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at93c.c

/*
 * Atmel AT93C46 serial eeprom driver
 *
 * Brian Murphy <brian.murphy@eicon.com>
 *
 */
#include <linux/kernel.h>
#include <linux/delay.h>
#include <asm/lasat/lasat.h>
#include <linux/module.h>
#include <linux/init.h>

#include "at93c.h"

#define AT93C_ADDR_SHIFT      7
#define AT93C_ADDR_MAX        ((1 << AT93C_ADDR_SHIFT) - 1)
#define AT93C_RCMD            (0x6 << AT93C_ADDR_SHIFT)
#define AT93C_WCMD            (0x5 << AT93C_ADDR_SHIFT)
#define AT93C_WENCMD          0x260
#define AT93C_WDSCMD          0x200

struct at93c_defs *at93c;

static void at93c_reg_write(u32 val)
{
      *at93c->reg = val;
}

static u32 at93c_reg_read(void)
{
      u32 tmp = *at93c->reg;
      return tmp;
}

static u32 at93c_datareg_read(void)
{
      u32 tmp = *at93c->rdata_reg;
      return tmp;
}

static void at93c_cycle_clk(u32 data)
{
      at93c_reg_write(data | at93c->clk);
      lasat_ndelay(250);
      at93c_reg_write(data & ~at93c->clk);
      lasat_ndelay(250);
}

static void at93c_write_databit(u8 bit)
{
      u32 data = at93c_reg_read();
      if (bit)
            data |= 1 << at93c->wdata_shift;
      else
            data &= ~(1 << at93c->wdata_shift);

      at93c_reg_write(data);
      lasat_ndelay(100);
      at93c_cycle_clk(data);
}

static unsigned int at93c_read_databit(void)
{
      u32 data;

      at93c_cycle_clk(at93c_reg_read());
      data = (at93c_datareg_read() >> at93c->rdata_shift) & 1;
      return data;
}

static u8 at93c_read_byte(void)
{
      int i;
      u8 data = 0;

      for (i = 0; i <= 7; i++) {
            data <<= 1;
            data |= at93c_read_databit();
      }
      return data;
}

static void at93c_write_bits(u32 data, int size)
{
      int i;
      int shift = size - 1;
      u32 mask = (1 << shift);

      for (i = 0; i < size; i++) {
            at93c_write_databit((data & mask) >> shift);
            data <<= 1;
      }
}

static void at93c_init_op(void)
{
      at93c_reg_write((at93c_reg_read() | at93c->cs) &
                  ~at93c->clk & ~(1 << at93c->rdata_shift));
      lasat_ndelay(50);
}

static void at93c_end_op(void)
{
      at93c_reg_write(at93c_reg_read() & ~at93c->cs);
      lasat_ndelay(250);
}

static void at93c_wait(void)
{
      at93c_init_op();
      while (!at93c_read_databit())
            ;
      at93c_end_op();
};

static void at93c_disable_wp(void)
{
      at93c_init_op();
      at93c_write_bits(AT93C_WENCMD, 10);
      at93c_end_op();
}

static void at93c_enable_wp(void)
{
      at93c_init_op();
      at93c_write_bits(AT93C_WDSCMD, 10);
      at93c_end_op();
}

u8 at93c_read(u8 addr)
{
      u8 byte;
      at93c_init_op();
      at93c_write_bits((addr & AT93C_ADDR_MAX)|AT93C_RCMD, 10);
      byte = at93c_read_byte();
      at93c_end_op();
      return byte;
}

void at93c_write(u8 addr, u8 data)
{
      at93c_disable_wp();
      at93c_init_op();
      at93c_write_bits((addr & AT93C_ADDR_MAX)|AT93C_WCMD, 10);
      at93c_write_bits(data, 8);
      at93c_end_op();
      at93c_wait();
      at93c_enable_wp();
}

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