git.oblomov.eu Git - linux-2.6/blob - 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
  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 static DEFINE_SPINLOCK(i2c_lock); /* Protect directions etc */
  83
  84 /****************** VARIABLE SECTION ************************************/
  85
  86 static struct crisv32_iopin cris_i2c_clk;
  87 static struct crisv32_iopin cris_i2c_data;
  88
  89 /****************** FUNCTION DEFINITION SECTION *************************/
  90
  91
  92 /* generate i2c start condition */
  93
  94 void
  95 i2c_start(void)
  96 {
  97         /*
  98          * SCL=1 SDA=1
  99          */
 100         i2c_dir_out();
 101         i2c_delay(CLOCK_HIGH_TIME/6);
 102         i2c_data(I2C_DATA_HIGH);
 103         i2c_clk(I2C_CLOCK_HIGH);
 104         i2c_delay(CLOCK_HIGH_TIME);
 105         /*
 106          * SCL=1 SDA=0
 107          */
 108         i2c_data(I2C_DATA_LOW);
 109         i2c_delay(START_CONDITION_HOLD_TIME);
 110         /*
 111          * SCL=0 SDA=0
 112          */
 113         i2c_clk(I2C_CLOCK_LOW);
 114         i2c_delay(CLOCK_LOW_TIME);
 115 }
 116
 117 /* generate i2c stop condition */
 118
 119 void
 120 i2c_stop(void)
 121 {
 122         i2c_dir_out();
 123
 124         /*
 125          * SCL=0 SDA=0
 126          */
 127         i2c_clk(I2C_CLOCK_LOW);
 128         i2c_data(I2C_DATA_LOW);
 129         i2c_delay(CLOCK_LOW_TIME*2);
 130         /*
 131          * SCL=1 SDA=0
 132          */
 133         i2c_clk(I2C_CLOCK_HIGH);
 134         i2c_delay(CLOCK_HIGH_TIME*2);
 135         /*
 136          * SCL=1 SDA=1
 137          */
 138         i2c_data(I2C_DATA_HIGH);
 139         i2c_delay(STOP_CONDITION_HOLD_TIME);
 140
 141         i2c_dir_in();
 142 }
 143
 144 /* write a byte to the i2c interface */
 145
 146 void
 147 i2c_outbyte(unsigned char x)
 148 {
 149         int i;
 150
 151         i2c_dir_out();
 152
 153         for (i = 0; i < 8; i++) {
 154                 if (x & 0x80) {
 155                         i2c_data(I2C_DATA_HIGH);
 156                 } else {
 157                         i2c_data(I2C_DATA_LOW);
 158                 }
 159
 160                 i2c_delay(CLOCK_LOW_TIME/2);
 161                 i2c_clk(I2C_CLOCK_HIGH);
 162                 i2c_delay(CLOCK_HIGH_TIME);
 163                 i2c_clk(I2C_CLOCK_LOW);
 164                 i2c_delay(CLOCK_LOW_TIME/2);
 165                 x <<= 1;
 166         }
 167         i2c_data(I2C_DATA_LOW);
 168         i2c_delay(CLOCK_LOW_TIME/2);
 169
 170         /*
 171          * enable input
 172          */
 173         i2c_dir_in();
 174 }
 175
 176 /* read a byte from the i2c interface */
 177
 178 unsigned char
 179 i2c_inbyte(void)
 180 {
 181         unsigned char aBitByte = 0;
 182         int i;
 183
 184         /* Switch off I2C to get bit */
 185         i2c_disable();
 186         i2c_dir_in();
 187         i2c_delay(CLOCK_HIGH_TIME/2);
 188
 189         /* Get bit */
 190         aBitByte |= i2c_getbit();
 191
 192         /* Enable I2C */
 193         i2c_enable();
 194         i2c_delay(CLOCK_LOW_TIME/2);
 195
 196         for (i = 1; i < 8; i++) {
 197                 aBitByte <<= 1;
 198                 /* Clock pulse */
 199                 i2c_clk(I2C_CLOCK_HIGH);
 200                 i2c_delay(CLOCK_HIGH_TIME);
 201                 i2c_clk(I2C_CLOCK_LOW);
 202                 i2c_delay(CLOCK_LOW_TIME);
 203
 204                 /* Switch off I2C to get bit */
 205                 i2c_disable();
 206                 i2c_dir_in();
 207                 i2c_delay(CLOCK_HIGH_TIME/2);
 208
 209                 /* Get bit */
 210                 aBitByte |= i2c_getbit();
 211
 212                 /* Enable I2C */
 213                 i2c_enable();
 214                 i2c_delay(CLOCK_LOW_TIME/2);
 215         }
 216         i2c_clk(I2C_CLOCK_HIGH);
 217         i2c_delay(CLOCK_HIGH_TIME);
 218
 219         /*
 220          * we leave the clock low, getbyte is usually followed
 221          * by sendack/nack, they assume the clock to be low
 222          */
 223         i2c_clk(I2C_CLOCK_LOW);
 224         return aBitByte;
 225 }
 226
 227 /*#---------------------------------------------------------------------------
