isa-rtc.c

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/*
 *  arch/arm/mach-footbridge/isa-rtc.c
 *
 *  Copyright (C) 1998 Russell King.
 *  Copyright (C) 1998 Phil Blundell
 *
 * CATS has a real-time clock, though the evaluation board doesn't.
 *
 * Changelog:
 *  21-Mar-1998 RMK Created
 *  27-Aug-1998 PJB CATS support
 *  28-Dec-1998 APH Made leds optional
 *  20-Jan-1999 RMK Started merge of EBSA285, CATS and NetWinder
 *  16-Mar-1999 RMK More support for EBSA285-like machines with RTCs in
 */

#define RTC_PORT(x)     (0x70+(x))
#define RTC_ALWAYS_BCD      0

#include <linux/init.h>
#include <linux/mc146818rtc.h>
#include <linux/bcd.h>
#include <linux/io.h>

#include "common.h"

void __init isa_rtc_init(void)
{
    int reg_d, reg_b;

    /*
     * Probe for the RTC.
     */
    reg_d = CMOS_READ(RTC_REG_D);

    /*
     * make sure the divider is set
     */
    CMOS_WRITE(RTC_REF_CLCK_32KHZ, RTC_REG_A);

    /*
     * Set control reg B
     *   (24 hour mode, update enabled)
     */
    reg_b = CMOS_READ(RTC_REG_B) & 0x7f;
    reg_b |= 2;
    CMOS_WRITE(reg_b, RTC_REG_B);

    if ((CMOS_READ(RTC_REG_A) & 0x7f) == RTC_REF_CLCK_32KHZ &&
        CMOS_READ(RTC_REG_B) == reg_b) {
        /*
         * We have a RTC.  Check the battery
         */
        if ((reg_d & 0x80) == 0)
            printk(KERN_WARNING "RTC: *** warning: CMOS battery bad\n");
    }
}