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 #define DEB(x) if (i2c_debug>=1) x; 37 #define DEB2(x) if (i2c_debug>=2) x; 38 #define DEBSTAT(x) if (i2c_debug>=3) x; /* print several statistical values*/ 39 #define DEBPROTO(x) if (i2c_debug>=9) { x; } 40 /* debug the protocol by showing transferred bits */ 41 42 43 /* ----- global variables --------------------------------------------- */ 44 45 /* module parameters: 46 */ 47 static int i2c_debug; 48 static int bit_test; /* see if the line-setting functions work */ 49 50 /* --- setting states on the bus with the right timing: --------------- */ 51 52 #define setsda(adap,val) adap->setsda(adap->data, val) 53 #define setscl(adap,val) adap->setscl(adap->data, val) 54 #define getsda(adap) adap->getsda(adap->data) 55 #define getscl(adap) adap->getscl(adap->data) 56 57 static inline void sdalo(struct i2c_algo_bit_data *adap) 58 { 59 setsda(adap,0); 60 udelay(adap->udelay); 61 } 62 63 static inline void sdahi(struct i2c_algo_bit_data *adap) 64 { 65 setsda(adap,1); 66 udelay(adap->udelay); 67 } 68 69 static inline void scllo(struct i2c_algo_bit_data *adap) 70 { 71 setscl(adap,0); 72 udelay(adap->udelay); 73 } 74 75 /* 76 * Raise scl line, and do checking for delays. This is necessary for slower 77 * devices. 78 */ 79 static int sclhi(struct i2c_algo_bit_data *adap) 80 { 81 unsigned long start; 82 83 setscl(adap,1); 84 85 /* Not all adapters have scl sense line... */ 86 if (!adap->getscl) 87 goto done; 88 89 start=jiffies; 90 while (! getscl(adap) ) { 91 /* the hw knows how to read the clock line, 92 * so we wait until it actually gets high. 93 * This is safer as some chips may hold it low 94 * while they are processing data internally. 95 */ 96 if (time_after_eq(jiffies, start+adap->timeout)) { 97 return -ETIMEDOUT; 98 } 99 cond_resched(); 100 } 101 DEBSTAT(printk(KERN_DEBUG "needed %ld jiffies\n", jiffies-start)); 102 103 done: 104 udelay(adap->udelay); 105 return 0; 106 } 107 108 109 /* --- other auxiliary functions -------------------------------------- */ 110 static void i2c_start(struct i2c_algo_bit_data *adap) 111 { 112 /* assert: scl, sda are high */ 113 DEBPROTO(printk("S ")); 114 sdalo(adap); 115 scllo(adap); 116 } 117 118 static void i2c_repstart(struct i2c_algo_bit_data *adap) 119 { 120 /* scl, sda may not be high */ 121 DEBPROTO(printk(" Sr ")); 122 setsda(adap,1); 123 sclhi(adap); 124 125 sdalo(adap); 126 scllo(adap); 127 } 128 129 130 static void i2c_stop(struct i2c_algo_bit_data *adap) 131 { 132 DEBPROTO(printk("P\n")); 133 /* assert: scl is low */ 134 sdalo(adap); 135 sclhi(adap); 136 sdahi(adap); 137 } 138 139 140 141 /* send a byte without start cond., look for arbitration, 142 check ackn. from slave */ 143 /* returns: 144 * 1 if the device acknowledged 145 * 0 if the device did not ack 146 * -ETIMEDOUT if an error occurred (while raising the scl line) 147 */ 148 static int i2c_outb(struct i2c_adapter *i2c_adap, char c) 149 { 150 int i; 151 int sb; 152 int ack; 153 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 154 155 /* assert: scl is low */ 156 for ( i=7 ; i>=0 ; i-- ) { 157 sb = c & ( 1 << i ); 158 setsda(adap,sb); 159 udelay(adap->udelay); 160 DEBPROTO(printk(KERN_DEBUG "%d",sb!