arch/cris/arch-v32/drivers/i2c.c

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