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/init.h>
  28 #include <linux/errno.h>
  29 #include <linux/sched.h>
  30 #include <linux/i2c.h>
  31 #include <linux/i2c-algo-bit.h>
  32
  33
  34 /* ----- global defines ----------------------------------------------- */
  35
  36 #ifdef DEBUG
  37 #define bit_dbg(level, dev, format, args...) \
  38         do { \
  39                 if (i2c_debug >= level) \
  40                         dev_dbg(dev, format, ##args); \
  41         } while (0)
  42 #else
  43 #define bit_dbg(level, dev, format, args...) \
  44         do {} while (0)
  45 #endif /* DEBUG */
  46
  47 /* ----- global variables --------------------------------------------- */
  48
  49 static int bit_test;    /* see if the line-setting functions work       */
  50 module_param(bit_test, bool, 0);
  51 MODULE_PARM_DESC(bit_test, "Test the lines of the bus to see if it is stuck");
  52
  53 #ifdef DEBUG
  54 static int i2c_debug = 1;
  55 module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
  56 MODULE_PARM_DESC(i2c_debug,
  57                  "debug level - 0 off; 1 normal; 2 verbose; 3 very verbose");
  58 #endif
  59
  60 /* --- setting states on the bus with the right timing: --------------- */
  61
  62 #define setsda(adap, val)       adap->setsda(adap->data, val)
  63 #define setscl(adap, val)       adap->setscl(adap->data, val)
  64 #define getsda(adap)            adap->getsda(adap->data)
  65 #define getscl(adap)            adap->getscl(adap->data)
  66
  67 static inline void sdalo(struct i2c_algo_bit_data *adap)
  68 {
  69         setsda(adap, 0);
  70         udelay((adap->udelay + 1) / 2);
  71 }
  72
  73 static inline void sdahi(struct i2c_algo_bit_data *adap)
  74 {
  75         setsda(adap, 1);
  76         udelay((adap->udelay + 1) / 2);
  77 }
  78
  79 static inline void scllo(struct i2c_algo_bit_data *adap)
  80 {
  81         setscl(adap, 0);
  82         udelay(adap->udelay / 2);
  83 }
  84
  85 /*
  86  * Raise scl line, and do checking for delays. This is necessary for slower
  87  * devices.
  88  */
  89 static int sclhi(struct i2c_algo_bit_data *adap)
  90 {
  91         unsigned long start;
  92
  93         setscl(adap, 1);
  94
  95         /* Not all adapters have scl sense line... */
  96         if (!adap->getscl)
  97                 goto done;
  98
  99         start = jiffies;
 100         while (!getscl(adap)) {
 101                 /* This hw knows how to read the clock line, so we wait
 102                  * until it actually gets high.  This is safer as some
 103                  * chips may hold it low ("clock stretching") while they
 104                  * are processing data internally.
 105                  */
 106                 if (time_after(jiffies, start + adap->timeout))
 107                         return -ETIMEDOUT;
 108                 cond_resched();
 109         }
 110 #ifdef DEBUG
 111         if (jiffies != start && i2c_debug >= 3)
 112                 pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go "
 113                          "high\n", jiffies - start);
 114 #endif
 115
 116 done:
 117         udelay(adap->udelay);
 118         return 0;
 119 }
 120
 121
 122 /* --- other auxiliary functions -------------------------------------- */
 123 static void i2c_start(struct i2c_algo_bit_data *adap)
 124 {
 125         /* assert: scl, sda are high */
 126         setsda(adap, 0);
 127         udelay(adap->udelay);
 128         scllo(adap);
 129 }
 130
 131 static void i2c_repstart(struct i2c_algo_bit_data *adap)
 132 {
 133         /* assert: scl is low */
 134         sdahi(adap);
 135         sclhi(adap);
 136         setsda(adap, 0);
 137         udelay(adap->udelay);
 138         scllo(adap);
 139 }
 140
 141
 142 static void i2c_stop(struct i2c_algo_bit_data *adap)
 143 {
 144         /* assert: scl is low */
 145         sdalo(adap);
 146         sclhi(adap);
 147         setsda(adap, 1);
 148         udelay(adap->udelay);
 149 }
 150
 151
 152
 153 /* send a byte without start cond., look for arbitration,
 154    check ackn. from slave */
 155 /* returns:
 156  * 1 if the device acknowledged
 157  * 0 if the device did not ack
 158  * -ETIMEDOUT if an error occurred (while raising the scl line)
 159  */
 160 static int i2c_outb(struct i2c_adapter *i2c_adap, unsigned char c)
 161 {
 162         int i;
 163         int sb;
 164         int ack;
 165         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 166
 167         /* assert: scl is low */
 168         for (i = 7; i >= 0; i--) {
 169                 sb = (c >> i) & 1;
 170                 setsda(adap, sb);
 171                 udelay((adap->udelay + 1) / 2);
 172                 if (sclhi(adap) < 0) { /* timed out */
 173                         bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
 174                                 "timeout at bit #%d\n", (int)c, i);
 175                         return -ETIMEDOUT;
 176                 }
 177                 /* FIXME do arbitration here:
 178                  * if (sb && !getsda(adap)) -> ouch! Get out of here.
