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 1999-2007 Axis Communications AB, LUND, SWEDEN
  23 *!
  24 *!***************************************************************************/
  25
  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/smp_lock.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 static DEFINE_SPINLOCK(i2c_lock); /* Protect directions etc */
  84
  85 /****************** VARIABLE SECTION ************************************/
  86
  87 static struct crisv32_iopin cris_i2c_clk;
  88 static struct crisv32_iopin cris_i2c_data;
  89
  90 /****************** FUNCTION DEFINITION SECTION *************************/
  91
  92
  93 /* generate i2c start condition */
  94
  95 void
  96 i2c_start(void)
  97 {
  98         /*
  99          * SCL=1 SDA=1
 100          */
 101         i2c_dir_out();
 102         i2c_delay(CLOCK_HIGH_TIME/6);
 103         i2c_data(I2C_DATA_HIGH);
 104         i2c_clk(I2C_CLOCK_HIGH);
 105         i2c_delay(CLOCK_HIGH_TIME);
 106         /*
 107          * SCL=1 SDA=0
 108          */
 109         i2c_data(I2C_DATA_LOW);
 110         i2c_delay(START_CONDITION_HOLD_TIME);
 111         /*
 112          * SCL=0 SDA=0
 113          */
 114         i2c_clk(I2C_CLOCK_LOW);
 115         i2c_delay(CLOCK_LOW_TIME);
 116 }
 117
 118 /* generate i2c stop condition */
 119
 120 void
 121 i2c_stop(void)
 122 {
 123         i2c_dir_out();
 124
 125         /*
 126          * SCL=0 SDA=0
 127          */
 128         i2c_clk(I2C_CLOCK_LOW);
 129         i2c_data(I2C_DATA_LOW);
 130         i2c_delay(CLOCK_LOW_TIME*2);
 131         /*
 132          * SCL=1 SDA=0
 133          */
 134         i2c_clk(I2C_CLOCK_HIGH);
 135         i2c_delay(CLOCK_HIGH_TIME*2);
 136         /*
 137          * SCL=1 SDA=1
 138          */
 139         i2c_data(I2C_DATA_HIGH);
 140         i2c_delay(STOP_CONDITION_HOLD_TIME);
 141
 142         i2c_dir_in();
 143 }
 144
 145 /* write a byte to the i2c interface */
 146
 147 void
 148 i2c_outbyte(unsigned char x)
 149 {
 150         int i;
 151
 152         i2c_dir_out();
 153
 154         for (i = 0; i < 8; i++) {
 155                 if (x & 0x80) {
 156                         i2c_data(I2C_DATA_HIGH);
 157                 } else {
 158                         i2c_data(I2C_DATA_LOW);
 159                 }
 160
 161                 i2c_delay(CLOCK_LOW_TIME/2);
 162                 i2c_clk(I2C_CLOCK_HIGH);
 163                 i2c_delay(CLOCK_HIGH_TIME);
 164                 i2c_clk(I2C_CLOCK_LOW);
 165                 i2c_delay(CLOCK_LOW_TIME/2);
 166                 x <<= 1;
 167         }
 168         i2c_data(I2C_DATA_LOW);
 169         i2c_delay(CLOCK_LOW_TIME/2);
 170
 171         /*
 172          * enable input
 173          */
 174         i2c_dir_in();
 175 }
 176
 177 /* read a byte from the i2c interface */
 178
 179 unsigned char
 180 i2c_inbyte(void)
 181 {
 182         unsigned char aBitByte = 0;
 183         int i;
 184
 185         /* Switch off I2C to get bit */
 186         i2c_disable();
 187         i2c_dir_in();
 188         i2c_delay(CLOCK_HIGH_TIME/2);
 189
 190         /* Get bit */
 191         aBitByte |= i2c_getbit();
 192
 193         /* Enable I2C */
 194         i2c_enable();
 195         i2c_delay(CLOCK_LOW_TIME/2);
 196
 197         for (i = 1; i < 8; i++) {
 198                 aBitByte <<= 1;
 199                 /* Clock pulse */
 200                 i2c_clk(I2C_CLOCK_HIGH);
 201                 i2c_delay(CLOCK_HIGH_TIME);
 202                 i2c_clk(I2C_CLOCK_LOW);
 203                 i2c_delay(CLOCK_LOW_TIME);
 204
 205                 /* Switch off I2C to get bit */
 206                 i2c_disable();
 207                 i2c_dir_in();
 208                 i2c_delay(CLOCK_HIGH_TIME/2);
 209
 210                 /* Get bit */
 211                 aBitByte |= i2c_getbit();
 212
 213                 /* Enable I2C */
 214                 i2c_enable();
 215                 i2c_delay(CLOCK_LOW_TIME/2);
 216         }
 217         i2c_clk(I2C_CLOCK_HIGH);
 218         i2c_delay(CLOCK_HIGH_TIME);
 219
 220         /*
 221          * we leave the clock low, getbyte is usually followed
 222          * by sendack/nack, they assume the clock to be low
 223          */
 224         i2c_clk(I2C_CLOCK_LOW);
