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 #endif
  32 #ifdef  CONFIG_AT91RM9200               /* need this for the at91rm9200 */
  33 #include <asm/io.h>
  34 #include <asm/arch/hardware.h>
  35 #endif
  36 #ifdef  CONFIG_IXP425                   /* only valid for IXP425 */
  37 #include <asm/arch/ixp425.h>
  38 #endif
  39 #ifdef CONFIG_LPC2292
  40 #include <asm/arch/hardware.h>
  41 #endif
  42 #include <i2c.h>
  43
  44 /* #define      DEBUG_I2C       */
  45
  46 #ifdef DEBUG_I2C
  47 DECLARE_GLOBAL_DATA_PTR;
  48 #endif
  49
  50
  51 /*-----------------------------------------------------------------------
  52  * Definitions
  53  */
  54
  55 #define RETRIES         0
  56
  57
  58 #define I2C_ACK         0               /* PD_SDA level to ack a byte */
  59 #define I2C_NOACK       1               /* PD_SDA level to noack a byte */
  60
  61
  62 #ifdef DEBUG_I2C
  63 #define PRINTD(fmt,args...)     do {    \
  64         if (gd->have_console)           \
  65                 printf (fmt ,##args);   \
  66         } while (0)
  67 #else
  68 #define PRINTD(fmt,args...)
  69 #endif
  70
  71 #if defined(CONFIG_I2C_MULTI_BUS)
  72 static unsigned int i2c_bus_num __attribute__ ((section ("data"))) = 0;
  73 #endif /* CONFIG_I2C_MULTI_BUS */
  74
  75 /*-----------------------------------------------------------------------
  76  * Local functions
  77  */
  78 #if !defined(CFG_I2C_INIT_BOARD)
  79 static void  send_reset (void);
  80 #endif
  81 static void  send_start (void);
  82 static void  send_stop  (void);
  83 static void  send_ack   (int);
  84 static int   write_byte (uchar byte);
  85 static uchar read_byte  (int);
  86
  87 #if !defined(CFG_I2C_INIT_BOARD)
  88 /*-----------------------------------------------------------------------
  89  * Send a reset sequence consisting of 9 clocks with the data signal high
  90  * to clock any confused device back into an idle state.  Also send a
  91  * <stop> at the end of the sequence for belts & suspenders.
  92  */
  93 static void send_reset(void)
  94 {
  95         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
  96         int j;
  97
  98         I2C_SCL(1);
  99         I2C_SDA(1);
 100 #ifdef  I2C_INIT
 101         I2C_INIT;
 102 #endif
 103         I2C_TRISTATE;
 104         for(j = 0; j < 9; j++) {
 105                 I2C_SCL(0);
 106                 I2C_DELAY;
 107                 I2C_DELAY;
 108                 I2C_SCL(1);
 109                 I2C_DELAY;
 110                 I2C_DELAY;
 111         }
 112         send_stop();
 113         I2C_TRISTATE;
 114 }
 115 #endif
 116
 117 /*-----------------------------------------------------------------------
 118  * START: High -> Low on SDA while SCL is High
 119  */
 120 static void send_start(void)
 121 {
 122         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 123
 124         I2C_DELAY;
 125         I2C_SDA(1);
 126         I2C_ACTIVE;
 127         I2C_DELAY;
 128         I2C_SCL(1);
 129         I2C_DELAY;
 130         I2C_SDA(0);
 131         I2C_DELAY;
 132 }
 133
 134 /*-----------------------------------------------------------------------
 135  * STOP: Low -> High on SDA while SCL is High
 136  */
 137 static void send_stop(void)
 138 {
 139         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 140
 141         I2C_SCL(0);
 142         I2C_DELAY;
 143         I2C_SDA(0);
 144         I2C_ACTIVE;
 145         I2C_DELAY;
 146         I2C_SCL(1);
 147         I2C_DELAY;
 148         I2C_SDA(1);
 149         I2C_DELAY;
 150         I2C_TRISTATE;
 151 }
 152
 153
 154 /*-----------------------------------------------------------------------
 155  * ack should be I2C_ACK or I2C_NOACK
 156  */
 157 static void send_ack(int ack)
 158 {
 159         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 160
 161         I2C_SCL(0);
 162         I2C_DELAY;
 163         I2C_ACTIVE;
 164         I2C_SDA(ack);
 165         I2C_DELAY;
