drivers/i2c/i2c-algo-bit.c

   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 Kyösti Mälkki <kmalkki@cc.hut.fi> and even
  22    Frodo Looijaard <frodol@dds.nl> */
  23
  24 /* $Id: i2c-algo-bit.c,v 1.44 2003/01/21 08:08:16 kmalkki Exp $ */
  25
  26 /* #define DEBUG 1 */
  27
  28 #include <linux/kernel.h>
  29 #include <linux/module.h>
  30 #include <linux/delay.h>
  31 #include <linux/slab.h>
  32 #include <linux/init.h>
  33 #include <linux/errno.h>
  34 #include <linux/sched.h>
  35 #include <linux/i2c.h>
  36 #include <linux/i2c-algo-bit.h>
  37
  38
  39 /* ----- global defines ----------------------------------------------- */
  40 #define DEB(x) if (i2c_debug>=1) x;
  41 #define DEB2(x) if (i2c_debug>=2) x;
  42 #define DEBSTAT(x) if (i2c_debug>=3) x; /* print several statistical values*/
  43 #define DEBPROTO(x) if (i2c_debug>=9) { x; }
  44         /* debug the protocol by showing transferred bits */
  45
  46
  47 /* ----- global variables --------------------------------------------- */
  48
  49 /* module parameters:
  50  */
  51 static int i2c_debug;
  52 static int bit_test;    /* see if the line-setting functions work       */
  53
  54 /* --- setting states on the bus with the right timing: --------------- */
  55
  56 #define setsda(adap,val) adap->setsda(adap->data, val)
  57 #define setscl(adap,val) adap->setscl(adap->data, val)
  58 #define getsda(adap) adap->getsda(adap->data)
  59 #define getscl(adap) adap->getscl(adap->data)
  60
  61 static inline void sdalo(struct i2c_algo_bit_data *adap)
  62 {
  63         setsda(adap,0);
  64         udelay(adap->udelay);
  65 }
  66
  67 static inline void sdahi(struct i2c_algo_bit_data *adap)
  68 {
  69         setsda(adap,1);
  70         udelay(adap->udelay);
  71 }
  72
  73 static inline void scllo(struct i2c_algo_bit_data *adap)
  74 {
  75         setscl(adap,0);
  76         udelay(adap->udelay);
  77 }
  78
  79 /*
  80  * Raise scl line, and do checking for delays. This is necessary for slower
  81  * devices.
  82  */
  83 static inline int sclhi(struct i2c_algo_bit_data *adap)
  84 {
  85         unsigned long start;
  86
  87         setscl(adap,1);
  88
  89         /* Not all adapters have scl sense line... */
  90         if (adap->getscl == NULL )
  91                 return 0;
  92
  93         start=jiffies;
  94         while (! getscl(adap) ) {
  95                 /* the hw knows how to read the clock line,
  96                  * so we wait until it actually gets high.
  97                  * This is safer as some chips may hold it low
  98                  * while they are processing data internally.
  99                  */
 100                 if (time_after_eq(jiffies, start+adap->timeout)) {
 101                         return -ETIMEDOUT;
 102                 }
 103                 cond_resched();
 104         }
 105         DEBSTAT(printk(KERN_DEBUG "needed %ld jiffies\n", jiffies-start));
 106         udelay(adap->udelay);
 107         return 0;
 108 }
 109
 110
 111 /* --- other auxiliary functions -------------------------------------- */
 112 static void i2c_start(struct i2c_algo_bit_data *adap)
 113 {
 114         /* assert: scl, sda are high */
 115         DEBPROTO(printk("S "));
 116         sdalo(adap);
 117         scllo(adap);
 118 }
 119
 120 static void i2c_repstart(struct i2c_algo_bit_data *adap)
 121 {
 122         /* scl, sda may not be high */
 123         DEBPROTO(printk(" Sr "));
 124         setsda(adap,1);
 125         sclhi(adap);
 126         udelay(adap->udelay);
 127
 128         sdalo(adap);
 129         scllo(adap);
 130 }
 131
 132
 133 static void i2c_stop(struct i2c_algo_bit_data *adap)
 134 {
 135         DEBPROTO(printk("P\n"));
 136         /* assert: scl is low */
 137         sdalo(adap);
 138         sclhi(adap);
 139         sdahi(adap);
 140 }
 141
 142
 143
 144 /* send a byte without start cond., look for arbitration,
 145    check ackn. from slave */
 146 /* returns:
 147  * 1 if the device acknowledged
 148  * 0 if the device did not ack
 149  * -ETIMEDOUT if an error occurred (while raising the scl line)
 150  */
 151 static int i2c_outb(struct i2c_adapter *i2c_adap, char c)
 152 {
 153         int i;
 154         int sb;
 155         int ack;
 156         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 157
 158         /* assert: scl is low */
 159         for ( i=7 ; i>=0 ; i-- ) {
 160                 sb = c & ( 1 << i );
 161                 setsda(adap,sb);
 162                 udelay(adap->udelay);
 163                 DEBPROTO(printk(KERN_DEBUG "%d",sb!=0));
 164                 if (sclhi(adap)<0) { /* timed out */
 165                         sdahi(adap); /* we don't want to block the net */
 166                         DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x, timeout at bit #%d\n", c&0xff, i));
 167                         return -ETIMEDOUT;
 168                 };
 169                 /* do arbitration here:
 170                  * if ( sb && ! getsda(adap) ) -> ouch! Get out of here.
