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 17 /* With some changes from Frodo Looijaard <frodol@dds.nl>, Kyösti Mälkki 18 <kmalkki@cc.hut.fi> and Jean Delvare <jdelvare@suse.de> */ 19 20 #include <linux/kernel.h> 21 #include <linux/module.h> 22 #include <linux/delay.h> 23 #include <linux/errno.h> 24 #include <linux/sched.h> 25 #include <linux/i2c.h> 26 #include <linux/i2c-algo-bit.h> 27 28 29 /* ----- global defines ----------------------------------------------- */ 30 31 #ifdef DEBUG 32 #define bit_dbg(level, dev, format, args...) \ 33 do { \ 34 if (i2c_debug >= level) \ 35 dev_dbg(dev, format, ##args); \ 36 } while (0) 37 #else 38 #define bit_dbg(level, dev, format, args...) \ 39 do {} while (0) 40 #endif /* DEBUG */ 41 42 /* ----- global variables --------------------------------------------- */ 43 44 static int bit_test; /* see if the line-setting functions work */ 45 module_param(bit_test, int, S_IRUGO); 46 MODULE_PARM_DESC(bit_test, "lines testing - 0 off; 1 report; 2 fail if stuck"); 47 48 #ifdef DEBUG 49 static int i2c_debug = 1; 50 module_param(i2c_debug, int, S_IRUGO | S_IWUSR); 51 MODULE_PARM_DESC(i2c_debug, 52 "debug level - 0 off; 1 normal; 2 verbose; 3 very verbose"); 53 #endif 54 55 /* --- setting states on the bus with the right timing: --------------- */ 56 57 #define setsda(adap, val) adap->setsda(adap->data, val) 58 #define setscl(adap, val) adap->setscl(adap->data, val) 59 #define getsda(adap) adap->getsda(adap->data) 60 #define getscl(adap) adap->getscl(adap->data) 61 62 static inline void sdalo(struct i2c_algo_bit_data *adap) 63 { 64 setsda(adap, 0); 65 udelay((adap->udelay + 1) / 2); 66 } 67 68 static inline void sdahi(struct i2c_algo_bit_data *adap) 69 { 70 setsda(adap, 1); 71 udelay((adap->udelay + 1) / 2); 72 } 73 74 static inline void scllo(struct i2c_algo_bit_data *adap) 75 { 76 setscl(adap, 0); 77 udelay(adap->udelay / 2); 78 } 79 80 /* 81 * Raise scl line, and do checking for delays. This is necessary for slower 82 * devices. 83 */ 84 static int sclhi(struct i2c_algo_bit_data *adap) 85 { 86 unsigned long start; 87 88 setscl(adap, 1); 89 90 /* Not all adapters have scl sense line... */ 91 if (!adap->getscl) 92 goto done; 93 94 start = jiffies; 95 while (!getscl(adap)) { 96 /* This hw knows how to read the clock line, so we wait 97 * until it actually gets high. This is safer as some 98 * chips may hold it low ("clock stretching") while they 99 * are processing data internally. 100 */ 101 if (time_after(jiffies, start + adap->timeout)) { 102 /* Test one last time, as we may have been preempted 103 * between last check and timeout test. 104 */ 105 if (getscl(adap)) 106 break; 107 return -ETIMEDOUT; 108 } 109 cpu_relax(); 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_adapter *i2c_adap) 237 { 238 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 239 const char *name = i2c_adap->name; 240 int scl, sda, ret; 241 242 if (adap->pre_xfer) { 243 ret = adap->pre_xfer(i2c_adap); 244 if (ret < 0) 245 return -ENODEV; 246 } 247 248 if (adap->getscl == NULL) 249 pr_info("%s: Testing SDA only, SCL is not readable\n", name); 250 251 sda = getsda(adap); 252 scl = (adap->getscl == NULL) ? 1 : getscl(adap); 253 if (!scl || !sda) { 254 printk(KERN_WARNING 255 "%s: bus seems to be busy (scl=%d, sda=%d)\n", 256 name, scl, sda); 257 goto bailout; 258 } 259 260 sdalo(adap); 261 sda = getsda(adap); 262 scl = (adap->getscl == NULL) ? 1 : getscl(adap); 263 if (sda) { 264 printk(KERN_WARNING "%s: SDA stuck high!\n", name); 265 goto bailout; 266 } 267 if (!scl) { 268 printk(KERN_WARNING "%s: SCL unexpected low " 269 "while pulling SDA low!