drivers/i2c/algos/i2c-algo-bit.c

   1 /* -------------------------------------------------------------------------
   2  * i2c-algo-bit.c i2c driver algorithms for bit-shift adapters
   3  * -------------------------------------------------------------------------
   4  *   Copyright (C) 1995-2000 Simon G. Vogl
   5
   6     This program is free software; you can redistribute it and/or modify
   7     it under the terms of the GNU General Public License as published by
   8     the Free Software Foundation; either version 2 of the License, or
   9     (at your option) any later version.
  10
  11     This program is distributed in the hope that it will be useful,
  12     but WITHOUT ANY WARRANTY; without even the implied warranty of
  13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14     GNU General Public License for more details.
  15
  16     You should have received a copy of the GNU General Public License
  17     along with this program; if not, write to the Free Software
  18     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19  * ------------------------------------------------------------------------- */
  20
  21 /* With some changes from Frodo Looijaard <frodol@dds.nl>, Kyösti Mälkki
  22    <kmalkki@cc.hut.fi> and Jean Delvare <khali@linux-fr.org> */
  23
  24 #include <linux/kernel.h>
  25 #include <linux/module.h>
  26 #include <linux/delay.h>
  27 #include <linux/slab.h>
  28 #include <linux/init.h>
  29 #include <linux/errno.h>
  30 #include <linux/sched.h>
  31 #include <linux/i2c.h>
  32 #include <linux/i2c-algo-bit.h>
  33
  34
  35 /* ----- global defines ----------------------------------------------- */
  36
  37 #ifdef DEBUG
  38 #define bit_dbg(level, dev, format, args...) \
  39         do { \
  40                 if (i2c_debug >= level) \
  41                         dev_dbg(dev, format, ##args); \
  42         } while (0)
  43 #else
  44 #define bit_dbg(level, dev, format, args...) \
  45         do {} while (0)
  46 #endif /* DEBUG */
  47
  48 /* ----- global variables --------------------------------------------- */
  49
  50 static int bit_test;    /* see if the line-setting functions work       */
  51 module_param(bit_test, bool, 0);
  52 MODULE_PARM_DESC(bit_test, "Test the lines of the bus to see if it is stuck");
  53
  54 #ifdef DEBUG
  55 static int i2c_debug = 1;
  56 module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
  57 MODULE_PARM_DESC(i2c_debug,
  58                  "debug level - 0 off; 1 normal; 2 verbose; 3 very verbose");
  59 #endif
  60
  61 /* --- setting states on the bus with the right timing: --------------- */
  62
  63 #define setsda(adap, val)       adap->setsda(adap->data, val)
  64 #define setscl(adap, val)       adap->setscl(adap->data, val)
  65 #define getsda(adap)            adap->getsda(adap->data)
  66 #define getscl(adap)            adap->getscl(adap->data)
  67
  68 static inline void sdalo(struct i2c_algo_bit_data *adap)
  69 {
  70         setsda(adap, 0);
  71         udelay((adap->udelay + 1) / 2);
  72 }
  73
  74 static inline void sdahi(struct i2c_algo_bit_data *adap)
  75 {
  76         setsda(adap, 1);
  77         udelay((adap->udelay + 1) / 2);
  78 }
  79
  80 static inline void scllo(struct i2c_algo_bit_data *adap)
  81 {
  82         setscl(adap, 0);
  83         udelay(adap->udelay / 2);
  84 }
  85
  86 /*
  87  * Raise scl line, and do checking for delays. This is necessary for slower
  88  * devices.
  89  */
  90 static int sclhi(struct i2c_algo_bit_data *adap)
  91 {
  92         unsigned long start;
  93
  94         setscl(adap, 1);
  95
  96         /* Not all adapters have scl sense line... */
  97         if (!adap->getscl)
  98                 goto done;
  99
 100         start = jiffies;
 101         while (!getscl(adap)) {
 102                 /* This hw knows how to read the clock line, so we wait
 103                  * until it actually gets high.  This is safer as some
 104                  * chips may hold it low ("clock stretching") while they
 105                  * are processing data internally.
