common/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 #include <i2c.h>
  33
  34 #if defined(CONFIG_SOFT_I2C)
  35
  36 /* #define      DEBUG_I2C       */
  37
  38
  39 /*-----------------------------------------------------------------------
  40  * Definitions
  41  */
  42
  43 #define RETRIES         0
  44
  45
  46 #define I2C_ACK         0               /* PD_SDA level to ack a byte */
  47 #define I2C_NOACK       1               /* PD_SDA level to noack a byte */
  48
  49
  50 #ifdef DEBUG_I2C
  51 #define PRINTD(fmt,args...)     do {    \
  52         DECLARE_GLOBAL_DATA_PTR;        \
  53         if (gd->have_console)           \
  54                 printf (fmt ,##args);   \
  55         } while (0)
  56 #else
  57 #define PRINTD(fmt,args...)
  58 #endif
  59
  60 /*-----------------------------------------------------------------------
  61  * Local functions
  62  */
  63 static void  send_reset (void);
  64 static void  send_start (void);
  65 static void  send_stop  (void);
  66 static void  send_ack   (int);
  67 static int   write_byte (uchar byte);
  68 static uchar read_byte  (int);
  69
  70
  71 /*-----------------------------------------------------------------------
  72  * Send a reset sequence consisting of 9 clocks with the data signal high
  73  * to clock any confused device back into an idle state.  Also send a
  74  * <stop> at the end of the sequence for belts & suspenders.
  75  */
  76 static void send_reset(void)
  77 {
  78 #ifdef  CONFIG_MPC8260
  79         volatile ioport_t *iop = ioport_addr((immap_t *)CFG_IMMR, I2C_PORT);
  80 #endif
  81 #ifdef  CONFIG_8xx
  82         volatile immap_t *immr = (immap_t *)CFG_IMMR;
  83 #endif
  84         int j;
  85
  86         I2C_SCL(1);
  87         I2C_SDA(1);
  88 #ifdef  I2C_INIT
  89         I2C_INIT;
  90 #endif
  91         I2C_TRISTATE;
  92         for(j = 0; j < 9; j++) {
  93                 I2C_SCL(0);
  94                 I2C_DELAY;
  95                 I2C_DELAY;
  96                 I2C_SCL(1);
  97                 I2C_DELAY;
  98                 I2C_DELAY;
  99         }
 100         send_stop();
 101         I2C_TRISTATE;
 102 }
 103
 104 /*-----------------------------------------------------------------------
 105  * START: High -> Low on SDA while SCL is High
 106  */
 107 static void send_start(void)
 108 {
 109 #ifdef  CONFIG_MPC8260
 110         volatile ioport_t *iop = ioport_addr((immap_t *)CFG_IMMR, I2C_PORT);
 111 #endif
 112 #ifdef  CONFIG_8xx
 113         volatile immap_t *immr = (immap_t *)CFG_IMMR;
 114 #endif
 115
 116         I2C_DELAY;
 117         I2C_SDA(1);
 118         I2C_ACTIVE;
 119         I2C_DELAY;
 120         I2C_SCL(1);
 121         I2C_DELAY;
 122         I2C_SDA(0);
 123         I2C_DELAY;
 124 }
 125
 126 /*-----------------------------------------------------------------------
 127  * STOP: Low -> High on SDA while SCL is High
 128  */
 129 static void send_stop(void)
 130 {
 131 #ifdef  CONFIG_MPC8260
 132         volatile ioport_t *iop = ioport_addr((immap_t *)CFG_IMMR, I2C_PORT);
 133 #endif
 134 #ifdef  CONFIG_8xx
 135         volatile immap_t *immr = (immap_t *)CFG_IMMR;
 136 #endif
 137
 138         I2C_SCL(0);
 139         I2C_DELAY;
 140         I2C_SDA(0);
 141         I2C_ACTIVE;
 142         I2C_DELAY;
 143         I2C_SCL(1);
 144         I2C_DELAY;
 145         I2C_SDA(1);
 146         I2C_DELAY;
 147         I2C_TRISTATE;
 148 }
 149
 150
 151 /*-----------------------------------------------------------------------
 152  * ack should be I2C_ACK or I2C_NOACK
 153  */
 154 static void send_ack(int ack)
 155 {
 156 #ifdef  CONFIG_MPC8260
 157         volatile ioport_t *iop = ioport_addr((immap_t *)CFG_IMMR, I2C_PORT);
 158 #endif
 159 #ifdef  CONFIG_8xx
 160         volatile immap_t *immr = (immap_t *)CFG_IMMR;
 161 #endif
 162
 163         I2C_ACTIVE;
 164         I2C_SCL(0);
 165         I2C_DELAY;
 166
 167         I2C_SDA(ack);
 168
 169         I2C_ACTIVE;
 170         I2C_DELAY;
 171         I2C_SCL(1);
 172         I2C_DELAY;
 173         I2C_DELAY;
 174         I2C_SCL(0);
 175         I2C_DELAY;
 176 }
 177
 178
 179 /*-----------------------------------------------------------------------
 180  * Send 8 bits and look for an acknowledgement.
