Mikael Starvik | 51533b6 | 2005-07-27 11:44:44 -0700 | [diff] [blame] | 1 | /*!*************************************************************************** |
| 2 | *! |
| 3 | *! FILE NAME : i2c.c |
| 4 | *! |
| 5 | *! DESCRIPTION: implements an interface for IIC/I2C, both directly from other |
| 6 | *! kernel modules (i2c_writereg/readreg) and from userspace using |
| 7 | *! ioctl()'s |
| 8 | *! |
| 9 | *! Nov 30 1998 Torbjorn Eliasson Initial version. |
| 10 | *! Bjorn Wesen Elinux kernel version. |
| 11 | *! Jan 14 2000 Johan Adolfsson Fixed PB shadow register stuff - |
| 12 | *! don't use PB_I2C if DS1302 uses same bits, |
| 13 | *! use PB. |
| 14 | *| June 23 2003 Pieter Grimmerink Added 'i2c_sendnack'. i2c_readreg now |
| 15 | *| generates nack on last received byte, |
| 16 | *| instead of ack. |
| 17 | *| i2c_getack changed data level while clock |
| 18 | *| was high, causing DS75 to see a stop condition |
| 19 | *! |
| 20 | *! --------------------------------------------------------------------------- |
| 21 | *! |
| 22 | *! (C) Copyright 1999-2002 Axis Communications AB, LUND, SWEDEN |
| 23 | *! |
| 24 | *!***************************************************************************/ |
| 25 | /* $Id: i2c.c,v 1.2 2005/05/09 15:29:49 starvik Exp $ */ |
| 26 | /****************** INCLUDE FILES SECTION ***********************************/ |
| 27 | |
| 28 | #include <linux/module.h> |
| 29 | #include <linux/sched.h> |
| 30 | #include <linux/slab.h> |
| 31 | #include <linux/errno.h> |
| 32 | #include <linux/kernel.h> |
| 33 | #include <linux/fs.h> |
| 34 | #include <linux/string.h> |
| 35 | #include <linux/init.h> |
| 36 | #include <linux/config.h> |
| 37 | |
| 38 | #include <asm/etraxi2c.h> |
| 39 | |
| 40 | #include <asm/system.h> |
| 41 | #include <asm/io.h> |
| 42 | #include <asm/delay.h> |
| 43 | |
| 44 | #include "i2c.h" |
| 45 | |
| 46 | /****************** I2C DEFINITION SECTION *************************/ |
| 47 | |
| 48 | #define D(x) |
| 49 | |
| 50 | #define I2C_MAJOR 123 /* LOCAL/EXPERIMENTAL */ |
| 51 | static const char i2c_name[] = "i2c"; |
| 52 | |
| 53 | #define CLOCK_LOW_TIME 8 |
| 54 | #define CLOCK_HIGH_TIME 8 |
| 55 | #define START_CONDITION_HOLD_TIME 8 |
| 56 | #define STOP_CONDITION_HOLD_TIME 8 |
| 57 | #define ENABLE_OUTPUT 0x01 |
| 58 | #define ENABLE_INPUT 0x00 |
| 59 | #define I2C_CLOCK_HIGH 1 |
| 60 | #define I2C_CLOCK_LOW 0 |
| 61 | #define I2C_DATA_HIGH 1 |
| 62 | #define I2C_DATA_LOW 0 |
| 63 | |
| 64 | #define i2c_enable() |
| 65 | #define i2c_disable() |
| 66 | |
| 67 | /* enable or disable output-enable, to select output or input on the i2c bus */ |
| 68 | |
| 69 | #define i2c_dir_out() crisv32_io_set_dir(&cris_i2c_data, crisv32_io_dir_out) |
| 70 | #define i2c_dir_in() crisv32_io_set_dir(&cris_i2c_data, crisv32_io_dir_in) |
| 71 | |