 106                  */
 107                 if (time_after(jiffies, start + adap->timeout))
 108                         return -ETIMEDOUT;
 109                 cond_resched();
 110         }
 111 #ifdef DEBUG
 112         if (jiffies != start && i2c_debug >= 3)
 113                 pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go "
 114                          "high\n", jiffies - start);
 115 #endif
 116
 117 done:
 118         udelay(adap->udelay);
 119         return 0;
 120 }
 121
 122
 123 /* --- other auxiliary functions -------------------------------------- */
 124 static void i2c_start(struct i2c_algo_bit_data *adap)
 125 {
 126         /* assert: scl, sda are high */
 127         setsda(adap, 0);
 128         udelay(adap->udelay);
 129         scllo(adap);
 130 }
 131
 132 static void i2c_repstart(struct i2c_algo_bit_data *adap)
 133 {
 134         /* assert: scl is low */
 135         sdahi(adap);
 136         sclhi(adap);
 137         setsda(adap, 0);
 138         udelay(adap->udelay);
 139         scllo(adap);
 140 }
 141
 142
 143 static void i2c_stop(struct i2c_algo_bit_data *adap)
 144 {
 145         /* assert: scl is low */
 146         sdalo(adap);
 147         sclhi(adap);
 148         setsda(adap, 1);
 149         udelay(adap->udelay);
 150 }
 151
 152
 153
 154 /* send a byte without start cond., look for arbitration,
 155    check ackn. from slave */
 156 /* returns:
 157  * 1 if the device acknowledged
 158  * 0 if the device did not ack
 159  * -ETIMEDOUT if an error occurred (while raising the scl line)
 160  */
 161 static int i2c_outb(struct i2c_adapter *i2c_adap, unsigned char c)
 162 {
 163         int i;
 164         int sb;
 165         int ack;
 166         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 167
 168         /* assert: scl is low */
 169         for (i = 7; i >= 0; i--) {
 170                 sb = (c >> i) & 1;
 171                 setsda(adap, sb);
 172                 udelay((adap->udelay + 1) / 2);
 173                 if (sclhi(adap) < 0) { /* timed out */
 174                         bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
 175                                 "timeout at bit #%d\n", (int)c, i);
 176                         return -ETIMEDOUT;
 177                 }
 178                 /* FIXME do arbitration here:
 179                  * if (sb && !getsda(adap)) -> ouch! Get out of here.
 180                  *
 181                  * Report a unique code, so higher level code can retry
 182                  * the whole (combined) message and *NOT* issue STOP.
 183                  */
 184                 scllo(adap);
 185         }
 186         sdahi(adap);
 187         if (sclhi(adap) < 0) { /* timeout */
 188                 bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
 189                         "timeout at ack\n", (int)c);
 190                 return -ETIMEDOUT;
 191         }
 192
 193         /* read ack: SDA should be pulled down by slave, or it may
 194          * NAK (usually to report problems with the data we wrote).
 195          */
 196         ack = !getsda(adap);    /* ack: sda is pulled low -> success */
 197         bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,
 198                 ack ? "A" : "NA");
 199
 200         scllo(adap);
 201         return ack;
 202         /* assert: scl is low (sda undef) */
 203 }
 204
 205
 206 static int i2c_inb(struct i2c_adapter *i2c_adap)
 207 {
 208         /* read byte via i2c port, without start/stop sequence  */
 209         /* acknowledge is sent in i2c_read.                     */
 210         int i;
 211         unsigned char indata = 0;
 212         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 213
 214         /* assert: scl is low */
 215         sdahi(adap);
 216         for (i = 0; i < 8; i++) {
 217                 if (sclhi(adap) < 0) { /* timeout */
 218                         bit_dbg(1, &i2c_adap->dev, "i2c_inb: timeout at bit "
 219                                 "#%d\n", 7 - i);
 220                         return -ETIMEDOUT;
 221                 }
 222                 indata *= 2;
 223                 if (getsda(adap))
 224                         indata |= 0x01;
 225                 setscl(adap, 0);
 226                 udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
 227         }
 228         /* assert: scl is low */
 229         return indata;
 230 }
 231
 232 /*
 233  * Sanity check for the adapter hardware - check the reaction of
 234  * the bus lines only if it seems to be idle.
