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 /* This hw knows how to read the clock line, so we wait 103 * until it actually gets high. This is safer as some 104 * chips may hold it low ("clock stretching") while they 105 * are processing data internally. 106 */ 107 if (time_after_eq(jiffies, start + adap->timeout)) 108 return -ETIMEDOUT; 109 cond_resched(); 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_algo_bit_data *adap, char *name) 237 { 238 int scl, sda; 239 240 if (adap->getscl == NULL) 241 pr_info("%s: Testing SDA only, SCL is not readable\n", name); 242 243 sda = getsda(adap); 244 scl = (adap->getscl == NULL) ? 1 : getscl(adap); 245 if (!scl || !sda) { 246 printk(KERN_WARNING "%s: bus seems to be busy\n", name); 247 goto bailout; 248 } 249 250 sdalo(adap); 251 sda = getsda(adap); 252 scl = (adap->getscl == NULL) ? 1 : getscl(adap); 253 if (sda) { 254 printk(KERN_WARNING "%s: SDA stuck high!\n", name); 255 goto bailout; 256 } 257 if (!scl) { 258 printk(KERN_WARNING "%s: SCL unexpected low " 259 "while pulling SDA low!\n", name); 260 goto bailout; 261 } 262 263 sdahi(adap); 264 sda = getsda(adap); 265 scl = (adap->getscl == NULL) ? 1 : getscl(adap); 266 if (!sda) { 267 printk(KERN_WARNING "%s: SDA stuck low!\n", name); 268 goto bailout; 269 } 270 if (!scl) { 271 printk(KERN_WARNING "%s: SCL unexpected low " 272 "while pulling SDA high!\n", name); 273 goto bailout; 274 } 275 276 scllo(adap); 277 sda = getsda(adap); 278 scl = (adap->getscl == NULL) ? 0 : getscl(adap); 279 if (scl) { 280 printk(KERN_WARNING "%s: SCL stuck high!\n", name); 281 goto bailout; 282 } 283 if (!sda) { 284 printk(KERN_WARNING "%s: SDA unexpected low " 285 "while pulling SCL low!\n", name); 286 goto bailout; 287 } 288 289 sclhi(adap); 290 sda = getsda(adap); 291 scl = (adap->getscl == NULL) ? 1 : getscl(adap); 292 if (!scl) { 293 printk(KERN_WARNING "%s: SCL stuck low!\n", name); 294 goto bailout; 295 } 296 if (!sda) { 297 printk(KERN_WARNING "%s: SDA unexpected low " 298 "while pulling SCL high!\n", name); 299 goto bailout; 300 } 301 pr_info("%s: Test OK\n", name); 302 return 0; 303 bailout: 304 sdahi(adap); 305 sclhi(adap); 306 return -ENODEV; 307 } 308 309 /* ----- Utility functions 310 */ 311 312 /* try_address tries to contact a chip for a number of 313 * times before it gives up. 314 * return values: 315 * 1 chip answered 316 * 0 chip did not answer 317 * -x transmission error 318 */ 319 static int try_address(struct i2c_adapter *i2c_adap, 320 unsigned char addr, int retries) 321 { 322 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 323 int i, ret = 0; 324 325 for (i = 0; i <= retries; i++) { 326 ret = i2c_outb(i2c_adap, addr); 327 if (ret == 1 || i == retries) 328 break; 329 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n"); 330 i2c_stop(adap); 331 udelay(adap->udelay); 332 yield(); 333 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n"); 334 i2c_start(adap); 335 } 336 if (i && ret) 337 bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at " 338 "0x%02x: %s\n", i + 1, 339 addr & 1 ? "read from" : "write to", addr >> 1, 340 ret == 1 ? "success" : "failed, timeout?"); 341 return ret; 342 } 343 344 static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg) 345 { 346 const unsigned char *temp = msg->buf; 347 int count = msg->len; 348 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK; 349 int retval; 350 int wrcount = 0; 351 352 while (count > 0) { 353 retval = i2c_outb(i2c_adap, *temp); 354 355 /* OK/ACK; or ignored NAK */ 356 if ((retval > 0) || (nak_ok && (retval == 0))) { 357 count--; 358 temp++; 359 wrcount++; 360 361 /* A slave NAKing the master means the slave didn't like 362 * something about the data it saw. For example, maybe 363 * the SMBus PEC was wrong. 