| 72 | /* control the i2c clock and data signals */ |
| 73 | |
| 74 | #define i2c_clk(x) crisv32_io_set(&cris_i2c_clk, x) |
| 75 | #define i2c_data(x) crisv32_io_set(&cris_i2c_data, x) |
| 76 | |
| 77 | /* read a bit from the i2c interface */ |
| 78 | |
| 79 | #define i2c_getbit() crisv32_io_rd(&cris_i2c_data) |
| 80 | |
| 81 | #define i2c_delay(usecs) udelay(usecs) |
| 82 | |
| 83 | /****************** VARIABLE SECTION ************************************/ |
| 84 | |
| 85 | static struct crisv32_iopin cris_i2c_clk; |
| 86 | static struct crisv32_iopin cris_i2c_data; |
| 87 | |
| 88 | /****************** FUNCTION DEFINITION SECTION *************************/ |
| 89 | |
| 90 | |
| 91 | /* generate i2c start condition */ |
| 92 | |
| 93 | void |
| 94 | i2c_start(void) |
| 95 | { |
| 96 | /* |
| 97 | * SCL=1 SDA=1 |
| 98 | */ |
| 99 | i2c_dir_out(); |
| 100 | i2c_delay(CLOCK_HIGH_TIME/6); |
| 101 | i2c_data(I2C_DATA_HIGH); |
| 102 | i2c_clk(I2C_CLOCK_HIGH); |
| 103 | i2c_delay(CLOCK_HIGH_TIME); |
| 104 | /* |
| 105 | * SCL=1 SDA=0 |
| 106 | */ |
| 107 | i2c_data(I2C_DATA_LOW); |
| 108 | i2c_delay(START_CONDITION_HOLD_TIME); |
| 109 | /* |
| 110 | * SCL=0 SDA=0 |
| 111 | */ |
| 112 | i2c_clk(I2C_CLOCK_LOW); |
| 113 | i2c_delay(CLOCK_LOW_TIME); |
| 114 | } |
| 115 | |
| 116 | /* generate i2c stop condition */ |
| 117 | |
| 118 | void |
| 119 | i2c_stop(void) |
| 120 | { |
| 121 | i2c_dir_out(); |
| 122 | |
| 123 | /* |
| 124 | * SCL=0 SDA=0 |
| 125 | */ |
| 126 | i2c_clk(I2C_CLOCK_LOW); |
| 127 | i2c_data(I2C_DATA_LOW); |
| 128 | i2c_delay(CLOCK_LOW_TIME*2); |
| 129 | /* |
| 130 | * SCL=1 SDA=0 |
| 131 | */ |
| 132 | i2c_clk(I2C_CLOCK_HIGH); |
| 133 | i2c_delay(CLOCK_HIGH_TIME*2); |
| 134 | /* |
| 135 | * SCL=1 SDA=1 |
| 136 | */ |
| 137 | i2c_data(I2C_DATA_HIGH); |
| 138 | i2c_delay(STOP_CONDITION_HOLD_TIME); |
| 139 | |
| 140 | i2c_dir_in(); |
| 141 | } |
| 142 | |
| 143 | /* write a byte to the i2c interface */ |
| 144 | |
| 145 | void |
| 146 | i2c_outbyte(unsigned char x) |
| 147 | { |
| 148 | int i; |
| 149 | |
| 150 | i2c_dir_out(); |
| 151 | |
| 152 | for (i = 0; i < 8; i++) { |
| 153 | if (x & 0x80) { |
| 154 | i2c_data(I2C_DATA_HIGH); |
| 155 | } else { |
| 156 | i2c_data(I2C_DATA_LOW); |
| 157 | } |
| 158 | |
| 159 | i2c_delay(CLOCK_LOW_TIME/2); |
| 160 | i2c_clk(I2C_CLOCK_HIGH); |
| 161 | i2c_delay(CLOCK_HIGH_TIME); |
| 162 | i2c_clk(I2C_CLOCK_LOW); |
| 163 | i2c_delay(CLOCK_LOW_TIME/2); |
| 164 | x <<= 1; |
| 165 | } |
| 166 | i2c_data(I2C_DATA_LOW); |
| 167 | i2c_delay(CLOCK_LOW_TIME/2); |
| 168 | |
| 169 | /* |
| 170 | * enable input |
| 171 | */ |
| 172 | i2c_dir_in(); |
| 173 | } |
| 174 | |
| 175 | /* read a byte from the i2c interface */ |
| 176 | |
| 177 | unsigned char |
| 178 | i2c_inbyte(void) |
| 179 | { |
| 180 | unsigned char aBitByte = 0; |
| 181 | int i; |
| 182 | |
| 183 | /* Switch off I2C to get bit */ |
