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, int, S_IRUGO); 51 MODULE_PARM_DESC(bit_test, "lines testing - 0 off; 1 report; 2 fail if 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_adapter *i2c_adap) 236 { 237 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 238 const char *name = i2c_adap->name; 239 int scl, sda, ret; 240 241 if (adap->pre_xfer) { 242 ret = adap->pre_xfer(i2c_adap); 243 if (ret < 0) 244 return -ENODEV; 245 } 246 247 if (adap->getscl == NULL) 248 pr_info("%s: Testing SDA only, SCL is not readable\n", name); 249 250 sda = getsda(adap); 251 scl = (adap->getscl == NULL) ? 1 : getscl(adap); 252 if (!scl || !sda) { 253 printk(KERN_WARNING 254 "%s: bus seems to be busy (scl=%d, sda=%d)\n", 255 name, scl, sda); 256 goto bailout; 257 } 258 259 sdalo(adap); 260 sda = getsda(adap); 261 scl = (adap->getscl == NULL) ? 1 : getscl(adap); 262 if (sda) { 263 printk(KERN_WARNING "%s: SDA stuck high!\n", name); 264 goto bailout; 265 } 266 if (!scl) { 267 printk(KERN_WARNING "%s: SCL unexpected low " 268 "while pulling SDA low!\n", name); 269 goto bailout; 270 } 271 272 sdahi(adap); 273 sda = getsda(adap); 274 scl = (adap->getscl == NULL) ? 1 : getscl(adap); 275 if (!sda) { 276 printk(KERN_WARNING "%s: SDA stuck low!\n", name); 277 goto bailout; 278 } 279 if (!scl) { 280 printk(KERN_WARNING "%s: SCL unexpected low " 281 "while pulling SDA high!\n", name); 282 goto bailout; 283 } 284 285 scllo(adap); 286 sda = getsda(adap); 287 scl = (adap->getscl == NULL) ? 0 : getscl(adap); 288 if (scl) { 289 printk(KERN_WARNING "%s: SCL stuck high!\n", name); 290 goto bailout; 291 } 292 if (!sda) { 293 printk(KERN_WARNING "%s: SDA unexpected low " 294 "while pulling SCL low!\n", name); 295 goto bailout; 296 } 297 298 sclhi(adap); 299 sda = getsda(adap); 300 scl = (adap->getscl == NULL) ? 1 : getscl(adap); 301 if (!scl) { 302 printk(KERN_WARNING "%s: SCL stuck low!\n", name); 303 goto bailout; 304 } 305 if (!sda) { 306 printk(KERN_WARNING "%s: SDA unexpected low " 307 "while pulling SCL high!\n", name); 308 goto bailout; 309 } 310 311 if (adap->post_xfer) 312 adap->post_xfer(i2c_adap); 313 314 pr_info("%s: Test OK\n", name); 315 return 0; 316 bailout: 317 sdahi(adap); 318 sclhi(adap); 319 320 if (adap->post_xfer) 321 adap->post_xfer(i2c_adap); 322 323 return -ENODEV; 324 } 325 326 /* ----- Utility functions 327 */ 328 329 /* try_address tries to contact a chip for a number of 330 * times before it gives up. 331 * return values: 332 * 1 chip answered 333 * 0 chip did not answer 334 * -x transmission error 335 */ 336 static int try_address(struct i2c_adapter *i2c_adap, 337 unsigned char addr, int retries) 338 { 339 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 340 int i, ret = 0; 341 342 for (i = 0; i <= retries; i++) { 343 ret = i2c_outb(i2c_adap, addr); 344 if (ret == 1 || i == retries) 345 break; 346 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n"); 347 i2c_stop(adap); 348 udelay(adap->udelay); 349 yield(); 350 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n"); 351 i2c_start(adap); 352 } 353 if (i && ret) 354 bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at " 355 "0x%02x: %s\n", i + 1, 356 addr & 1 ? "read from" : "write to", addr >> 1, 357 ret == 1 ? "success" : "failed, timeout?"); 358 return ret; 359 } 360 361 static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg) 362 { 363 const unsigned char *temp = msg->buf; 364 int count = msg->len; 365 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK; 366 int retval; 367 int wrcount = 0; 368 369 while (count > 0) { 370 retval = i2c_outb(i2c_adap, *temp); 371 372 /* OK/ACK; or ignored NAK */ 373 if ((retval > 0) || (nak_ok && (retval == 0))) { 374 count--; 375 temp++; 376 wrcount++; 377 378 /* A slave NAKing the master means the slave didn't like 379 * something about the data it saw. For example, maybe 380 * the SMBus PEC was wrong. 