 179                  *
 180                  * Report a unique code, so higher level code can retry
 181                  * the whole (combined) message and *NOT* issue STOP.
 182                  */
 183                 scllo(adap);
 184         }
 185         sdahi(adap);
 186         if (sclhi(adap) < 0) { /* timeout */
 187                 bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
 188                         "timeout at ack\n", (int)c);
 189                 return -ETIMEDOUT;
 190         }
 191
 192         /* read ack: SDA should be pulled down by slave, or it may
 193          * NAK (usually to report problems with the data we wrote).
 194          */
 195         ack = !getsda(adap);    /* ack: sda is pulled low -> success */
 196         bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,
 197                 ack ? "A" : "NA");
 198
 199         scllo(adap);
 200         return ack;
 201         /* assert: scl is low (sda undef) */
 202 }
 203
 204
 205 static int i2c_inb(struct i2c_adapter *i2c_adap)
 206 {
 207         /* read byte via i2c port, without start/stop sequence  */
 208         /* acknowledge is sent in i2c_read.                     */
 209         int i;
 210         unsigned char indata = 0;
 211         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 212
 213         /* assert: scl is low */
 214         sdahi(adap);
 215         for (i = 0; i < 8; i++) {
 216                 if (sclhi(adap) < 0) { /* timeout */
 217                         bit_dbg(1, &i2c_adap->dev, "i2c_inb: timeout at bit "
 218                                 "#%d\n", 7 - i);
 219                         return -ETIMEDOUT;
 220                 }
 221                 indata *= 2;
 222                 if (getsda(adap))
 223                         indata |= 0x01;
 224                 setscl(adap, 0);
 225                 udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
 226         }
 227         /* assert: scl is low */
 228         return indata;
 229 }
 230
 231 /*
 232  * Sanity check for the adapter hardware - check the reaction of
 233  * the bus lines only if it seems to be idle.
 234  */
 235 static int test_bus(struct i2c_algo_bit_data *adap, char *name)
 236 {
 237         int scl, sda;
 238
 239         if (adap->getscl == NULL)
 240                 pr_info("%s: Testing SDA only, SCL is not readable\n", name);
 241
 242         sda = getsda(adap);
 243         scl = (adap->getscl == NULL) ? 1 : getscl(adap);
 244         if (!scl || !sda) {
 245                 printk(KERN_WARNING "%s: bus seems to be busy\n", name);
 246                 goto bailout;
 247         }
 248
 249         sdalo(adap);
 250         sda = getsda(adap);
 251         scl = (adap->getscl == NULL) ? 1 : getscl(adap);
 252         if (sda) {
 253                 printk(KERN_WARNING "%s: SDA stuck high!\n", name);
 254                 goto bailout;
 255         }
 256         if (!scl) {
 257                 printk(KERN_WARNING "%s: SCL unexpected low "
 258                        "while pulling SDA low!\n", name);
 259                 goto bailout;
 260         }
 261
 262         sdahi(adap);
 263         sda = getsda(adap);
 264         scl = (adap->getscl == NULL) ? 1 : getscl(adap);
 265         if (!sda) {
 266                 printk(KERN_WARNING "%s: SDA stuck low!\n", name);
 267                 goto bailout;
 268         }
 269         if (!scl) {
 270                 printk(KERN_WARNING "%s: SCL unexpected low "
 271                        "while pulling SDA high!\n", name);
 272                 goto bailout;
 273         }
 274
 275         scllo(adap);
 276         sda = getsda(adap);
 277         scl = (adap->getscl == NULL) ? 0 : getscl(adap);
 278         if (scl) {
