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 static void  send_reset (void);
  79 static void  send_start (void);
  80 static void  send_stop  (void);
  81 static void  send_ack   (int);
  82 static int   write_byte (uchar byte);
  83 static uchar read_byte  (int);
  84
  85 /*-----------------------------------------------------------------------
  86  * Send a reset sequence consisting of 9 clocks with the data signal high
  87  * to clock any confused device back into an idle state.  Also send a
  88  * <stop> at the end of the sequence for belts & suspenders.
  89  */
  90 static void send_reset(void)
  91 {
  92         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
  93         int j;
  94
  95         I2C_SCL(1);
  96         I2C_SDA(1);
  97 #ifdef  I2C_INIT
  98         I2C_INIT;
  99 #endif
 100         I2C_TRISTATE;
 101         for(j = 0; j < 9; j++) {
 102                 I2C_SCL(0);
 103                 I2C_DELAY;
 104                 I2C_DELAY;
 105                 I2C_SCL(1);
 106                 I2C_DELAY;
 107                 I2C_DELAY;
 108         }
 109         send_stop();
 110         I2C_TRISTATE;
 111 }
 112
 113 /*-----------------------------------------------------------------------
 114  * START: High -> Low on SDA while SCL is High
 115  */
 116 static void send_start(void)
 117 {
 118         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 119
 120         I2C_DELAY;
 121         I2C_SDA(1);
 122         I2C_ACTIVE;
 123         I2C_DELAY;
 124         I2C_SCL(1);
 125         I2C_DELAY;
 126         I2C_SDA(0);
 127         I2C_DELAY;
 128 }
 129
 130 /*-----------------------------------------------------------------------
 131  * STOP: Low -> High on SDA while SCL is High
 132  */
 133 static void send_stop(void)
 134 {
 135         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 136
 137         I2C_SCL(0);
 138         I2C_DELAY;
 139         I2C_SDA(0);
 140         I2C_ACTIVE;
 141         I2C_DELAY;
 142         I2C_SCL(1);
 143         I2C_DELAY;
 144         I2C_SDA(1);
 145         I2C_DELAY;
 146         I2C_TRISTATE;
 147 }
 148
 149
 150 /*-----------------------------------------------------------------------
 151  * ack should be I2C_ACK or I2C_NOACK
 152  */
 153 static void send_ack(int ack)
 154 {
 155         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 156
 157         I2C_SCL(0);
 158         I2C_DELAY;
 159         I2C_ACTIVE;
 160         I2C_SDA(ack);
 161         I2C_DELAY;
 162         I2C_SCL(1);
 163         I2C_DELAY;
 164         I2C_DELAY;
 165         I2C_SCL(0);
 166         I2C_DELAY;
 167 }
 168
 169
 170 /*-----------------------------------------------------------------------
 171  * Send 8 bits and look for an acknowledgement.
 172  */
 173 static int write_byte(uchar data)
 174 {
 175         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 176         int j;
 177         int nack;
 178
 179         I2C_ACTIVE;
 180         for(j = 0; j < 8; j++) {
 181                 I2C_SCL(0);
 182                 I2C_DELAY;
 183                 I2C_SDA(data & 0x80);
 184                 I2C_DELAY;
 185                 I2C_SCL(1);
 186                 I2C_DELAY;
 187                 I2C_DELAY;
 188
 189                 data <<= 1;
 190         }
 191
 192         /*
 193          * Look for an <ACK>(negative logic) and return it.
 194          */
 195         I2C_SCL(0);
 196         I2C_DELAY;
 197         I2C_SDA(1);
 198         I2C_TRISTATE;
 199         I2C_DELAY;
 200         I2C_SCL(1);
 201         I2C_DELAY;
 202         I2C_DELAY;
 203         nack = I2C_READ;
 204         I2C_SCL(0);
 205         I2C_DELAY;
 206         I2C_ACTIVE;
 207
 208         return(nack);   /* not a nack is an ack */
 209 }
 210
 211 #if defined(CONFIG_I2C_MULTI_BUS)
 212 /*
 213  * Functions for multiple I2C bus handling
 214  */
 215 unsigned int i2c_get_bus_num(void)
 216 {
 217         return i2c_bus_num;
 218 }
 219
 220 int i2c_set_bus_num(unsigned int bus)
 221 {
 222         if (bus >= CFG_MAX_I2C_BUS)
 223                 return -1;
 224         i2c_bus_num = bus;
 225
 226         return 0;
 227 }
 228
 229 /* TODO: add 100/400k switching */
 230 unsigned int i2c_get_bus_speed(void)
 231 {
 232         return CFG_I2C_SPEED;
 233 }
 234
 235 int i2c_set_bus_speed(unsigned int speed)
 236 {
 237         if (speed != CFG_I2C_SPEED)
 238                 return -1;
 239
 240         return 0;
 241 }
 242 #endif
 243
 244 /*-----------------------------------------------------------------------
 245  * if ack == I2C_ACK, ACK the byte so can continue reading, else
 246  * send I2C_NOACK to end the read.
 247  */
 248 static uchar read_byte(int ack)
 249 {
 250         I2C_SOFT_DECLARATIONS   /* intentional without ';' */
 251         int  data;
 252         int  j;
 253
 254         /*
 255          * Read 8 bits, MSB first.