| 184 | i2c_disable(); |
| 185 | i2c_dir_in(); |
| 186 | i2c_delay(CLOCK_HIGH_TIME/2); |
| 187 | |
| 188 | /* Get bit */ |
| 189 | aBitByte |= i2c_getbit(); |
| 190 | |
| 191 | /* Enable I2C */ |
| 192 | i2c_enable(); |
| 193 | i2c_delay(CLOCK_LOW_TIME/2); |
| 194 | |
| 195 | for (i = 1; i < 8; i++) { |
| 196 | aBitByte <<= 1; |
| 197 | /* Clock pulse */ |
| 198 | i2c_clk(I2C_CLOCK_HIGH); |
| 199 | i2c_delay(CLOCK_HIGH_TIME); |
| 200 | i2c_clk(I2C_CLOCK_LOW); |
| 201 | i2c_delay(CLOCK_LOW_TIME); |
| 202 | |
| 203 | /* Switch off I2C to get bit */ |
| 204 | i2c_disable(); |
| 205 | i2c_dir_in(); |
| 206 | i2c_delay(CLOCK_HIGH_TIME/2); |
| 207 | |
| 208 | /* Get bit */ |
| 209 | aBitByte |= i2c_getbit(); |
| 210 | |
| 211 | /* Enable I2C */ |
| 212 | i2c_enable(); |
| 213 | i2c_delay(CLOCK_LOW_TIME/2); |
| 214 | } |
| 215 | i2c_clk(I2C_CLOCK_HIGH); |
| 216 | i2c_delay(CLOCK_HIGH_TIME); |
| 217 | |
| 218 | /* |
| 219 | * we leave the clock low, getbyte is usually followed |
| 220 | * by sendack/nack, they assume the clock to be low |
| 221 | */ |
| 222 | i2c_clk(I2C_CLOCK_LOW); |
| 223 | return aBitByte; |
| 224 | } |
| 225 | |
| 226 | /*#--------------------------------------------------------------------------- |
| 227 | *# |
| 228 | *# FUNCTION NAME: i2c_getack |
| 229 | *# |
| 230 | *# DESCRIPTION : checks if ack was received from ic2 |
| 231 | *# |
| 232 | *#--------------------------------------------------------------------------*/ |
| 233 | |
| 234 | int |
| 235 | i2c_getack(void) |
| 236 | { |
| 237 | int ack = 1; |
| 238 | /* |
| 239 | * enable output |
| 240 | */ |
| 241 | i2c_dir_out(); |
| 242 | /* |
| 243 | * Release data bus by setting |
| 244 | * data high |
| 245 | */ |
| 246 | i2c_data(I2C_DATA_HIGH); |
| 247 | /* |
| 248 | * enable input |
| 249 | */ |
| 250 | i2c_dir_in(); |
| 251 | i2c_delay(CLOCK_HIGH_TIME/4); |
| 252 | /* |
| 253 | * generate ACK clock pulse |
| 254 | */ |
| 255 | i2c_clk(I2C_CLOCK_HIGH); |
| 256 | /* |
| 257 | * Use PORT PB instead of I2C |
| 258 | * for input. (I2C not working) |
| 259 | */ |
| 260 | i2c_clk(1); |
| 261 | i2c_data(1); |
| 262 | /* |
| 263 | * switch off I2C |
| 264 | */ |
| 265 | i2c_data(1); |
| 266 | i2c_disable(); |
| 267 | i2c_dir_in(); |
| 268 | /* |
| 269 | * now wait for ack |
| 270 | */ |
| 271 | i2c_delay(CLOCK_HIGH_TIME/2); |
| 272 | /* |
| 273 | * check for ack |
| 274 | */ |
| 275 | if(i2c_getbit()) |
| 276 | ack = 0; |
| 277 | i2c_delay(CLOCK_HIGH_TIME/2); |
| 278 | if(!ack){ |
| 279 | if(!i2c_getbit()) /* receiver pulld SDA low */ |
| 280 | ack = 1; |
| 281 | i2c_delay(CLOCK_HIGH_TIME/2); |
| 282 | } |
| 283 | |
| 284 | /* |
| 285 | * our clock is high now, make sure data is low |
| 286 | * before we enable our output. If we keep data high |
| 287 | * and enable output, we would generate a stop condition. |
