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_eq(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 = -1;
 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                 } else { /* arbitration or no acknowledge */
 361                         dev_err(&i2c_adap->dev, "sendbytes: error - bailout.\n");
 362                         return (retval<0)? retval : -EFAULT;
 363                                 /* got a better one ?? */
 364                 }
 365         }
 366         return wrcount;
 367 }
 368
 369 static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
 370 {
 371         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 372
 373         /* assert: sda is high */
 374         if (is_ack)             /* send ack */
 375                 setsda(adap, 0);
 376         udelay((adap->udelay + 1) / 2);
 377         if (sclhi(adap) < 0) {  /* timeout */
 378                 dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
 379                 return -ETIMEDOUT;
 380         }
 381         scllo(adap);
 382         return 0;
 383 }
 384
 385 static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 386 {
 387         int inval;
 388         int rdcount = 0;        /* counts bytes read */
 389         unsigned char *temp = msg->buf;
 390         int count = msg->len;
 391         const unsigned flags = msg->flags;
 392
 393         while (count > 0) {
 394                 inval = i2c_inb(i2c_adap);
 395                 if (inval >= 0) {
 396                         *temp = inval;
 397                         rdcount++;
 398                 } else {   /* read timed out */
 399                         break;
 400                 }
 401
 402                 temp++;
 403                 count--;
 404
 405                 /* Some SMBus transactions require that we receive the
 406                    transaction length as the first read byte. */
 407                 if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) {
 408                         if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) {
 409                                 if (!(flags & I2C_M_NO_RD_ACK))
 410                                         acknak(i2c_adap, 0);
 411                                 dev_err(&i2c_adap->dev, "readbytes: invalid "
 412                                         "block length (%d)\n", inval);
 413                                 return -EREMOTEIO;
 414                         }
 415                         /* The original count value accounts for the extra
 416                            bytes, that is, either 1 for a regular transaction,
 417                            or 2 for a PEC transaction. */
 418                         count += inval;
 419                         msg->len += inval;
 420                 }
 421
 422                 bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",
 423                         inval,
 424                         (flags & I2C_M_NO_RD_ACK)
 425                                 ? "(no ack/nak)"
 426                                 : (count ? "A" : "NA"));
 427
 428                 if (!(flags & I2C_M_NO_RD_ACK)) {
 429                         inval = acknak(i2c_adap, count);
 430                         if (inval < 0)
 431                                 return inval;
 432                 }
 433         }
 434         return rdcount;
 435 }
 436
 437 /* doAddress initiates the transfer by generating the start condition (in
 438  * try_address) and transmits the address in the necessary format to handle
 439  * reads, writes as well as 10bit-addresses.
 440  * returns:
 441  *  0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
 442  * -x an error occurred (like: -EREMOTEIO if the device did not answer, or
 443  *      -ETIMEDOUT, for example if the lines are stuck...)
 444  */
 445 static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 446 {
 447         unsigned short flags = msg->flags;
 448         unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
 449         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 450
 451         unsigned char addr;
 452         int ret, retries;
 453
 454         retries = nak_ok ? 0 : i2c_adap->retries;
 455
 456         if (flags & I2C_M_TEN) {
 457                 /* a ten bit address */
 458                 addr = 0xf0 | ((msg->addr >> 7) & 0x03);
 459                 bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
 460                 /* try extended address code...*/
 461                 ret = try_address(i2c_adap, addr, retries);
 462                 if ((ret != 1) && !nak_ok)  {
 463                         dev_err(&i2c_adap->dev,
 464                                 "died at extended address code\n");
 465                         return -EREMOTEIO;
 466                 }
 467                 /* the remaining 8 bit address */
 468                 ret = i2c_outb(i2c_adap, msg->addr & 0x7f);
 469                 if ((ret != 1) && !nak_ok) {
 470                         /* the chip did not ack / xmission error occurred */
 471                         dev_err(&i2c_adap->dev, "died at 2nd address code\n");
 472                         return -EREMOTEIO;
 473                 }
 474                 if (flags & I2C_M_RD) {
 475                         bit_dbg(3, &i2c_adap->dev, "emitting repeated "
 476                                 "start condition\n");
 477                         i2c_repstart(adap);
 478                         /* okay, now switch into reading mode */
 479                         addr |= 0x01;
 480                         ret = try_address(i2c_adap, addr, retries);
