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>, Ky�sti M�lkki 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 50static int bit_test; /* see if the line-setting functions work */ 51module_param(bit_test, bool, 0); 52MODULE_PARM_DESC(bit_test, "Test the lines of the bus to see if it is stuck"); 53 54#ifdef DEBUG 55static int i2c_debug = 1; 56module_param(i2c_debug, int, S_IRUGO | S_IWUSR); 57MODULE_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 68static inline void sdalo(struct i2c_algo_bit_data *adap) 69{ 70 setsda(adap,0); 71 udelay((adap->udelay + 1) / 2); 72} 73 74static inline void sdahi(struct i2c_algo_bit_data *adap) 75{ 76 setsda(adap,1); 77 udelay((adap->udelay + 1) / 2); 78} 79 80static 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 */ 90static 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 /* the hw knows how to read the clock line, 103 * so we wait until it actually gets high. 104 * This is safer as some chips may hold it low 105 * while they are processing data internally. 106 */ 107 if (time_after_eq(jiffies, start+adap->timeout)) { 108 return -ETIMEDOUT; 109 } 110 cond_resched(); 111 } 112#ifdef DEBUG 113 if (jiffies != start && i2c_debug >= 3) 114 pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go " 115 "high\n", jiffies - start); 116#endif 117 118done: 119 udelay(adap->udelay); 120 return 0; 121} 122 123 124/* --- other auxiliary functions -------------------------------------- */ 125static void i2c_start(struct i2c_algo_bit_data *adap) 126{ 127 /* assert: scl, sda are high */ 128 setsda(adap, 0); 129 udelay(adap->udelay); 130 scllo(adap); 131} 132 133static void i2c_repstart(struct i2c_algo_bit_data *adap) 134{ 135 /* assert: scl is low */ 136 sdahi(adap); 137 sclhi(adap); 138 setsda(adap, 0); 139 udelay(adap->udelay); 140 scllo(adap); 141} 142 143 144static void i2c_stop(struct i2c_algo_bit_data *adap) 145{ 146 /* assert: scl is low */ 147 sdalo(adap); 148 sclhi(adap); 149 setsda(adap, 1); 150 udelay(adap->udelay); 151} 152 153 154 155/* send a byte without start cond., look for arbitration, 156 check ackn. from slave */ 157/* returns: 158 * 1 if the device acknowledged 159 * 0 if the device did not ack 160 * -ETIMEDOUT if an error occurred (while raising the scl line) 161 */ 162static int i2c_outb(struct i2c_adapter *i2c_adap, unsigned char c) 163{ 164 int i; 165 int sb; 166 int ack; 167 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 168 169 /* assert: scl is low */ 170 for ( i=7 ; i>=0 ; i-- ) { 171 sb = (c >> i) & 1; 172 setsda(adap,sb); 173 udelay((adap->udelay + 1) / 2); 174 if (sclhi(adap)<0) { /* timed out */ 175 bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, " 176 "timeout at bit #%d\n", (int)c, i); 177 return -ETIMEDOUT; 178 }; 179 /* do arbitration here: 180 * if ( sb && ! getsda(adap) ) -> ouch! Get out of here. 181 */ 182 scllo(adap); 183 } 184 sdahi(adap); 185 if (sclhi(adap)<0){ /* timeout */ 186 bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, " 187 "timeout at ack\n", (int)c); 188 return -ETIMEDOUT; 189 }; 190 /* read ack: SDA should be pulled down by slave */ 191 ack = !getsda(adap); /* ack: sda is pulled low -> success */ 192 bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c, 193 ack ? "A" : "NA"); 194 195 scllo(adap); 196 return ack; 197 /* assert: scl is low (sda undef) */ 198} 199 200 201static int i2c_inb(struct i2c_adapter *i2c_adap) 202{ 203 /* read byte via i2c port, without start/stop sequence */ 204 /* acknowledge is sent in i2c_read. */ 205 int i; 206 unsigned char indata=0; 207 