381 */ 382 } else if (retval == 0) { 383 dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n"); 384 return -EIO; 385 386 /* Timeout; or (someday) lost arbitration 387 * 388 * FIXME Lost ARB implies retrying the transaction from 389 * the first message, after the "winning" master issues 390 * its STOP. As a rule, upper layer code has no reason 391 * to know or care about this ... it is *NOT* an error. 392 */ 393 } else { 394 dev_err(&i2c_adap->dev, "sendbytes: error %d\n", 395 retval); 396 return retval; 397 } 398 } 399 return wrcount; 400 } 401 402 static int acknak(struct i2c_adapter *i2c_adap, int is_ack) 403 { 404 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 405 406 /* assert: sda is high */ 407 if (is_ack) /* send ack */ 408 setsda(adap, 0); 409 udelay((adap->udelay + 1) / 2); 410 if (sclhi(adap) < 0) { /* timeout */ 411 dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n"); 412 return -ETIMEDOUT; 413 } 414 scllo(adap); 415 return 0; 416 } 417 418 static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg) 419 { 420 int inval; 421 int rdcount = 0; /* counts bytes read */ 422 unsigned char *temp = msg->buf; 423 int count = msg->len; 424 const unsigned flags = msg->flags; 425 426 while (count > 0) { 427 inval = i2c_inb(i2c_adap); 428 if (inval >= 0) { 429 *temp = inval; 430 rdcount++; 431 } else { /* read timed out */ 432 break; 433 } 434 435 temp++; 436 count--; 437 438 /* Some SMBus transactions require that we receive the 439 transaction length as the first read byte. */ 440 if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) { 441 if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) { 442 if (!(flags & I2C_M_NO_RD_ACK)) 443 acknak(i2c_adap, 0); 444 dev_err(&i2c_adap->dev, "readbytes: invalid " 445 "block length (%d)\n", inval); 446 return -EPROTO; 447 } 448 /* The original count value accounts for the extra 449 bytes, that is, either 1 for a regular transaction, 450 or 2 for a PEC transaction. */ 451 count += inval; 452 msg->len += inval; 453 } 454 455 bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n", 456 inval, 457 (flags & I2C_M_NO_RD_ACK) 458 ? "(no ack/nak)" 459 : (count ? "A" : "NA")); 460 461 if (!(flags & I2C_M_NO_RD_ACK)) { 462 inval = acknak(i2c_adap, count); 463 if (inval < 0) 464 return inval; 465 } 466 } 467 return rdcount; 468 } 469 470 /* doAddress initiates the transfer by generating the start condition (in 471 * try_address) and transmits the address in the necessary format to handle 472 * reads, writes as well as 10bit-addresses. 473 * returns: 474 * 0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set 475 * -x an error occurred (like: -ENXIO if the device did not answer, or 476 * -ETIMEDOUT, for example if the lines are stuck...) 477 */ 478 static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg) 479 { 480 unsigned short flags = msg->flags; 481 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK; 482 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 483 484 unsigned char addr; 485 int ret, retries; 486 487 retries = nak_ok ? 0 : i2c_adap->retries; 488 489 if (flags & I2C_M_TEN) { 490 /* a ten bit address */ 491 addr = 0xf0 | ((msg->addr >> 7) & 0x06); 492 bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr); 493 /* try extended address code...*/ 494 ret = try_address(i2c_adap, addr, retries); 495 if ((ret != 1) && !nak_ok) { 496 dev_err(&i2c_adap->dev, 497 "died at extended address code\n"); 498 return -ENXIO; 499 } 500 /* the remaining 8 bit address */ 501 ret = i2c_outb(i2c_adap, msg->addr & 0xff); 502 if ((ret != 1) && !nak_ok) { 503 /* the chip did not ack / xmission error occurred */ 504 dev_err(&i2c_adap->dev, "died at 2nd address code\n"); 505 return -ENXIO; 506 } 507 if (flags & I2C_M_RD) { 508 bit_dbg(3, &i2c_adap->dev, "emitting repeated " 509 "start condition\n"); 510 i2c_repstart(adap); 511 /* okay, now switch into reading mode */ 512 addr |= 0x01; 513 ret = try_address(i2c_adap, addr, retries); 514 if ((ret != 1) && !nak_ok) { 515 dev_err(&i2c_adap->dev, 516 "died at repeated address code\n"); 517 return -EIO; 518 } 519 } 520 } else { /* normal 7bit address */ 521 addr = msg->addr << 1; 522 if (flags & I2C_M_RD) 523 addr |= 1; 524 if (flags & I2C_M_REV_DIR_ADDR) 525 addr ^= 1; 526 ret = try_address(i2c_adap, addr, retries); 527 if ((ret != 1) && !nak_ok) 528 return -ENXIO; 529 } 530 531 return 0; 532 } 533 534 static int bit_xfer(struct i2c_adapter *i2c_adap, 535 struct i2c_msg msgs[], int num) 536 { 537 struct i2c_msg *pmsg; 538 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 539 int i, ret; 540 unsigned short nak_ok; 541 542 if (adap->pre_xfer) { 543 ret = adap->pre_xfer(i2c_adap); 544 if (ret < 0) 545 return ret; 546 } 547 548 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n"); 549 i2c_start(adap); 550 for (i = 0; i < num; i++) { 551 pmsg = &msgs[i]; 552 nak_ok = pmsg->flags & I2C_M_IGNORE_NAK; 553 if (!(pmsg->flags & I2C_M_NOSTART)) { 554 if (i) { 555 bit_dbg(3, &i2c_adap->dev, "emitting " 556 "repeated start condition\n"); 557 i2c_repstart(adap); 558 } 559 ret = bit_doAddress(i2c_adap, pmsg); 560 if ((ret != 0) && !nak_ok) { 561 bit_dbg(1, &i2c_adap->dev, "NAK from " 562 "device addr 0x%02x msg #%d\n", 563 msgs[i].addr, i); 564 goto bailout; 565 } 566 } 567 if (pmsg->flags & I2C_M_RD) { 568 /* read bytes into buffer*/ 569 ret = readbytes(i2c_adap, pmsg); 570 if (ret >= 1) 571 bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n", 572 ret, ret == 1 ? "" : "s"); 573 if (ret < pmsg->len) { 574 if (ret >= 0) 575 ret = -EIO; 576 goto bailout; 577 } 578 } else { 579 /* write bytes from buffer */ 580 ret = sendbytes(i2c_adap, pmsg); 581 if (ret >= 1) 582 bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n", 583 ret, ret == 1 ? "" : "s"); 584 if (ret < pmsg->len) { 585 if (ret >= 0) 586 ret = -EIO; 587 goto bailout; 588 } 589 } 590 } 591 ret = i; 592 593 bailout: 594 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n"); 595 i2c_stop(adap); 596 597 if (adap->post_xfer) 598 adap->post_xfer(i2c_adap); 599 return ret; 600 } 601 602 static u32 bit_func(struct i2c_adapter *adap) 603 { 604 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | 605 I2C_FUNC_SMBUS_READ_BLOCK_DATA | 606 I2C_FUNC_SMBUS_BLOCK_PROC_CALL | 607 I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING; 608 } 609 610 611 /* -----exported algorithm data: ------------------------------------- */ 612 613 static const struct i2c_algorithm i2c_bit_algo = { 614 .master_xfer = bit_xfer, 615 .functionality = bit_func, 616 }; 617 618 /* 619 * registering functions to load algorithms at runtime 620 */ 621 static int __i2c_bit_add_bus(struct i2c_adapter *adap, 622 int (*add_adapter)(struct i2c_adapter *)) 623 { 624 struct i2c_algo_bit_data *bit_adap = adap->algo_data; 625 int ret; 626 627 if (bit_test) { 628 ret = test_bus(adap); 629 if (bit_test >= 2 && ret < 0) 630 return -ENODEV; 631 } 632 633 /* register new adapter to i2c module... */ 634 adap->algo = &i2c_bit_algo; 635 adap->retries = 3; 636 637 ret = add_adapter(adap); 638 if (ret < 0) 639 return ret; 640 641 /* Complain if SCL can't be read */ 642 if (bit_adap->getscl == NULL) { 643 dev_warn(&adap->dev, "Not I2C compliant: can't read SCL\n"); 644 dev_warn(&adap->dev, "Bus may be unreliable\n"); 645 } 646 return 0; 647 } 648 649 int i2c_bit_add_bus(struct i2c_adapter *adap) 650 { 651 return __i2c_bit_add_bus(adap, i2c_add_adapter); 652 } 653 EXPORT_SYMBOL(i2c_bit_add_bus); 654 655 int i2c_bit_add_numbered_bus(struct i2c_adapter *adap) 656 { 657 return __i2c_bit_add_bus(adap, i2c_add_numbered_adapter); 658 } 659 EXPORT_SYMBOL(i2c_bit_add_numbered_bus); 660 661 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>"); 662 MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm"); 663 MODULE_LICENSE("GPL"); 664