 166         I2C_SCL(1);
 167         I2C_DELAY;
 168         I2C_DELAY;
 169         I2C_SCL(0);
 170         I2C_DELAY;
 171 }
 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 (bus >= CFG_MAX_I2C_BUS)
 227                 return -1;
 228         i2c_bus_num = bus;
 229
 230         return 0;
 231 }
 232
 233 /* TODO: add 100/400k switching */
 234 unsigned int i2c_get_bus_speed(void)
 235 {
 236         return CFG_I2C_SPEED;
 237 }
 238
 239 int i2c_set_bus_speed(unsigned int speed)
 240 {
 241         if (speed != CFG_I2C_SPEED)
 242                 return -1;
 243
 244         return 0;
 245 }
 246 #endif
 247
 248 /*-----------------------------------------------------------------------
 249  * if ack == I2C_ACK, ACK the byte so can continue reading, else
 250  * send I2C_NOACK to end the read.
 251  */
 252 static uchar read_byte(int ack)
 253 {
 254         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 255         int  data;
 256         int  j;
 257
 258         /*
 259          * Read 8 bits, MSB first.
 260          */
 261         I2C_TRISTATE;
 262         I2C_SDA(1);
 263         data = 0;
 264         for(j = 0; j < 8; j++) {
 265                 I2C_SCL(0);
 266                 I2C_DELAY;
 267                 I2C_SCL(1);
 268                 I2C_DELAY;
 269                 data <<= 1;
 270                 data |= I2C_READ;
 271                 I2C_DELAY;
 272         }
 273         send_ack(ack);
 274
 275         return(data);
 276 }
 277
 278 /*=====================================================================*/
 279 /*                         Public Functions                            */
 280 /*=====================================================================*/
 281
 282 /*-----------------------------------------------------------------------
 283  * Initialization
 284  */
 285 void i2c_init (int speed, int slaveaddr)
 286 {
 287 #if defined(CFG_I2C_INIT_BOARD)
 288         /* call board specific i2c bus reset routine before accessing the   */
 289         /* environment, which might be in a chip on that bus. For details   */
 290         /* about this problem see doc/I2C_Edge_Conditions.                  */
 291         i2c_init_board();
 292 #else
 293         /*
 294          * WARNING: Do NOT save speed in a static variable: if the
 295          * I2C routines are called before RAM is initialized (to read
 296          * the DIMM SPD, for instance), RAM won't be usable and your
 297          * system will crash.
 298          */
 299         send_reset ();
 300 #endif
 301 }
 302
 303 /*-----------------------------------------------------------------------
 304  * Probe to see if a chip is present.  Also good for checking for the
 305  * completion of EEPROM writes since the chip stops responding until
 306  * the write completes (typically 10mSec).
 307  */
 308 int i2c_probe(uchar addr)
 309 {
 310         int rc;
 311
 312         /*
 313          * perform 1 byte write transaction with just address byte
 314          * (fake write)
 315          */
 316         send_start();
 317         rc = write_byte ((addr << 1) | 0);
 318         send_stop();
 319
 320         return (rc ? 1 : 0);
 321 }
 322
 323 /*-----------------------------------------------------------------------
 324  * Read bytes
 325  */
 326 int  i2c_read(uchar chip, uint addr, int alen, uchar *buffer, int len)
 327 {
 328         int shift;
 329         PRINTD("i2c_read: chip %02X addr %02X alen %d buffer %p len %d\n",
 330                 chip, addr, alen, buffer, len);
 331
 332 #ifdef CFG_I2C_EEPROM_ADDR_OVERFLOW
 333         /*
 334          * EEPROM chips that implement "address overflow" are ones
 335          * like Catalyst 24WC04/08/16 which has 9/10/11 bits of
 336          * address and the extra bits end up in the "chip address"
 337          * bit slots. This makes a 24WC08 (1Kbyte) chip look like
 338          * four 256 byte chips.
