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 #ifdef  CONFIG_MPC866                   /* only valid for 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 /*-----------------------------------------------------------------------
  56  * Definitions
  57  */
  58
  59 #define RETRIES         0
  60
  61
  62 #define I2C_ACK         0               /* PD_SDA level to ack a byte */
  63 #define I2C_NOACK       1               /* PD_SDA level to noack a byte */
  64
  65
  66 #ifdef DEBUG_I2C
  67 #define PRINTD(fmt,args...)     do {    \
  68         if (gd->have_console)           \
  69                 printf (fmt ,##args);   \
  70         } while (0)
  71 #else
  72 #define PRINTD(fmt,args...)
  73 #endif
  74
  75 #if defined(CONFIG_I2C_MULTI_BUS)
  76 static unsigned int i2c_bus_num __attribute__ ((section (".data"))) = 0;
  77 #endif /* CONFIG_I2C_MULTI_BUS */
  78
  79 /*-----------------------------------------------------------------------
  80  * Local functions
  81  */
  82 #if !defined(CONFIG_SYS_I2C_INIT_BOARD)
  83 static void  send_reset (void);
  84 #endif
  85 static void  send_start (void);
  86 static void  send_stop  (void);
  87 static void  send_ack   (int);
  88 static int   write_byte (uchar byte);
  89 static uchar read_byte  (int);
  90
  91 #if !defined(CONFIG_SYS_I2C_INIT_BOARD)
  92 /*-----------------------------------------------------------------------
  93  * Send a reset sequence consisting of 9 clocks with the data signal high
  94  * to clock any confused device back into an idle state.  Also send a
  95  * <stop> at the end of the sequence for belts & suspenders.
  96  */
  97 static void send_reset(void)
  98 {
  99         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 100         int j;
 101
 102         I2C_SCL(1);
 103         I2C_SDA(1);
 104 #ifdef  I2C_INIT
 105         I2C_INIT;
 106 #endif
 107         I2C_TRISTATE;
 108         for(j = 0; j < 9; j++) {
 109                 I2C_SCL(0);
 110                 I2C_DELAY;
 111                 I2C_DELAY;
 112                 I2C_SCL(1);
 113                 I2C_DELAY;
 114                 I2C_DELAY;
 115         }
 116         send_stop();
 117         I2C_TRISTATE;
 118 }
 119 #endif
 120
 121 /*-----------------------------------------------------------------------
 122  * START: High -> Low on SDA while SCL is High
 123  */
 124 static void send_start(void)
 125 {
 126         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 127
 128         I2C_DELAY;
 129         I2C_SDA(1);
 130         I2C_ACTIVE;
 131         I2C_DELAY;
 132         I2C_SCL(1);
 133         I2C_DELAY;
 134         I2C_SDA(0);
 135         I2C_DELAY;
 136 }
 137
 138 /*-----------------------------------------------------------------------
 139  * STOP: Low -> High on SDA while SCL is High
 140  */
 141 static void send_stop(void)
 142 {
 143         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 144
 145         I2C_SCL(0);
 146         I2C_DELAY;
 147         I2C_SDA(0);
 148         I2C_ACTIVE;
 149         I2C_DELAY;
 150         I2C_SCL(1);
 151         I2C_DELAY;
 152         I2C_SDA(1);
 153         I2C_DELAY;
 154         I2C_TRISTATE;
 155 }
 156
 157
 158 /*-----------------------------------------------------------------------
 159  * ack should be I2C_ACK or I2C_NOACK
 160  */
 161 static void send_ack(int ack)
 162 {
 163         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 164
 165         I2C_SCL(0);
 166         I2C_DELAY;
 167         I2C_ACTIVE;
 168         I2C_SDA(ack);
 169         I2C_DELAY;
 170         I2C_SCL(1);
 171         I2C_DELAY;
 172         I2C_DELAY;
 173         I2C_SCL(0);
 174         I2C_DELAY;
 175 }
 176
 177
 178 /*-----------------------------------------------------------------------
 179  * Send 8 bits and look for an acknowledgement.
