firmware/target/arm/i2c-telechips.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Copyright (C) 2008 by Rob Purchase
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License
  14  * as published by the Free Software Foundation; either version 2
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  18  * KIND, either express or implied.
  19  *
  20  ****************************************************************************/
  21 #include "config.h"
  22
  23 #include "system.h"
  24 #include "i2c.h"
  25 #include "i2c-target.h"
  26
  27 /* Delay loop based on CPU frequency (FREQ>>22 is 7..45 for 32MHz..192MHz) */
  28 static inline void delay_loop(void)
  29 {
  30     unsigned long x;
  31     for (x = (unsigned)(FREQ>>22); x; x--);
  32 }
  33 #define DELAY delay_loop()
  34
  35 static struct mutex i2c_mtx;
  36
  37 void i2c_init(void)
  38 {
  39     /* nothing to do */
  40 }
  41
  42 void i2c_start(void)
  43 {
  44     SDA_OUTPUT;
  45
  46     SCL_HI;
  47     SDA_HI;
  48     DELAY;
  49
  50     SDA_LO;
  51     DELAY;
  52     SCL_LO;
  53     DELAY;
  54 }
  55
  56 void i2c_stop(void)
  57 {
  58     SDA_OUTPUT;
  59
  60     SDA_LO;
  61     DELAY;
  62
  63     SCL_HI;
  64     DELAY;
  65     SDA_HI;
  66     DELAY;
  67 }
  68
  69 void i2c_outb(unsigned char byte)
  70 {
  71     int bit;
  72
  73     SDA_OUTPUT;
  74
  75     for (bit = 0; bit < 8; bit++)
  76     {
  77         if ((byte<<bit) & 0x80)
  78           SDA_HI;
  79         else
  80           SDA_LO;
  81
  82         DELAY;
  83
  84         SCL_HI;
  85         DELAY;
  86         SCL_LO;
  87         DELAY;
  88     }
  89 }
  90
  91 unsigned char i2c_inb(int ack)
  92 {
  93     int i;
  94     unsigned char byte = 0;
  95
  96     SDA_INPUT;
  97
  98     /* clock in each bit, MSB first */
  99     for ( i=0x80; i; i>>=1 )
 100     {
 101         SCL_HI;
 102         DELAY;
 103
 104         if ( SDA ) byte |= i;
 105
 106         SCL_LO;
 107         DELAY;
 108     }
 109
 110     i2c_ack(ack);
 111     return byte;
 112 }
 113
 114 void i2c_ack(int bit)
 115 {
 116     SDA_OUTPUT;
 117
 118     if (bit)
 119       SDA_HI;
 120     else
 121       SDA_LO;
 122
 123     SCL_HI;
 124     DELAY;
 125     SCL_LO;
 126     DELAY;
 127 }
 128
 129 int i2c_getack(void)
 130 {
 131     bool ack_bit;
 132
 133     SDA_INPUT;
 134
 135     SCL_HI;
 136     DELAY;
 137
 138     ack_bit = SDA;
 139     DELAY;
 140
 141     SCL_LO;
 142     DELAY;
 143
 144     return ack_bit;
 145 }
 146
 147 /* device = 8 bit slave address */
 148 int i2c_write(int device, const unsigned char* buf, int count )
 149 {
 150     int i = 0;
 151     mutex_lock(&i2c_mtx);
 152
 153     i2c_start();
 154     i2c_outb(device & 0xfe);
 155
 156     while (!i2c_getack() && i < count)
 157     {
 158         i2c_outb(buf[i++]);
 159     }
 160
 161     i2c_stop();
 162     mutex_unlock(&i2c_mtx);
 163     return 0;
 164 }
 165
 166
 167 /* device = 8 bit slave address */
 168 int i2c_readmem(int device, int address, unsigned char* buf, int count )
 169 {
 170     int i = 0;
 171     mutex_lock(&i2c_mtx);
 172
 173     i2c_start();
 174     i2c_outb(device & 0xfe);
 175     if (i2c_getack()) goto exit;
 176
 177     i2c_outb(address);
 178     if (i2c_getack()) goto exit;
 179
 180     i2c_start();
 181     i2c_outb(device | 1);
 182     if (i2c_getack()) goto exit;
 183
 184     while (i < count)
 185     {
 186         buf[i] = i2c_inb(i == (count-1));
 187         i++;
 188     }
 189
 190 exit:
 191     i2c_stop();
 192     mutex_unlock(&i2c_mtx);
 193     return 0;
 194 }