 228 *#
 229 *# FUNCTION NAME: i2c_getack
 230 *#
 231 *# DESCRIPTION  : checks if ack was received from ic2
 232 *#
 233 *#--------------------------------------------------------------------------*/
 234
 235 int
 236 i2c_getack(void)
 237 {
 238         int ack = 1;
 239         /*
 240          * enable output
 241          */
 242         i2c_dir_out();
 243         /*
 244          * Release data bus by setting
 245          * data high
 246          */
 247         i2c_data(I2C_DATA_HIGH);
 248         /*
 249          * enable input
 250          */
 251         i2c_dir_in();
 252         i2c_delay(CLOCK_HIGH_TIME/4);
 253         /*
 254          * generate ACK clock pulse
 255          */
 256         i2c_clk(I2C_CLOCK_HIGH);
 257 #if 0
 258         /*
 259          * Use PORT PB instead of I2C
 260          * for input. (I2C not working)
 261          */
 262         i2c_clk(1);
 263         i2c_data(1);
 264         /*
 265          * switch off I2C
 266          */
 267         i2c_data(1);
 268         i2c_disable();
 269         i2c_dir_in();
 270 #endif
 271
 272         /*
 273          * now wait for ack
 274          */
 275         i2c_delay(CLOCK_HIGH_TIME/2);
 276         /*
 277          * check for ack
 278          */
 279         if (i2c_getbit())
 280                 ack = 0;
 281         i2c_delay(CLOCK_HIGH_TIME/2);
 282         if (!ack) {
 283                 if (!i2c_getbit()) /* receiver pulld SDA low */
 284                         ack = 1;
 285                 i2c_delay(CLOCK_HIGH_TIME/2);
 286         }
 287
 288    /*
 289     * our clock is high now, make sure data is low
 290     * before we enable our output. If we keep data high
 291     * and enable output, we would generate a stop condition.
 292     */
 293 #if 0
 294    i2c_data(I2C_DATA_LOW);
 295
 296         /*
 297          * end clock pulse
 298          */
 299         i2c_enable();
 300         i2c_dir_out();
 301 #endif
 302         i2c_clk(I2C_CLOCK_LOW);
 303         i2c_delay(CLOCK_HIGH_TIME/4);
 304         /*
 305          * enable output
 306          */
 307         i2c_dir_out();
 308         /*
 309          * remove ACK clock pulse
 310          */
 311         i2c_data(I2C_DATA_HIGH);
 312         i2c_delay(CLOCK_LOW_TIME/2);
 313         return ack;
 314 }
 315
 316 /*#---------------------------------------------------------------------------
 317 *#
 318 *# FUNCTION NAME: I2C::sendAck
 319 *#
 320 *# DESCRIPTION  : Send ACK on received data
 321 *#
 322 *#--------------------------------------------------------------------------*/
 323 void
 324 i2c_sendack(void)
 325 {
 326         /*
 327          * enable output
 328          */
 329         i2c_delay(CLOCK_LOW_TIME);
 330         i2c_dir_out();
 331         /*
 332          * set ack pulse high
 333          */
 334         i2c_data(I2C_DATA_LOW);
 335         /*
 336          * generate clock pulse
 337          */
 338         i2c_delay(CLOCK_HIGH_TIME/6);
 339         i2c_clk(I2C_CLOCK_HIGH);
 340         i2c_delay(CLOCK_HIGH_TIME);
 341         i2c_clk(I2C_CLOCK_LOW);
 342         i2c_delay(CLOCK_LOW_TIME/6);
 343         /*
 344          * reset data out
 345          */
 346         i2c_data(I2C_DATA_HIGH);
 347         i2c_delay(CLOCK_LOW_TIME);
 348
 349         i2c_dir_in();
 350 }
 351
 352 /*#---------------------------------------------------------------------------
 353 *#
 354 *# FUNCTION NAME: i2c_sendnack
 355 *#
 356 *# DESCRIPTION  : Sends NACK on received data
 357 *#
 358 *#--------------------------------------------------------------------------*/
 359 void
 360 i2c_sendnack(void)
 361 {
 362         /*
 363          * enable output
 364          */
 365         i2c_delay(CLOCK_LOW_TIME);
 366         i2c_dir_out();
 367         /*
 368          * set data high
 369          */
 370         i2c_data(I2C_DATA_HIGH);
 371         /*
 372          * generate clock pulse
 373          */
 374         i2c_delay(CLOCK_HIGH_TIME/6);
 375         i2c_clk(I2C_CLOCK_HIGH);
 376         i2c_delay(CLOCK_HIGH_TIME);
 377         i2c_clk(I2C_CLOCK_LOW);
 378         i2c_delay(CLOCK_LOW_TIME);
 379
 380         i2c_dir_in();
 381 }
 382