 180  */
 181 static int write_byte(uchar data)
 182 {
 183         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 184         int j;
 185         int nack;
 186
 187         I2C_ACTIVE;
 188         for(j = 0; j < 8; j++) {
 189                 I2C_SCL(0);
 190                 I2C_DELAY;
 191                 I2C_SDA(data & 0x80);
 192                 I2C_DELAY;
 193                 I2C_SCL(1);
 194                 I2C_DELAY;
 195                 I2C_DELAY;
 196
 197                 data <<= 1;
 198         }
 199
 200         /*
 201          * Look for an <ACK>(negative logic) and return it.
 202          */
 203         I2C_SCL(0);
 204         I2C_DELAY;
 205         I2C_SDA(1);
 206         I2C_TRISTATE;
 207         I2C_DELAY;
 208         I2C_SCL(1);
 209         I2C_DELAY;
 210         I2C_DELAY;
 211         nack = I2C_READ;
 212         I2C_SCL(0);
 213         I2C_DELAY;
 214         I2C_ACTIVE;
 215
 216         return(nack);   /* not a nack is an ack */
 217 }
 218
 219 #if defined(CONFIG_I2C_MULTI_BUS)
 220 /*
 221  * Functions for multiple I2C bus handling
 222  */
 223 unsigned int i2c_get_bus_num(void)
 224 {
 225         return i2c_bus_num;
 226 }
 227
 228 int i2c_set_bus_num(unsigned int bus)
 229 {
 230 #if defined(CONFIG_I2C_MUX)
 231         if (bus < CONFIG_SYS_MAX_I2C_BUS) {
 232                 i2c_bus_num = bus;
 233         } else {
 234                 int     ret;
 235
 236                 ret = i2x_mux_select_mux(bus);
 237                 if (ret == 0)
 238                         i2c_bus_num = bus;
 239                 else
 240                         return ret;
 241         }
 242 #else
 243         if (bus >= CONFIG_SYS_MAX_I2C_BUS)
 244                 return -1;
 245         i2c_bus_num = bus;
 246 #endif
 247         return 0;
 248 }
 249
 250 /* TODO: add 100/400k switching */
 251 unsigned int i2c_get_bus_speed(void)
 252 {
 253         return CONFIG_SYS_I2C_SPEED;
 254 }
 255
 256 int i2c_set_bus_speed(unsigned int speed)
 257 {
 258         if (speed != CONFIG_SYS_I2C_SPEED)
 259                 return -1;
 260
 261         return 0;
 262 }
 263 #endif
 264
 265 /*-----------------------------------------------------------------------
 266  * if ack == I2C_ACK, ACK the byte so can continue reading, else
 267  * send I2C_NOACK to end the read.
 268  */
 269 static uchar read_byte(int ack)
 270 {
 271         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 272         int  data;
 273         int  j;
 274
 275         /*
 276          * Read 8 bits, MSB first.
 277          */
 278         I2C_TRISTATE;
 279         I2C_SDA(1);
 280         data = 0;
 281         for(j = 0; j < 8; j++) {
 282                 I2C_SCL(0);
 283                 I2C_DELAY;
 284                 I2C_SCL(1);
 285                 I2C_DELAY;
 286                 data <<= 1;
 287                 data |= I2C_READ;
 288                 I2C_DELAY;
 289         }
 290         send_ack(ack);
 291
 292         return(data);
 293 }
 294
 295 /*=====================================================================*/
 296 /*                         Public Functions                            */
 297 /*=====================================================================*/
 298
 299 /*-----------------------------------------------------------------------
 300  * Initialization
 301  */
 302 void i2c_init (int speed, int slaveaddr)
 303 {
 304 #if defined(CONFIG_SYS_I2C_INIT_BOARD)
 305         /* call board specific i2c bus reset routine before accessing the   */
 306         /* environment, which might be in a chip on that bus. For details   */
 307         /* about this problem see doc/I2C_Edge_Conditions.                  */
 308         i2c_init_board();
 309 #else
 310         /*
 311          * WARNING: Do NOT save speed in a static variable: if the
 312          * I2C routines are called before RAM is initialized (to read
 313          * the DIMM SPD, for instance), RAM won't be usable and your
 314          * system will crash.
 315          */
 316         send_reset ();
 317 #endif
 318 }
 319
 320 /*-----------------------------------------------------------------------
 321  * Probe to see if a chip is present.  Also good for checking for the
 322  * completion of EEPROM writes since the chip stops responding until
 323  * the write completes (typically 10mSec).
