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         /* perform 1 byte read transaction */
 291         send_start();
 292         rc = write_byte ((addr << 1) | 0);
 293         send_stop();
 294
 295         return (rc ? 1 : 0);
 296 }
 297
 298 /*-----------------------------------------------------------------------
 299  * Read bytes
 300  */
 301 int  i2c_read(uchar chip, uint addr, int alen, uchar *buffer, int len)
 302 {
 303         int shift;
 304         PRINTD("i2c_read: chip %02X addr %02X alen %d buffer %p len %d\n",
 305                 chip, addr, alen, buffer, len);
 306
 307 #ifdef CFG_I2C_EEPROM_ADDR_OVERFLOW
 308         /*
 309          * EEPROM chips that implement "address overflow" are ones
 310          * like Catalyst 24WC04/08/16 which has 9/10/11 bits of
 311          * address and the extra bits end up in the "chip address"
 312          * bit slots. This makes a 24WC08 (1Kbyte) chip look like
 313          * four 256 byte chips.
 314          *
 315          * Note that we consider the length of the address field to
 316          * still be one byte because the extra address bits are
 317          * hidden in the chip address.
 318          */
 319         chip |= ((addr >> (alen * 8)) & CFG_I2C_EEPROM_ADDR_OVERFLOW);
 320
 321         PRINTD("i2c_read: fix addr_overflow: chip %02X addr %02X\n",
 322                 chip, addr);
 323 #endif
 324
 325         /*
 326          * Do the addressing portion of a write cycle to set the
 327          * chip's address pointer.  If the address length is zero,
 328          * don't do the normal write cycle to set the address pointer,
 329          * there is no address pointer in this chip.
 330          */
 331         send_start();
 332         if(alen > 0) {
 333                 if(write_byte(chip << 1)) {     /* write cycle */
 334                         send_stop();
 335                         PRINTD("i2c_read, no chip responded %02X\n", chip);
 336                         return(1);
 337                 }
 338                 shift = (alen-1) * 8;
 339                 while(alen-- > 0) {
 340                         if(write_byte(addr >> shift)) {
 341                                 PRINTD("i2c_read, address not <ACK>ed\n");
 342                                 return(1);
 343                         }
 344                         shift -= 8;
 345                 }
 346                 send_stop();    /* reportedly some chips need a full stop */
 347                 send_start();
 348         }
 349         /*
 350          * Send the chip address again, this time for a read cycle.
 351          * Then read the data.  On the last byte, we do a NACK instead
 352          * of an ACK(len == 0) to terminate the read.
 353          */
 354         write_byte((chip << 1) | 1);    /* read cycle */
 355         while(len-- > 0) {
 356                 *buffer++ = read_byte(len == 0);
 357         }
 358         send_stop();
 359         return(0);
 360 }
 361
 362 /*-----------------------------------------------------------------------
 363  * Write bytes
 364  */
 365 int  i2c_write(uchar chip, uint addr, int alen, uchar *buffer, int len)
 366 {
 367         int shift, failures = 0;
 368
 369         PRINTD("i2c_write: chip %02X addr %02X alen %d buffer %p len %d\n",
 370                 chip, addr, alen, buffer, len);
 371
 372         send_start();
 373         if(write_byte(chip << 1)) {     /* write cycle */
 374                 send_stop();
 375                 PRINTD("i2c_write, no chip responded %02X\n", chip);
 376                 return(1);
 377         }
 378         shift = (alen-1) * 8;
 379         while(alen-- > 0) {
 380                 if(write_byte(addr >> shift)) {
 381                         PRINTD("i2c_write, address not <ACK>ed\n");
 382                         return(1);
 383                 }
 384                 shift -= 8;
 385         }
 386
 387         while(len-- > 0) {
 388                 if(write_byte(*buffer++)) {
 389                         failures++;
 390                 }
 391         }
 392         send_stop();
 393         return(failures);
 394 }
 395
 396 /*-----------------------------------------------------------------------
 397  * Read a register
 398  */
 399 uchar i2c_reg_read(uchar i2c_addr, uchar reg)
 400 {
 401         char buf;
 402
 403         i2c_read(i2c_addr, reg, 1, &buf, 1);
 404
 405         return(buf);
 406 }
 407
 408 /*-----------------------------------------------------------------------
 409  * Write a register
 410  */
 411 void i2c_reg_write(uchar i2c_addr, uchar reg, uchar val)
 412 {
 413         i2c_write(i2c_addr, reg, 1, &val, 1);
 414 }
 415
 416
 417 #endif  /* CONFIG_SOFT_I2C */