 383 /*#---------------------------------------------------------------------------
 384 *#
 385 *# FUNCTION NAME: i2c_write
 386 *#
 387 *# DESCRIPTION  : Writes a value to an I2C device
 388 *#
 389 *#--------------------------------------------------------------------------*/
 390 int
 391 i2c_write(unsigned char theSlave, void *data, size_t nbytes)
 392 {
 393         int error, cntr = 3;
 394         unsigned char bytes_wrote = 0;
 395         unsigned char value;
 396         unsigned long flags;
 397
 398         spin_lock_irqsave(&i2c_lock, flags);
 399
 400         do {
 401                 error = 0;
 402
 403                 i2c_start();
 404                 /*
 405                  * send slave address
 406                  */
 407                 i2c_outbyte((theSlave & 0xfe));
 408                 /*
 409                  * wait for ack
 410                  */
 411                 if (!i2c_getack())
 412                         error = 1;
 413                 /*
 414                  * send data
 415                  */
 416                 for (bytes_wrote = 0; bytes_wrote < nbytes; bytes_wrote++) {
 417                         memcpy(&value, data + bytes_wrote, sizeof value);
 418                         i2c_outbyte(value);
 419                         /*
 420                          * now it's time to wait for ack
 421                          */
 422                         if (!i2c_getack())
 423                                 error |= 4;
 424                 }
 425                 /*
 426                  * end byte stream
 427                  */
 428                 i2c_stop();
 429
 430         } while (error && cntr--);
 431
 432         i2c_delay(CLOCK_LOW_TIME);
 433
 434         spin_unlock_irqrestore(&i2c_lock, flags);
 435
 436         return -error;
 437 }
 438
 439 /*#---------------------------------------------------------------------------
 440 *#
 441 *# FUNCTION NAME: i2c_read
 442 *#
 443 *# DESCRIPTION  : Reads a value from an I2C device
 444 *#
 445 *#--------------------------------------------------------------------------*/
 446 int
 447 i2c_read(unsigned char theSlave, void *data, size_t nbytes)
 448 {
 449         unsigned char b = 0;
 450         unsigned char bytes_read = 0;
 451         int error, cntr = 3;
 452         unsigned long flags;
 453
 454         spin_lock_irqsave(&i2c_lock, flags);
 455
 456         do {
 457                 error = 0;
 458                 memset(data, 0, nbytes);
 459                 /*
 460                  * generate start condition
 461                  */
 462                 i2c_start();
 463                 /*
 464                  * send slave address
 465                  */
 466                 i2c_outbyte((theSlave | 0x01));
 467                 /*
 468                  * wait for ack
 469                  */
 470                 if (!i2c_getack())
 471                         error = 1;
 472                 /*
 473                  * fetch data
 474                  */
 475                 for (bytes_read = 0; bytes_read < nbytes; bytes_read++) {
 476                         b = i2c_inbyte();
 477                         memcpy(data + bytes_read, &b, sizeof b);
 478
 479                         if (bytes_read < (nbytes - 1))
 480                                 i2c_sendack();
 481                 }
 482                 /*
 483                  * last received byte needs to be nacked
 484                  * instead of acked
 485                  */
 486                 i2c_sendnack();
 487                 /*
 488                  * end sequence
 489                  */
 490                 i2c_stop();
 491         } while (error && cntr--);
 492
 493         spin_unlock_irqrestore(&i2c_lock, flags);
 494
 495         return -error;
 496 }
 497
 498 /*#---------------------------------------------------------------------------
 499 *#
 500 *# FUNCTION NAME: i2c_writereg
 501 *#
 502 *# DESCRIPTION  : Writes a value to an I2C device
 503 *#
 504 *#--------------------------------------------------------------------------*/
 505 int
 506 i2c_writereg(unsigned char theSlave, unsigned char theReg,
 507              unsigned char theValue)
 508 {
 509         int error, cntr = 3;
 510         unsigned long flags;