| 288 | */ |
| 289 | i2c_data(I2C_DATA_LOW); |
| 290 | |
| 291 | /* |
| 292 | * end clock pulse |
| 293 | */ |
| 294 | i2c_enable(); |
| 295 | i2c_dir_out(); |
| 296 | i2c_clk(I2C_CLOCK_LOW); |
| 297 | i2c_delay(CLOCK_HIGH_TIME/4); |
| 298 | /* |
| 299 | * enable output |
| 300 | */ |
| 301 | i2c_dir_out(); |
| 302 | /* |
| 303 | * remove ACK clock pulse |
| 304 | */ |
| 305 | i2c_data(I2C_DATA_HIGH); |
| 306 | i2c_delay(CLOCK_LOW_TIME/2); |
| 307 | return ack; |
| 308 | } |
| 309 | |
| 310 | /*#--------------------------------------------------------------------------- |
| 311 | *# |
| 312 | *# FUNCTION NAME: I2C::sendAck |
| 313 | *# |
| 314 | *# DESCRIPTION : Send ACK on received data |
| 315 | *# |
| 316 | *#--------------------------------------------------------------------------*/ |
| 317 | void |
| 318 | i2c_sendack(void) |
| 319 | { |
| 320 | /* |
| 321 | * enable output |
| 322 | */ |
| 323 | i2c_delay(CLOCK_LOW_TIME); |
| 324 | i2c_dir_out(); |
| 325 | /* |
| 326 | * set ack pulse high |
| 327 | */ |
| 328 | i2c_data(I2C_DATA_LOW); |
| 329 | /* |
| 330 | * generate clock pulse |
| 331 | */ |
| 332 | i2c_delay(CLOCK_HIGH_TIME/6); |
| 333 | i2c_clk(I2C_CLOCK_HIGH); |
| 334 | i2c_delay(CLOCK_HIGH_TIME); |
| 335 | i2c_clk(I2C_CLOCK_LOW); |
| 336 | i2c_delay(CLOCK_LOW_TIME/6); |
| 337 | /* |
| 338 | * reset data out |
| 339 | */ |
| 340 | i2c_data(I2C_DATA_HIGH); |
| 341 | i2c_delay(CLOCK_LOW_TIME); |
| 342 | |
| 343 | i2c_dir_in(); |
| 344 | } |
| 345 | |
| 346 | /*#--------------------------------------------------------------------------- |
| 347 | *# |
| 348 | *# FUNCTION NAME: i2c_sendnack |
| 349 | *# |
| 350 | *# DESCRIPTION : Sends NACK on received data |
| 351 | *# |
| 352 | *#--------------------------------------------------------------------------*/ |
| 353 | void |
| 354 | i2c_sendnack(void) |
| 355 | { |
| 356 | /* |
| 357 | * enable output |
| 358 | */ |
| 359 | i2c_delay(CLOCK_LOW_TIME); |
| 360 | i2c_dir_out(); |
| 361 | /* |
| 362 | * set data high |
| 363 | */ |
| 364 | i2c_data(I2C_DATA_HIGH); |
| 365 | /* |
| 366 | * generate clock pulse |
| 367 | */ |
| 368 | i2c_delay(CLOCK_HIGH_TIME/6); |
| 369 | i2c_clk(I2C_CLOCK_HIGH); |
| 370 | i2c_delay(CLOCK_HIGH_TIME); |
| 371 | i2c_clk(I2C_CLOCK_LOW); |
| 372 | i2c_delay(CLOCK_LOW_TIME); |
| 373 | |
| 374 | i2c_dir_in(); |
| 375 | } |
| 376 | |
| 377 | /*#--------------------------------------------------------------------------- |
| 378 | *# |
| 379 | *# FUNCTION NAME: i2c_writereg |
| 380 | *# |
| 381 | *# DESCRIPTION : Writes a value to an I2C device |
| 382 | *# |
| 383 | *#--------------------------------------------------------------------------*/ |
| 384 | int |
| 385 | i2c_writereg(unsigned char theSlave, unsigned char theReg, |
| 386 | unsigned char theValue) |
| 387 | { |
| 388 | int error, cntr = 3; |
