1 /*
2 * arch/mips/pmc-sierra/yosemite/atmel_read_eeprom.c
3 *
4 * Copyright (C) 2003 PMC-Sierra Inc.
5 * Author: Manish Lachwani (lachwani@pmc-sierra.com)
6 *
7 * This program is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License as published by the
9 * Free Software Foundation; either version 2 of the License, or (at your
10 * option) any later version.
11 *
12 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
13 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
14 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
15 * NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
16 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
17 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
18 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
19 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
20 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
21 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
22 *
23 * You should have received a copy of the GNU General Public License along
24 * with this program; if not, write to the Free Software Foundation, Inc.,
25 * 675 Mass Ave, Cambridge, MA 02139, USA.
26 */
27
28 /*
29 * Description:
30 *
31 * This code reads the ATMEL 24CXX EEPROM. The PMC-Sierra Yosemite board uses the ATMEL
32 * 24C32/24C64 which uses two byte addressing as compared to 24C16. Note that this program
33 * uses the serial port like /dev/ttyS0, to communicate with the EEPROM. Hence, you are
34 * expected to have a connectivity from the EEPROM to the serial port. This program does
35 * __not__ communicate using the I2C protocol
36 */
37
38 #include "atmel_read_eeprom.h"
39
delay(int delay)40 static void delay(int delay)
41 {
42 while (delay--);
43 }
44
send_bit(unsigned char bit)45 static void send_bit(unsigned char bit)
46 {
47 scl_lo;
48 delay(TXX);
49 if (bit)
50 sda_hi;
51 else
52 sda_lo;
53
54 delay(TXX);
55 scl_hi;
56 delay(TXX);
57 }
58
send_ack(void)59 static void send_ack(void)
60 {
61 send_bit(0);
62 }
63
send_byte(unsigned char byte)64 static void send_byte(unsigned char byte)
65 {
66 int i = 0;
67
68 for (i = 7; i >= 0; i--)
69 send_bit((byte >> i) & 0x01);
70 }
71
send_start(void)72 static void send_start(void)
73 {
74 sda_hi;
75 delay(TXX);
76 scl_hi;
77 delay(TXX);
78 sda_lo;
79 delay(TXX);
80 }
81
send_stop(void)82 static void send_stop(void)
83 {
84 sda_lo;
85 delay(TXX);
86 scl_hi;
87 delay(TXX);
88 sda_hi;
89 delay(TXX);
90 }
91
do_idle(void)92 static void do_idle(void)
93 {
94 sda_hi;
95 scl_hi;
96 vcc_off;
97 }
98
recv_bit(void)99 static int recv_bit(void)
100 {
101 int status;
102
103 scl_lo;
104 delay(TXX);
105 sda_hi;
106 delay(TXX);
107 scl_hi;
108 delay(TXX);
109
110 return 1;
111 }
112
recv_byte(void)113 static unsigned char recv_byte(void) {
114 int i;
115 unsigned char byte=0;
116
117 for (i=7;i>=0;i--)
118 byte |= (recv_bit() << i);
119
120 return byte;
121 }
122
recv_ack(void)123 static int recv_ack(void)
124 {
125 unsigned int ack;
126
127 ack = (unsigned int)recv_bit();
128 scl_lo;
129
130 if (ack) {
131 do_idle();
132 printk(KERN_ERR "Error reading the Atmel 24C32/24C64 EEPROM \n");
133 return -1;
134 }
135
136 return ack;
137 }
138
139 /*
140 * This function does the actual read of the EEPROM. It needs the buffer into which the
141 * read data is copied, the size of the EEPROM being read and the buffer size
142 */
read_eeprom(char * buffer,int eeprom_size,int size)143 int read_eeprom(char *buffer, int eeprom_size, int size)
144 {
145 int i = 0, err;
146
147 send_start();
148 send_byte(W_HEADER);
149 recv_ack();
150
151 /* EEPROM with size of more than 2K need two byte addressing */
152 if (eeprom_size > 2048) {
153 send_byte(0x00);
154 recv_ack();
155 }
156
157 send_start();
158 send_byte(R_HEADER);
159 err = recv_ack();
160 if (err == -1)
161 return err;
162
163 for (i = 0; i < size; i++) {
164 *buffer++ = recv_byte();
165 send_ack();
166 }
167
168 /* Note : We should do some check if the buffer contains correct information */
169
170 send_stop();
171 }
172