=0)); 161 if (sclhi(adap)<0) { /* timed out */ 162 sdahi(adap); /* we don't want to block the net */ 163 DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x, timeout at bit #%d\n", c&0xff, i)); 164 return -ETIMEDOUT; 165 }; 166 /* do arbitration here: 167 * if ( sb && ! getsda(adap) ) -> ouch! Get out of here. 168 */ 169 setscl(adap, 0 ); 170 udelay(adap->udelay); 171 } 172 sdahi(adap); 173 if (sclhi(adap)<0){ /* timeout */ 174 DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x, timeout at ack\n", c&0xff)); 175 return -ETIMEDOUT; 176 }; 177 /* read ack: SDA should be pulled down by slave */ 178 ack=getsda(adap); /* ack: sda is pulled low ->success. */ 179 DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x , getsda() = %d\n", c & 0xff, ack)); 180 181 DEBPROTO( printk(KERN_DEBUG "[%2.2x]",c&0xff) ); 182 DEBPROTO(if (0==ack){ printk(KERN_DEBUG " A ");} else printk(KERN_DEBUG " NA ") ); 183 scllo(adap); 184 return 0==ack; /* return 1 if device acked */ 185 /* assert: scl is low (sda undef) */ 186 } 187 188 189 static int i2c_inb(struct i2c_adapter *i2c_adap) 190 { 191 /* read byte via i2c port, without start/stop sequence */ 192 /* acknowledge is sent in i2c_read. */ 193 int i; 194 unsigned char indata=0; 195 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 196 197 /* assert: scl is low */ 198 sdahi(adap); 199 for (i=0;i<8;i++) { 200 if (sclhi(adap)<0) { /* timeout */ 201 DEB2(printk(KERN_DEBUG " i2c_inb: timeout at bit #%d\n", 7-i)); 202 return -ETIMEDOUT; 203 }; 204 indata *= 2; 205 if ( getsda(adap) ) 206 indata |= 0x01; 207 scllo(adap); 208 } 209 /* assert: scl is low */ 210 DEB2(printk(KERN_DEBUG "i2c_inb: 0x%02x\n", indata & 0xff)); 211 212 DEBPROTO(printk(KERN_DEBUG " 0x%02x", indata & 0xff)); 213 return (int) (indata & 0xff); 214 } 215 216 /* 217 * Sanity check for the adapter hardware - check the reaction of 218 * the bus lines only if it seems to be idle. 219 */ 220 static int test_bus(struct i2c_algo_bit_data *adap, char* name) { 221 int scl,sda; 222 223 if (adap->getscl==NULL) 224 printk(KERN_INFO "i2c-algo-bit.o: Testing SDA only, " 225 "SCL is not readable.\n"); 226 227 sda=getsda(adap); 228 scl=(adap->getscl==NULL?1:getscl(adap)); 229 printk(KERN_DEBUG "i2c-algo-bit.o: (0) scl=%d, sda=%d\n",scl,sda); 230 if (!scl || !sda ) { 231 printk(KERN_WARNING "i2c-algo-bit.o: %s seems to be busy.\n", name); 232 goto bailout; 233 } 234 235 sdalo(adap); 236 sda=getsda(adap); 237 scl=(adap->getscl==NULL?1:getscl(adap)); 238 printk(KERN_DEBUG "i2c-algo-bit.o: (1) scl=%d, sda=%d\n",scl,sda); 239 if ( 0 != sda ) { 240 printk(KERN_WARNING "i2c-algo-bit.o: SDA stuck high!\n"); 241 goto bailout; 242 } 243 if ( 0 == scl ) { 244 printk(KERN_WARNING "i2c-algo-bit.o: SCL unexpected low " 245 "while pulling SDA low!\n"); 246 goto bailout; 247 } 248 249 sdahi(adap); 250 sda=getsda(adap); 251 scl=(adap->getscl==NULL?1:getscl(adap)); 252 printk(KERN_DEBUG "i2c-algo-bit.o: (2) scl=%d, sda=%d\n",scl,sda); 253 if ( 0 == sda ) { 254 printk(KERN_WARNING "i2c-algo-bit.o: SDA stuck low!\n"); 255 goto bailout; 256 } 257 if ( 0 == scl ) { 258 printk(KERN_WARNING "i2c-algo-bit.o: SCL unexpected low " 259 "while pulling SDA high!\n"); 260 goto bailout; 261 } 262 263 scllo(adap); 264 sda=getsda(adap); 265 scl=(adap->getscl==NULL?0:getscl(adap)); 266 printk(KERN_DEBUG "i2c-algo-bit.o: (3) scl=%d, sda=%d\n",scl,sda); 267 if ( 0 != scl ) { 268 printk(KERN_WARNING "i2c-algo-bit.o: SCL stuck high!\n"); 269 goto bailout; 270 } 271 if ( 0 == sda ) { 272 printk(KERN_WARNING "i2c-algo-bit.o: SDA unexpected low " 273 "while pulling SCL low!\n"); 274 goto bailout; 275 } 276 277 sclhi(adap); 278 sda=getsda(adap); 279 scl=(adap->getscl==NULL?1:getscl(adap)); 280 printk(KERN_DEBUG "i2c-algo-bit.o: (4) scl=%d, sda=%d\n",scl,sda); 281 if ( 0 == scl ) { 282 printk(KERN_WARNING "i2c-algo-bit.o: SCL stuck low!\n"); 283 goto bailout; 284 } 285 if ( 0 == sda ) { 286 printk(KERN_WARNING "i2c-algo-bit.o: SDA unexpected low " 287 "while pulling SCL high!\n"); 288 goto bailout; 289 } 290 printk(KERN_INFO "i2c-algo-bit.o: %s passed test.