364 */ 365 } else if (retval == 0) { 366 dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n"); 367 return -EIO; 368 369 /* Timeout; or (someday) lost arbitration 370 * 371 * FIXME Lost ARB implies retrying the transaction from 372 * the first message, after the "winning" master issues 373 * its STOP. As a rule, upper layer code has no reason 374 * to know or care about this ... it is *NOT* an error. 375 */ 376 } else { 377 dev_err(&i2c_adap->dev, "sendbytes: error %d\n", 378 retval); 379 return retval; 380 } 381 } 382 return wrcount; 383 } 384 385 static int acknak(struct i2c_adapter *i2c_adap, int is_ack) 386 { 387 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 388 389 /* assert: sda is high */ 390 if (is_ack) /* send ack */ 391 setsda(adap, 0); 392 udelay((adap->udelay + 1) / 2); 393 if (sclhi(adap) < 0) { /* timeout */ 394 dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n"); 395 return -ETIMEDOUT; 396 } 397 scllo(adap); 398 return 0; 399 } 400 401 static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg) 402 { 403 int inval; 404 int rdcount = 0; /* counts bytes read */ 405 unsigned char *temp = msg->buf; 406 int count = msg->len; 407 const unsigned flags = msg->flags; 408 409 while (count > 0) { 410 inval = i2c_inb(i2c_adap); 411 if (inval >= 0) { 412 *temp = inval; 413 rdcount++; 414 } else { /* read timed out */ 415 break; 416 } 417 418 temp++; 419 count--; 420 421 /* Some SMBus transactions require that we receive the 422 transaction length as the first read byte. */ 423 if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) { 424 if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) { 425 if (!(flags & I2C_M_NO_RD_ACK)) 426 acknak(i2c_adap, 0); 427 dev_err(&i2c_adap->dev, "readbytes: invalid " 428 "block length (%d)\n", inval); 429 return -EREMOTEIO; 430 } 431 /* The original count value accounts for the extra 432 bytes, that is, either 1 for a regular transaction, 433 or 2 for a PEC transaction. */ 434 count += inval; 435 msg->len += inval; 436 } 437 438 bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n", 439 inval, 440 (flags & I2C_M_NO_RD_ACK) 441 ? "(no ack/nak)" 442 : (count ? "A" : "NA")); 443 444 if (!(flags & I2C_M_NO_RD_ACK)) { 445 inval = acknak(i2c_adap, count); 446 if (inval < 0) 447 return inval; 448 } 449 } 450 return rdcount; 451 } 452 453 /* doAddress initiates the transfer by generating the start condition (in 454 * try_address) and transmits the address in the necessary format to handle 455 * reads, writes as well as 10bit-addresses. 456 * returns: 457 * 0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set 458 * -x an error occurred (like: -EREMOTEIO if the device did not answer, or 459 * -ETIMEDOUT, for example if the lines are stuck...) 460 */ 461 static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg) 462 { 463 unsigned short flags = msg->flags; 464 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK; 465 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 466 467 unsigned char addr; 468 int ret, retries; 469 470 retries = nak_ok ? 0 : i2c_adap->retries; 471 472 if (flags & I2C_M_TEN) { 473 /* a ten bit address */ 474 addr = 0xf0 | ((msg->addr >> 7) & 0x03); 475 bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr); 476 /* try extended address code...