 279                 printk(KERN_WARNING "%s: SCL stuck high!\n", name);
 280                 goto bailout;
 281         }
 282         if (!sda) {
 283                 printk(KERN_WARNING "%s: SDA unexpected low "
 284                        "while pulling SCL low!\n", name);
 285                 goto bailout;
 286         }
 287
 288         sclhi(adap);
 289         sda = getsda(adap);
 290         scl = (adap->getscl == NULL) ? 1 : getscl(adap);
 291         if (!scl) {
 292                 printk(KERN_WARNING "%s: SCL stuck low!\n", name);
 293                 goto bailout;
 294         }
 295         if (!sda) {
 296                 printk(KERN_WARNING "%s: SDA unexpected low "
 297                        "while pulling SCL high!\n", name);
 298                 goto bailout;
 299         }
 300         pr_info("%s: Test OK\n", name);
 301         return 0;
 302 bailout:
 303         sdahi(adap);
 304         sclhi(adap);
 305         return -ENODEV;
 306 }
 307
 308 /* ----- Utility functions
 309  */
 310
 311 /* try_address tries to contact a chip for a number of
 312  * times before it gives up.
 313  * return values:
 314  * 1 chip answered
 315  * 0 chip did not answer
 316  * -x transmission error
 317  */
 318 static int try_address(struct i2c_adapter *i2c_adap,
 319                        unsigned char addr, int retries)
 320 {
 321         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 322         int i, ret = 0;
 323
 324         for (i = 0; i <= retries; i++) {
 325                 ret = i2c_outb(i2c_adap, addr);
 326                 if (ret == 1 || i == retries)
 327                         break;
 328                 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
 329                 i2c_stop(adap);
 330                 udelay(adap->udelay);
 331                 yield();
 332                 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
 333                 i2c_start(adap);
 334         }
 335         if (i && ret)
 336                 bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at "
 337                         "0x%02x: %s\n", i + 1,
 338                         addr & 1 ? "read from" : "write to", addr >> 1,
 339                         ret == 1 ? "success" : "failed, timeout?");
 340         return ret;
 341 }
 342
 343 static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 344 {
 345         const unsigned char *temp = msg->buf;
 346         int count = msg->len;
 347         unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
 348         int retval;
 349         int wrcount = 0;
 350
 351         while (count > 0) {
 352                 retval = i2c_outb(i2c_adap, *temp);
 353
 354                 /* OK/ACK; or ignored NAK */
 355                 if ((retval > 0) || (nak_ok && (retval == 0))) {
 356                         count--;
 357                         temp++;
 358                         wrcount++;
 359
 360                 /* A slave NAKing the master means the slave didn't like
 361                  * something about the data it saw.  For example, maybe
 362                  * the SMBus PEC was wrong.
 363                  */
 364                 } else if (retval == 0) {
 365                         dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n");
 366                         return -EIO;
 367
 368                 /* Timeout; or (someday) lost arbitration
 369                  *
 370                  * FIXME Lost ARB implies retrying the transaction from
 371                  * the first message, after the "winning" master issues
 372                  * its STOP.  As a rule, upper layer code has no reason
 373                  * to know or care about this ... it is *NOT* an error.