 171                  */
 172                 setscl(adap, 0 );
 173                 udelay(adap->udelay);
 174         }
 175         sdahi(adap);
 176         if (sclhi(adap)<0){ /* timeout */
 177             DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x, timeout at ack\n", c&0xff));
 178             return -ETIMEDOUT;
 179         };
 180         /* read ack: SDA should be pulled down by slave */
 181         ack=getsda(adap);       /* ack: sda is pulled low ->success.     */
 182         DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x , getsda() = %d\n", c & 0xff, ack));
 183
 184         DEBPROTO( printk(KERN_DEBUG "[%2.2x]",c&0xff) );
 185         DEBPROTO(if (0==ack){ printk(KERN_DEBUG " A ");} else printk(KERN_DEBUG " NA ") );
 186         scllo(adap);
 187         return 0==ack;          /* return 1 if device acked      */
 188         /* assert: scl is low (sda undef) */
 189 }
 190
 191
 192 static int i2c_inb(struct i2c_adapter *i2c_adap)
 193 {
 194         /* read byte via i2c port, without start/stop sequence  */
 195         /* acknowledge is sent in i2c_read.                     */
 196         int i;
 197         unsigned char indata=0;
 198         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 199
 200         /* assert: scl is low */
 201         sdahi(adap);
 202         for (i=0;i<8;i++) {
 203                 if (sclhi(adap)<0) { /* timeout */
 204                         DEB2(printk(KERN_DEBUG " i2c_inb: timeout at bit #%d\n", 7-i));
 205                         return -ETIMEDOUT;
 206                 };
 207                 indata *= 2;
 208                 if ( getsda(adap) )
 209                         indata |= 0x01;
 210                 scllo(adap);
 211         }
 212         /* assert: scl is low */
 213         DEB2(printk(KERN_DEBUG "i2c_inb: 0x%02x\n", indata & 0xff));
 214
 215         DEBPROTO(printk(KERN_DEBUG " 0x%02x", indata & 0xff));
 216         return (int) (indata & 0xff);
 217 }
 218
 219 /*
 220  * Sanity check for the adapter hardware - check the reaction of
 221  * the bus lines only if it seems to be idle.