*/ 477 ret = try_address(i2c_adap, addr, retries); 478 if ((ret != 1) && !nak_ok) { 479 dev_err(&i2c_adap->dev, 480 "died at extended address code\n"); 481 return -EREMOTEIO; 482 } 483 /* the remaining 8 bit address */ 484 ret = i2c_outb(i2c_adap, msg->addr & 0x7f); 485 if ((ret != 1) && !nak_ok) { 486 /* the chip did not ack / xmission error occurred */ 487 dev_err(&i2c_adap->dev, "died at 2nd address code\n"); 488 return -EREMOTEIO; 489 } 490 if (flags & I2C_M_RD) { 491 bit_dbg(3, &i2c_adap->dev, "emitting repeated " 492 "start condition\n"); 493 i2c_repstart(adap); 494 /* okay, now switch into reading mode */ 495 addr |= 0x01; 496 ret = try_address(i2c_adap, addr, retries); 497 if ((ret != 1) && !nak_ok) { 498 dev_err(&i2c_adap->dev, 499 "died at repeated address code\n"); 500 return -EREMOTEIO; 501 } 502 } 503 } else { /* normal 7bit address */ 504 addr = msg->addr << 1; 505 if (flags & I2C_M_RD) 506 addr |= 1; 507 if (flags & I2C_M_REV_DIR_ADDR) 508 addr ^= 1; 509 ret = try_address(i2c_adap, addr, retries); 510 if ((ret != 1) && !nak_ok) 511 return -ENXIO; 512 } 513 514 return 0; 515 } 516 517 static int bit_xfer(struct i2c_adapter *i2c_adap, 518 struct i2c_msg msgs[], int num) 519 { 520 struct i2c_msg *pmsg; 521 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 522 int i, ret; 523 unsigned short nak_ok; 524 525 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n"); 526 i2c_start(adap); 527 for (i = 0; i < num; i++) { 528 pmsg = &msgs[i]; 529 nak_ok = pmsg->flags & I2C_M_IGNORE_NAK; 530 if (!(pmsg->flags & I2C_M_NOSTART)) { 531 if (i) { 532 bit_dbg(3, &i2c_adap->dev, "emitting " 533 "repeated start condition\n"); 534 i2c_repstart(adap); 535 } 536 ret = bit_doAddress(i2c_adap, pmsg); 537 if ((ret != 0) && !nak_ok) { 538 bit_dbg(1, &i2c_adap->dev, "NAK from " 539 "device addr 0x%02x msg #%d\n", 540 msgs[i].addr, i); 541 goto bailout; 542 } 543 } 544 if (pmsg->flags & I2C_M_RD) { 545 /* read bytes into buffer*/ 546 ret = readbytes(i2c_adap, pmsg); 547 if (ret >= 1) 548 bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n", 549 ret, ret == 1 ? "" : "s"); 550 if (ret < pmsg->len) { 551 if (ret >= 0) 552 ret = -EREMOTEIO; 553 goto bailout; 554 } 555 } else { 556 /* write bytes from buffer */ 557 ret = sendbytes(i2c_adap, pmsg); 558 if (ret >= 1) 559 bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n", 560 ret, ret == 1 ? "" : "s"); 561 if (ret < pmsg->len) { 562 if (ret >= 0) 563 ret = -EREMOTEIO; 564 goto bailout; 565 } 566 } 567 } 568 ret = i; 569 570 bailout: 571 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n"); 572 i2c_stop(adap); 573 return ret; 574 } 575 576 static u32 bit_func(struct i2c_adapter *adap) 577 { 578 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | 579 I2C_FUNC_SMBUS_READ_BLOCK_DATA | 580 I2C_FUNC_SMBUS_BLOCK_PROC_CALL | 581 I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING; 582 } 583 584 585 /* -----exported algorithm data: ------------------------------------- */ 586 587 static const struct i2c_algorithm i2c_bit_algo = { 588 .master_xfer = bit_xfer, 589 .functionality = bit_func, 590 }; 591 592 /* 593 * registering functions to load algorithms at runtime 594 */ 595 static int i2c_bit_prepare_bus(struct i2c_adapter *adap) 596 { 597 struct i2c_algo_bit_data *bit_adap = adap->algo_data; 598 599 if (bit_test) { 600 int ret = test_bus(bit_adap, adap->name); 601 if (ret < 0) 602 return -ENODEV; 603 } 604 605 /* register new adapter to i2c module... */ 606 adap->algo = &i2c_bit_algo; 607 608 adap->timeout = 100; /* default values, should */ 609 adap->retries = 3; /* be replaced by defines */ 610 611 return 0; 612 } 613 614 int i2c_bit_add_bus(struct i2c_adapter *adap) 615 { 616 int err; 617 618 err = i2c_bit_prepare_bus(adap); 619 if (err) 620 return err; 621 622 return i2c_add_adapter(adap); 623 } 624 EXPORT_SYMBOL(i2c_bit_add_bus); 625 626 int i2c_bit_add_numbered_bus(struct i2c_adapter *adap) 627 { 628 int err; 629 630 err = i2c_bit_prepare_bus(adap); 631 if (err) 632 return err; 633 634 return i2c_add_numbered_adapter(adap); 635 } 636 EXPORT_SYMBOL(i2c_bit_add_numbered_bus); 637 638 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>"); 639 MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm"); 640 MODULE_LICENSE("GPL"); 641