 374                  */
 375                 } else {
 376                         dev_err(&i2c_adap->dev, "sendbytes: error %d\n",
 377                                         retval);
 378                         return retval;
 379                 }
 380         }
 381         return wrcount;
 382 }
 383
 384 static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
 385 {
 386         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 387
 388         /* assert: sda is high */
 389         if (is_ack)             /* send ack */
 390                 setsda(adap, 0);
 391         udelay((adap->udelay + 1) / 2);
 392         if (sclhi(adap) < 0) {  /* timeout */
 393                 dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
 394                 return -ETIMEDOUT;
 395         }
 396         scllo(adap);
 397         return 0;
 398 }
 399
 400 static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 401 {
 402         int inval;
 403         int rdcount = 0;        /* counts bytes read */
 404         unsigned char *temp = msg->buf;
 405         int count = msg->len;
 406         const unsigned flags = msg->flags;
 407
 408         while (count > 0) {
 409                 inval = i2c_inb(i2c_adap);
 410                 if (inval >= 0) {
 411                         *temp = inval;
 412                         rdcount++;
 413                 } else {   /* read timed out */
 414                         break;
 415                 }
 416
 417                 temp++;
 418                 count--;
 419
 420                 /* Some SMBus transactions require that we receive the
 421                    transaction length as the first read byte. */
 422                 if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) {
 423                         if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) {
 424                                 if (!(flags & I2C_M_NO_RD_ACK))
 425                                         acknak(i2c_adap, 0);
 426                                 dev_err(&i2c_adap->dev, "readbytes: invalid "
 427                                         "block length (%d)\n", inval);
 428                                 return -EREMOTEIO;
 429                         }
 430                         /* The original count value accounts for the extra
 431                            bytes, that is, either 1 for a regular transaction,
 432                            or 2 for a PEC transaction. */
 433                         count += inval;
 434                         msg->len += inval;
 435                 }
 436
 437                 bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",
 438                         inval,
 439                         (flags & I2C_M_NO_RD_ACK)
 440                                 ? "(no ack/nak)"
 441                                 : (count ? "A" : "NA"));
 442
 443                 if (!(flags & I2C_M_NO_RD_ACK)) {
 444                         inval = acknak(i2c_adap, count);
 445                         if (inval < 0)
 446                                 return inval;
 447                 }
 448         }
 449         return rdcount;
 450 }
 451
 452 /* doAddress initiates the transfer by generating the start condition (in
 453  * try_address) and transmits the address in the necessary format to handle
 454  * reads, writes as well as 10bit-addresses.
 455  * returns:
 456  *  0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
 457  * -x an error occurred (like: -EREMOTEIO if the device did not answer, or
 458  *      -ETIMEDOUT, for example if the lines are stuck...)
 459  */
 460 static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 461 {
 462         unsigned short flags = msg->flags;
 463         unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
 464         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 465
 466         unsigned char addr;
 467         int ret, retries;
 468
 469         retries = nak_ok ? 0 : i2c_adap->retries;
 470
 471         if (flags & I2C_M_TEN) {
 472                 /* a ten bit address */
 473                 addr = 0xf0 | ((msg->addr >> 7) & 0x03);
 474                 bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
 475                 /* try extended address code...*/
 476                 ret = try_address(i2c_adap, addr, retries);
 477                 if ((ret != 1) && !nak_ok)  {
 478                         dev_err(&i2c_adap->dev,
 479                                 "died at extended address code\n");
 480                         return -EREMOTEIO;
 481                 }
 482                 /* the remaining 8 bit address */
 483                 ret = i2c_outb(i2c_adap, msg->addr & 0x7f);
 484                 if ((ret != 1) && !nak_ok) {
 485                         /* the chip did not ack / xmission error occurred */
 486                         dev_err(&i2c_adap->dev, "died at 2nd address code\n");
 487                         return -EREMOTEIO;
 488                 }
 489                 if (flags & I2C_M_RD) {
 490                         bit_dbg(3, &i2c_adap->dev, "emitting repeated "
 491                                 "start condition\n");
 492                         i2c_repstart(adap);
 493                         /* okay, now switch into reading mode */
 494                         addr |= 0x01;
 495                         ret = try_address(i2c_adap, addr, retries);
 496                         if ((ret != 1) && !nak_ok) {
 497                                 dev_err(&i2c_adap->dev,
 498                                         "died at repeated address code\n");