\n",name); 291 return 0; 292 bailout: 293 sdahi(adap); 294 sclhi(adap); 295 return -ENODEV; 296 } 297 298 /* ----- Utility functions 299 */ 300 301 /* try_address tries to contact a chip for a number of 302 * times before it gives up. 303 * return values: 304 * 1 chip answered 305 * 0 chip did not answer 306 * -x transmission error 307 */ 308 static int try_address(struct i2c_adapter *i2c_adap, 309 unsigned char addr, int retries) 310 { 311 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 312 int i,ret = -1; 313 for (i=0;i<=retries;i++) { 314 ret = i2c_outb(i2c_adap,addr); 315 if (ret==1) 316 break; /* success! */ 317 i2c_stop(adap); 318 udelay(5/*adap->udelay*/); 319 if (i==retries) /* no success */ 320 break; 321 i2c_start(adap); 322 udelay(adap->udelay); 323 } 324 DEB2(if (i) 325 printk(KERN_DEBUG "i2c-algo-bit.o: Used %d tries to %s client at 0x%02x : %s\n", 326 i+1, addr & 1 ? "read" : "write", addr>>1, 327 ret==1 ? "success" : ret==0 ? "no ack" : "failed, timeout?" ) 328 ); 329 return ret; 330 } 331 332 static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg) 333 { 334 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 335 char c; 336 const char *temp = msg->buf; 337 int count = msg->len; 338 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK; 339 int retval; 340 int wrcount=0; 341 342 while (count > 0) { 343 c = *temp; 344 DEB2(dev_dbg(&i2c_adap->dev, "sendbytes: writing %2.2X\n", c&0xff)); 345 retval = i2c_outb(i2c_adap,c); 346 if ((retval>0) || (nak_ok && (retval==0))) { /* ok or ignored NAK */ 347 count--; 348 temp++; 349 wrcount++; 350 } else { /* arbitration or no acknowledge */ 351 dev_err(&i2c_adap->dev, "sendbytes: error - bailout.\n"); 352 i2c_stop(adap); 353 return (retval<0)? retval : -EFAULT; 354 /* got a better one ?? */ 355 } 356 } 357 return wrcount; 358 } 359 360 static 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 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 printk(KERN_ERR "i2c-algo-bit.o: readbytes: i2c_inb timed out.\n"); 375 break; 376 } 377 378 temp++; 379 count--; 380 381 if (msg->flags & I2C_M_NO_RD_ACK) 382 continue; 383 384 if ( count > 0 ) { /* send ack */ 385 sdalo(adap); 386 DEBPROTO(printk(" Am ")); 387 } else { 388 sdahi(adap); /* neg. ack on last byte */ 389 DEBPROTO(printk(" NAm ")); 390 } 391 if (sclhi(adap)<0) { /* timeout */ 392 sdahi(adap); 393 printk(KERN_ERR "i2c-algo-bit.o: readbytes: Timeout at ack\n"); 394 return -ETIMEDOUT; 395 }; 396 scllo(adap); 397 sdahi(adap); 398 } 399 return rdcount; 400 } 401 402 /* doAddress initiates the transfer by generating the start condition (in 403 * try_address) and transmits the address in the necessary format to handle 404 * reads, writes as well as 10bit-addresses. 405 * returns: 406 * 0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set 407 * -x an error occurred (like: -EREMOTEIO if the device did not answer, or 408 * -ETIMEDOUT, for example if the lines are stuck...) 409 */ 410 static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg) 411 { 412 unsigned short flags = msg->flags; 413 unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK; 414 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 415 416 unsigned char addr; 417 int ret, retries; 418 419 retries = nak_ok ? 0 : i2c_adap->retries; 420 421 if ( (flags & I2C_M_TEN) ) { 422 /* a ten bit address */ 423 addr = 0xf0 | (( msg->addr >> 7) & 0x03); 424 DEB2(printk(KERN_DEBUG "addr0: %d\n",addr)); 425 /* try extended address code...*/ 426 ret = try_address(i2c_adap, addr, retries); 427 if ((ret != 1) && !nak_ok) { 428 printk(KERN_ERR "died at extended address code.