\n", name); 270 goto bailout; 271 } 272 273 sdahi(adap); 274 sda = getsda(adap); 275 scl = (adap->getscl == NULL) ? 1 : getscl(adap); 276 if (!sda) { 277 printk(KERN_WARNING "%s: SDA stuck low!\n", name); 278 goto bailout; 279 } 280 if (!scl) { 281 printk(KERN_WARNING "%s: SCL unexpected low " 282 "while pulling SDA high!\n", name); 283 goto bailout; 284 } 285 286 scllo(adap); 287 sda = getsda(adap); 288 scl = (adap->getscl == NULL) ? 0 : getscl(adap); 289 if (scl) { 290 printk(KERN_WARNING "%s: SCL stuck high!\n", name); 291 goto bailout; 292 } 293 if (!sda) { 294 printk(KERN_WARNING "%s: SDA unexpected low " 295 "while pulling SCL low!\n", name); 296 goto bailout; 297 } 298 299 sclhi(adap); 300 sda = getsda(adap); 301 scl = (adap->getscl == NULL) ? 1 : getscl(adap); 302 if (!scl) { 303 printk(KERN_WARNING "%s: SCL stuck low!\n", name); 304 goto bailout; 305 } 306 if (!sda) { 307 printk(KERN_WARNING "%s: SDA unexpected low " 308 "while pulling SCL high!\n", name); 309 goto bailout; 310 } 311 312 if (adap->post_xfer) 313 adap->post_xfer(i2c_adap); 314 315 pr_info("%s: Test OK\n", name); 316 return 0; 317 bailout: 318 sdahi(adap); 319 sclhi(adap); 320 321 if (adap->post_xfer) 322 adap->post_xfer(i2c_adap); 323 324 return -ENODEV; 325 } 326 327 /* ----- Utility functions 328 */ 329 330 /* try_address tries to contact a chip for a number of 331 * times before it gives up. 332 * return values: 333 * 1 chip answered 334 * 0 chip did not answer 335 * -x transmission error 336 */ 337 static int try_address(struct i2c_adapter *i2c_adap, 338 unsigned char addr, int retries) 339 { 340 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 341 int i, ret = 0; 342 343 for (i = 0; i <= retries; i++) { 344 ret = i2c_outb(i2c_adap, addr); 345 if (ret == 1 || i == retries) 346 break; 347 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n"); 348 i2c_stop(adap); 349 udelay(adap->udelay); 350 yield(); 351 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n"); 352 i2c_start(adap); 353 } 354 if (i && ret) 355 bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at " 356 "0x%02x: %s\n", i + 1, 357 addr & 1 ? "read from" : "write to", addr >> 1, 358 ret == 1 ? "success" : "failed, timeout?"); 359 return ret; 360 } 361 362 static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg) 363 { 364 const unsigned char *temp = msg->buf; 365 int count = msg->len; 366 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK; 367 int retval; 368 int wrcount = 0; 369 370 while (count > 0) { 371 retval = i2c_outb(i2c_adap, *temp); 372 373 /* OK/ACK; or ignored NAK */ 374 if ((retval > 0) || (nak_ok && (retval == 0))) { 375 count--; 376 temp++; 377 wrcount++; 378 379 /* A slave NAKing the master means the slave didn't like 380 * something about the data it saw. For example, maybe 381 * the SMBus PEC was wrong. 382 */ 383 } else if (retval == 0) { 384 dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n"); 385 return -EIO; 386 387 /* Timeout; or (someday) lost arbitration 388 * 389 * FIXME Lost ARB implies retrying the transaction from 390 * the first message, after the "winning" master issues 391 * its STOP. As a rule, upper layer code has no reason 392 * to know or care about this ... it is *NOT* an error. 