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