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         asm volatile("nop");
  33 }
  34
  35 #define DELAY delay_loop()
  36
  37 static struct mutex i2c_mtx;
  38
  39 void i2c_init(void)
  40 {
  41     mutex_init(&i2c_mtx);
  42 }
  43
  44 void i2c_start(void)
  45 {
  46     SDA_OUTPUT;
  47
  48     SCL_HI;
  49     SDA_HI;
  50     DELAY;
  51
  52     SDA_LO;
  53     DELAY;
  54     SCL_LO;
  55     DELAY;
  56 }
  57
  58 void i2c_stop(void)
  59 {
  60     SDA_OUTPUT;
  61
  62     SDA_LO;
  63     DELAY;
  64
  65     SCL_HI;
  66     DELAY;
  67     SDA_HI;
  68     DELAY;
  69 }
  70
  71 void i2c_outb(unsigned char byte)
  72 {
  73     int bit;
  74
  75     SDA_OUTPUT;
  76
  77     for (bit = 0; bit < 8; bit++)
  78     {
  79         if ((byte<<bit) & 0x80)
  80           SDA_HI;
  81         else
  82           SDA_LO;
  83
  84         DELAY;
  85
  86         SCL_HI;
  87         DELAY;
  88         SCL_LO;
  89         DELAY;
  90     }
  91 }
  92
  93 unsigned char i2c_inb(int ack)
  94 {
  95     int i;
  96     unsigned char byte = 0;
  97
  98     SDA_INPUT;
  99
 100     /* clock in each bit, MSB first */
 101     for ( i=0x80; i; i>>=1 )
 102     {
 103         SCL_HI;
 104         DELAY;
 105
 106         if ( SDA ) byte |= i;
 107
 108         SCL_LO;
 109         DELAY;
 110     }
 111
 112     i2c_ack(ack);
 113     return byte;
 114 }
 115
 116 void i2c_ack(int bit)
 117 {
 118     SDA_OUTPUT;
 119
 120     if (bit)
 121       SDA_HI;
 122     else
 123       SDA_LO;
 124
 125     SCL_HI;
 126     DELAY;
 127     SCL_LO;
 128     DELAY;
 129 }
 130
 131 int i2c_getack(void)
 132 {
 133     bool ack_bit;
 134
 135     SDA_INPUT;
 136
 137     SCL_HI;
 138     DELAY;
 139
 140     ack_bit = SDA;
 141     DELAY;
 142
 143     SCL_LO;
 144     DELAY;
 145
 146     return ack_bit;
 147 }
 148
 149 /* device = 8 bit slave address */
 150 int i2c_write(int device, const unsigned char* buf, int count )
 151 {
 152     int i = 0;
 153     mutex_lock(&i2c_mtx);
 154
 155     i2c_start();
 156     i2c_outb(device & 0xfe);
 157
 158     while (!i2c_getack() && i < count)
 159     {
 160         i2c_outb(buf[i++]);
 161     }
 162
 163     i2c_stop();
 164     mutex_unlock(&i2c_mtx);
 165     return 0;
 166 }
 167
 168
 169 /* device = 8 bit slave address */
 170 int i2c_readmem(int device, int address, unsigned char* buf, int count )
 171 {
 172     int i = 0;
 173     mutex_lock(&i2c_mtx);
 174
 175     i2c_start();
 176     i2c_outb(device & 0xfe);
 177     if (i2c_getack()) goto exit;
 178
 179     i2c_outb(address);
 180     if (i2c_getack()) goto exit;
 181
 182     i2c_start();
 183     i2c_outb(device | 1);
 184     if (i2c_getack()) goto exit;
 185
 186     while (i < count)
 187     {
 188         buf[i] = i2c_inb(i == (count-1));
 189         i++;
 190     }
 191
 192 exit:
 193     i2c_stop();
 194     mutex_unlock(&i2c_mtx);
 195     return 0;
 196 }