| 389 | unsigned long flags; |
| 390 | |
| 391 | do { |
| 392 | error = 0; |
| 393 | /* |
| 394 | * we don't like to be interrupted |
| 395 | */ |
| 396 | local_irq_save(flags); |
| 397 | |
| 398 | i2c_start(); |
| 399 | /* |
| 400 | * send slave address |
| 401 | */ |
| 402 | i2c_outbyte((theSlave & 0xfe)); |
| 403 | /* |
| 404 | * wait for ack |
| 405 | */ |
| 406 | if(!i2c_getack()) |
| 407 | error = 1; |
| 408 | /* |
| 409 | * now select register |
| 410 | */ |
| 411 | i2c_dir_out(); |
| 412 | i2c_outbyte(theReg); |
| 413 | /* |
| 414 | * now it's time to wait for ack |
| 415 | */ |
| 416 | if(!i2c_getack()) |
| 417 | error |= 2; |
| 418 | /* |
| 419 | * send register register data |
| 420 | */ |
| 421 | i2c_outbyte(theValue); |
| 422 | /* |
| 423 | * now it's time to wait for ack |
| 424 | */ |
| 425 | if(!i2c_getack()) |
| 426 | error |= 4; |
| 427 | /* |
| 428 | * end byte stream |
| 429 | */ |
| 430 | i2c_stop(); |
| 431 | /* |
| 432 | * enable interrupt again |
| 433 | */ |
| 434 | local_irq_restore(flags); |
| 435 | |
| 436 | } while(error && cntr--); |
| 437 | |
| 438 | i2c_delay(CLOCK_LOW_TIME); |
| 439 | |
| 440 | return -error; |
| 441 | } |
| 442 | |
| 443 | /*#--------------------------------------------------------------------------- |
| 444 | *# |
| 445 | *# FUNCTION NAME: i2c_readreg |
| 446 | *# |
| 447 | *# DESCRIPTION : Reads a value from the decoder registers. |
| 448 | *# |
| 449 | *#--------------------------------------------------------------------------*/ |
| 450 | unsigned char |
| 451 | i2c_readreg(unsigned char theSlave, unsigned char theReg) |
| 452 | { |
| 453 | unsigned char b = 0; |
| 454 | int error, cntr = 3; |
| 455 | unsigned long flags; |
| 456 | |
| 457 | do { |
| 458 | error = 0; |
| 459 | /* |
| 460 | * we don't like to be interrupted |
| 461 | */ |
| 462 | local_irq_save(flags); |
| 463 | /* |
| 464 | * generate start condition |
| 465 | */ |
| 466 | i2c_start(); |
| 467 | |
| 468 | /* |
| 469 | * send slave address |
| 470 | */ |
| 471 | i2c_outbyte((theSlave & 0xfe)); |
| 472 | /* |
| 473 | * wait for ack |
| 474 | */ |
| 475 | if(!i2c_getack()) |
| 476 | error = 1; |
| 477 | /* |
| 478 | * now select register |
| 479 | */ |
| 480 | i2c_dir_out(); |
| 481 | i2c_outbyte(theReg); |
| 482 | /* |
| 483 | * now it's time to wait for ack |
| 484 | */ |
| 485 | if(!i2c_getack()) |
| 486 | error = 1; |
| 487 | /* |
| 488 | * repeat start condition |
| 489 | */ |
| 490 | i2c_delay(CLOCK_LOW_TIME); |
| 491 | i2c_start(); |
| 492 | /* |
| 493 | * send slave address |
| 494 | */ |
| 495 | i2c_outbyte(theSlave | 0x01); |
| 496 | /* |
| 497 | * wait for ack |
| 498 | */ |
| 499 | if(!i2c_getack()) |
| 500 | error = 1; |
| 501 | /* |
| 502 | * fetch register |
| 503 | */ |
| 504 | b = i2c_inbyte(); |
| 505 | /* |
| 506 | * last received byte needs to be nacked |
