drivers/i2c/soft_i2c.c

   1 /*
   2  * (C) Copyright 2001, 2002
   3  * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
   4  *
   5  * See file CREDITS for list of people who contributed to this
   6  * project.
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License as
  10  * published by the Free Software Foundation; either version 2 of
  11  * the License, or (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  21  * MA 02111-1307 USA
  22  *
  23  * This has been changed substantially by Gerald Van Baren, Custom IDEAS,
  24  * vanbaren@cideas.com.  It was heavily influenced by LiMon, written by
  25  * Neil Russell.
  26  */
  27
  28 #include <common.h>
  29 #ifdef  CONFIG_MPC8260                  /* only valid for MPC8260 */
  30 #include <ioports.h>
  31 #include <asm/io.h>
  32 #endif
  33 #ifdef  CONFIG_AT91RM9200               /* need this for the at91rm9200 */
  34 #include <asm/io.h>
  35 #include <asm/arch/hardware.h>
  36 #endif
  37 #ifdef  CONFIG_IXP425                   /* only valid for IXP425 */
  38 #include <asm/arch/ixp425.h>
  39 #endif
  40 #ifdef CONFIG_LPC2292
  41 #include <asm/arch/hardware.h>
  42 #endif
  43 #if defined(CONFIG_MPC852T) || defined(CONFIG_MPC866)
  44 #include <asm/io.h>
  45 #endif
  46 #include <i2c.h>
  47
  48 /* #define      DEBUG_I2C       */
  49
  50 #ifdef DEBUG_I2C
  51 DECLARE_GLOBAL_DATA_PTR;
  52 #endif
  53
  54 /*-----------------------------------------------------------------------
  55  * Definitions
  56  */
  57
  58 #define RETRIES         0
  59
  60 #define I2C_ACK         0               /* PD_SDA level to ack a byte */
  61 #define I2C_NOACK       1               /* PD_SDA level to noack a byte */
  62
  63
  64 #ifdef DEBUG_I2C
  65 #define PRINTD(fmt,args...)     do {    \
  66         if (gd->have_console)           \
  67                 printf (fmt ,##args);   \
  68         } while (0)
  69 #else
  70 #define PRINTD(fmt,args...)
  71 #endif
  72
  73 #if defined(CONFIG_I2C_MULTI_BUS)
  74 static unsigned int i2c_bus_num __attribute__ ((section (".data"))) = 0;
  75 #endif /* CONFIG_I2C_MULTI_BUS */
  76
  77 /*-----------------------------------------------------------------------
  78  * Local functions
  79  */
  80 #if !defined(CONFIG_SYS_I2C_INIT_BOARD)
  81 static void  send_reset (void);
  82 #endif
  83 static void  send_start (void);
  84 static void  send_stop  (void);
  85 static void  send_ack   (int);
  86 static int   write_byte (uchar byte);
  87 static uchar read_byte  (int);
  88
  89 #if !defined(CONFIG_SYS_I2C_INIT_BOARD)
  90 /*-----------------------------------------------------------------------
  91  * Send a reset sequence consisting of 9 clocks with the data signal high
  92  * to clock any confused device back into an idle state.  Also send a
  93  * <stop> at the end of the sequence for belts & suspenders.
  94  */
  95 static void send_reset(void)
  96 {
  97         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
  98         int j;
  99
 100         I2C_SCL(1);
 101         I2C_SDA(1);
 102 #ifdef  I2C_INIT
 103         I2C_INIT;
 104 #endif
 105         I2C_TRISTATE;
 106         for(j = 0; j < 9; j++) {
 107                 I2C_SCL(0);
 108                 I2C_DELAY;
 109                 I2C_DELAY;
 110                 I2C_SCL(1);
 111                 I2C_DELAY;
 112                 I2C_DELAY;
 113         }
 114         send_stop();
 115         I2C_TRISTATE;
 116 }
 117 #endif
 118
 119 /*-----------------------------------------------------------------------
 120  * START: High -> Low on SDA while SCL is High
 121  */
 122 static void send_start(void)
 123 {
 124         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 125
 126         I2C_DELAY;
 127         I2C_SDA(1);
 128         I2C_ACTIVE;
 129         I2C_DELAY;
 130         I2C_SCL(1);
 131         I2C_DELAY;
 132         I2C_SDA(0);
 133         I2C_DELAY;
 134 }
 135
 136 /*-----------------------------------------------------------------------
 137  * STOP: Low -> High on SDA while SCL is High
 138  */
 139 static void send_stop(void)
 140 {
 141         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 142
 143         I2C_SCL(0);
 144         I2C_DELAY;
 145         I2C_SDA(0);
 146         I2C_ACTIVE;
 147         I2C_DELAY;
 148         I2C_SCL(1);
 149         I2C_DELAY;
 150         I2C_SDA(1);
 151         I2C_DELAY;
 152         I2C_TRISTATE;
 153 }
 154
 155 /*-----------------------------------------------------------------------
 156  * ack should be I2C_ACK or I2C_NOACK
 157  */
 158 static void send_ack(int ack)
 159 {
 160         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 161
 162         I2C_SCL(0);
 163         I2C_DELAY;
 164         I2C_ACTIVE;
 165         I2C_SDA(ack);
 166         I2C_DELAY;
 167         I2C_SCL(1);
 168         I2C_DELAY;
 169         I2C_DELAY;
 170         I2C_SCL(0);
 171         I2C_DELAY;
 172 }
 173
 174 /*-----------------------------------------------------------------------
 175  * Send 8 bits and look for an acknowledgement.
