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ds1603.c

/*
 * Dallas Semiconductors 1603 RTC driver
 *
 * Brian Murphy <brian@murphy.dk>
 *
 */
#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);
}

unsigned long read_persistent_clock(void)
{
      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);

      return word;
}

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);
}

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