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 208 209 /* assert: scl is low */ 210 sdahi(adap); 211 for (i=0;i<8;i++) { 212 if (sclhi(adap)<0) { /* timeout */ 213 bit_dbg(1, &i2c_adap->dev, "i2c_inb: timeout at bit " 214 "#%d\n", 7 - i); 215 return -ETIMEDOUT; 216 }; 217 indata *= 2; 218 if ( getsda(adap) ) 219 indata |= 0x01; 220 setscl(adap, 0); 221 udelay(i == 7 ? adap->udelay / 2 : adap->udelay); 222 } 223 /* assert: scl is low */ 224 return indata; 225} 226 227/* 228 * Sanity check for the adapter hardware - check the reaction of 229 * the bus lines only if it seems to be idle. 230 */ 231static int test_bus(struct i2c_algo_bit_data *adap, char* name) { 232 int scl,sda; 233 234 if (adap->getscl==NULL) 235 pr_info("%s: Testing SDA only, SCL is not readable\n", name); 236 237 sda=getsda(adap); 238 scl=(adap->getscl==NULL?1:getscl(adap)); 239 if (!scl || !sda ) { 240 printk(KERN_WARNING "%s: bus seems to be busy\n", name); 241 goto bailout; 242 } 243 244 sdalo(adap); 245 sda=getsda(adap); 246 scl=(adap->getscl==NULL?1:getscl(adap)); 247 if ( 0 != sda ) { 248 printk(KERN_WARNING "%s: SDA stuck high!\n", name); 249 goto bailout; 250 } 251 if ( 0 == scl ) { 252 printk(KERN_WARNING "%s: SCL unexpected low " 253 "while pulling SDA low!\n", name); 254 goto bailout; 255 } 256 257 sdahi(adap); 258 sda=getsda(adap); 259 scl=(adap->getscl==NULL?1:getscl(adap)); 260 if ( 0 == sda ) { 261 printk(KERN_WARNING "%s: SDA stuck low!\n", name); 262 goto bailout; 263 } 264 if ( 0 == scl ) { 265 printk(KERN_WARNING "%s: SCL unexpected low " 266 "while pulling SDA high!\n", name); 267 goto bailout; 268 } 269 270 scllo(adap); 271 sda=getsda(adap); 272 scl=(adap->getscl==NULL?0:getscl(adap)); 273 if ( 0 != scl ) { 274 printk(KERN_WARNING "%s: SCL stuck high!\n", name); 275 goto bailout; 276 } 277 if ( 0 == sda ) { 278 printk(KERN_WARNING "%s: SDA unexpected low " 279 "while pulling SCL low!\n", name); 280 goto bailout; 281 } 282 283 sclhi(adap); 284 sda=getsda(adap); 285 scl=(adap->getscl==NULL?1:getscl(adap)); 286 if ( 0 == scl ) { 287 printk(KERN_WARNING "%s: SCL stuck low!\n", name); 288 goto bailout; 289 } 290 if ( 0 == sda ) { 291 printk(KERN_WARNING "%s: SDA unexpected low " 292 "while pulling SCL high!\n", name); 293 goto bailout; 294 } 295 pr_info("%s: Test OK\n", name); 296 return 0; 297bailout: 298 sdahi(adap); 299 sclhi(adap); 300 return -ENODEV; 301} 302 303/* ----- Utility functions 304 */ 305 306/* try_address tries to contact a chip for a number of 307 * times before it gives up. 308 * return values: 309 * 1 chip answered 310 * 0 chip did not answer 311 * -x transmission error 312 */ 313static int try_address(struct i2c_adapter *i2c_adap, 314 unsigned char addr, int retries) 315{ 316 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 317 int i,ret = -1; 318 for (i=0;i<=retries;i++) { 319 ret = i2c_outb(i2c_adap,addr); 320 if (ret == 1 || i == retries) 321 break; 322 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n"); 323 i2c_stop(adap); 324 udelay(adap->udelay); 325 yield(); 326 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n"); 327 i2c_start(adap); 328 } 329 if (i && ret) 330 bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at " 331 "0x%02x: %s\n", i + 1, 332 addr & 1 ? "read from" : "write to", addr >> 1, 333 ret == 1 ? "success" : "failed, timeout?"); 334 return ret; 335} 336 337static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg) 338{ 339 const unsigned char *temp = msg->buf; 340 int count = msg->len; 341 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK; 342 int retval; 343 int wrcount=0; 344 345 while (count > 0) { 346 retval = i2c_outb(i2c_adap, *temp); 347 if ((retval>0) || (nak_ok && (retval==0))) { /* ok or ignored NAK */ 348 count--; 349 temp++; 350 wrcount++; 351 } else { /* arbitration or no acknowledge */ 352 dev_err(&i2c_adap->dev, "sendbytes: error - bailout.