\n"); 429 return -EREMOTEIO; 430 } 431 /* the remaining 8 bit address */ 432 ret = i2c_outb(i2c_adap,msg->addr & 0x7f); 433 if ((ret != 1) && !nak_ok) { 434 /* the chip did not ack / xmission error occurred */ 435 printk(KERN_ERR "died at 2nd address code.\n"); 436 return -EREMOTEIO; 437 } 438 if ( flags & I2C_M_RD ) { 439 i2c_repstart(adap); 440 /* okay, now switch into reading mode */ 441 addr |= 0x01; 442 ret = try_address(i2c_adap, addr, retries); 443 if ((ret!=1) && !nak_ok) { 444 printk(KERN_ERR "died at extended address code.\n"); 445 return -EREMOTEIO; 446 } 447 } 448 } else { /* normal 7bit address */ 449 addr = ( msg->addr << 1 ); 450 if (flags & I2C_M_RD ) 451 addr |= 1; 452 if (flags & I2C_M_REV_DIR_ADDR ) 453 addr ^= 1; 454 ret = try_address(i2c_adap, addr, retries); 455 if ((ret!=1) && !nak_ok) 456 return -EREMOTEIO; 457 } 458 459 return 0; 460 } 461 462 static int bit_xfer(struct i2c_adapter *i2c_adap, 463 struct i2c_msg msgs[], int num) 464 { 465 struct i2c_msg *pmsg; 466 struct i2c_algo_bit_data *adap = i2c_adap->algo_data; 467 468 int i,ret; 469 unsigned short nak_ok; 470 471 i2c_start(adap); 472 for (i=0;i<num;i++) { 473 pmsg = &msgs[i]; 474 nak_ok = pmsg->flags & I2C_M_IGNORE_NAK; 475 if (!(pmsg->flags & I2C_M_NOSTART)) { 476 if (i) { 477 i2c_repstart(adap); 478 } 479 ret = bit_doAddress(i2c_adap, pmsg); 480 if ((ret != 0) && !nak_ok) { 481 DEB2(printk(KERN_DEBUG "i2c-algo-bit.o: NAK from device addr %2.2x msg #%d\n" 482 ,msgs[i].addr,i)); 483 return (ret<0) ? ret : -EREMOTEIO; 484 } 485 } 486 if (pmsg->flags & I2C_M_RD ) { 487 /* read bytes into buffer*/ 488 ret = readbytes(i2c_adap, pmsg); 489 DEB2(printk(KERN_DEBUG "i2c-algo-bit.o: read %d bytes.\n",ret)); 490 if (ret < pmsg->len ) { 491 return (ret<0)? ret : -EREMOTEIO; 492 } 493 } else { 494 /* write bytes from buffer */ 495 ret = sendbytes(i2c_adap, pmsg); 496 DEB2(printk(KERN_DEBUG "i2c-algo-bit.o: wrote %d bytes.\n",ret)); 497 if (ret < pmsg->len ) { 498 return (ret<0) ? ret : -EREMOTEIO; 499 } 500 } 501 } 502 i2c_stop(adap); 503 return num; 504 } 505 506 static u32 bit_func(struct i2c_adapter *adap) 507 { 508 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | 509 I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING; 510 } 511 512 513 /* -----exported algorithm data: ------------------------------------- */ 514 515 static const struct i2c_algorithm i2c_bit_algo = { 516 .master_xfer = bit_xfer, 517 .functionality = bit_func, 518 }; 519 520 /* 521 * registering functions to load algorithms at runtime 522 */ 523 int i2c_bit_add_bus(struct i2c_adapter *adap) 524 { 525 struct i2c_algo_bit_data *bit_adap = adap->algo_data; 526 527 if (bit_test) { 528 int ret = test_bus(bit_adap, adap->name); 529 if (ret<0) 530 return -ENODEV; 531 } 532 533 DEB2(dev_dbg(&adap->dev, "hw routines registered.\n")); 534 535 /* register new adapter to i2c module... */ 536 adap->algo = &i2c_bit_algo; 537 538 adap->timeout = 100; /* default values, should */ 539 adap->retries = 3; /* be replaced by defines */ 540 541 return i2c_add_adapter(adap); 542 } 543 544 545 int i2c_bit_del_bus(struct i2c_adapter *adap) 546 { 547 return i2c_del_adapter(adap); 548 } 549 550 EXPORT_SYMBOL(i2c_bit_add_bus); 551 EXPORT_SYMBOL(i2c_bit_del_bus); 552 553 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>"); 554 MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm"); 555 MODULE_LICENSE("GPL"); 556 557 module_param(bit_test, bool, 0); 558 module_param(i2c_debug, int, S_IRUGO | S_IWUSR); 559 560 MODULE_PARM_DESC(bit_test, "Test the lines of the bus to see if it is stuck"); 561 MODULE_PARM_DESC(i2c_debug, 562 "debug level - 0 off; 1 normal; 2,3 more verbose; 9 bit-protocol"); 563