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"); 647