 481                         if ((ret != 1) && !nak_ok) {
 482                                 dev_err(&i2c_adap->dev,
 483                                         "died at repeated address code\n");
 484                                 return -EREMOTEIO;
 485                         }
 486                 }
 487         } else {                /* normal 7bit address  */
 488                 addr = msg->addr << 1;
 489                 if (flags & I2C_M_RD)
 490                         addr |= 1;
 491                 if (flags & I2C_M_REV_DIR_ADDR)
 492                         addr ^= 1;
 493                 ret = try_address(i2c_adap, addr, retries);
 494                 if ((ret != 1) && !nak_ok)
 495                         return -EREMOTEIO;
 496         }
 497
 498         return 0;
 499 }
 500
 501 static int bit_xfer(struct i2c_adapter *i2c_adap,
 502                     struct i2c_msg msgs[], int num)
 503 {
 504         struct i2c_msg *pmsg;
 505         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 506         int i, ret;
 507         unsigned short nak_ok;
 508
 509         bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
 510         i2c_start(adap);
 511         for (i = 0; i < num; i++) {
 512                 pmsg = &msgs[i];
 513                 nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;
 514                 if (!(pmsg->flags & I2C_M_NOSTART)) {
 515                         if (i) {
 516                                 bit_dbg(3, &i2c_adap->dev, "emitting "
 517                                         "repeated start condition\n");
 518                                 i2c_repstart(adap);
 519                         }
 520                         ret = bit_doAddress(i2c_adap, pmsg);
 521                         if ((ret != 0) && !nak_ok) {
 522                                 bit_dbg(1, &i2c_adap->dev, "NAK from "
 523                                         "device addr 0x%02x msg #%d\n",
 524                                         msgs[i].addr, i);
 525                                 goto bailout;
 526                         }
 527                 }
 528                 if (pmsg->flags & I2C_M_RD) {
 529                         /* read bytes into buffer*/
 530                         ret = readbytes(i2c_adap, pmsg);
 531                         if (ret >= 1)
 532                                 bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n",
 533                                         ret, ret == 1 ? "" : "s");
 534                         if (ret < pmsg->len) {
 535                                 if (ret >= 0)
 536                                         ret = -EREMOTEIO;
 537                                 goto bailout;
 538                         }
 539                 } else {
 540                         /* write bytes from buffer */
 541                         ret = sendbytes(i2c_adap, pmsg);
 542                         if (ret >= 1)
 543                                 bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n",
 544                                         ret, ret == 1 ? "" : "s");
 545                         if (ret < pmsg->len) {
 546                                 if (ret >= 0)
 547                                         ret = -EREMOTEIO;
 548                                 goto bailout;
 549                         }
 550                 }
 551         }
 552         ret = i;
 553
 554 bailout:
 555         bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
 556         i2c_stop(adap);
 557         return ret;
 558 }
 559
 560 static u32 bit_func(struct i2c_adapter *adap)
 561 {
 562         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
 563                I2C_FUNC_SMBUS_READ_BLOCK_DATA |
 564                I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
 565                I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
 566 }
 567
 568
 569 /* -----exported algorithm data: -------------------------------------  */
 570
 571 static const struct i2c_algorithm i2c_bit_algo = {
 572         .master_xfer    = bit_xfer,
 573         .functionality  = bit_func,
 574 };
 575
 576 /*
 577  * registering functions to load algorithms at runtime
 578  */
 579 static int i2c_bit_prepare_bus(struct i2c_adapter *adap)
 580 {
 581         struct i2c_algo_bit_data *bit_adap = adap->algo_data;
 582
 583         if (bit_test) {
 584                 int ret = test_bus(bit_adap, adap->name);
 585                 if (ret < 0)
 586                         return -ENODEV;
 587         }
 588
 589         /* register new adapter to i2c module... */
 590         adap->algo = &i2c_bit_algo;
 591
 592         adap->timeout = 100;    /* default values, should       */
 593         adap->retries = 3;      /* be replaced by defines       */
 594
 595         return 0;
 596 }
 597
 598 int i2c_bit_add_bus(struct i2c_adapter *adap)
 599 {
 600         int err;
 601
 602         err = i2c_bit_prepare_bus(adap);
 603         if (err)
 604                 return err;
 605
 606         return i2c_add_adapter(adap);
 607 }
 608 EXPORT_SYMBOL(i2c_bit_add_bus);
 609
 610 int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
 611 {
 612         int err;
 613
 614         err = i2c_bit_prepare_bus(adap);
 615         if (err)
 616                 return err;
 617
 618         return i2c_add_numbered_adapter(adap);
 619 }
 620 EXPORT_SYMBOL(i2c_bit_add_numbered_bus);
 621
 622 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
 623 MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
 624 MODULE_LICENSE("GPL");