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_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 "%s: bus seems to be busy\n", name); 254 goto bailout; 255 } 256 257 sdalo(adap); 258 sda = getsda(adap); 259 scl = (adap->getscl == NULL) ? 1 : getscl(adap); 260 if (sda) { 261 printk(KERN_WARNING "%s: SDA stuck high!\n", name); 262 goto bailout; 263 } 264 if (!scl) { 265 printk(KERN_WARNING "%s: SCL unexpected low " 266 "while pulling SDA low!\n", name); 267 goto bailout; 268 } 269 270 sdahi(adap); 271 sda = getsda(adap); 272 scl = (adap->getscl == NULL) ? 1 : getscl(adap); 273 if (!sda) { 274 printk(KERN_WARNING "%s: SDA stuck low!\n", name); 275 goto bailout; 276 } 277 if (!scl) { 278 printk(KERN_WARNING "%s: SCL unexpected low " 279 "while pulling SDA high!\n", name); 280 goto bailout; 281 } 282 283 scllo(adap); 284 sda = getsda(adap); 285 scl = (adap->getscl == NULL) ? 0 : getscl(adap); 286 if (scl) { 287 printk(KERN_WARNING "%s: SCL stuck high!\n", name); 288 goto bailout; 289 } 290 if (!sda) { 291 printk(KERN_WARNING "%s: SDA unexpected low " 292 "while pulling SCL low!\n", name); 293 goto bailout; 294 } 295 296 sclhi(adap); 297 sda = getsda(adap); 298 scl = (adap->getscl == NULL) ? 1 : getscl(adap); 299 if (!scl) { 300 printk(KERN_WARNING "%s: SCL stuck low!\n", name); 301 goto bailout; 302 } 303 if (!sda) { 304 printk(KERN_WARNING "%s: SDA unexpected low " 305 "while pulling SCL high!\n", name); 306 goto bailout; 307 } 308 309 if (adap->post_xfer) 310 adap->post_xfer(i2c_adap); 311 312 pr_info("%s: Test OK\n", name); 313 return 0; 314 bailout: 315 sdahi(adap); 316 sclhi(adap); 317 318 if (adap->post_xfer) 319 adap->post_xfer(i2c_adap); 320 321 return -ENODEV; 322 } 323 324 /* ----- Utility functions 325 */ 326 327 /* try_address tries to contact a chip for a number of 328 * times before it gives up. 329 * return values: 330 * 1 chip answered 331 * 0 chip did not answer 332 * -x transmission error 333 */ 334 static int try_address(struct i2c_adapter *i2c_adap, 335 unsigned char addr, int retries) 336 { 337 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 338 int i, ret = 0; 339 340 for (i = 0; i <= retries; i++) { 341 ret = i2c_outb(i2c_adap, addr); 342 if (ret == 1 || i == retries) 343 break; 344 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n"); 345 i2c_stop(adap); 346 udelay(adap->udelay); 347 yield(); 348 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n"); 349 i2c_start(adap); 350 } 351 if (i && ret) 352 bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at " 353 "0x%02x: %s\n", i + 1, 354 addr & 1 ? "read from" : "write to", addr >> 1, 355 ret == 1 ? "success" : "failed, timeout?"); 356 return ret; 357 } 358 359 static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg) 360 { 361 const unsigned char *temp = msg->buf; 362 int count = msg->len; 363 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK; 364 int retval; 365 int wrcount = 0; 366 367 while (count > 0) { 368 retval = i2c_outb(i2c_adap, *temp); 369 370 /* OK/ACK; or ignored NAK */ 371 if ((retval > 0) || (nak_ok && (retval == 0))) { 372 count--; 373 temp++; 374 wrcount++; 375 376 /* A slave NAKing the master means the slave didn't like 377 * something about the data it saw. For example, maybe 378 * the SMBus PEC was wrong. 379 */ 380 } else if (retval == 0) { 381 dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n"); 382 return -EIO; 383 384 /* Timeout; or (someday) lost arbitration 385 * 386 * FIXME Lost ARB implies retrying the transaction from 387 * the first message, after the "winning" master issues 388 * its STOP. As a rule, upper layer code has no reason 389 * to know or care about this ... it is *NOT* an error. 