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     asm volatile ("   mov  %[freq], %[freq], asr#22 \n\t"
  31                   "1: subs %[freq], %[freq], #1     \n\t"
  32                   "   bne  1b"
  33                   : : [freq] "r" (cpu_frequency) : "memory");
  34 }
  35
  36 #define DELAY delay_loop()
  37
  38 static struct mutex i2c_mtx;
  39
  40 void i2c_init(void)
  41 {
  42     mutex_init(&i2c_mtx);
  43 }
  44
  45 void i2c_start(void)
  46 {
  47     SDA_OUTPUT;
  48
  49     SCL_HI;
  50     SDA_HI;
  51     DELAY;
  52
  53     SDA_LO;
  54     DELAY;
  55     SCL_LO;
  56     DELAY;
  57 }
  58
  59 void i2c_stop(void)
  60 {
  61     SDA_OUTPUT;
  62
  63     SDA_LO;
  64     DELAY;
  65
  66     SCL_HI;
  67     DELAY;
  68     SDA_HI;
  69     DELAY;
  70 }
  71
  72 void i2c_outb(unsigned char byte)
  73 {
  74     int bit;
  75
  76     SDA_OUTPUT;
  77
  78     for (bit = 0; bit < 8; bit++)
  79     {
  80         if ((byte<<bit) & 0x80)
  81           SDA_HI;
  82         else
  83           SDA_LO;
  84
  85         DELAY;
  86
  87         SCL_HI;
  88         DELAY;
  89         SCL_LO;
  90         DELAY;
  91     }
  92 }
  93
  94 unsigned char i2c_inb(int ack)
  95 {
  96     int i;
  97     unsigned char byte = 0;
  98
  99     SDA_INPUT;
 100
 101     /* clock in each bit, MSB first */
 102     for ( i=0x80; i; i>>=1 )
 103     {
 104         SCL_HI;
 105         DELAY;
 106
 107         if ( SDA ) byte |= i;
 108
 109         SCL_LO;
 110         DELAY;
 111     }
 112
 113     i2c_ack(ack);
 114     return byte;
 115 }
 116
 117 void i2c_ack(int bit)
 118 {
 119     SDA_OUTPUT;
 120
 121     if (bit)
 122       SDA_HI;
 123     else
 124       SDA_LO;
 125
 126     SCL_HI;
 127     DELAY;
 128     SCL_LO;
 129     DELAY;
 130 }
 131
 132 int i2c_getack(void)
 133 {
 134     bool ack_bit;
 135
 136     SDA_INPUT;
 137
 138     SCL_HI;
 139     DELAY;
 140
 141     ack_bit = SDA;
 142     DELAY;
 143
 144     SCL_LO;
 145     DELAY;
 146
 147     return ack_bit;
 148 }
 149
 150 /* device = 8 bit slave address */
 151 int i2c_write(int device, const unsigned char* buf, int count )
 152 {
 153     int i = 0;
 154     mutex_lock(&i2c_mtx);
 155
 156     i2c_start();
 157     i2c_outb(device & 0xfe);
 158
 159     while (!i2c_getack() && i < count)
 160     {
 161         i2c_outb(buf[i++]);
 162     }
 163
 164     i2c_stop();
 165     mutex_unlock(&i2c_mtx);
 166     return 0;
 167 }
 168
 169
 170 /* device = 8 bit slave address */
 171 int i2c_readmem(int device, int address, unsigned char* buf, int count )
 172 {
 173     int i = 0;
 174     mutex_lock(&i2c_mtx);
 175
 176     i2c_start();
 177     i2c_outb(device & 0xfe);
 178     if (i2c_getack()) goto exit;
 179
 180     i2c_outb(address);
 181     if (i2c_getack()) goto exit;
 182
 183     i2c_start();
 184     i2c_outb(device | 1);
 185     if (i2c_getack()) goto exit;
 186
 187     while (i < count)
 188     {
 189         buf[i] = i2c_inb(i == (count-1));
 190         i++;
 191     }
 192
 193 exit:
 194     i2c_stop();
 195     mutex_unlock(&i2c_mtx);
 196     return 0;
 197 }