 176  */
 177 static int write_byte(uchar data)
 178 {
 179         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 180         int j;
 181         int nack;
 182
 183         I2C_ACTIVE;
 184         for(j = 0; j < 8; j++) {
 185                 I2C_SCL(0);
 186                 I2C_DELAY;
 187                 I2C_SDA(data & 0x80);
 188                 I2C_DELAY;
 189                 I2C_SCL(1);
 190                 I2C_DELAY;
 191                 I2C_DELAY;
 192
 193                 data <<= 1;
 194         }
 195
 196         /*
 197          * Look for an <ACK>(negative logic) and return it.
 198          */
 199         I2C_SCL(0);
 200         I2C_DELAY;
 201         I2C_SDA(1);
 202         I2C_TRISTATE;
 203         I2C_DELAY;
 204         I2C_SCL(1);
 205         I2C_DELAY;
 206         I2C_DELAY;
 207         nack = I2C_READ;
 208         I2C_SCL(0);
 209         I2C_DELAY;
 210         I2C_ACTIVE;
 211
 212         return(nack);   /* not a nack is an ack */
 213 }
 214
 215 #if defined(CONFIG_I2C_MULTI_BUS)
 216 /*
 217  * Functions for multiple I2C bus handling
 218  */
 219 unsigned int i2c_get_bus_num(void)
 220 {
 221         return i2c_bus_num;
 222 }
 223
 224 int i2c_set_bus_num(unsigned int bus)
 225 {
 226 #if defined(CONFIG_I2C_MUX)
 227         if (bus < CONFIG_SYS_MAX_I2C_BUS) {
 228                 i2c_bus_num = bus;
 229         } else {
 230                 int     ret;
 231
 232                 ret = i2x_mux_select_mux(bus);
 233                 if (ret == 0)
 234                         i2c_bus_num = bus;
 235                 else
 236                         return ret;
 237         }
 238 #else
 239         if (bus >= CONFIG_SYS_MAX_I2C_BUS)
 240                 return -1;
 241         i2c_bus_num = bus;
 242 #endif
 243         return 0;
 244 }
 245 #endif
 246
 247 /*-----------------------------------------------------------------------
 248  * if ack == I2C_ACK, ACK the byte so can continue reading, else
 249  * send I2C_NOACK to end the read.
 250  */
 251 static uchar read_byte(int ack)
 252 {
 253         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 254         int  data;
 255         int  j;
 256
 257         /*
 258          * Read 8 bits, MSB first.
 259          */
 260         I2C_TRISTATE;
 261         I2C_SDA(1);
 262         data = 0;
 263         for(j = 0; j < 8; j++) {
 264                 I2C_SCL(0);
 265                 I2C_DELAY;
 266                 I2C_SCL(1);
 267                 I2C_DELAY;
 268                 data <<= 1;
 269                 data |= I2C_READ;
 270                 I2C_DELAY;
 271         }
 272         send_ack(ack);
 273
 274         return(data);
 275 }
 276
 277 /*=====================================================================*/
 278 /*                         Public Functions                            */
 279 /*=====================================================================*/
 280
 281 /*-----------------------------------------------------------------------
 282  * Initialization
 283  */
 284 void i2c_init (int speed, int slaveaddr)
 285 {
 286 #if defined(CONFIG_SYS_I2C_INIT_BOARD)
 287         /* call board specific i2c bus reset routine before accessing the   */
 288         /* environment, which might be in a chip on that bus. For details   */
 289         /* about this problem see doc/I2C_Edge_Conditions.                  */
 290         i2c_init_board();
 291 #else
 292         /*
 293          * WARNING: Do NOT save speed in a static variable: if the
 294          * I2C routines are called before RAM is initialized (to read
 295          * the DIMM SPD, for instance), RAM won't be usable and your
 296          * system will crash.