 225         return aBitByte;
 226 }
 227
 228 /*#---------------------------------------------------------------------------
 229 *#
 230 *# FUNCTION NAME: i2c_getack
 231 *#
 232 *# DESCRIPTION  : checks if ack was received from ic2
 233 *#
 234 *#--------------------------------------------------------------------------*/
 235
 236 int
 237 i2c_getack(void)
 238 {
 239         int ack = 1;
 240         /*
 241          * enable output
 242          */
 243         i2c_dir_out();
 244         /*
 245          * Release data bus by setting
 246          * data high
 247          */
 248         i2c_data(I2C_DATA_HIGH);
 249         /*
 250          * enable input
 251          */
 252         i2c_dir_in();
 253         i2c_delay(CLOCK_HIGH_TIME/4);
 254         /*
 255          * generate ACK clock pulse
 256          */
 257         i2c_clk(I2C_CLOCK_HIGH);
 258 #if 0
 259         /*
 260          * Use PORT PB instead of I2C
 261          * for input. (I2C not working)
 262          */
 263         i2c_clk(1);
 264         i2c_data(1);
 265         /*
 266          * switch off I2C
 267          */
 268         i2c_data(1);
 269         i2c_disable();
 270         i2c_dir_in();
 271 #endif
 272
 273         /*
 274          * now wait for ack
 275          */
 276         i2c_delay(CLOCK_HIGH_TIME/2);
 277         /*
 278          * check for ack
 279          */
 280         if (i2c_getbit())
 281                 ack = 0;
 282         i2c_delay(CLOCK_HIGH_TIME/2);
 283         if (!ack) {
 284                 if (!i2c_getbit()) /* receiver pulld SDA low */
 285                         ack = 1;
 286                 i2c_delay(CLOCK_HIGH_TIME/2);
 287         }
 288
 289    /*
 290     * our clock is high now, make sure data is low
 291     * before we enable our output. If we keep data high
 292     * and enable output, we would generate a stop condition.
 293     */
 294 #if 0
 295    i2c_data(I2C_DATA_LOW);
 296
 297         /*
 298          * end clock pulse
 299          */
 300         i2c_enable();
 301         i2c_dir_out();
 302 #endif
 303         i2c_clk(I2C_CLOCK_LOW);
 304         i2c_delay(CLOCK_HIGH_TIME/4);
 305         /*
 306          * enable output
 307          */
 308         i2c_dir_out();
 309         /*
 310          * remove ACK clock pulse
 311          */
 312         i2c_data(I2C_DATA_HIGH);
 313         i2c_delay(CLOCK_LOW_TIME/2);
 314         return ack;
 315 }
 316
 317 /*#---------------------------------------------------------------------------
 318 *#
 319 *# FUNCTION NAME: I2C::sendAck
 320 *#
 321 *# DESCRIPTION  : Send ACK on received data
 322 *#
 323 *#--------------------------------------------------------------------------*/
 324 void
 325 i2c_sendack(void)
 326 {
 327         /*
 328          * enable output
 329          */
 330         i2c_delay(CLOCK_LOW_TIME);
 331         i2c_dir_out();
 332         /*
 333          * set ack pulse high
 334          */
 335         i2c_data(I2C_DATA_LOW);
 336         /*
 337          * generate clock pulse
 338          */
 339         i2c_delay(CLOCK_HIGH_TIME/6);
 340         i2c_clk(I2C_CLOCK_HIGH);
 341         i2c_delay(CLOCK_HIGH_TIME);
 342         i2c_clk(I2C_CLOCK_LOW);
 343         i2c_delay(CLOCK_LOW_TIME/6);
 344         /*
 345          * reset data out
 346          */
 347         i2c_data(I2C_DATA_HIGH);
 348         i2c_delay(CLOCK_LOW_TIME);
 349
 350         i2c_dir_in();
 351 }
 352
 353 /*#---------------------------------------------------------------------------
 354 *#
 355 *# FUNCTION NAME: i2c_sendnack
 356 *#
 357 *# DESCRIPTION  : Sends NACK on received data
 358 *#
 359 *#--------------------------------------------------------------------------*/
 360 void
 361 i2c_sendnack(void)
 362 {
 363         /*
 364          * enable output
 365          */
 366         i2c_delay(CLOCK_LOW_TIME);
 367         i2c_dir_out();
 368         /*
 369          * set data high
 370          */
 371         i2c_data(I2C_DATA_HIGH);
 372         /*
 373          * generate clock pulse
 374          */
 375         i2c_delay(CLOCK_HIGH_TIME/6);
 376         i2c_clk(I2C_CLOCK_HIGH);
 377         i2c_delay(CLOCK_HIGH_TIME);
 378         i2c_clk(I2C_CLOCK_LOW);
 379         i2c_delay(CLOCK_LOW_TIME);
 380