 339          *
 340          * Note that we consider the length of the address field to
 341          * still be one byte because the extra address bits are
 342          * hidden in the chip address.
 343          */
 344         chip |= ((addr >> (alen * 8)) & CFG_I2C_EEPROM_ADDR_OVERFLOW);
 345
 346         PRINTD("i2c_read: fix addr_overflow: chip %02X addr %02X\n",
 347                 chip, addr);
 348 #endif
 349
 350         /*
 351          * Do the addressing portion of a write cycle to set the
 352          * chip's address pointer.  If the address length is zero,
 353          * don't do the normal write cycle to set the address pointer,
 354          * there is no address pointer in this chip.
 355          */
 356         send_start();
 357         if(alen > 0) {
 358                 if(write_byte(chip << 1)) {     /* write cycle */
 359                         send_stop();
 360                         PRINTD("i2c_read, no chip responded %02X\n", chip);
 361                         return(1);
 362                 }
 363                 shift = (alen-1) * 8;
 364                 while(alen-- > 0) {
 365                         if(write_byte(addr >> shift)) {
 366                                 PRINTD("i2c_read, address not <ACK>ed\n");
 367                                 return(1);
 368                         }
 369                         shift -= 8;
 370                 }
 371                 send_stop();    /* reportedly some chips need a full stop */
 372                 send_start();
 373         }
 374         /*
 375          * Send the chip address again, this time for a read cycle.
 376          * Then read the data.  On the last byte, we do a NACK instead
 377          * of an ACK(len == 0) to terminate the read.
 378          */
 379         write_byte((chip << 1) | 1);    /* read cycle */
 380         while(len-- > 0) {
 381                 *buffer++ = read_byte(len == 0);
 382         }
 383         send_stop();
 384         return(0);
 385 }
 386
 387 /*-----------------------------------------------------------------------
 388  * Write bytes
 389  */
 390 int  i2c_write(uchar chip, uint addr, int alen, uchar *buffer, int len)
 391 {
 392         int shift, failures = 0;
 393
 394         PRINTD("i2c_write: chip %02X addr %02X alen %d buffer %p len %d\n",
 395                 chip, addr, alen, buffer, len);
 396
 397         send_start();
 398         if(write_byte(chip << 1)) {     /* write cycle */
 399                 send_stop();
 400                 PRINTD("i2c_write, no chip responded %02X\n", chip);
 401                 return(1);
 402         }
 403         shift = (alen-1) * 8;
 404         while(alen-- > 0) {
 405                 if(write_byte(addr >> shift)) {
 406                         PRINTD("i2c_write, address not <ACK>ed\n");
 407                         return(1);
 408                 }
 409                 shift -= 8;
 410         }
 411
 412         while(len-- > 0) {
 413                 if(write_byte(*buffer++)) {
 414                         failures++;
 415                 }
 416         }
 417         send_stop();
 418         return(failures);
 419 }
 420
 421 /*-----------------------------------------------------------------------
 422  * Read a register
 423  */
 424 uchar i2c_reg_read(uchar i2c_addr, uchar reg)
 425 {
 426         uchar buf;
 427
 428         i2c_read(i2c_addr, reg, 1, &buf, 1);
 429
 430         return(buf);
 431 }
 432
 433 /*-----------------------------------------------------------------------
 434  * Write a register
 435  */
 436 void i2c_reg_write(uchar i2c_addr, uchar reg, uchar val)
 437 {
 438         i2c_write(i2c_addr, reg, 1, &val, 1);
 439 }