aboutsummaryrefslogtreecommitdiffstats
path: root/arch/mips/pmc-sierra/yosemite/atmel_read_eeprom.c
blob: b067988614c34ce6c871a26d2d10d23d8749d16e (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
/*
 *  arch/mips/pmc-sierra/yosemite/atmel_read_eeprom.c
 *
 *  Copyright (C) 2003 PMC-Sierra Inc.
 *  Author: Manish Lachwani (lachwani@pmc-sierra.com)
 *
 *  This program is free software; you can redistribute  it and/or modify it
 *  under  the terms of  the GNU General  Public License as published by the
 *  Free Software Foundation;  either version 2 of the  License, or (at your
 *  option) any later version.
 *
 *  THIS  SOFTWARE  IS PROVIDED   ``AS  IS'' AND   ANY  EXPRESS OR IMPLIED
 *  WARRANTIES,   INCLUDING, BUT NOT  LIMITED  TO, THE IMPLIED WARRANTIES OF
 *  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN
 *  NO  EVENT  SHALL   THE AUTHOR  BE    LIABLE FOR ANY   DIRECT, INDIRECT,
 *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 *  NOT LIMITED   TO, PROCUREMENT OF  SUBSTITUTE GOODS  OR SERVICES; LOSS OF
 *  USE, DATA,  OR PROFITS; OR  BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 *  ANY THEORY OF LIABILITY, WHETHER IN  CONTRACT, STRICT LIABILITY, OR TORT
 *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 *  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *  You should have received a copy of the  GNU General Public License along
 *  with this program; if not, write  to the Free Software Foundation, Inc.,
 *  675 Mass Ave, Cambridge, MA 02139, USA.
 */

/*
 * Description:
 *
 * This code reads the ATMEL 24CXX EEPROM. The PMC-Sierra Yosemite board uses the ATMEL
 * 24C32/24C64 which uses two byte addressing as compared to 24C16. Note that this program
 * uses the serial port like /dev/ttyS0, to communicate with the EEPROM. Hence, you are 
 * expected to have a connectivity from the EEPROM to the serial port. This program does
 * __not__ communicate using the I2C protocol
 */

#include "atmel_read_eeprom.h"

static void delay(int delay)
{
	while (delay--);
}

static void send_bit(unsigned char bit)
{
	scl_lo;
	delay(TXX);
	if (bit)
		sda_hi;
	else
		sda_lo;

	delay(TXX);
	scl_hi;
	delay(TXX);
}

static void send_ack(void)
{
	send_bit(0);
}

static void send_byte(unsigned char byte)
{
	int	i = 0;
	
	for (i = 7; i >= 0; i--) 
		send_bit((byte >> i) & 0x01);
}
	
static void send_start(void)
{
	sda_hi; 
	delay(TXX);
	scl_hi;
	delay(TXX);
	sda_lo;
	delay(TXX);
}

static void send_stop(void)
{
	sda_lo;
	delay(TXX);
	scl_hi;
	delay(TXX);
	sda_hi;
	delay(TXX);
}

static void do_idle(void)
{
	sda_hi;
	scl_hi;
	vcc_off;
}

static int recv_bit(void)
{
	int	status;

	scl_lo;
	delay(TXX);
	sda_hi;
	delay(TXX);
	scl_hi;
	delay(TXX);

	return 1;
}

static unsigned char recv_byte(void) {
        int i;
        unsigned char byte=0;

        for (i=7;i>=0;i--)                             
                byte |= (recv_bit() << i);
 
        return byte;
}

static int recv_ack(void)
{
	unsigned int	ack;

	ack = (unsigned int)recv_bit();
	scl_lo;

	if (ack) {
		do_idle();
		printk(KERN_ERR "Error reading the Atmel 24C32/24C64 EEPROM \n");
		return -1;
	}

	return ack;
}

/*
 * This function does the actual read of the EEPROM. It needs the buffer into which the
 * read data is copied, the size of the EEPROM being read and the buffer size
 */
int read_eeprom(char *buffer, int eeprom_size, int size)
{
	int	i = 0, err;

	send_start();
	send_byte(W_HEADER);
	recv_ack();

	/* EEPROM with size of more then 2K need two byte addressing */
	if (eeprom_size > 2048) {
		send_byte(0x00);
		recv_ack();
	}

	send_start();
	send_byte(R_HEADER);
	err = recv_ack();
	if (err == -1)
		return err;

	for (i = 0; i < size; i++) {
		*buffer++ = recv_byte();
		send_ack();
	}

	/* Note : We should do some check if the buffer contains correct information */

	send_stop();
}