 381         i2c_dir_in();
 382 }
 383
 384 /*#---------------------------------------------------------------------------
 385 *#
 386 *# FUNCTION NAME: i2c_write
 387 *#
 388 *# DESCRIPTION  : Writes a value to an I2C device
 389 *#
 390 *#--------------------------------------------------------------------------*/
 391 int
 392 i2c_write(unsigned char theSlave, void *data, size_t nbytes)
 393 {
 394         int error, cntr = 3;
 395         unsigned char bytes_wrote = 0;
 396         unsigned char value;
 397         unsigned long flags;
 398
 399         spin_lock_irqsave(&i2c_lock, flags);
 400
 401         do {
 402                 error = 0;
 403
 404                 i2c_start();
 405                 /*
 406                  * send slave address
 407                  */
 408                 i2c_outbyte((theSlave & 0xfe));
 409                 /*
 410                  * wait for ack
 411                  */
 412                 if (!i2c_getack())
 413                         error = 1;
 414                 /*
 415                  * send data
 416                  */
 417                 for (bytes_wrote = 0; bytes_wrote < nbytes; bytes_wrote++) {
 418                         memcpy(&value, data + bytes_wrote, sizeof value);
 419                         i2c_outbyte(value);
 420                         /*
 421                          * now it's time to wait for ack
 422                          */
 423                         if (!i2c_getack())
 424                                 error |= 4;
 425                 }
 426                 /*
 427                  * end byte stream
 428                  */
 429                 i2c_stop();
 430
 431         } while (error && cntr--);
 432
 433         i2c_delay(CLOCK_LOW_TIME);
 434
 435         spin_unlock_irqrestore(&i2c_lock, flags);
 436
 437         return -error;
 438 }
 439
 440 /*#---------------------------------------------------------------------------
 441 *#
 442 *# FUNCTION NAME: i2c_read
 443 *#
 444 *# DESCRIPTION  : Reads a value from an I2C device
 445 *#
 446 *#--------------------------------------------------------------------------*/
 447 int
 448 i2c_read(unsigned char theSlave, void *data, size_t nbytes)
 449 {
 450         unsigned char b = 0;
 451         unsigned char bytes_read = 0;
 452         int error, cntr = 3;
 453         unsigned long flags;
 454
 455         spin_lock_irqsave(&i2c_lock, flags);
 456
 457         do {
 458                 error = 0;
 459                 memset(data, 0, nbytes);
 460                 /*
 461                  * generate start condition
 462                  */
 463                 i2c_start();
 464                 /*
 465                  * send slave address
 466                  */
 467                 i2c_outbyte((theSlave | 0x01));
 468                 /*
 469                  * wait for ack
 470                  */
 471                 if (!i2c_getack())
 472                         error = 1;
 473                 /*
 474                  * fetch data
 475                  */
 476                 for (bytes_read = 0; bytes_read < nbytes; bytes_read++) {
 477                         b = i2c_inbyte();
 478                         memcpy(data + bytes_read, &b, sizeof b);
 479
 480                         if (bytes_read < (nbytes - 1))
 481                                 i2c_sendack();
 482                 }
 483                 /*
 484                  * last received byte needs to be nacked
 485                  * instead of acked
 486                  */
 487                 i2c_sendnack();
 488                 /*
 489                  * end sequence
 490                  */
 491                 i2c_stop();
 492         } while (error && cntr--);
 493
 494         spin_unlock_irqrestore(&i2c_lock, flags);
 495
 496         return -error;
 497 }
 498
 499 /*#---------------------------------------------------------------------------
 500 *#
 501 *# FUNCTION NAME: i2c_writereg
 502 *#
 503 *# DESCRIPTION  : Writes a value to an I2C device
 504 *#
 505 *#--------------------------------------------------------------------------*/
 506 int
 507 i2c_writereg(unsigned char theSlave, unsigned char theReg,
 508              unsigned char theValue)
 509 {
 510         int error, cntr = 3;