 511
 512         spin_lock_irqsave(&i2c_lock, flags);
 513
 514         do {
 515                 error = 0;
 516
 517                 i2c_start();
 518                 /*
 519                  * send slave address
 520                  */
 521                 i2c_outbyte((theSlave & 0xfe));
 522                 /*
 523                  * wait for ack
 524                  */
 525                 if(!i2c_getack())
 526                         error = 1;
 527                 /*
 528                  * now select register
 529                  */
 530                 i2c_dir_out();
 531                 i2c_outbyte(theReg);
 532                 /*
 533                  * now it's time to wait for ack
 534                  */
 535                 if(!i2c_getack())
 536                         error |= 2;
 537                 /*
 538                  * send register register data
 539                  */
 540                 i2c_outbyte(theValue);
 541                 /*
 542                  * now it's time to wait for ack
 543                  */
 544                 if(!i2c_getack())
 545                         error |= 4;
 546                 /*
 547                  * end byte stream
 548                  */
 549                 i2c_stop();
 550         } while(error && cntr--);
 551
 552         i2c_delay(CLOCK_LOW_TIME);
 553
 554         spin_unlock_irqrestore(&i2c_lock, flags);
 555
 556         return -error;
 557 }
 558
 559 /*#---------------------------------------------------------------------------
 560 *#
 561 *# FUNCTION NAME: i2c_readreg
 562 *#
 563 *# DESCRIPTION  : Reads a value from the decoder registers.
 564 *#
 565 *#--------------------------------------------------------------------------*/
 566 unsigned char
 567 i2c_readreg(unsigned char theSlave, unsigned char theReg)
 568 {
 569         unsigned char b = 0;
 570         int error, cntr = 3;
 571         unsigned long flags;
 572
 573         spin_lock_irqsave(&i2c_lock, flags);
 574
 575         do {
 576                 error = 0;
 577                 /*
 578                  * generate start condition
 579                  */
 580                 i2c_start();
 581
 582                 /*
 583                  * send slave address
 584                  */
 585                 i2c_outbyte((theSlave & 0xfe));
 586                 /*
 587                  * wait for ack
 588                  */
 589                 if(!i2c_getack())
 590                         error = 1;
 591                 /*
 592                  * now select register
 593                  */
 594                 i2c_dir_out();
 595                 i2c_outbyte(theReg);
 596                 /*
 597                  * now it's time to wait for ack
 598                  */
 599                 if(!i2c_getack())
 600                         error |= 2;
 601                 /*
 602                  * repeat start condition
 603                  */
 604                 i2c_delay(CLOCK_LOW_TIME);
 605                 i2c_start();
 606                 /*
 607                  * send slave address
 608                  */
 609                 i2c_outbyte(theSlave | 0x01);
 610                 /*
 611                  * wait for ack
 612                  */
 613                 if(!i2c_getack())
 614                         error |= 4;
 615                 /*
 616                  * fetch register
 617                  */
 618                 b = i2c_inbyte();
 619                 /*
 620                  * last received byte needs to be nacked
 621                  * instead of acked
 622                  */
 623                 i2c_sendnack();
 624                 /*
 625                  * end sequence
 626                  */
 627                 i2c_stop();
 628
 629         } while(error && cntr--);
 630
 631         spin_unlock_irqrestore(&i2c_lock, flags);
 632
 633         return b;
 634 }
 635
 636 static int
 637 i2c_open(struct inode *inode, struct file *filp)
 638 {
 639         return 0;
 640 }
 641
 642 static int
 643 i2c_release(struct inode *inode, struct file *filp)
 644 {
 645         return 0;
 646 }
 647
 648 /* Main device API. ioctl's to write or read to/from i2c registers.