 297          */
 298         send_reset ();
 299 #endif
 300 }
 301
 302 /*-----------------------------------------------------------------------
 303  * Probe to see if a chip is present.  Also good for checking for the
 304  * completion of EEPROM writes since the chip stops responding until
 305  * the write completes (typically 10mSec).
 306  */
 307 int i2c_probe(uchar addr)
 308 {
 309         int rc;
 310
 311         /*
 312          * perform 1 byte write transaction with just address byte
 313          * (fake write)
 314          */
 315         send_start();
 316         rc = write_byte ((addr << 1) | 0);
 317         send_stop();
 318
 319         return (rc ? 1 : 0);
 320 }
 321
 322 /*-----------------------------------------------------------------------
 323  * Read bytes
 324  */
 325 int  i2c_read(uchar chip, uint addr, int alen, uchar *buffer, int len)
 326 {
 327         int shift;
 328         PRINTD("i2c_read: chip %02X addr %02X alen %d buffer %p len %d\n",
 329                 chip, addr, alen, buffer, len);
 330
 331 #ifdef CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW
 332         /*
 333          * EEPROM chips that implement "address overflow" are ones
 334          * like Catalyst 24WC04/08/16 which has 9/10/11 bits of
 335          * address and the extra bits end up in the "chip address"
 336          * bit slots. This makes a 24WC08 (1Kbyte) chip look like
 337          * four 256 byte chips.
 338          *
 339          * Note that we consider the length of the address field to
 340          * still be one byte because the extra address bits are
 341          * hidden in the chip address.
 342          */
 343         chip |= ((addr >> (alen * 8)) & CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW);
 344
 345         PRINTD("i2c_read: fix addr_overflow: chip %02X addr %02X\n",
 346                 chip, addr);
 347 #endif
 348
 349         /*
 350          * Do the addressing portion of a write cycle to set the
 351          * chip's address pointer.  If the address length is zero,
 352          * don't do the normal write cycle to set the address pointer,
 353          * there is no address pointer in this chip.
 354          */
 355         send_start();
 356         if(alen > 0) {
 357                 if(write_byte(chip << 1)) {     /* write cycle */
 358                         send_stop();
 359                         PRINTD("i2c_read, no chip responded %02X\n", chip);
 360                         return(1);
 361                 }
 362                 shift = (alen-1) * 8;
 363                 while(alen-- > 0) {
 364                         if(write_byte(addr >> shift)) {
 365                                 PRINTD("i2c_read, address not <ACK>ed\n");
 366                                 return(1);
 367                         }
 368                         shift -= 8;
 369                 }
 370
 371                 /* Some I2C chips need a stop/start sequence here,
 372                  * other chips don't work with a full stop and need
 373                  * only a start.  Default behaviour is to send the
 374                  * stop/start sequence.
 375                  */
 376 #ifdef CONFIG_SOFT_I2C_READ_REPEATED_START
 377                 send_start();
 378 #else
 379                 send_stop();
 380                 send_start();
 381 #endif
 382         }
 383         /*
 384          * Send the chip address again, this time for a read cycle.
 385          * Then read the data.  On the last byte, we do a NACK instead
 386          * of an ACK(len == 0) to terminate the read.
 387          */
 388         write_byte((chip << 1) | 1);    /* read cycle */
 389         while(len-- > 0) {
 390                 *buffer++ = read_byte(len == 0);
 391         }
 392         send_stop();
 393         return(0);
 394 }
 395
 396 /*-----------------------------------------------------------------------
 397  * Write bytes
 398  */
 399 int  i2c_write(uchar chip, uint addr, int alen, uchar *buffer, int len)
 400 {
 401         int shift, failures = 0;
 402
 403         PRINTD("i2c_write: chip %02X addr %02X alen %d buffer %p len %d\n",
 404                 chip, addr, alen, buffer, len);
 405
 406         send_start();
 407         if(write_byte(chip << 1)) {     /* write cycle */
 408                 send_stop();
 409                 PRINTD("i2c_write, no chip responded %02X\n", chip);
 410                 return(1);
 411         }
 412         shift = (alen-1) * 8;
 413         while(alen-- > 0) {
 414                 if(write_byte(addr >> shift)) {
 415                         PRINTD("i2c_write, address not <ACK>ed\n");
 416                         return(1);
 417                 }
 418                 shift -= 8;
 419         }
 420
 421         while(len-- > 0) {
 422                 if(write_byte(*buffer++)) {
 423                         failures++;
 424                 }
 425         }
 426         send_stop();
 427         return(failures);
 428 }