 511         unsigned long flags;
 512
 513         spin_lock_irqsave(&i2c_lock, flags);
 514
 515         do {
 516                 error = 0;
 517
 518                 i2c_start();
 519                 /*
 520                  * send slave address
 521                  */
 522                 i2c_outbyte((theSlave & 0xfe));
 523                 /*
 524                  * wait for ack
 525                  */
 526                 if(!i2c_getack())
 527                         error = 1;
 528                 /*
 529                  * now select register
 530                  */
 531                 i2c_dir_out();
 532                 i2c_outbyte(theReg);
 533                 /*
 534                  * now it's time to wait for ack
 535                  */
 536                 if(!i2c_getack())
 537                         error |= 2;
 538                 /*
 539                  * send register register data
 540                  */
 541                 i2c_outbyte(theValue);
 542                 /*
 543                  * now it's time to wait for ack
 544                  */
 545                 if(!i2c_getack())
 546                         error |= 4;
 547                 /*
 548                  * end byte stream
 549                  */
 550                 i2c_stop();
 551         } while(error && cntr--);
 552
 553         i2c_delay(CLOCK_LOW_TIME);
 554
 555         spin_unlock_irqrestore(&i2c_lock, flags);
 556
 557         return -error;
 558 }
 559
 560 /*#---------------------------------------------------------------------------
 561 *#
 562 *# FUNCTION NAME: i2c_readreg
 563 *#
 564 *# DESCRIPTION  : Reads a value from the decoder registers.
 565 *#
 566 *#--------------------------------------------------------------------------*/
 567 unsigned char
 568 i2c_readreg(unsigned char theSlave, unsigned char theReg)
 569 {
 570         unsigned char b = 0;
 571         int error, cntr = 3;
 572         unsigned long flags;
 573
 574         spin_lock_irqsave(&i2c_lock, flags);
 575
 576         do {
 577                 error = 0;
 578                 /*
 579                  * generate start condition
 580                  */
 581                 i2c_start();
 582
 583                 /*
 584                  * send slave address
 585                  */
 586                 i2c_outbyte((theSlave & 0xfe));
 587                 /*
 588                  * wait for ack
 589                  */
 590                 if(!i2c_getack())
 591                         error = 1;
 592                 /*
 593                  * now select register
 594                  */
 595                 i2c_dir_out();
 596                 i2c_outbyte(theReg);
 597                 /*
 598                  * now it's time to wait for ack
 599                  */
 600                 if(!i2c_getack())
 601                         error |= 2;
 602                 /*
 603                  * repeat start condition
 604                  */
 605                 i2c_delay(CLOCK_LOW_TIME);
 606                 i2c_start();
 607                 /*
 608                  * send slave address
 609                  */
 610                 i2c_outbyte(theSlave | 0x01);
 611                 /*
 612                  * wait for ack
 613                  */
 614                 if(!i2c_getack())
 615                         error |= 4;
 616                 /*
 617                  * fetch register
 618                  */
 619                 b = i2c_inbyte();
 620                 /*
 621                  * last received byte needs to be nacked
 622                  * instead of acked
 623                  */
 624                 i2c_sendnack();
 625                 /*
 626                  * end sequence
 627                  */
 628                 i2c_stop();
 629
 630         } while(error && cntr--);
 631
 632         spin_unlock_irqrestore(&i2c_lock, flags);
 633
 634         return b;
 635 }
 636
 637 static int
 638 i2c_open(struct inode *inode, struct file *filp)
 639 {
 640         cycle_kernel_lock();
 641         return 0;
 642 }
 643
 644 static int
 645 i2c_release(struct inode *inode, struct file *filp)
 646 {
 647         return 0;
 648 }
 649
 650 /* Main device API. ioctl's to write or read to/from i2c registers.
