1 /*
2 * Copyright (C) 2003 PMC-Sierra Inc.
3 * Author: Manish Lachwani (lachwani@pmc-sierra.com)
4 *
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License as published by the
7 * Free Software Foundation; either version 2 of the License, or (at your
8 * option) any later version.
9 *
10 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
11 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
12 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
13 * NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
14 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
15 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
16 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
17 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
18 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
19 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
20 *
21 * You should have received a copy of the GNU General Public License along
22 * with this program; if not, write to the Free Software Foundation, Inc.,
23 * 675 Mass Ave, Cambridge, MA 02139, USA.
24 */
25
26 /*
27 * Description:
28 *
29 * This code reads the ATMEL 24CXX EEPROM. The PMC-Sierra Yosemite board uses the ATMEL
30 * 24C32/24C64 which uses two byte addressing as compared to 24C16. Note that this program
31 * uses the serial port like /dev/ttyS0, to communicate with the EEPROM. Hence, you are
32 * expected to have a connectivity from the EEPROM to the serial port. This program does
33 * __not__ communicate using the I2C protocol
34 */
35
36 #include "atmel_read_eeprom.h"
37
delay(int delay)38 static void delay(int delay)
39 {
40 while (delay--);
41 }
42
send_bit(unsigned char bit)43 static void send_bit(unsigned char bit)
44 {
45 scl_lo;
46 delay(TXX);
47 if (bit)
48 sda_hi;
49 else
50 sda_lo;
51
52 delay(TXX);
53 scl_hi;
54 delay(TXX);
55 }
56
send_ack(void)57 static void send_ack(void)
58 {
59 send_bit(0);
60 }
61
send_byte(unsigned char byte)62 static void send_byte(unsigned char byte)
63 {
64 int i = 0;
65
66 for (i = 7; i >= 0; i--)
67 send_bit((byte >> i) & 0x01);
68 }
69
send_start(void)70 static void send_start(void)
71 {
72 sda_hi;
73 delay(TXX);
74 scl_hi;
75 delay(TXX);
76 sda_lo;
77 delay(TXX);
78 }
79
send_stop(void)80 static void send_stop(void)
81 {
82 sda_lo;
83 delay(TXX);
84 scl_hi;
85 delay(TXX);
86 sda_hi;
87 delay(TXX);
88 }
89
do_idle(void)90 static void do_idle(void)
91 {
92 sda_hi;
93 scl_hi;
94 vcc_off;
95 }
96
recv_bit(void)97 static int recv_bit(void)
98 {
99 int status;
100
101 scl_lo;
102 delay(TXX);
103 sda_hi;
104 delay(TXX);
105 scl_hi;
106 delay(TXX);
107
108 return 1;
109 }
110
recv_byte(void)111 static unsigned char recv_byte(void) {
112 int i;
113 unsigned char byte=0;
114
115 for (i=7;i>=0;i--)
116 byte |= (recv_bit() << i);
117
118 return byte;
119 }
120
recv_ack(void)121 static int recv_ack(void)
122 {
123 unsigned int ack;
124
125 ack = (unsigned int)recv_bit();
126 scl_lo;
127
128 if (ack) {
129 do_idle();
130 printk(KERN_ERR "Error reading the Atmel 24C32/24C64 EEPROM\n");
131 return -1;
132 }
133
134 return ack;
135 }
136
137 /*
138 * This function does the actual read of the EEPROM. It needs the buffer into which the
139 * read data is copied, the size of the EEPROM being read and the buffer size
140 */
read_eeprom(char * buffer,int eeprom_size,int size)141 int read_eeprom(char *buffer, int eeprom_size, int size)
142 {
143 int i = 0, err;
144
145 send_start();
146 send_byte(W_HEADER);
147 recv_ack();
148
149 /* EEPROM with size of more than 2K need two byte addressing */
150 if (eeprom_size > 2048) {
151 send_byte(0x00);
152 recv_ack();
153 }
154
155 send_start();
156 send_byte(R_HEADER);
157 err = recv_ack();
158 if (err == -1)
159 return err;
160
161 for (i = 0; i < size; i++) {
162 *buffer++ = recv_byte();
163 send_ack();
164 }
165
166 /* Note : We should do some check if the buffer contains correct information */
167
168 send_stop();
169 }
170