 235  */
 236 static int test_bus(struct i2c_algo_bit_data *adap, char *name)
 237 {
 238         int scl, sda;
 239
 240         if (adap->getscl == NULL)
 241                 pr_info("%s: Testing SDA only, SCL is not readable\n", name);
 242
 243         sda = getsda(adap);
 244         scl = (adap->getscl == NULL) ? 1 : getscl(adap);
 245         if (!scl || !sda) {
 246                 printk(KERN_WARNING "%s: bus seems to be busy\n", name);
 247                 goto bailout;
 248         }
 249
 250         sdalo(adap);
 251         sda = getsda(adap);
 252         scl = (adap->getscl == NULL) ? 1 : getscl(adap);
 253         if (sda) {
 254                 printk(KERN_WARNING "%s: SDA stuck high!\n", name);
 255                 goto bailout;
 256         }
 257         if (!scl) {
 258                 printk(KERN_WARNING "%s: SCL unexpected low "
 259                        "while pulling SDA low!\n", name);
 260                 goto bailout;
 261         }
 262
 263         sdahi(adap);
 264         sda = getsda(adap);
 265         scl = (adap->getscl == NULL) ? 1 : getscl(adap);
 266         if (!sda) {
 267                 printk(KERN_WARNING "%s: SDA stuck low!\n", name);
 268                 goto bailout;
 269         }
 270         if (!scl) {
 271                 printk(KERN_WARNING "%s: SCL unexpected low "
 272                        "while pulling SDA high!\n", name);
 273                 goto bailout;
 274         }
 275
 276         scllo(adap);
 277         sda = getsda(adap);
 278         scl = (adap->getscl == NULL) ? 0 : getscl(adap);
 279         if (scl) {
 280                 printk(KERN_WARNING "%s: SCL stuck high!\n", name);
 281                 goto bailout;
 282         }
 283         if (!sda) {
 284                 printk(KERN_WARNING "%s: SDA unexpected low "
 285                        "while pulling SCL low!\n", name);
 286                 goto bailout;
 287         }
 288
 289         sclhi(adap);
 290         sda = getsda(adap);
 291         scl = (adap->getscl == NULL) ? 1 : getscl(adap);
 292         if (!scl) {
 293                 printk(KERN_WARNING "%s: SCL stuck low!\n", name);
 294                 goto bailout;
 295         }
 296         if (!sda) {
 297                 printk(KERN_WARNING "%s: SDA unexpected low "
 298                        "while pulling SCL high!\n", name);
 299                 goto bailout;
 300         }
 301         pr_info("%s: Test OK\n", name);
 302         return 0;
 303 bailout:
 304         sdahi(adap);
 305         sclhi(adap);
 306         return -ENODEV;
 307 }
 308
 309 /* ----- Utility functions
 310  */
 311
 312 /* try_address tries to contact a chip for a number of
 313  * times before it gives up.
 314  * return values:
 315  * 1 chip answered
 316  * 0 chip did not answer
 317  * -x transmission error
 318  */
 319 static int try_address(struct i2c_adapter *i2c_adap,
 320                        unsigned char addr, int retries)
 321 {
 322         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 323         int i, ret = 0;
 324
 325         for (i = 0; i <= retries; i++) {
 326                 ret = i2c_outb(i2c_adap, addr);
 327                 if (ret == 1 || i == retries)
 328                         break;
 329                 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
 330                 i2c_stop(adap);
 331                 udelay(adap->udelay);
 332                 yield();
 333                 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
 334                 i2c_start(adap);
 335         }
 336         if (i && ret)
 337                 bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at "
 338                         "0x%02x: %s\n", i + 1,
 339                         addr & 1 ? "read from" : "write to", addr >> 1,
 340                         ret == 1 ? "success" : "failed, timeout?");
 341         return ret;
 342 }
 343
 344 static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 345 {
 346         const unsigned char *temp = msg->buf;
 347         int count = msg->len;
 348         unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
 349         int retval;
 350         int wrcount = 0;
 351
 352         while (count > 0) {
 353                 retval = i2c_outb(i2c_adap, *temp);
 354
 355                 /* OK/ACK; or ignored NAK */
 356                 if ((retval > 0) || (nak_ok && (retval == 0))) {
 357                         count--;
 358                         temp++;
 359                         wrcount++;
 360
 361                 /* A slave NAKing the master means the slave didn't like
 362                  * something about the data it saw.  For example, maybe
 363                  * the SMBus PEC was wrong.
 364                  */
 365                 } else if (retval == 0) {
 366                         dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n");
 367                         return -EIO;
 368
 369                 /* Timeout; or (someday) lost arbitration
 370                  *
 371                  * FIXME Lost ARB implies retrying the transaction from
 372                  * the first message, after the "winning" master issues
 373                  * its STOP.  As a rule, upper layer code has no reason
 374                  * to know or care about this ... it is *NOT* an error.