 651  */
 652
 653 static int
 654 i2c_ioctl(struct inode *inode, struct file *file,
 655           unsigned int cmd, unsigned long arg)
 656 {
 657         if(_IOC_TYPE(cmd) != ETRAXI2C_IOCTYPE) {
 658                 return -ENOTTY;
 659         }
 660
 661         switch (_IOC_NR(cmd)) {
 662                 case I2C_WRITEREG:
 663                         /* write to an i2c slave */
 664                         D(printk("i2cw %d %d %d\n",
 665                                  I2C_ARGSLAVE(arg),
 666                                  I2C_ARGREG(arg),
 667                                  I2C_ARGVALUE(arg)));
 668
 669                         return i2c_writereg(I2C_ARGSLAVE(arg),
 670                                             I2C_ARGREG(arg),
 671                                             I2C_ARGVALUE(arg));
 672                 case I2C_READREG:
 673                 {
 674                         unsigned char val;
 675                         /* read from an i2c slave */
 676                         D(printk("i2cr %d %d ",
 677                                 I2C_ARGSLAVE(arg),
 678                                 I2C_ARGREG(arg)));
 679                         val = i2c_readreg(I2C_ARGSLAVE(arg), I2C_ARGREG(arg));
 680                         D(printk("= %d\n", val));
 681                         return val;
 682                 }
 683                 default:
 684                         return -EINVAL;
 685
 686         }
 687
 688         return 0;
 689 }
 690
 691 static const struct file_operations i2c_fops = {
 692         .owner =    THIS_MODULE,
 693         .ioctl =    i2c_ioctl,
 694         .open =     i2c_open,
 695         .release =  i2c_release,
 696 };
 697
 698 static int __init i2c_init(void)
 699 {
 700         static int res;
 701         static int first = 1;
 702
 703         if (!first)
 704                 return res;
 705
 706         first = 0;
 707
 708         /* Setup and enable the DATA and CLK pins */
 709
 710         res = crisv32_io_get_name(&cris_i2c_data,
 711                 CONFIG_ETRAX_V32_I2C_DATA_PORT);
 712         if (res < 0)
 713                 return res;
 714
 715         res = crisv32_io_get_name(&cris_i2c_clk, CONFIG_ETRAX_V32_I2C_CLK_PORT);
 716         crisv32_io_set_dir(&cris_i2c_clk, crisv32_io_dir_out);
 717
 718         return res;
 719 }
 720
 721
 722 static int __init i2c_register(void)
 723 {
 724         int res;
 725
 726         res = i2c_init();
 727         if (res < 0)
 728                 return res;
 729
 730         /* register char device */
 731
 732         res = register_chrdev(I2C_MAJOR, i2c_name, &i2c_fops);
 733         if (res < 0) {
 734                 printk(KERN_ERR "i2c: couldn't get a major number.\n");
 735                 return res;
 736         }
 737
 738         printk(KERN_INFO
 739                 "I2C driver v2.2, (c) 1999-2007 Axis Communications AB\n");
 740
 741         return 0;
 742 }
 743 /* this makes sure that i2c_init is called during boot */
 744 module_init(i2c_register);
 745
 746 /****************** END OF FILE i2c.c ********************************/