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_ACTIVE;
  87         I2C_SDA(1);
  88         for(j = 0; j < 9; j++) {
  89                 I2C_SCL(0);
  90                 I2C_DELAY;
  91                 I2C_DELAY;
  92                 I2C_SCL(1);
  93                 I2C_DELAY;
  94                 I2C_DELAY;
  95         }
  96         send_stop();
  97         I2C_TRISTATE;
  98 }
  99
 100 /*-----------------------------------------------------------------------
 101  * START: High -> Low on SDA while SCL is High
 102  */
 103 static void send_start(void)
 104 {
 105 #ifdef  CONFIG_MPC8260
 106         volatile ioport_t *iop = ioport_addr((immap_t *)CFG_IMMR, I2C_PORT);
 107 #endif
 108 #ifdef  CONFIG_8xx
 109         volatile immap_t *immr = (immap_t *)CFG_IMMR;
 110 #endif
 111
 112         I2C_DELAY;
 113         I2C_SDA(1);
 114         I2C_ACTIVE;
 115         I2C_DELAY;
 116         I2C_SCL(1);
 117         I2C_DELAY;
 118         I2C_SDA(0);
 119         I2C_DELAY;
 120 }
 121
 122 /*-----------------------------------------------------------------------
 123  * STOP: Low -> High on SDA while SCL is High
 124  */
 125 static void send_stop(void)
 126 {
 127 #ifdef  CONFIG_MPC8260
 128         volatile ioport_t *iop = ioport_addr((immap_t *)CFG_IMMR, I2C_PORT);
 129 #endif
 130 #ifdef  CONFIG_8xx
 131         volatile immap_t *immr = (immap_t *)CFG_IMMR;
 132 #endif
 133
 134         I2C_SCL(0);
 135         I2C_DELAY;
 136         I2C_SDA(0);
 137         I2C_ACTIVE;
 138         I2C_DELAY;
 139         I2C_SCL(1);
 140         I2C_DELAY;
 141         I2C_SDA(1);
 142         I2C_DELAY;
 143         I2C_TRISTATE;
 144 }
 145
 146
 147 /*-----------------------------------------------------------------------
 148  * ack should be I2C_ACK or I2C_NOACK
 149  */
 150 static void send_ack(int ack)
 151 {
 152 #ifdef  CONFIG_MPC8260
 153         volatile ioport_t *iop = ioport_addr((immap_t *)CFG_IMMR, I2C_PORT);
 154 #endif
 155 #ifdef  CONFIG_8xx
 156         volatile immap_t *immr = (immap_t *)CFG_IMMR;
 157 #endif
 158
 159         I2C_ACTIVE;
 160         I2C_SCL(0);
 161         I2C_DELAY;
 162
 163         I2C_SDA(ack);
 164
 165         I2C_ACTIVE;
 166         I2C_DELAY;
 167         I2C_SCL(1);
 168         I2C_DELAY;
 169         I2C_DELAY;
 170         I2C_SCL(0);
 171         I2C_DELAY;
 172 }
 173
 174
 175 /*-----------------------------------------------------------------------
 176  * Send 8 bits and look for an acknowledgement.
 177  */
 178 static int write_byte(uchar data)
 179 {
 180 #ifdef  CONFIG_MPC8260
 181         volatile ioport_t *iop = ioport_addr((immap_t *)CFG_IMMR, I2C_PORT);
 182 #endif
 183 #ifdef  CONFIG_8xx
 184         volatile immap_t *immr = (immap_t *)CFG_IMMR;
 185 #endif
 186         int j;
 187         int nack;
 188
 189         I2C_ACTIVE;
 190         for(j = 0; j < 8; j++) {
 191                 I2C_SCL(0);
 192                 I2C_DELAY;
 193                 I2C_SDA(data & 0x80);
 194                 I2C_DELAY;
 195                 I2C_SCL(1);
 196                 I2C_DELAY;
 197                 I2C_DELAY;
 198
 199                 data <<= 1;
 200         }
 201
 202         /*
 203          * Look for an <ACK>(negative logic) and return it.
 204          */
 205         I2C_SCL(0);
 206         I2C_DELAY;
 207         I2C_SDA(1);
 208         I2C_TRISTATE;
 209         I2C_DELAY;
 210         I2C_SCL(1);
 211         I2C_DELAY;
 212         I2C_DELAY;
 213         nack = I2C_READ;
 214         I2C_SCL(0);
 215         I2C_DELAY;
 216         I2C_ACTIVE;
 217
 218         return(nack);   /* not a nack is an ack */
 219 }
 220
 221
 222 /*-----------------------------------------------------------------------
 223  * if ack == I2C_ACK, ACK the byte so can continue reading, else
 224  * send I2C_NOACK to end the read.
 225  */
 226 static uchar read_byte(int ack)
 227 {
 228 #ifdef  CONFIG_MPC8260
 229         volatile ioport_t *iop = ioport_addr((immap_t *)CFG_IMMR, I2C_PORT);
 230 #endif
 231 #ifdef  CONFIG_8xx
 232         volatile immap_t *immr = (immap_t *)CFG_IMMR;
 233 #endif
 234         int  data;
 235         int  j;
 236
 237         /*
 238          * Read 8 bits, MSB first.