| 507 | * instead of acked |
| 508 | */ |
| 509 | i2c_sendnack(); |
| 510 | /* |
| 511 | * end sequence |
| 512 | */ |
| 513 | i2c_stop(); |
| 514 | /* |
| 515 | * enable interrupt again |
| 516 | */ |
| 517 | local_irq_restore(flags); |
| 518 | |
| 519 | } while(error && cntr--); |
| 520 | |
| 521 | return b; |
| 522 | } |
| 523 | |
| 524 | static int |
| 525 | i2c_open(struct inode *inode, struct file *filp) |
| 526 | { |
| 527 | return 0; |
| 528 | } |
| 529 | |
| 530 | static int |
| 531 | i2c_release(struct inode *inode, struct file *filp) |
| 532 | { |
| 533 | return 0; |
| 534 | } |
| 535 | |
| 536 | /* Main device API. ioctl's to write or read to/from i2c registers. |
| 537 | */ |
| 538 | |
| 539 | static int |
| 540 | i2c_ioctl(struct inode *inode, struct file *file, |
| 541 | unsigned int cmd, unsigned long arg) |
| 542 | { |
| 543 | if(_IOC_TYPE(cmd) != ETRAXI2C_IOCTYPE) { |
| 544 | return -EINVAL; |
| 545 | } |
| 546 | |
| 547 | switch (_IOC_NR(cmd)) { |
| 548 | case I2C_WRITEREG: |
| 549 | /* write to an i2c slave */ |
| 550 | D(printk("i2cw %d %d %d\n", |
| 551 | I2C_ARGSLAVE(arg), |
| 552 | I2C_ARGREG(arg), |
| 553 | I2C_ARGVALUE(arg))); |
| 554 | |
| 555 | return i2c_writereg(I2C_ARGSLAVE(arg), |
| 556 | I2C_ARGREG(arg), |
| 557 | I2C_ARGVALUE(arg)); |
| 558 | case I2C_READREG: |
| 559 | { |
| 560 | unsigned char val; |
| 561 | /* read from an i2c slave */ |
| 562 | D(printk("i2cr %d %d ", |
| 563 | I2C_ARGSLAVE(arg), |
| 564 | I2C_ARGREG(arg))); |
| 565 | val = i2c_readreg(I2C_ARGSLAVE(arg), I2C_ARGREG(arg)); |
| 566 | D(printk("= %d\n", val)); |
| 567 | return val; |
| 568 | } |
| 569 | default: |
| 570 | return -EINVAL; |
| 571 | |
| 572 | } |
| 573 | |
| 574 | return 0; |
| 575 | } |
| 576 | |
| 577 | static struct file_operations i2c_fops = { |
| 578 | owner: THIS_MODULE, |
| 579 | ioctl: i2c_ioctl, |
| 580 | open: i2c_open, |
| 581 | release: i2c_release, |
| 582 | }; |
| 583 | |
| 584 | int __init |
| 585 | i2c_init(void) |
| 586 | { |
| 587 | int res; |
| 588 | |
| 589 | /* Setup and enable the Port B I2C interface */ |
| 590 | |
| 591 | crisv32_io_get_name(&cris_i2c_data, CONFIG_ETRAX_I2C_DATA_PORT); |
| 592 | crisv32_io_get_name(&cris_i2c_clk, CONFIG_ETRAX_I2C_CLK_PORT); |
| 593 | |
| 594 | /* register char device */ |
| 595 | |
| 596 | res = register_chrdev(I2C_MAJOR, i2c_name, &i2c_fops); |
| 597 | if(res < 0) { |
| 598 | printk(KERN_ERR "i2c: couldn't get a major number.\n"); |
| 599 | return res; |
| 600 | } |
| 601 | |
| 602 | printk(KERN_INFO "I2C driver v2.2, (c) 1999-2001 Axis Communications AB\n"); |
| 603 | |
| 604 | return 0; |
| 605 | } |
| 606 | |
| 607 | /* this makes sure that i2c_init is called during boot */ |
| 608 | |
| 609 | module_init(i2c_init); |
| 610 | |
| 611 | /****************** END OF FILE i2c.c ********************************/ |