 256          */
 257         I2C_TRISTATE;
 258         I2C_SDA(1);
 259         data = 0;
 260         for(j = 0; j < 8; j++) {
 261                 I2C_SCL(0);
 262                 I2C_DELAY;
 263                 I2C_SCL(1);
 264                 I2C_DELAY;
 265                 data <<= 1;
 266                 data |= I2C_READ;
 267                 I2C_DELAY;
 268         }
 269         send_ack(ack);
 270
 271         return(data);
 272 }
 273
 274 /*=====================================================================*/
 275 /*                         Public Functions                            */
 276 /*=====================================================================*/
 277
 278 /*-----------------------------------------------------------------------
 279  * Initialization
 280  */
 281 void i2c_init (int speed, int slaveaddr)
 282 {
 283         /*
 284          * WARNING: Do NOT save speed in a static variable: if the
 285          * I2C routines are called before RAM is initialized (to read
 286          * the DIMM SPD, for instance), RAM won't be usable and your
 287          * system will crash.
 288          */
 289         send_reset ();
 290 }
 291
 292 /*-----------------------------------------------------------------------
 293  * Probe to see if a chip is present.  Also good for checking for the
 294  * completion of EEPROM writes since the chip stops responding until
 295  * the write completes (typically 10mSec).
 296  */
 297 int i2c_probe(uchar addr)
 298 {
 299         int rc;
 300
 301         /*
 302          * perform 1 byte write transaction with just address byte
 303          * (fake write)
 304          */
 305         send_start();
 306         rc = write_byte ((addr << 1) | 0);
 307         send_stop();
 308
 309         return (rc ? 1 : 0);
 310 }
 311
 312 /*-----------------------------------------------------------------------
 313  * Read bytes
 314  */
 315 int  i2c_read(uchar chip, uint addr, int alen, uchar *buffer, int len)
 316 {
 317         int shift;
 318         PRINTD("i2c_read: chip %02X addr %02X alen %d buffer %p len %d\n",
 319                 chip, addr, alen, buffer, len);
 320
 321 #ifdef CFG_I2C_EEPROM_ADDR_OVERFLOW
 322         /*
 323          * EEPROM chips that implement "address overflow" are ones
 324          * like Catalyst 24WC04/08/16 which has 9/10/11 bits of
 325          * address and the extra bits end up in the "chip address"
 326          * bit slots. This makes a 24WC08 (1Kbyte) chip look like
 327          * four 256 byte chips.
 328          *
 329          * Note that we consider the length of the address field to
 330          * still be one byte because the extra address bits are
 331          * hidden in the chip address.
 332          */
 333         chip |= ((addr >> (alen * 8)) & CFG_I2C_EEPROM_ADDR_OVERFLOW);
 334
 335         PRINTD("i2c_read: fix addr_overflow: chip %02X addr %02X\n",
 336                 chip, addr);
 337 #endif
 338
 339         /*
 340          * Do the addressing portion of a write cycle to set the
 341          * chip's address pointer.  If the address length is zero,
 342          * don't do the normal write cycle to set the address pointer,
 343          * there is no address pointer in this chip.
 344          */
 345         send_start();
 346         if(alen > 0) {
 347                 if(write_byte(chip << 1)) {     /* write cycle */
 348                         send_stop();
 349                         PRINTD("i2c_read, no chip responded %02X\n", chip);
 350                         return(1);
 351                 }
 352                 shift = (alen-1) * 8;
 353                 while(alen-- > 0) {
 354                         if(write_byte(addr >> shift)) {
 355                                 PRINTD("i2c_read, address not <ACK>ed\n");
 356                                 return(1);
 357                         }
 358                         shift -= 8;
 359                 }
 360                 send_stop();    /* reportedly some chips need a full stop */
 361                 send_start();
 362         }
 363         /*
 364          * Send the chip address again, this time for a read cycle.
 365          * Then read the data.  On the last byte, we do a NACK instead
 366          * of an ACK(len == 0) to terminate the read.
 367          */
 368         write_byte((chip << 1) | 1);    /* read cycle */
 369         while(len-- > 0) {
 370                 *buffer++ = read_byte(len == 0);
 371         }
 372         send_stop();
 373         return(0);
 374 }
 375
 376 /*-----------------------------------------------------------------------
 377  * Write bytes
 378  */
 379 int  i2c_write(uchar chip, uint addr, int alen, uchar *buffer, int len)
 380 {
 381         int shift, failures = 0;
 382
 383         PRINTD("i2c_write: chip %02X addr %02X alen %d buffer %p len %d\n",
 384                 chip, addr, alen, buffer, len);
 385
 386         send_start();
 387         if(write_byte(chip << 1)) {     /* write cycle */
 388                 send_stop();
 389                 PRINTD("i2c_write, no chip responded %02X\n", chip);
 390                 return(1);
 391         }
 392         shift = (alen-1) * 8;
 393         while(alen-- > 0) {
 394                 if(write_byte(addr >> shift)) {
 395                         PRINTD("i2c_write, address not <ACK>ed\n");
 396                         return(1);
 397                 }
 398                 shift -= 8;
 399         }
 400
 401         while(len-- > 0) {
 402                 if(write_byte(*buffer++)) {
 403                         failures++;
 404                 }
 405         }
 406         send_stop();
 407         return(failures);
 408 }
 409
 410 /*-----------------------------------------------------------------------
 411  * Read a register
 412  */
 413 uchar i2c_reg_read(uchar i2c_addr, uchar reg)
 414 {
 415         uchar buf;
 416
 417         i2c_read(i2c_addr, reg, 1, &buf, 1);
 418
 419         return(buf);
 420 }
 421
 422 /*-----------------------------------------------------------------------
 423  * Write a register
 424  */
 425 void i2c_reg_write(uchar i2c_addr, uchar reg, uchar val)
 426 {
 427         i2c_write(i2c_addr, reg, 1, &val, 1);
 428 }