 239          */
 240         I2C_TRISTATE;
 241         data = 0;
 242         for(j = 0; j < 8; j++) {
 243                 I2C_SCL(0);
 244                 I2C_DELAY;
 245                 I2C_SCL(1);
 246                 I2C_DELAY;
 247                 data <<= 1;
 248                 data |= I2C_READ;
 249                 I2C_DELAY;
 250         }
 251         send_ack(ack);
 252
 253         return(data);
 254 }
 255
 256 /*=====================================================================*/
 257 /*                         Public Functions                            */
 258 /*=====================================================================*/
 259
 260 /*-----------------------------------------------------------------------
 261  * Initialization
 262  */
 263 void i2c_init (int speed, int slaveaddr)
 264 {
 265 #ifdef  CONFIG_8xx
 266         volatile immap_t *immr = (immap_t *)CFG_IMMR;
 267 #endif
 268
 269 #ifdef  I2C_INIT
 270         I2C_INIT;
 271 #endif
 272         /*
 273          * WARNING: Do NOT save speed in a static variable: if the
 274          * I2C routines are called before RAM is initialized (to read
 275          * the DIMM SPD, for instance), RAM won't be usable and your
 276          * system will crash.
 277          */
 278         send_reset ();
 279 }
 280
 281 /*-----------------------------------------------------------------------
 282  * Probe to see if a chip is present.  Also good for checking for the
 283  * completion of EEPROM writes since the chip stops responding until
 284  * the write completes (typically 10mSec).
 285  */
 286 int i2c_probe(uchar addr)
 287 {
 288         int rc;
 289
 290         send_start();
 291         rc = write_byte ((addr << 1) | 1);
 292         send_stop();
 293
 294         return (rc ? 1 : 0);
 295 }
 296
 297 /*-----------------------------------------------------------------------
 298  * Read bytes
 299  */
 300 int  i2c_read(uchar chip, uint addr, int alen, uchar *buffer, int len)
 301 {
 302         int shift;
 303         PRINTD("i2c_read: chip %02X addr %02X alen %d buffer %p len %d\n",
 304                 chip, addr, alen, buffer, len);
 305
 306 #ifdef CFG_I2C_EEPROM_ADDR_OVERFLOW
 307         /*
 308          * EEPROM chips that implement "address overflow" are ones
 309          * like Catalyst 24WC04/08/16 which has 9/10/11 bits of
 310          * address and the extra bits end up in the "chip address"
 311          * bit slots. This makes a 24WC08 (1Kbyte) chip look like
 312          * four 256 byte chips.
 313          *
 314          * Note that we consider the length of the address field to
 315          * still be one byte because the extra address bits are
 316          * hidden in the chip address.
 317          */
 318         chip |= ((addr >> (alen * 8)) & CFG_I2C_EEPROM_ADDR_OVERFLOW);
 319
 320         PRINTD("i2c_read: fix addr_overflow: chip %02X addr %02X\n",
 321                 chip, addr);
 322 #endif
 323
 324         /*
 325          * Do the addressing portion of a write cycle to set the
 326          * chip's address pointer.  If the address length is zero,
 327          * don't do the normal write cycle to set the address pointer,
 328          * there is no address pointer in this chip.
 329          */
 330         send_start();
 331         if(alen > 0) {
 332                 if(write_byte(chip << 1)) {     /* write cycle */
 333                         send_stop();
 334                         PRINTD("i2c_read, no chip responded %02X\n", chip);
 335                         return(1);
 336                 }
 337                 shift = (alen-1) * 8;
 338                 while(alen-- > 0) {
 339                         if(write_byte(addr >> shift)) {
 340                                 PRINTD("i2c_read, address not <ACK>ed\n");
 341                                 return(1);
 342                         }
 343                         shift -= 8;
 344                 }
 345                 send_stop();    /* reportedly some chips need a full stop */
 346                 send_start();
 347         }
 348         /*
 349          * Send the chip address again, this time for a read cycle.
 350          * Then read the data.  On the last byte, we do a NACK instead
 351          * of an ACK(len == 0) to terminate the read.
 352          */
 353         write_byte((chip << 1) | 1);    /* read cycle */
 354         while(len-- > 0) {
 355                 *buffer++ = read_byte(len == 0);
 356         }
 357         send_stop();
 358         return(0);
 359 }
 360
 361 /*-----------------------------------------------------------------------
 362  * Write bytes
 363  */
 364 int  i2c_write(uchar chip, uint addr, int alen, uchar *buffer, int len)
 365 {
 366         int shift, failures = 0;
 367
 368         PRINTD("i2c_write: chip %02X addr %02X alen %d buffer %p len %d\n",
 369                 chip, addr, alen, buffer, len);
 370
 371         send_start();
 372         if(write_byte(chip << 1)) {     /* write cycle */
 373                 send_stop();
 374                 PRINTD("i2c_write, no chip responded %02X\n", chip);
 375                 return(1);
 376         }
 377         shift = (alen-1) * 8;
 378         while(alen-- > 0) {
 379                 if(write_byte(addr >> shift)) {
 380                         PRINTD("i2c_write, address not <ACK>ed\n");
 381                         return(1);
 382                 }
 383                 shift -= 8;
 384         }
 385
 386         while(len-- > 0) {
 387                 if(write_byte(*buffer++)) {
 388                         failures++;
 389                 }
 390         }
 391         send_stop();
 392         return(failures);
 393 }
 394
 395 /*-----------------------------------------------------------------------
 396  * Read a register
 397  */
 398 uchar i2c_reg_read(uchar i2c_addr, uchar reg)
 399 {
 400         char buf;
 401
 402         i2c_read(i2c_addr, reg, 1, &buf, 1);
 403
 404         return(buf);
 405 }
 406
 407 /*-----------------------------------------------------------------------
 408  * Write a register
 409  */
 410 void i2c_reg_write(uchar i2c_addr, uchar reg, uchar val)
 411 {
 412         i2c_write(i2c_addr, reg, 1, &val, 1);
 413 }
 414
 415
 416 #endif  /* CONFIG_SOFT_I2C */