390 */ 391 } else { 392 dev_err(&i2c_adap->dev, "sendbytes: error %d\n", 393 retval); 394 return retval; 395 } 396 } 397 return wrcount; 398 } 399 400 static int acknak(struct i2c_adapter *i2c_adap, int is_ack) 401 { 402 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 403 404 /* assert: sda is high */ 405 if (is_ack) /* send ack */ 406 setsda(adap, 0); 407 udelay((adap->udelay + 1) / 2); 408 if (sclhi(adap) < 0) { /* timeout */ 409 dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n"); 410 return -ETIMEDOUT; 411 } 412 scllo(adap); 413 return 0; 414 } 415 416 static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg) 417 { 418 int inval; 419 int rdcount = 0; /* counts bytes read */ 420 unsigned char *temp = msg->buf; 421 int count = msg->len; 422 const unsigned flags = msg->flags; 423 424 while (count > 0) { 425 inval = i2c_inb(i2c_adap); 426 if (inval >= 0) { 427 *temp = inval; 428 rdcount++; 429 } else { /* read timed out */ 430 break; 431 } 432 433 temp++; 434 count--; 435 436 /* Some SMBus transactions require that we receive the 437 transaction length as the first read byte. */ 438 if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) { 439 if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) { 440 if (!(flags & I2C_M_NO_RD_ACK)) 441 acknak(i2c_adap, 0); 442 dev_err(&i2c_adap->dev, "readbytes: invalid " 443 "block length (%d)\n", inval); 444 return -EREMOTEIO; 445 } 446 /* The original count value accounts for the extra 447 bytes, that is, either 1 for a regular transaction, 448 or 2 for a PEC transaction. */ 449 count += inval; 450 msg->len += inval; 451 } 452 453 bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n", 454 inval, 455 (flags & I2C_M_NO_RD_ACK) 456 ? "(no ack/nak)" 457 : (count ? "A" : "NA")); 458 459 if (!(flags & I2C_M_NO_RD_ACK)) { 460 inval = acknak(i2c_adap, count); 461 if (inval < 0) 462 return inval; 463 } 464 } 465 return rdcount; 466 } 467 468 /* doAddress initiates the transfer by generating the start condition (in 469 * try_address) and transmits the address in the necessary format to handle 470 * reads, writes as well as 10bit-addresses. 471 * returns: 472 * 0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set 473 * -x an error occurred (like: -EREMOTEIO if the device did not answer, or 474 * -ETIMEDOUT, for example if the lines are stuck...) 475 */ 476 static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg) 477 { 478 unsigned short flags = msg->flags; 479 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK; 480 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 481 482 unsigned char addr; 483 int ret, retries; 484 485 retries = nak_ok ? 0 : i2c_adap->retries; 486 487 if (flags & I2C_M_TEN) { 488 /* a ten bit address */ 489 addr = 0xf0 | ((msg->addr >> 7) & 0x03); 490 bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr); 491 /* try extended address code...*/ 492 ret = try_address(i2c_adap, addr, retries); 493 if ((ret != 1) && !nak_ok) { 494 dev_err(&i2c_adap->dev, 495 "died at extended address code\n"); 496 return -EREMOTEIO; 497 } 498 /* the remaining 8 bit address */ 499 ret = i2c_outb(i2c_adap, msg->addr & 0x7f); 500 if ((ret != 1) && !nak_ok) { 501 /* the chip did not ack / xmission error occurred */ 502 dev_err(&i2c_adap->dev, "died at 2nd address code\n"); 503 return -EREMOTEIO; 504 } 505 if (flags & I2C_M_RD) { 506 bit_dbg(3, &i2c_adap->dev, "emitting repeated " 507 "start condition\n"); 508 i2c_repstart(adap); 509 /* okay, now switch into reading mode */ 510 addr |= 0x01; 511 ret = try_address(i2c_adap, addr, retries); 512 if ((ret != 1) && !nak_ok) { 513 dev_err(&i2c_adap->dev, 514 "died at repeated address code\n"); 515 return -EREMOTEIO; 516 } 517 } 518 } else { /* normal 7bit address */ 519 addr = msg->addr << 1; 520 if (flags & I2C_M_RD) 521 addr |= 1; 522 if (flags & I2C_M_REV_DIR_ADDR) 523 addr ^= 1; 524 ret = try_address(i2c_adap, addr, retries); 525 if ((ret != 1) && !nak_ok) 526 return -ENXIO; 527 } 528 529 return 0; 530 } 531 532 static int bit_xfer(struct i2c_adapter *i2c_adap, 533 struct i2c_msg msgs[], int num) 534 { 535 struct i2c_msg *pmsg; 536 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 537 int i, ret; 538 unsigned short nak_ok; 539 540 if (adap->pre_xfer) { 541 ret = adap->pre_xfer(i2c_adap); 542 if (ret < 0) 543 return ret; 544 } 545 546 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n"); 547 i2c_start(adap); 548 for (i = 0; i < num; i++) { 549 pmsg = &msgs[i]; 550 nak_ok = pmsg->flags & I2C_M_IGNORE_NAK; 551 if (!(pmsg->flags & I2C_M_NOSTART)) { 552 if (i) { 553 bit_dbg(3, &i2c_adap->dev, "emitting " 554 "repeated start condition\n"); 555 i2c_repstart(adap); 556 } 557 ret = bit_doAddress(i2c_adap, pmsg); 558 if ((ret != 0) && !nak_ok) { 559 bit_dbg(1, &i2c_adap->dev, "NAK from " 560 "device addr 0x%02x msg #%d\n", 561 msgs[i].addr, i); 562 goto bailout; 563 } 564 } 565 if (pmsg->flags & I2C_M_RD) { 566 /* read bytes into buffer*/ 567 ret = readbytes(i2c_adap, pmsg); 568 if (ret >= 1) 569 bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n", 570 ret, ret == 1 ? "" : "s"); 571 if (ret < pmsg->len) { 572 if (ret >= 0) 573 ret = -EREMOTEIO; 574 goto bailout; 575 } 576 } else { 577 /* write bytes from buffer */ 578 ret = sendbytes(i2c_adap, pmsg); 579 if (ret >= 1) 580 bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n", 581 ret, ret == 1 ? "" : "s"); 582 if (ret < pmsg->len) { 583 if (ret >= 0) 584 ret = -EREMOTEIO; 585 goto bailout; 586 } 587 } 588 } 589 ret = i; 590 591 bailout: 592 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n"); 593 i2c_stop(adap); 594 595 if (adap->post_xfer) 596 adap->post_xfer(i2c_adap); 597 return ret; 598 } 599 600 static u32 bit_func(struct i2c_adapter *adap) 601 { 602 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | 603 I2C_FUNC_SMBUS_READ_BLOCK_DATA | 604 I2C_FUNC_SMBUS_BLOCK_PROC_CALL | 605 I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING; 606 } 607 608 609 /* -----exported algorithm data: ------------------------------------- */ 610 611 static const struct i2c_algorithm i2c_bit_algo = { 612 .master_xfer = bit_xfer, 613 .functionality = bit_func, 614 }; 615 616 /* 617 * registering functions to load algorithms at runtime 618 */ 619 static int __i2c_bit_add_bus(struct i2c_adapter *adap, 620 int (*add_adapter)(struct i2c_adapter *)) 621 { 622 struct i2c_algo_bit_data *bit_adap = adap->algo_data; 623 int ret; 624 625 if (bit_test) { 626 ret = test_bus(adap); 627 if (ret < 0) 628 return -ENODEV; 629 } 630 631 /* register new adapter to i2c module... */ 632 adap->algo = &i2c_bit_algo; 633 adap->retries = 3; 634 635 ret = add_adapter(adap); 636 if (ret < 0) 637 return ret; 638 639 /* Complain if SCL can't be read */ 640 if (bit_adap->getscl == NULL) { 641 dev_warn(&adap->dev, "Not I2C compliant: can't read SCL\n"); 642 dev_warn(&adap->dev, "Bus may be unreliable\n"); 643 } 644 return 0; 645 } 646 647 int i2c_bit_add_bus(struct i2c_adapter *adap) 648 { 649 return __i2c_bit_add_bus(adap, i2c_add_adapter); 650 } 651 EXPORT_SYMBOL(i2c_bit_add_bus); 652 653 int i2c_bit_add_numbered_bus(struct i2c_adapter *adap) 654 { 655 return __i2c_bit_add_bus(adap, i2c_add_numbered_adapter); 656 } 657 EXPORT_SYMBOL(i2c_bit_add_numbered_bus); 658 659 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>"); 660 MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm"); 661 MODULE_LICENSE("GPL"); 662