 181  */
 182 static int write_byte(uchar data)
 183 {
 184 #ifdef  CONFIG_MPC8260
 185         volatile ioport_t *iop = ioport_addr((immap_t *)CFG_IMMR, I2C_PORT);
 186 #endif
 187 #ifdef  CONFIG_8xx
 188         volatile immap_t *immr = (immap_t *)CFG_IMMR;
 189 #endif
 190         int j;
 191         int nack;
 192
 193         I2C_ACTIVE;
 194         for(j = 0; j < 8; j++) {
 195                 I2C_SCL(0);
 196                 I2C_DELAY;
 197                 I2C_SDA(data & 0x80);
 198                 I2C_DELAY;
 199                 I2C_SCL(1);
 200                 I2C_DELAY;
 201                 I2C_DELAY;
 202
 203                 data <<= 1;
 204         }
 205
 206         /*
 207          * Look for an <ACK>(negative logic) and return it.
 208          */
 209         I2C_SCL(0);
 210         I2C_DELAY;
 211         I2C_SDA(1);
 212         I2C_TRISTATE;
 213         I2C_DELAY;
 214         I2C_SCL(1);
 215         I2C_DELAY;
 216         I2C_DELAY;
 217         nack = I2C_READ;
 218         I2C_SCL(0);
 219         I2C_DELAY;
 220         I2C_ACTIVE;
 221
 222         return(nack);   /* not a nack is an ack */
 223 }
 224
 225
 226 /*-----------------------------------------------------------------------
 227  * if ack == I2C_ACK, ACK the byte so can continue reading, else
 228  * send I2C_NOACK to end the read.
 229  */
 230 static uchar read_byte(int ack)
 231 {
 232 #ifdef  CONFIG_MPC8260
 233         volatile ioport_t *iop = ioport_addr((immap_t *)CFG_IMMR, I2C_PORT);
 234 #endif
 235 #ifdef  CONFIG_8xx
 236         volatile immap_t *immr = (immap_t *)CFG_IMMR;
 237 #endif
 238         int  data;
 239         int  j;
 240
 241         /*
 242          * Read 8 bits, MSB first.
 243          */
 244         I2C_TRISTATE;
 245         data = 0;
 246         for(j = 0; j < 8; j++) {
 247                 I2C_SCL(0);
 248                 I2C_DELAY;
 249                 I2C_SCL(1);
 250                 I2C_DELAY;
 251                 data <<= 1;
 252                 data |= I2C_READ;
 253                 I2C_DELAY;
 254         }
 255         send_ack(ack);
 256
 257         return(data);
 258 }
 259
 260 /*=====================================================================*/
 261 /*                         Public Functions                            */
 262 /*=====================================================================*/
 263
 264 /*-----------------------------------------------------------------------
 265  * Initialization
 266  */
 267 void i2c_init (int speed, int slaveaddr)
 268 {
 269         /*
 270          * WARNING: Do NOT save speed in a static variable: if the
 271          * I2C routines are called before RAM is initialized (to read
 272          * the DIMM SPD, for instance), RAM won't be usable and your
 273          * system will crash.
 274          */
 275         send_reset ();
 276 }
 277
 278 /*-----------------------------------------------------------------------
 279  * Probe to see if a chip is present.  Also good for checking for the
 280  * completion of EEPROM writes since the chip stops responding until
 281  * the write completes (typically 10mSec).
