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