arch/mips/pmc-sierra/yosemite/atmel_read_eeprom.c

   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
  38 static void delay(int delay)
  39 {
  40         while (delay--);
  41 }
  42
  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
  57 static void send_ack(void)
  58 {
  59         send_bit(0);
  60 }
  61
  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
  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
  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
  90 static void do_idle(void)
  91 {
  92         sda_hi;
  93         scl_hi;
  94         vcc_off;
  95 }
  96
  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
 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
 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  */
 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 }