 499                                 return -EREMOTEIO;
 500                         }
 501                 }
 502         } else {                /* normal 7bit address  */
 503                 addr = msg->addr << 1;
 504                 if (flags & I2C_M_RD)
 505                         addr |= 1;
 506                 if (flags & I2C_M_REV_DIR_ADDR)
 507                         addr ^= 1;
 508                 ret = try_address(i2c_adap, addr, retries);
 509                 if ((ret != 1) && !nak_ok)
 510                         return -ENXIO;
 511         }
 512
 513         return 0;
 514 }
 515
 516 static int bit_xfer(struct i2c_adapter *i2c_adap,
 517                     struct i2c_msg msgs[], int num)
 518 {
 519         struct i2c_msg *pmsg;
 520         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 521         int i, ret;
 522         unsigned short nak_ok;
 523
 524         if (adap->pre_xfer) {
 525                 ret = adap->pre_xfer(i2c_adap);
 526                 if (ret < 0)
 527                         return ret;
 528         }
 529
 530         bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
 531         i2c_start(adap);
 532         for (i = 0; i < num; i++) {
 533                 pmsg = &msgs[i];
 534                 nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;
 535                 if (!(pmsg->flags & I2C_M_NOSTART)) {
 536                         if (i) {
 537                                 bit_dbg(3, &i2c_adap->dev, "emitting "
 538                                         "repeated start condition\n");
 539                                 i2c_repstart(adap);
 540                         }
 541                         ret = bit_doAddress(i2c_adap, pmsg);
 542                         if ((ret != 0) && !nak_ok) {
 543                                 bit_dbg(1, &i2c_adap->dev, "NAK from "
 544                                         "device addr 0x%02x msg #%d\n",
 545                                         msgs[i].addr, i);
 546                                 goto bailout;
 547                         }
 548                 }
 549                 if (pmsg->flags & I2C_M_RD) {
 550                         /* read bytes into buffer*/
 551                         ret = readbytes(i2c_adap, pmsg);
 552                         if (ret >= 1)
 553                                 bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n",
 554                                         ret, ret == 1 ? "" : "s");
 555                         if (ret < pmsg->len) {
 556                                 if (ret >= 0)
 557                                         ret = -EREMOTEIO;
 558                                 goto bailout;
 559                         }
 560                 } else {
 561                         /* write bytes from buffer */
 562                         ret = sendbytes(i2c_adap, pmsg);
 563                         if (ret >= 1)
 564                                 bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n",
 565                                         ret, ret == 1 ? "" : "s");
 566                         if (ret < pmsg->len) {
 567                                 if (ret >= 0)
 568                                         ret = -EREMOTEIO;
 569                                 goto bailout;
 570                         }
 571                 }
 572         }
 573         ret = i;
 574
 575 bailout:
 576         bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
 577         i2c_stop(adap);
 578
 579         if (adap->post_xfer)
 580                 adap->post_xfer(i2c_adap);
 581         return ret;
 582 }
 583
 584 static u32 bit_func(struct i2c_adapter *adap)
 585 {
 586         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
 587                I2C_FUNC_SMBUS_READ_BLOCK_DATA |
 588                I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
 589                I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
 590 }
 591
 592
 593 /* -----exported algorithm data: -------------------------------------  */
 594
 595 static const struct i2c_algorithm i2c_bit_algo = {
 596         .master_xfer    = bit_xfer,
 597         .functionality  = bit_func,
 598 };
 599
 600 /*
 601  * registering functions to load algorithms at runtime
 602  */
 603 static int i2c_bit_prepare_bus(struct i2c_adapter *adap)
 604 {
 605         struct i2c_algo_bit_data *bit_adap = adap->algo_data;
 606
 607         if (bit_test) {
 608                 int ret = test_bus(bit_adap, adap->name);
 609                 if (ret < 0)
 610                         return -ENODEV;
 611         }
 612
 613         /* register new adapter to i2c module... */
 614         adap->algo = &i2c_bit_algo;
 615         adap->retries = 3;
 616
 617         return 0;
 618 }
 619
 620 int i2c_bit_add_bus(struct i2c_adapter *adap)
 621 {
 622         int err;
 623
 624         err = i2c_bit_prepare_bus(adap);
 625         if (err)
 626                 return err;
 627
 628         return i2c_add_adapter(adap);
 629 }
 630 EXPORT_SYMBOL(i2c_bit_add_bus);
 631
 632 int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
 633 {
 634         int err;
 635
 636         err = i2c_bit_prepare_bus(adap);
 637         if (err)
 638                 return err;
 639
 640         return i2c_add_numbered_adapter(adap);
 641 }
 642 EXPORT_SYMBOL(i2c_bit_add_numbered_bus);
 643
 644 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
 645 MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
 646 MODULE_LICENSE("GPL");