 375                  */
 376                 } else {
 377                         dev_err(&i2c_adap->dev, "sendbytes: error %d\n",
 378                                         retval);
 379                         return retval;
 380                 }
 381         }
 382         return wrcount;
 383 }
 384
 385 static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
 386 {
 387         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 388
 389         /* assert: sda is high */
 390         if (is_ack)             /* send ack */
 391                 setsda(adap, 0);
 392         udelay((adap->udelay + 1) / 2);
 393         if (sclhi(adap) < 0) {  /* timeout */
 394                 dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
 395                 return -ETIMEDOUT;
 396         }
 397         scllo(adap);
 398         return 0;
 399 }
 400
 401 static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 402 {
 403         int inval;
 404         int rdcount = 0;        /* counts bytes read */
 405         unsigned char *temp = msg->buf;
 406         int count = msg->len;
 407         const unsigned flags = msg->flags;
 408
 409         while (count > 0) {
 410                 inval = i2c_inb(i2c_adap);
 411                 if (inval >= 0) {
 412                         *temp = inval;
 413                         rdcount++;
 414                 } else {   /* read timed out */
 415                         break;
 416                 }
 417
 418                 temp++;
 419                 count--;
 420
 421                 /* Some SMBus transactions require that we receive the
 422                    transaction length as the first read byte. */
 423                 if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) {
 424                         if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) {
 425                                 if (!(flags & I2C_M_NO_RD_ACK))
 426                                         acknak(i2c_adap, 0);
 427                                 dev_err(&i2c_adap->dev, "readbytes: invalid "
 428                                         "block length (%d)\n", inval);
 429                                 return -EREMOTEIO;
 430                         }
 431                         /* The original count value accounts for the extra
 432                            bytes, that is, either 1 for a regular transaction,
 433                            or 2 for a PEC transaction. */
 434                         count += inval;
 435                         msg->len += inval;
 436                 }
 437
 438                 bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",
 439                         inval,
 440                         (flags & I2C_M_NO_RD_ACK)
 441                                 ? "(no ack/nak)"
 442                                 : (count ? "A" : "NA"));
 443
 444                 if (!(flags & I2C_M_NO_RD_ACK)) {
 445                         inval = acknak(i2c_adap, count);
 446                         if (inval < 0)
 447                                 return inval;
 448                 }
 449         }
 450         return rdcount;
 451 }
 452
 453 /* doAddress initiates the transfer by generating the start condition (in
 454  * try_address) and transmits the address in the necessary format to handle
 455  * reads, writes as well as 10bit-addresses.
 456  * returns:
 457  *  0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
 458  * -x an error occurred (like: -EREMOTEIO if the device did not answer, or
 459  *      -ETIMEDOUT, for example if the lines are stuck...)
 460  */
 461 static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 462 {
 463         unsigned short flags = msg->flags;
 464         unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
 465         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 466
 467         unsigned char addr;
 468         int ret, retries;
 469
 470         retries = nak_ok ? 0 : i2c_adap->retries;
 471
 472         if (flags & I2C_M_TEN) {
 473                 /* a ten bit address */
 474                 addr = 0xf0 | ((msg->addr >> 7) & 0x03);
 475                 bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
 476                 /* try extended address code...*/
 477                 ret = try_address(i2c_adap, addr, retries);
 478                 if ((ret != 1) && !nak_ok)  {
 479                         dev_err(&i2c_adap->dev,
 480                                 "died at extended address code\n");
 481                         return -EREMOTEIO;
 482                 }
 483                 /* the remaining 8 bit address */
 484                 ret = i2c_outb(i2c_adap, msg->addr & 0x7f);
 485                 if ((ret != 1) && !nak_ok) {
 486                         /* the chip did not ack / xmission error occurred */
 487                         dev_err(&i2c_adap->dev, "died at 2nd address code\n");
 488                         return -EREMOTEIO;
 489                 }
 490                 if (flags & I2C_M_RD) {
 491                         bit_dbg(3, &i2c_adap->dev, "emitting repeated "
 492                                 "start condition\n");
 493                         i2c_repstart(adap);
 494                         /* okay, now switch into reading mode */
 495                         addr |= 0x01;
 496                         ret = try_address(i2c_adap, addr, retries);
 497                         if ((ret != 1) && !nak_ok) {