 222  */
 223 static int test_bus(struct i2c_algo_bit_data *adap, char* name) {
 224         int scl,sda;
 225         sda=getsda(adap);
 226         if (adap->getscl==NULL) {
 227                 printk(KERN_WARNING "i2c-algo-bit.o: Warning: Adapter can't read from clock line - skipping test.\n");
 228                 return 0;
 229         }
 230         scl=getscl(adap);
 231         printk(KERN_INFO "i2c-algo-bit.o: Adapter: %s scl: %d  sda: %d -- testing...\n",
 232                name,getscl(adap),getsda(adap));
 233         if (!scl || !sda ) {
 234                 printk(KERN_INFO " i2c-algo-bit.o: %s seems to be busy.\n",name);
 235                 goto bailout;
 236         }
 237         sdalo(adap);
 238         printk(KERN_DEBUG "i2c-algo-bit.o:1 scl: %d  sda: %d \n",getscl(adap),
 239                getsda(adap));
 240         if ( 0 != getsda(adap) ) {
 241                 printk(KERN_WARNING "i2c-algo-bit.o: %s SDA stuck high!\n",name);
 242                 sdahi(adap);
 243                 goto bailout;
 244         }
 245         if ( 0 == getscl(adap) ) {
 246                 printk(KERN_WARNING "i2c-algo-bit.o: %s SCL unexpected low while pulling SDA low!\n",
 247                         name);
 248                 goto bailout;
 249         }
 250         sdahi(adap);
 251         printk(KERN_DEBUG "i2c-algo-bit.o:2 scl: %d  sda: %d \n",getscl(adap),
 252                getsda(adap));
 253         if ( 0 == getsda(adap) ) {
 254                 printk(KERN_WARNING "i2c-algo-bit.o: %s SDA stuck low!\n",name);
 255                 sdahi(adap);
 256                 goto bailout;
 257         }
 258         if ( 0 == getscl(adap) ) {
 259                 printk(KERN_WARNING "i2c-algo-bit.o: %s SCL unexpected low while SDA high!\n",
 260                        name);
 261         goto bailout;
 262         }
 263         scllo(adap);
 264         printk(KERN_DEBUG "i2c-algo-bit.o:3 scl: %d  sda: %d \n",getscl(adap),
 265                getsda(adap));
 266         if ( 0 != getscl(adap) ) {
 267                 printk(KERN_WARNING "i2c-algo-bit.o: %s SCL stuck high!\n",name);
 268                 sclhi(adap);
 269                 goto bailout;
 270         }
 271         if ( 0 == getsda(adap) ) {
 272                 printk(KERN_WARNING "i2c-algo-bit.o: %s SDA unexpected low while pulling SCL low!\n",
 273                         name);
 274                 goto bailout;
 275         }
 276         sclhi(adap);
 277         printk(KERN_DEBUG "i2c-algo-bit.o:4 scl: %d  sda: %d \n",getscl(adap),
 278                getsda(adap));
 279         if ( 0 == getscl(adap) ) {
 280                 printk(KERN_WARNING "i2c-algo-bit.o: %s SCL stuck low!\n",name);
 281                 sclhi(adap);
 282                 goto bailout;
 283         }
 284         if ( 0 == getsda(adap) ) {
 285                 printk(KERN_WARNING "i2c-algo-bit.o: %s SDA unexpected low while SCL high!\n",
 286                         name);
 287                 goto bailout;
 288         }
 289         printk(KERN_INFO "i2c-algo-bit.o: %s passed test.\n",name);
 290         return 0;
 291 bailout:
 292         sdahi(adap);
 293         sclhi(adap);
 294         return -ENODEV;
 295 }
 296
 297 /* ----- Utility functions
 298  */
 299
 300 /* try_address tries to contact a chip for a number of
 301  * times before it gives up.
 302  * return values:
 303  * 1 chip answered
 304  * 0 chip did not answer
 305  * -x transmission error
 306  */
 307 static inline int try_address(struct i2c_adapter *i2c_adap,
 308                        unsigned char addr, int retries)
 309 {
 310         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 311         int i,ret = -1;
 312         for (i=0;i<=retries;i++) {
 313                 ret = i2c_outb(i2c_adap,addr);
 314                 if (ret==1)
 315                         break;  /* success! */
 316                 i2c_stop(adap);
 317                 udelay(5/*adap->udelay*/);
 318                 if (i==retries)  /* no success */
 319                         break;
 320                 i2c_start(adap);
 321                 udelay(adap->udelay);
 322         }
 323         DEB2(if (i)
 324              printk(KERN_DEBUG "i2c-algo-bit.o: Used %d tries to %s client at 0x%02x : %s\n",
 325                     i+1, addr & 1 ? "read" : "write", addr>>1,
 326                     ret==1 ? "success" : ret==0 ? "no ack" : "failed, timeout?" )
 327             );
 328         return ret;
 329 }
 330
 331 static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 332 {
 333         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 334         char c;
 335         const char *temp = msg->buf;