 324  */
 325 int i2c_probe(uchar addr)
 326 {
 327         int rc;
 328
 329         /*
 330          * perform 1 byte write transaction with just address byte
 331          * (fake write)
 332          */
 333         send_start();
 334         rc = write_byte ((addr << 1) | 0);
 335         send_stop();
 336
 337         return (rc ? 1 : 0);
 338 }
 339
 340 /*-----------------------------------------------------------------------
 341  * Read bytes
 342  */
 343 int  i2c_read(uchar chip, uint addr, int alen, uchar *buffer, int len)
 344 {
 345         int shift;
 346         PRINTD("i2c_read: chip %02X addr %02X alen %d buffer %p len %d\n",
 347                 chip, addr, alen, buffer, len);
 348
 349 #ifdef CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW
 350         /*
 351          * EEPROM chips that implement "address overflow" are ones
 352          * like Catalyst 24WC04/08/16 which has 9/10/11 bits of
 353          * address and the extra bits end up in the "chip address"
 354          * bit slots. This makes a 24WC08 (1Kbyte) chip look like
 355          * four 256 byte chips.
 356          *
 357          * Note that we consider the length of the address field to
 358          * still be one byte because the extra address bits are
 359          * hidden in the chip address.
 360          */
 361         chip |= ((addr >> (alen * 8)) & CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW);
 362
 363         PRINTD("i2c_read: fix addr_overflow: chip %02X addr %02X\n",
 364                 chip, addr);
 365 #endif
 366
 367         /*
 368          * Do the addressing portion of a write cycle to set the
 369          * chip's address pointer.  If the address length is zero,
 370          * don't do the normal write cycle to set the address pointer,
 371          * there is no address pointer in this chip.
 372          */
 373         send_start();
 374         if(alen > 0) {
 375                 if(write_byte(chip << 1)) {     /* write cycle */
 376                         send_stop();
 377                         PRINTD("i2c_read, no chip responded %02X\n", chip);
 378                         return(1);
 379                 }
 380                 shift = (alen-1) * 8;
 381                 while(alen-- > 0) {
 382                         if(write_byte(addr >> shift)) {
 383                                 PRINTD("i2c_read, address not <ACK>ed\n");
 384                                 return(1);
 385                         }
 386                         shift -= 8;
 387                 }
 388
 389                 /* Some I2C chips need a stop/start sequence here,
 390                  * other chips don't work with a full stop and need
 391                  * only a start.  Default behaviour is to send the
 392                  * stop/start sequence.
 393                  */
 394 #ifdef CONFIG_SOFT_I2C_READ_REPEATED_START
 395                 send_start();
 396 #else
 397                 send_stop();
 398                 send_start();
 399 #endif
 400         }
 401         /*
 402          * Send the chip address again, this time for a read cycle.
 403          * Then read the data.  On the last byte, we do a NACK instead
 404          * of an ACK(len == 0) to terminate the read.
 405          */
 406         write_byte((chip << 1) | 1);    /* read cycle */
 407         while(len-- > 0) {
 408                 *buffer++ = read_byte(len == 0);
 409         }
 410         send_stop();
 411         return(0);
 412 }
 413
 414 /*-----------------------------------------------------------------------
 415  * Write bytes
 416  */
 417 int  i2c_write(uchar chip, uint addr, int alen, uchar *buffer, int len)
 418 {
 419         int shift, failures = 0;
 420
 421         PRINTD("i2c_write: chip %02X addr %02X alen %d buffer %p len %d\n",
 422                 chip, addr, alen, buffer, len);
 423
 424         send_start();
 425         if(write_byte(chip << 1)) {     /* write cycle */
 426                 send_stop();
 427                 PRINTD("i2c_write, no chip responded %02X\n", chip);
 428                 return(1);
 429         }
 430         shift = (alen-1) * 8;
 431         while(alen-- > 0) {
 432                 if(write_byte(addr >> shift)) {
 433                         PRINTD("i2c_write, address not <ACK>ed\n");
 434                         return(1);
 435                 }
 436                 shift -= 8;
 437         }
 438
 439         while(len-- > 0) {
 440                 if(write_byte(*buffer++)) {
 441                         failures++;
 442                 }
 443         }
 444         send_stop();
 445         return(failures);
 446 }