393 */ 394 } else { 395 dev_err(&i2c_adap->dev, "sendbytes: error %d\n", 396 retval); 397 return retval; 398 } 399 } 400 return wrcount; 401 } 402 403 static int acknak(struct i2c_adapter *i2c_adap, int is_ack) 404 { 405 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 406 407 /* assert: sda is high */ 408 if (is_ack) /* send ack */ 409 setsda(adap, 0); 410 udelay((adap->udelay + 1) / 2); 411 if (sclhi(adap) < 0) { /* timeout */ 412 dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n"); 413 return -ETIMEDOUT; 414 } 415 scllo(adap); 416 return 0; 417 } 418 419 static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg) 420 { 421 int inval; 422 int rdcount = 0; /* counts bytes read */ 423 unsigned char *temp = msg->buf; 424 int count = msg->len; 425 const unsigned flags = msg->flags; 426 427 while (count > 0) { 428 inval = i2c_inb(i2c_adap); 429 if (inval >= 0) { 430 *temp = inval; 431 rdcount++; 432 } else { /* read timed out */ 433 break; 434 } 435 436 temp++; 437 count--; 438 439 /* Some SMBus transactions require that we receive the 440 transaction length as the first read byte. */ 441 if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) { 442 if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) { 443 if (!(flags & I2C_M_NO_RD_ACK)) 444 acknak(i2c_adap, 0); 445 dev_err(&i2c_adap->dev, "readbytes: invalid " 446 "block length (%d)\n", inval); 447 return -EPROTO; 448 } 449 /* The original count value accounts for the extra 450 bytes, that is, either 1 for a regular transaction, 451 or 2 for a PEC transaction. */ 452 count += inval; 453 msg->len += inval; 454 } 455 456 bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n", 457 inval, 458 (flags & I2C_M_NO_RD_ACK) 459 ? "(no ack/nak)" 460 : (count ? "A" : "NA")); 461 462 if (!(flags & I2C_M_NO_RD_ACK)) { 463 inval = acknak(i2c_adap, count); 464 if (inval < 0) 465 return inval; 466 } 467 } 468 return rdcount; 469 } 470 471 /* doAddress initiates the transfer by generating the start condition (in 472 * try_address) and transmits the address in the necessary format to handle 473 * reads, writes as well as 10bit-addresses. 474 * returns: 475 * 0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set 476 * -x an error occurred (like: -ENXIO if the device did not answer, or 477 * -ETIMEDOUT, for example if the lines are stuck...) 478 */ 479 static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg) 480 { 481 unsigned short flags = msg->flags; 482 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK; 483 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 484 485 unsigned char addr; 486 int ret, retries; 487 488 retries = nak_ok ? 0 : i2c_adap->retries; 489 490 if (flags & I2C_M_TEN) { 491 /* a ten bit address */ 492 addr = 0xf0 | ((msg->addr >> 7) & 0x06); 493 bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr); 494 /* try extended address code...*/ 495 ret = try_address(i2c_adap, addr, retries); 496 if ((ret != 1) && !nak_ok) { 497 dev_err(&i2c_adap->dev, 498 "died at extended address code\n"); 499 return -ENXIO; 500 } 501 /* the remaining 8 bit address */ 502 ret = i2c_outb(i2c_adap, msg->addr & 0xff); 503 if ((ret != 1) && !nak_ok) { 504 /* the chip did not ack / xmission error occurred */ 505 dev_err(&i2c_adap->dev, "died at 2nd address code\n"); 506 return -ENXIO; 507 } 508 if (flags & I2C_M_RD) { 509 bit_dbg(3, &i2c_adap->dev, "emitting repeated " 510 "start condition\n"); 511 i2c_repstart(adap); 512 /* okay, now switch into reading mode */ 513 addr |= 0x01; 514 ret = try_address(i2c_adap, addr, retries); 515 if ((ret != 1) && !nak_ok) { 516 dev_err(&i2c_adap->dev, 517 "died at repeated address code\n"); 518 return -EIO; 519 } 520 } 521 } else { /* normal 7bit address */ 522 addr = msg->addr << 1; 523 if (flags & I2C_M_RD) 524 addr |= 1; 525 if (flags & I2C_M_REV_DIR_ADDR) 526 addr ^= 1; 527 ret = try_address(i2c_adap, addr, retries); 528 if ((ret != 1) && !nak_ok) 529 return -ENXIO; 530 } 531 532 return 0; 533 } 534 535 static int bit_xfer(struct i2c_adapter *i2c_adap, 536 struct i2c_msg msgs[], int num) 537 { 538 struct i2c_msg *pmsg; 539 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 540 int i, ret; 541 unsigned short nak_ok; 542 543 if (adap->pre_xfer) { 544 ret = adap->pre_xfer(i2c_adap); 545 if (ret < 0) 546 return ret; 547 } 548 549 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n"); 550 i2c_start(adap); 551 for (i = 0; i < num; i++) { 552 pmsg = &msgs[i]; 553 nak_ok = pmsg->flags & I2C_M_IGNORE_NAK; 554 if (!