 336         int count = msg->len;
 337         unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
 338         int retval;
 339         int wrcount=0;
 340
 341         while (count > 0) {
 342                 c = *temp;
 343                 DEB2(dev_dbg(&i2c_adap->dev, "sendbytes: writing %2.2X\n", c&0xff));
 344                 retval = i2c_outb(i2c_adap,c);
 345                 if ((retval>0) || (nak_ok && (retval==0)))  { /* ok or ignored NAK */
 346                         count--;
 347                         temp++;
 348                         wrcount++;
 349                 } else { /* arbitration or no acknowledge */
 350                         dev_err(&i2c_adap->dev, "sendbytes: error - bailout.\n");
 351                         i2c_stop(adap);
 352                         return (retval<0)? retval : -EFAULT;
 353                                 /* got a better one ?? */
 354                 }
 355 #if 0
 356                 /* from asm/delay.h */
 357                 __delay(adap->mdelay * (loops_per_sec / 1000) );
 358 #endif
 359         }
 360         return wrcount;
 361 }
 362
 363 static inline int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 364 {
 365         int inval;
 366         int rdcount=0;          /* counts bytes read */
 367         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 368         char *temp = msg->buf;
 369         int count = msg->len;
 370
 371         while (count > 0) {
 372                 inval = i2c_inb(i2c_adap);
 373 /*printk("%#02x ",inval); if ( ! (count % 16) ) printk("\n"); */
 374                 if (inval>=0) {
 375                         *temp = inval;
 376                         rdcount++;
 377                 } else {   /* read timed out */
 378                         printk(KERN_ERR "i2c-algo-bit.o: readbytes: i2c_inb timed out.\n");
 379                         break;
 380                 }
 381
 382                 if ( count > 1 ) {              /* send ack */
 383                         sdalo(adap);
 384                         DEBPROTO(printk(" Am "));
 385                 } else {
 386                         sdahi(adap);    /* neg. ack on last byte */
 387                         DEBPROTO(printk(" NAm "));
 388                 }
 389                 if (sclhi(adap)<0) {    /* timeout */
 390                         sdahi(adap);
 391                         printk(KERN_ERR "i2c-algo-bit.o: readbytes: Timeout at ack\n");
 392                         return -ETIMEDOUT;
 393                 };
 394                 scllo(adap);
 395                 sdahi(adap);
 396                 temp++;
 397                 count--;
 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 inline 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_SMBUS_EMUL | I2C_FUNC_10BIT_ADDR |
 509                I2C_FUNC_PROTOCOL_MANGLING;
 510 }
 511
 512
 513 /* -----exported algorithm data: -------------------------------------  */
 514
 515 static struct i2c_algorithm i2c_bit_algo = {
 516         .name           = "Bit-shift algorithm",
 517         .id             = I2C_ALGO_BIT,
 518         .master_xfer    = bit_xfer,
 519         .functionality  = bit_func,
 520 };
 521
 522 /*
 523  * registering functions to load algorithms at runtime
 524  */
 525 int i2c_bit_add_bus(struct i2c_adapter *adap)
 526 {
 527         struct i2c_algo_bit_data *bit_adap = adap->algo_data;
 528
 529         if (bit_test) {
 530                 int ret = test_bus(bit_adap, adap->name);
 531                 if (ret<0)
 532                         return -ENODEV;
 533         }
 534
 535         DEB2(dev_dbg(&adap->dev, "hw routines registered.\n"));
 536
 537         /* register new adapter to i2c module... */
 538
 539         adap->id |= i2c_bit_algo.id;
 540         adap->algo = &i2c_bit_algo;
 541
 542         adap->timeout = 100;    /* default values, should       */
 543         adap->retries = 3;      /* be replaced by defines       */
 544
 545         i2c_add_adapter(adap);
 546         return 0;
 547 }
 548
 549
 550 int i2c_bit_del_bus(struct i2c_adapter *adap)
 551 {
 552         return i2c_del_adapter(adap);
 553 }
 554
 555 EXPORT_SYMBOL(i2c_bit_add_bus);
 556 EXPORT_SYMBOL(i2c_bit_del_bus);
 557
 558 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
 559 MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
 560 MODULE_LICENSE("GPL");
 561
 562 MODULE_PARM(bit_test, "i");
 563 MODULE_PARM(i2c_debug,"i");
 564
 565 MODULE_PARM_DESC(bit_test, "Test the lines of the bus to see if it is stuck");
 566 MODULE_PARM_DESC(i2c_debug,
 567                  "debug level - 0 off; 1 normal; 2,3 more verbose; 9 bit-protocol");