 649  */
 650
 651 static int
 652 i2c_ioctl(struct inode *inode, struct file *file,
 653           unsigned int cmd, unsigned long arg)
 654 {
 655         if(_IOC_TYPE(cmd) != ETRAXI2C_IOCTYPE) {
 656                 return -ENOTTY;
 657         }
 658
 659         switch (_IOC_NR(cmd)) {
 660                 case I2C_WRITEREG:
 661                         /* write to an i2c slave */
 662                         D(printk("i2cw %d %d %d\n",
 663                                  I2C_ARGSLAVE(arg),
 664                                  I2C_ARGREG(arg),
 665                                  I2C_ARGVALUE(arg)));
 666
 667                         return i2c_writereg(I2C_ARGSLAVE(arg),
 668                                             I2C_ARGREG(arg),
 669                                             I2C_ARGVALUE(arg));
 670                 case I2C_READREG:
 671                 {
 672                         unsigned char val;
 673                         /* read from an i2c slave */
 674                         D(printk("i2cr %d %d ",
 675                                 I2C_ARGSLAVE(arg),
 676                                 I2C_ARGREG(arg)));
 677                         val = i2c_readreg(I2C_ARGSLAVE(arg), I2C_ARGREG(arg));
 678                         D(printk("= %d\n", val));
 679                         return val;
 680                 }
 681                 default:
 682                         return -EINVAL;
 683
 684         }
 685
 686         return 0;
 687 }
 688
 689 static const struct file_operations i2c_fops = {
 690         .owner =    THIS_MODULE,
 691         .ioctl =    i2c_ioctl,
 692         .open =     i2c_open,
 693         .release =  i2c_release,
 694 };
 695
 696 static int __init i2c_init(void)
 697 {
 698         static int res;
 699         static int first = 1;
 700
 701         if (!first)
 702                 return res;
 703
 704         first = 0;
 705
 706         /* Setup and enable the DATA and CLK pins */
 707
 708         res = crisv32_io_get_name(&cris_i2c_data,
 709                 CONFIG_ETRAX_V32_I2C_DATA_PORT);
 710         if (res < 0)
 711                 return res;
 712
 713         res = crisv32_io_get_name(&cris_i2c_clk, CONFIG_ETRAX_V32_I2C_CLK_PORT);
 714         crisv32_io_set_dir(&cris_i2c_clk, crisv32_io_dir_out);
 715
 716         return res;
 717 }
 718
 719
 720 static int __init i2c_register(void)
 721 {
 722         int res;
 723
 724         res = i2c_init();
 725         if (res < 0)
 726                 return res;
 727
 728         /* register char device */
 729
 730         res = register_chrdev(I2C_MAJOR, i2c_name, &i2c_fops);
 731         if (res < 0) {
 732                 printk(KERN_ERR "i2c: couldn't get a major number.\n");
 733                 return res;
 734         }
 735
 736         printk(KERN_INFO
 737                 "I2C driver v2.2, (c) 1999-2007 Axis Communications AB\n");
 738
 739         return 0;
 740 }
 741 /* this makes sure that i2c_init is called during boot */
 742 module_init(i2c_register);
 743
 744 /****************** END OF FILE i2c.c ********************************/