ds1603.c

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/*
 * Dallas Semiconductors 1603 RTC driver
 *
 * Brian Murphy <[email protected]>
 *
 */
#include <linux/kernel.h>
#include <asm/lasat/lasat.h>
#include <linux/delay.h>
#include <asm/lasat/ds1603.h>
#include <asm/time.h>

#include "ds1603.h"

#define READ_TIME_CMD 0x81
#define SET_TIME_CMD 0x80
#define TRIMMER_SET_CMD 0xC0
#define TRIMMER_VALUE_MASK 0x38
#define TRIMMER_SHIFT 3

struct ds_defs *ds1603;

/* HW specific register functions */
static void rtc_reg_write(unsigned long val)
{
    *ds1603->reg = val;
}

static unsigned long rtc_reg_read(void)
{
    unsigned long tmp = *ds1603->reg;
    return tmp;
}

static unsigned long rtc_datareg_read(void)
{
    unsigned long tmp = *ds1603->data_reg;
    return tmp;
}

static void rtc_nrst_high(void)
{
    rtc_reg_write(rtc_reg_read() | ds1603->rst);
}

static void rtc_nrst_low(void)
{
    rtc_reg_write(rtc_reg_read() & ~ds1603->rst);
}

static void rtc_cycle_clock(unsigned long data)
{
    data |= ds1603->clk;
    rtc_reg_write(data);
    lasat_ndelay(250);
    if (ds1603->data_reversed)
        data &= ~ds1603->data;
    else
        data |= ds1603->data;
    data &= ~ds1603->clk;
    rtc_reg_write(data);
    lasat_ndelay(250 + ds1603->huge_delay);
}

static void rtc_write_databit(unsigned int bit)
{
    unsigned long data = rtc_reg_read();
    if (ds1603->data_reversed)
        bit = !bit;
    if (bit)
        data |= ds1603->data;
    else
        data &= ~ds1603->data;

    rtc_reg_write(data);
    lasat_ndelay(50 + ds1603->huge_delay);
    rtc_cycle_clock(data);
}

static unsigned int rtc_read_databit(void)
{
    unsigned int data;

    data = (rtc_datareg_read() & (1 << ds1603->data_read_shift))
        >> ds1603->data_read_shift;
    rtc_cycle_clock(rtc_reg_read());
    return data;
}

static void rtc_write_byte(unsigned int byte)
{
    int i;

    for (i = 0; i <= 7; i++) {
        rtc_write_databit(byte & 1L);
        byte >>= 1;
    }
}

static void rtc_write_word(unsigned long word)
{
    int i;

    for (i = 0; i <= 31; i++) {
        rtc_write_databit(word & 1L);
        word >>= 1;
    }
}

static unsigned long rtc_read_word(void)
{
    int i;
    unsigned long word = 0;
    unsigned long shift = 0;

    for (i = 0; i <= 31; i++) {
        word |= rtc_read_databit() << shift;
        shift++;
    }
    return word;
}

static void rtc_init_op(void)
{
    rtc_nrst_high();

    rtc_reg_write(rtc_reg_read() & ~ds1603->clk);

    lasat_ndelay(50);
}

static void rtc_end_op(void)
{
    rtc_nrst_low();
    lasat_ndelay(1000);
}

void read_persistent_clock(struct timespec *ts)
{
    unsigned long word;
    unsigned long flags;

    spin_lock_irqsave(&rtc_lock, flags);
    rtc_init_op();
    rtc_write_byte(READ_TIME_CMD);
    word = rtc_read_word();
    rtc_end_op();
    spin_unlock_irqrestore(&rtc_lock, flags);

    ts->tv_sec = word;
    ts->tv_nsec = 0;
}

int rtc_mips_set_mmss(unsigned long time)
{
    unsigned long flags;

    spin_lock_irqsave(&rtc_lock, flags);
    rtc_init_op();
    rtc_write_byte(SET_TIME_CMD);
    rtc_write_word(time);
    rtc_end_op();
    spin_unlock_irqrestore(&rtc_lock, flags);

    return 0;
}

void ds1603_set_trimmer(unsigned int trimval)
{
    rtc_init_op();
    rtc_write_byte(((trimval << TRIMMER_SHIFT) & TRIMMER_VALUE_MASK)
            | (TRIMMER_SET_CMD));
    rtc_end_op();
}

void ds1603_disable(void)
{
    ds1603_set_trimmer(TRIMMER_DISABLE_RTC);
}

void ds1603_enable(void)
{
    ds1603_set_trimmer(TRIMMER_DEFAULT);
}