include <const.h>

#include <kernel/console.h>
#include <kernel/semaphore.h>

#include <kernel/time.h>

//! The real-time clock semaphore.
semaphore_t rtc_lock;

//! \brief Initialize the Real-Time Clock.
void time_init()
{
        INIT_MUTEX(&rtc_lock);
}

//! \brief
//!     Get the seconds passed since midnight 1970-01-01
//!     (Unix timestamp).
//! \return
//!     The UNIX timestamp.
time_t time_read()
{
        unsigned int year, mon, day, hour, min, sec;
        int i;

        DOWN(&rtc_lock);

        // When the Update-In-Progress (UIP) flag goes from 1 to 0,     //
        // the RTC registers show the second which has precisely just   //
        // started.                                                     //
        // Read RTC exactly on falling edge of update flag.             //

        for (i=0; i<1000000 ; i++)      // may take up to 1 second...   //
                if ( CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP )
                        break;

        for (i=0 ; i<1000000 ; i++)     // must try at least 2.228 ms   //
                if ( !(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
                        break;

        do { /* Isn't this overkill ? UIP above should guarantee consistency */
                sec =   CMOS_READ(RTC_SECONDS);
                min =   CMOS_READ(RTC_MINUTES);
                hour =  CMOS_READ(RTC_HOURS);
                day =   CMOS_READ(RTC_DAY_OF_MONTH);
                mon =   CMOS_READ(RTC_MONTH);
                year =  CMOS_READ(RTC_YEAR);
        } while (sec != CMOS_READ(RTC_SECONDS));

        if ( !(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) )
        {
                sec =   BCD2BIN( sec );
                min =   BCD2BIN( min );
                hour =  BCD2BIN( hour );
                day =   BCD2BIN( day );
                mon =   BCD2BIN( mon );
                year =  BCD2BIN( year );
        }

        UP(&rtc_lock);

        if ( (year += 1900) < 1970 )
                year += 100;

        return( mktime(year, mon, day, hour, min, sec) );
}

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