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

   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
  40 static void delay(int delay)
  41 {
  42         while (delay--);
  43 }
  44
  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
  59 static void send_ack(void)
  60 {
  61         send_bit(0);
  62 }
  63
  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
  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
  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
  92 static void do_idle(void)
  93 {
  94         sda_hi;
  95         scl_hi;
  96         vcc_off;
  97 }
  98
  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
 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
 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  */
 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 then 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 }