 282  */
 283 int i2c_probe(uchar addr)
 284 {
 285         int rc;
 286
 287         /* perform 1 byte read transaction */
 288         send_start();
 289         rc = write_byte ((addr << 1) | 0);
 290         send_stop();
 291
 292         return (rc ? 1 : 0);
 293 }
 294
 295 /*-----------------------------------------------------------------------
 296  * Read bytes
 297  */
 298 int  i2c_read(uchar chip, uint addr, int alen, uchar *buffer, int len)
 299 {
 300         int shift;
 301         PRINTD("i2c_read: chip %02X addr %02X alen %d buffer %p len %d\n",
 302                 chip, addr, alen, buffer, len);
 303
 304 #ifdef CFG_I2C_EEPROM_ADDR_OVERFLOW
 305         /*
 306          * EEPROM chips that implement "address overflow" are ones
 307          * like Catalyst 24WC04/08/16 which has 9/10/11 bits of
 308          * address and the extra bits end up in the "chip address"
 309          * bit slots. This makes a 24WC08 (1Kbyte) chip look like
 310          * four 256 byte chips.
 311          *
 312          * Note that we consider the length of the address field to
 313          * still be one byte because the extra address bits are
 314          * hidden in the chip address.
 315          */
 316         chip |= ((addr >> (alen * 8)) & CFG_I2C_EEPROM_ADDR_OVERFLOW);
 317
 318         PRINTD("i2c_read: fix addr_overflow: chip %02X addr %02X\n",
 319                 chip, addr);
 320 #endif
 321
 322         /*
 323          * Do the addressing portion of a write cycle to set the
 324          * chip's address pointer.  If the address length is zero,
 325          * don't do the normal write cycle to set the address pointer,
 326          * there is no address pointer in this chip.
 327          */
 328         send_start();
 329         if(alen > 0) {
 330                 if(write_byte(chip << 1)) {     /* write cycle */
 331                         send_stop();
 332                         PRINTD("i2c_read, no chip responded %02X\n", chip);
 333                         return(1);
 334                 }
 335                 shift = (alen-1) * 8;
 336                 while(alen-- > 0) {
 337                         if(write_byte(addr >> shift)) {
 338                                 PRINTD("i2c_read, address not <ACK>ed\n");
 339                                 return(1);
 340                         }
 341                         shift -= 8;
 342                 }
 343                 send_stop();    /* reportedly some chips need a full stop */
 344                 send_start();
 345         }
 346         /*
 347          * Send the chip address again, this time for a read cycle.
 348          * Then read the data.  On the last byte, we do a NACK instead
 349          * of an ACK(len == 0) to terminate the read.
 350          */
 351         write_byte((chip << 1) | 1);    /* read cycle */
 352         while(len-- > 0) {
 353                 *buffer++ = read_byte(len == 0);
 354         }
 355         send_stop();
 356         return(0);
 357 }
 358
 359 /*-----------------------------------------------------------------------
 360  * Write bytes
 361  */
 362 int  i2c_write(uchar chip, uint addr, int alen, uchar *buffer, int len)
 363 {
 364         int shift, failures = 0;
 365
 366         PRINTD("i2c_write: chip %02X addr %02X alen %d buffer %p len %d\n",
 367                 chip, addr, alen, buffer, len);
 368
 369         send_start();
 370         if(write_byte(chip << 1)) {     /* write cycle */
 371                 send_stop();
 372                 PRINTD("i2c_write, no chip responded %02X\n", chip);
 373                 return(1);
 374         }
 375         shift = (alen-1) * 8;
 376         while(alen-- > 0) {
 377                 if(write_byte(addr >> shift)) {
 378                         PRINTD("i2c_write, address not <ACK>ed\n");
 379                         return(1);
 380                 }
 381                 shift -= 8;
 382         }
 383
 384         while(len-- > 0) {
 385                 if(write_byte(*buffer++)) {
 386                         failures++;
 387                 }
 388         }
 389         send_stop();
 390         return(failures);
 391 }
 392
 393 /*-----------------------------------------------------------------------
 394  * Read a register
 395  */
 396 uchar i2c_reg_read(uchar i2c_addr, uchar reg)
 397 {
 398         char buf;
 399
 400         i2c_read(i2c_addr, reg, 1, &buf, 1);
 401
 402         return(buf);
 403 }
 404
 405 /*-----------------------------------------------------------------------
 406  * Write a register
 407  */
 408 void i2c_reg_write(uchar i2c_addr, uchar reg, uchar val)
 409 {
 410         i2c_write(i2c_addr, reg, 1, &val, 1);
 411 }
 412
 413
 414 #endif  /* CONFIG_SOFT_I2C */