 498                                 dev_err(&i2c_adap->dev,
 499                                         "died at repeated address code\n");
 500                                 return -EREMOTEIO;
 501                         }
 502                 }
 503         } else {                /* normal 7bit address  */
 504                 addr = msg->addr << 1;
 505                 if (flags & I2C_M_RD)
 506                         addr |= 1;
 507                 if (flags & I2C_M_REV_DIR_ADDR)
 508                         addr ^= 1;
 509                 ret = try_address(i2c_adap, addr, retries);
 510                 if ((ret != 1) && !nak_ok)
 511                         return -ENXIO;
 512         }
 513
 514         return 0;
 515 }
 516
 517 static int bit_xfer(struct i2c_adapter *i2c_adap,
 518                     struct i2c_msg msgs[], int num)
 519 {
 520         struct i2c_msg *pmsg;
 521         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 522         int i, ret;
 523         unsigned short nak_ok;
 524
 525         bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
 526         i2c_start(adap);
 527         for (i = 0; i < num; i++) {
 528                 pmsg = &msgs[i];
 529                 nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;
 530                 if (!(pmsg->flags & I2C_M_NOSTART)) {
 531                         if (i) {
 532                                 bit_dbg(3, &i2c_adap->dev, "emitting "
 533                                         "repeated start condition\n");
 534                                 i2c_repstart(adap);
 535                         }
 536                         ret = bit_doAddress(i2c_adap, pmsg);
 537                         if ((ret != 0) && !nak_ok) {
 538                                 bit_dbg(1, &i2c_adap->dev, "NAK from "
 539                                         "device addr 0x%02x msg #%d\n",
 540                                         msgs[i].addr, i);
 541                                 goto bailout;
 542                         }
 543                 }
 544                 if (pmsg->flags & I2C_M_RD) {
 545                         /* read bytes into buffer*/
 546                         ret = readbytes(i2c_adap, pmsg);
 547                         if (ret >= 1)
 548                                 bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n",
 549                                         ret, ret == 1 ? "" : "s");
 550                         if (ret < pmsg->len) {
 551                                 if (ret >= 0)
 552                                         ret = -EREMOTEIO;
 553                                 goto bailout;
 554                         }
 555                 } else {
 556                         /* write bytes from buffer */
 557                         ret = sendbytes(i2c_adap, pmsg);
 558                         if (ret >= 1)
 559                                 bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n",
 560                                         ret, ret == 1 ? "" : "s");
 561                         if (ret < pmsg->len) {
 562                                 if (ret >= 0)
 563                                         ret = -EREMOTEIO;
 564                                 goto bailout;
 565                         }
 566                 }
 567         }
 568         ret = i;
 569
 570 bailout:
 571         bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
 572         i2c_stop(adap);
 573         return ret;
 574 }
 575
 576 static u32 bit_func(struct i2c_adapter *adap)
 577 {
 578         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
 579                I2C_FUNC_SMBUS_READ_BLOCK_DATA |
 580                I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
 581                I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
 582 }
 583
 584
 585 /* -----exported algorithm data: -------------------------------------  */
 586
 587 static const struct i2c_algorithm i2c_bit_algo = {
 588         .master_xfer    = bit_xfer,
 589         .functionality  = bit_func,
 590 };
 591
 592 /*
 593  * registering functions to load algorithms at runtime
 594  */
 595 static int i2c_bit_prepare_bus(struct i2c_adapter *adap)
 596 {
 597         struct i2c_algo_bit_data *bit_adap = adap->algo_data;
 598
 599         if (bit_test) {
 600                 int ret = test_bus(bit_adap, adap->name);
 601                 if (ret < 0)
 602                         return -ENODEV;
 603         }
 604
 605         /* register new adapter to i2c module... */
 606         adap->algo = &i2c_bit_algo;
 607         adap->retries = 3;
 608
 609         return 0;
 610 }
 611
 612 int i2c_bit_add_bus(struct i2c_adapter *adap)
 613 {
 614         int err;
 615
 616         err = i2c_bit_prepare_bus(adap);
 617         if (err)
 618                 return err;
 619
 620         return i2c_add_adapter(adap);
 621 }
 622 EXPORT_SYMBOL(i2c_bit_add_bus);
 623
 624 int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
 625 {
 626         int err;
 627
 628         err = i2c_bit_prepare_bus(adap);
 629         if (err)
 630                 return err;
 631
 632         return i2c_add_numbered_adapter(adap);
 633 }
 634 EXPORT_SYMBOL(i2c_bit_add_numbered_bus);
 635
 636 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
 637 MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
 638 MODULE_LICENSE("GPL");