\n"); 353 return (retval<0)? retval : -EFAULT; 354 /* got a better one ?? */ 355 } 356 } 357 return wrcount; 358} 359 360static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg) 361{ 362 int inval; 363 int rdcount=0; /* counts bytes read */ 364 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 365 unsigned char *temp = msg->buf; 366 int count = msg->len; 367 368 while (count > 0) { 369 inval = i2c_inb(i2c_adap); 370 if (inval>=0) { 371 *temp = inval; 372 rdcount++; 373 } else { /* read timed out */ 374 break; 375 } 376 377 temp++; 378 count--; 379 380 if (msg->flags & I2C_M_NO_RD_ACK) { 381 bit_dbg(2, &i2c_adap->dev, "i2c_inb: 0x%02x\n", 382 inval); 383 continue; 384 } 385 386 /* assert: sda is high */ 387 if (count) /* send ack */ 388 setsda(adap, 0); 389 udelay((adap->udelay + 1) / 2); 390 bit_dbg(2, &i2c_adap->dev, "i2c_inb: 0x%02x %s\n", inval, 391 count ? "A" : "NA"); 392 if (sclhi(adap)<0) { /* timeout */ 393 dev_err(&i2c_adap->dev, "readbytes: timeout at ack\n"); 394 return -ETIMEDOUT; 395 }; 396 scllo(adap); 397 398 /* Some SMBus transactions require that we receive the 399 transaction length as the first read byte. */ 400 if (rdcount == 1 && (msg->flags & I2C_M_RECV_LEN)) { 401 if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) { 402 dev_err(&i2c_adap->dev, "readbytes: invalid " 403 "block length (%d)\n", inval); 404 return -EREMOTEIO; 405 } 406 /* The original count value accounts for the extra 407 bytes, that is, either 1 for a regular transaction, 408 or 2 for a PEC transaction. */ 409 count += inval; 410 msg->len += inval; 411 } 412 } 413 return rdcount; 414} 415 416/* doAddress initiates the transfer by generating the start condition (in 417 * try_address) and transmits the address in the necessary format to handle 418 * reads, writes as well as 10bit-addresses. 419 * returns: 420 * 0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set 421 * -x an error occurred (like: -EREMOTEIO if the device did not answer, or 422 * -ETIMEDOUT, for example if the lines are stuck...) 423 */ 424static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg) 425{ 426 unsigned short flags = msg->flags; 427 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK; 428 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 429 430 unsigned char addr; 431 int ret, retries; 432 433 retries = nak_ok ? 0 : i2c_adap->retries; 434 435 if ( (flags & I2C_M_TEN) ) { 436 /* a ten bit address */ 437 addr = 0xf0 | (( msg->addr >> 7) & 0x03); 438 bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr); 439 /* try extended address code...*/ 440 ret = try_address(i2c_adap, addr, retries); 441 if ((ret != 1) && !nak_ok) { 442 dev_err(&i2c_adap->dev, 443 "died at extended address code\n"); 444 return -EREMOTEIO; 445 } 446 /* the remaining 8 bit address */ 447 ret = i2c_outb(i2c_adap,msg->addr & 0x7f); 448 if ((ret != 1) && !nak_ok) { 449 /* the chip did not ack / xmission error occurred */ 450 dev_err(&i2c_adap->dev, "died at 2nd address code\n"); 451 return -EREMOTEIO; 452 } 453 if ( flags & I2C_M_RD ) { 454 bit_dbg(3, &i2c_adap->dev, "emitting repeated " 455 "start condition\n"); 456 i2c_repstart(adap); 457 /* okay, now switch into reading mode */ 458 addr |= 0x01; 459 ret = try_address(i2c_adap, addr, retries); 460 if ((ret!