(pmsg->flags & I2C_M_NOSTART)) { 555 if (i) { 556 bit_dbg(3, &i2c_adap->dev, "emitting " 557 "repeated start condition\n"); 558 i2c_repstart(adap); 559 } 560 ret = bit_doAddress(i2c_adap, pmsg); 561 if ((ret != 0) && !nak_ok) { 562 bit_dbg(1, &i2c_adap->dev, "NAK from " 563 "device addr 0x%02x msg #%d\n", 564 msgs[i].addr, i); 565 goto bailout; 566 } 567 } 568 if (pmsg->flags & I2C_M_RD) { 569 /* read bytes into buffer*/ 570 ret = readbytes(i2c_adap, pmsg); 571 if (ret >= 1) 572 bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n", 573 ret, ret == 1 ? "" : "s"); 574 if (ret < pmsg->len) { 575 if (ret >= 0) 576 ret = -EIO; 577 goto bailout; 578 } 579 } else { 580 /* write bytes from buffer */ 581 ret = sendbytes(i2c_adap, pmsg); 582 if (ret >= 1) 583 bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n", 584 ret, ret == 1 ? "" : "s"); 585 if (ret < pmsg->len) { 586 if (ret >= 0) 587 ret = -EIO; 588 goto bailout; 589 } 590 } 591 } 592 ret = i; 593 594 bailout: 595 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n"); 596 i2c_stop(adap); 597 598 if (adap->post_xfer) 599 adap->post_xfer(i2c_adap); 600 return ret; 601 } 602 603 static u32 bit_func(struct i2c_adapter *adap) 604 { 605 return I2C_FUNC_I2C | I2C_FUNC_NOSTART | I2C_FUNC_SMBUS_EMUL | 606 I2C_FUNC_SMBUS_READ_BLOCK_DATA | 607 I2C_FUNC_SMBUS_BLOCK_PROC_CALL | 608 I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING; 609 } 610 611 612 /* -----exported algorithm data: ------------------------------------- */ 613 614 const struct i2c_algorithm i2c_bit_algo = { 615 .master_xfer = bit_xfer, 616 .functionality = bit_func, 617 }; 618 EXPORT_SYMBOL(i2c_bit_algo); 619 620 static const struct i2c_adapter_quirks i2c_bit_quirk_no_clk_stretch = { 621 .flags = I2C_AQ_NO_CLK_STRETCH, 622 }; 623 624 /* 625 * registering functions to load algorithms at runtime 626 */ 627 static int __i2c_bit_add_bus(struct i2c_adapter *adap, 628 int (*add_adapter)(struct i2c_adapter *)) 629 { 630 struct i2c_algo_bit_data *bit_adap = adap->algo_data; 631 int ret; 632 633 if (bit_test) { 634 ret = test_bus(adap); 635 if (bit_test >= 2 && ret < 0) 636 return -ENODEV; 637 } 638 639 /* register new adapter to i2c module... */ 640 adap->algo = &i2c_bit_algo; 641 adap->retries = 3; 642 if (bit_adap->getscl == NULL) 643 adap->quirks = &i2c_bit_quirk_no_clk_stretch; 644 645 ret = add_adapter(adap); 646 if (ret < 0) 647 return ret; 648 649 /* Complain if SCL can't be read */ 650 if (bit_adap->getscl == NULL) { 651 dev_warn(&adap->dev, "Not I2C compliant: can't read SCL\n"); 652 dev_warn(&adap->dev, "Bus may be unreliable\n"); 653 } 654 return 0; 655 } 656 657 int i2c_bit_add_bus(struct i2c_adapter *adap) 658 { 659 return __i2c_bit_add_bus(adap, i2c_add_adapter); 660 } 661 EXPORT_SYMBOL(i2c_bit_add_bus); 662 663 int i2c_bit_add_numbered_bus(struct i2c_adapter *adap) 664 { 665 return __i2c_bit_add_bus(adap, i2c_add_numbered_adapter); 666 } 667 EXPORT_SYMBOL(i2c_bit_add_numbered_bus); 668 669 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>"); 670 MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm"); 671 MODULE_LICENSE("GPL"); 672