1/*
  2 * Atmel AT93C46 serial eeprom driver
  3 *
  4 * Brian Murphy <brian.murphy@eicon.com>
  5 *
  6 */
  7#include <linux/kernel.h>
  8#include <linux/delay.h>
  9#include <asm/lasat/lasat.h>
 10#include <linux/module.h>
 11#include <linux/init.h>
 12
 13#include "at93c.h"
 14
 15#define AT93C_ADDR_SHIFT	7
 16#define AT93C_ADDR_MAX		((1 << AT93C_ADDR_SHIFT) - 1)
 17#define AT93C_RCMD		(0x6 << AT93C_ADDR_SHIFT)
 18#define AT93C_WCMD		(0x5 << AT93C_ADDR_SHIFT)
 19#define AT93C_WENCMD		0x260
 20#define AT93C_WDSCMD		0x200
 21
 22struct at93c_defs *at93c;
 23
 24static void at93c_reg_write(u32 val)
 25{
 26	*at93c->reg = val;
 27}
 28
 29static u32 at93c_reg_read(void)
 30{
 31	u32 tmp = *at93c->reg;
 32	return tmp;
 33}
 34
 35static u32 at93c_datareg_read(void)
 36{
 37	u32 tmp = *at93c->rdata_reg;
 38	return tmp;
 39}
 40
 41static void at93c_cycle_clk(u32 data)
 42{
 43	at93c_reg_write(data | at93c->clk);
 44	lasat_ndelay(250);
 45	at93c_reg_write(data & ~at93c->clk);
 46	lasat_ndelay(250);
 47}
 48
 49static void at93c_write_databit(u8 bit)
 50{
 51	u32 data = at93c_reg_read();
 52	if (bit)
 53		data |= 1 << at93c->wdata_shift;
 54	else
 55		data &= ~(1 << at93c->wdata_shift);
 56
 57	at93c_reg_write(data);
 58	lasat_ndelay(100);
 59	at93c_cycle_clk(data);
 60}
 61
 62static unsigned int at93c_read_databit(void)
 63{
 64	u32 data;
 65
 66	at93c_cycle_clk(at93c_reg_read());
 67	data = (at93c_datareg_read() >> at93c->rdata_shift) & 1;
 68	return data;
 69}
 70
 71static u8 at93c_read_byte(void)
 72{
 73	int i;
 74	u8 data = 0;
 75
 76	for (i = 0; i <= 7; i++) {
 77		data <<= 1;
 78		data |= at93c_read_databit();
 79	}
 80	return data;
 81}
 82
 83static void at93c_write_bits(u32 data, int size)
 84{
 85	int i;
 86	int shift = size - 1;
 87	u32 mask = (1 << shift);
 88
 89	for (i = 0; i < size; i++) {
 90		at93c_write_databit((data & mask) >> shift);
 91		data <<= 1;
 92	}
 93}
 94
 95static void at93c_init_op(void)
 96{
 97	at93c_reg_write((at93c_reg_read() | at93c->cs) &
 98			~at93c->clk & ~(1 << at93c->rdata_shift));
 99	lasat_ndelay(50);
100}
101
102static void at93c_end_op(void)
103{
104	at93c_reg_write(at93c_reg_read() & ~at93c->cs);
105	lasat_ndelay(250);
106}
107
108static void at93c_wait(void)
109{
110	at93c_init_op();
111	while (!at93c_read_databit())
112		;
113	at93c_end_op();
114};
115
116static void at93c_disable_wp(void)
117{
118	at93c_init_op();
119	at93c_write_bits(AT93C_WENCMD, 10);
120	at93c_end_op();
121}
122
123static void at93c_enable_wp(void)
124{
125	at93c_init_op();
126	at93c_write_bits(AT93C_WDSCMD, 10);
127	at93c_end_op();
128}
129
130u8 at93c_read(u8 addr)
131{
132	u8 byte;
133	at93c_init_op();
134	at93c_write_bits((addr & AT93C_ADDR_MAX)|AT93C_RCMD, 10);
135	byte = at93c_read_byte();
136	at93c_end_op();
137	return byte;
138}
139
140void at93c_write(u8 addr, u8 data)
141{
142	at93c_disable_wp();
143	at93c_init_op();
144	at93c_write_bits((addr & AT93C_ADDR_MAX)|AT93C_WCMD, 10);
145	at93c_write_bits(data, 8);
146	at93c_end_op();
147	at93c_wait();
148	at93c_enable_wp();
149}