=1) && !nak_ok) { 461 dev_err(&i2c_adap->dev, 462 "died at repeated address code\n"); 463 return -EREMOTEIO; 464 } 465 } 466 } else { /* normal 7bit address */ 467 addr = ( msg->addr << 1 ); 468 if (flags & I2C_M_RD ) 469 addr |= 1; 470 if (flags & I2C_M_REV_DIR_ADDR ) 471 addr ^= 1; 472 ret = try_address(i2c_adap, addr, retries); 473 if ((ret!=1) && !nak_ok) 474 return -EREMOTEIO; 475 } 476 477 return 0; 478} 479 480static int bit_xfer(struct i2c_adapter *i2c_adap, 481 struct i2c_msg msgs[], int num) 482{ 483 struct i2c_msg *pmsg; 484 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 485 486 int i,ret; 487 unsigned short nak_ok; 488 489 bit_dbg(3, &i2c_adap->dev, "emitting start condition\n"); 490 i2c_start(adap); 491 for (i=0;i<num;i++) { 492 pmsg = &msgs[i]; 493 nak_ok = pmsg->flags & I2C_M_IGNORE_NAK; 494 if (!(pmsg->flags & I2C_M_NOSTART)) { 495 if (i) { 496 bit_dbg(3, &i2c_adap->dev, "emitting " 497 "repeated start condition\n"); 498 i2c_repstart(adap); 499 } 500 ret = bit_doAddress(i2c_adap, pmsg); 501 if ((ret != 0) && !nak_ok) { 502 bit_dbg(1, &i2c_adap->dev, "NAK from " 503 "device addr 0x%02x msg #%d\n", 504 msgs[i].addr, i); 505 goto bailout; 506 } 507 } 508 if (pmsg->flags & I2C_M_RD ) { 509 /* read bytes into buffer*/ 510 ret = readbytes(i2c_adap, pmsg); 511 if (ret >= 1) 512 bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n", 513 ret, ret == 1 ? "" : "s"); 514 if (ret < pmsg->len) { 515 if (ret >= 0) 516 ret = -EREMOTEIO; 517 goto bailout; 518 } 519 } else { 520 /* write bytes from buffer */ 521 ret = sendbytes(i2c_adap, pmsg); 522 if (ret >= 1) 523 bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n", 524 ret, ret == 1 ? "" : "s"); 525 if (ret < pmsg->len) { 526 if (ret >= 0) 527 ret = -EREMOTEIO; 528 goto bailout; 529 } 530 } 531 } 532 ret = i; 533 534bailout: 535 bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n"); 536 i2c_stop(adap); 537 return ret; 538} 539 540static u32 bit_func(struct i2c_adapter *adap) 541{ 542 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | 543 I2C_FUNC_SMBUS_READ_BLOCK_DATA | 544 I2C_FUNC_SMBUS_BLOCK_PROC_CALL | 545 I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING; 546} 547 548 549/* -----exported algorithm data: ------------------------------------- */ 550 551static const struct i2c_algorithm i2c_bit_algo = { 552 .master_xfer = bit_xfer, 553 .functionality = bit_func, 554}; 555 556/* 557 * registering functions to load algorithms at runtime 558 */ 559static int i2c_bit_prepare_bus(struct i2c_adapter *adap) 560{ 561 struct i2c_algo_bit_data *bit_adap = adap->algo_data; 562 563 if (bit_test) { 564 int ret = test_bus(bit_adap, adap->name); 565 if (ret<0) 566 return -ENODEV; 567 } 568 569 /* register new adapter to i2c module... */ 570 adap->algo = &i2c_bit_algo; 571 572 adap->timeout = 100; /* default values, should */ 573 adap->retries = 3; /* be replaced by defines */ 574 575 return 0; 576} 577 578int i2c_bit_add_bus(struct i2c_adapter *adap) 579{ 580 int err; 581 582 err = i2c_bit_prepare_bus(adap); 583 if (err) 584 return err; 585 586 return i2c_add_adapter(adap); 587} 588EXPORT_SYMBOL(i2c_bit_add_bus); 589 590int i2c_bit_add_numbered_bus(struct i2c_adapter *adap) 591{ 592 int err; 593 594 err = i2c_bit_prepare_bus(adap); 595 if (err) 596 return err; 597 598 return i2c_add_numbered_adapter(adap); 599} 600EXPORT_SYMBOL(i2c_bit_add_numbered_bus); 601 602MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>"); 603MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm"); 604MODULE_LICENSE("GPL"); 605