cpu/at91rm9200/i2c.c

   1 /*
   2  *  i2c Support for Atmel's AT91RM9200 Two-Wire Interface
   3  *
   4  *  (c) Rick Bronson
   5  *
   6  *  Borrowed heavily from original work by:
   7  *  Copyright (c) 2000 Philip Edelbrock <phil@stimpy.netroedge.com>
   8  *
   9  *  Modified to work with u-boot by (C) 2004 Gary Jennejohn garyj@denx.de
  10  *
  11  *  This program is free software; you can redistribute it and/or modify
  12  *  it under the terms of the GNU General Public License as published by
  13  *  the Free Software Foundation; either version 2 of the License, or
  14  *  (at your option) any later version.
  15  *
  16  *  This program is distributed in the hope that it will be useful,
  17  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  *  GNU General Public License for more details.
  20  *
  21  *  You should have received a copy of the GNU General Public License
  22  *  along with this program; if not, write to the Free Software
  23  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  24  *
  25 */
  26 #include <common.h>
  27
  28 #ifdef CONFIG_HARD_I2C
  29
  30 #include <i2c.h>
  31 #include <asm/io.h>
  32 #include <asm/arch/hardware.h>
  33
  34 #include <at91rm9200_i2c.h>
  35
  36 static int debug = 0;
  37
  38 /*
  39  * Poll the i2c status register until the specified bit is set.
  40  * Returns 0 if timed out (100 msec)
  41  */
  42 static short at91_poll_status(AT91PS_TWI twi, unsigned long bit) {
  43         int loop_cntr = 10000;
  44         do {
  45                 udelay(100);
  46         } while (!(twi->TWI_SR & bit) && (--loop_cntr > 0));
  47
  48         return (loop_cntr > 0);
  49 }
  50
  51 /*
  52  * Generic i2c master transfer entrypoint
  53  *
  54  * rw == 1 means that this is a read
  55  */
  56 static int
  57 at91_xfer(unsigned char chip, unsigned int addr, int alen,
  58                                                 unsigned char *buffer, int len, int rw)
  59 {
  60         AT91PS_TWI twi = (AT91PS_TWI) AT91_TWI_BASE;
  61         int length;
  62         unsigned char *buf;
  63
  64         /* Set the TWI Master Mode Register */
  65         twi->TWI_MMR = (chip << 16) | (alen << 8)
  66                 | ((rw == 1) ? AT91C_TWI_MREAD : 0);
  67
  68         /* Set TWI Internal Address Register with first messages data field */
  69         /* only one address byte is supported  */
  70         if (alen > 0)
  71                 twi->TWI_IADR = addr & 0xff;
  72
  73         length = len;
  74         buf = buffer;
  75         if (length && buf) {    /* sanity check */
  76                 if (rw) {
  77                         twi->TWI_CR = AT91C_TWI_START;
  78                         while (length--) {
  79                                 if (!length)
  80                                         twi->TWI_CR = AT91C_TWI_STOP;
  81                                 /* Wait until transfer is finished */
  82                                 if (!at91_poll_status(twi, AT91C_TWI_RXRDY)) {
  83                                         if (debug)
  84                                                 printf("at91_i2c: timeout 1\n");
  85                                         return 1;
  86                                 }
  87                                 *buf++ = twi->TWI_RHR;
  88                         }
  89                         if (!at91_poll_status(twi, AT91C_TWI_TXCOMP)) {
  90                                 if (debug)
  91                                         printf("at91_i2c: timeout 2\n");
  92                                 return 1;
  93                         }
  94                 } else {
  95                         twi->TWI_CR = AT91C_TWI_START;
  96                         while (length--) {
  97                                 twi->TWI_THR = *buf++;
  98                                 if (!length)
  99                                         twi->TWI_CR = AT91C_TWI_STOP;
 100                                 if (!at91_poll_status(twi, AT91C_TWI_TXRDY)) {
 101                                         if (debug)
 102                                                 printf("at91_i2c: timeout 3\n");
 103                                         return 1;
 104                                 }
 105                         }
 106                         /* Wait until transfer is finished */
 107                         if (!at91_poll_status(twi, AT91C_TWI_TXCOMP)) {
 108                                 if (debug)
 109                                         printf("at91_i2c: timeout 4\n");
 110                                 return 1;
 111                         }
 112                 }
 113         }
 114         return 0;
 115 }
 116
 117 int
 118 i2c_probe(unsigned char chip)
 119 {
 120         char buffer[1];
 121
 122         return at91_xfer(chip, 0, 0, buffer, 1, 1);
 123 }
 124
 125 int
 126 i2c_read(unsigned char chip, unsigned int addr, int alen,
 127                                                         unsigned char *buffer, int len)
 128 {
 129         /* we only allow one address byte */
 130         if (alen > 1)
 131                 return 1;
 132 #ifdef CFG_I2C_EEPROM_ADDR_OVERFLOW
 133         /* XXX assume an ATMEL AT24C16 */
 134         if (alen == 1) {
 135                 chip |= (addr >> 8) & 0xff;
 136                 addr = addr & 0xff;
 137         }
 138 #endif
 139         return at91_xfer(chip, addr, alen, buffer, len, 1);
 140 }
 141
 142 int
 143 i2c_write(unsigned char chip, unsigned int addr, int alen,
 144                                                         unsigned char *buffer, int len)
 145 {
 146         int i;
 147         unsigned char *buf;
 148
 149         /* we only allow one address byte */
 150         if (alen > 1)
 151                 return 1;
 152 #ifdef CFG_I2C_EEPROM_ADDR_OVERFLOW
 153         /* XXX assume an ATMEL AT24C16 */
 154         if (alen == 1) {
 155                 buf = buffer;
 156                 /* do single byte writes */
 157                 for (i = 0; i < len; i++) {
 158                         chip |= (addr >> 8) & 0xff;
 159                         addr = addr & 0xff;
 160                         if (at91_xfer(chip, addr, alen, buf++, 1, 0))
 161                                 return 1;
 162                 }
 163         }
 164         return 0;
 165 #endif
 166         return at91_xfer(chip, addr, alen, buffer, len, 0);
 167 }
 168
 169 /*
 170  * Main initialization routine
 171  */
 172 void
 173 i2c_init(int speed, int slaveaddr)
 174 {
 175         AT91PS_TWI twi = (AT91PS_TWI) AT91_TWI_BASE;
 176
 177         *AT91C_PIOA_PDR = AT91C_PA25_TWD | AT91C_PA26_TWCK;
 178         *AT91C_PIOA_ASR = AT91C_PA25_TWD | AT91C_PA26_TWCK;
 179         *AT91C_PIOA_MDER = AT91C_PA25_TWD | AT91C_PA26_TWCK;
 180         *AT91C_PMC_PCER = 1 << AT91C_ID_TWI;            /* enable peripheral clock */
 181
 182         twi->TWI_IDR = 0x3ff;                           /* Disable all interrupts */
 183         twi->TWI_CR = AT91C_TWI_SWRST;                  /* Reset peripheral */
 184         twi->TWI_CR = AT91C_TWI_MSEN | AT91C_TWI_SVDIS; /* Set Master mode */
 185
 186         /* Here, CKDIV = 1 and CHDIV=CLDIV  ==> CLDIV = CHDIV = 1/4*((Fmclk/FTWI) -6) */
 187         twi->TWI_CWGR = AT91C_TWI_CKDIV1 | AT91C_TWI_CLDIV3 | (AT91C_TWI_CLDIV3 << 8);
 188
 189         printf("Found AT91 i2c\n");
 190         return;
 191 }
 192 #endif /* CONFIG_HARD_I2C */