drivers/i2c/algos/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 Frodo Looijaard <frodol@dds.nl>, Kyösti Mälkki
  22    <kmalkki@cc.hut.fi> and Jean Delvare <khali@linux-fr.org> */
  23
  24 #include <linux/kernel.h>
  25 #include <linux/module.h>
  26 #include <linux/delay.h>
  27 #include <linux/slab.h>
  28 #include <linux/init.h>
  29 #include <linux/errno.h>
  30 #include <linux/sched.h>
  31 #include <linux/i2c.h>
  32 #include <linux/i2c-algo-bit.h>
  33
  34
  35 /* ----- global defines ----------------------------------------------- */
  36 #define DEB(x) if (i2c_debug>=1) x;
  37 #define DEB2(x) if (i2c_debug>=2) x;
  38 #define DEBSTAT(x) if (i2c_debug>=3) x; /* print several statistical values*/
  39 #define DEBPROTO(x) if (i2c_debug>=9) { x; }
  40         /* debug the protocol by showing transferred bits */
  41
  42
  43 /* ----- global variables --------------------------------------------- */
  44
  45 /* module parameters:
  46  */
  47 static int i2c_debug;
  48 static int bit_test;    /* see if the line-setting functions work       */
  49
  50 /* --- setting states on the bus with the right timing: --------------- */
  51
  52 #define setsda(adap,val) adap->setsda(adap->data, val)
  53 #define setscl(adap,val) adap->setscl(adap->data, val)
  54 #define getsda(adap) adap->getsda(adap->data)
  55 #define getscl(adap) adap->getscl(adap->data)
  56
  57 static inline void sdalo(struct i2c_algo_bit_data *adap)
  58 {
  59         setsda(adap,0);
  60         udelay(adap->udelay);
  61 }
  62
  63 static inline void sdahi(struct i2c_algo_bit_data *adap)
  64 {
  65         setsda(adap,1);
  66         udelay(adap->udelay);
  67 }
  68
  69 static inline void scllo(struct i2c_algo_bit_data *adap)
  70 {
  71         setscl(adap,0);
  72         udelay(adap->udelay);
  73 }
  74
  75 /*
  76  * Raise scl line, and do checking for delays. This is necessary for slower
  77  * devices.
  78  */
  79 static inline int sclhi(struct i2c_algo_bit_data *adap)
  80 {
  81         unsigned long start;
  82
  83         setscl(adap,1);
  84
  85         /* Not all adapters have scl sense line... */
  86         if (adap->getscl == NULL ) {
  87                 udelay(adap->udelay);
  88                 return 0;
  89         }
  90
  91         start=jiffies;
  92         while (! getscl(adap) ) {
  93                 /* the hw knows how to read the clock line,
  94                  * so we wait until it actually gets high.
  95                  * This is safer as some chips may hold it low
  96                  * while they are processing data internally.
  97                  */
  98                 if (time_after_eq(jiffies, start+adap->timeout)) {
  99                         return -ETIMEDOUT;
 100                 }
 101                 cond_resched();
 102         }
 103         DEBSTAT(printk(KERN_DEBUG "needed %ld jiffies\n", jiffies-start));
 104         udelay(adap->udelay);
 105         return 0;
 106 }
 107
 108
 109 /* --- other auxiliary functions -------------------------------------- */
 110 static void i2c_start(struct i2c_algo_bit_data *adap)
 111 {
 112         /* assert: scl, sda are high */
 113         DEBPROTO(printk("S "));
 114         sdalo(adap);
 115         scllo(adap);
 116 }
 117
 118 static void i2c_repstart(struct i2c_algo_bit_data *adap)
 119 {
 120         /* scl, sda may not be high */
 121         DEBPROTO(printk(" Sr "));
 122         setsda(adap,1);
 123         sclhi(adap);
 124         udelay(adap->udelay);
 125
 126         sdalo(adap);
 127         scllo(adap);
 128 }
 129
 130
 131 static void i2c_stop(struct i2c_algo_bit_data *adap)
 132 {
 133         DEBPROTO(printk("P\n"));
 134         /* assert: scl is low */
 135         sdalo(adap);
 136         sclhi(adap);
 137         sdahi(adap);
 138 }
 139
 140
 141
 142 /* send a byte without start cond., look for arbitration,
 143    check ackn. from slave */
 144 /* returns:
 145  * 1 if the device acknowledged
 146  * 0 if the device did not ack
 147  * -ETIMEDOUT if an error occurred (while raising the scl line)
 148  */
 149 static int i2c_outb(struct i2c_adapter *i2c_adap, char c)
 150 {
 151         int i;
 152         int sb;
 153         int ack;
 154         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 155
 156         /* assert: scl is low */
 157         for ( i=7 ; i>=0 ; i-- ) {
 158                 sb = c & ( 1 << i );
 159                 setsda(adap,sb);
 160                 udelay(adap->udelay);
 161                 DEBPROTO(printk(KERN_DEBUG "%d",sb!=0));
 162                 if (sclhi(adap)<0) { /* timed out */
 163                         sdahi(adap); /* we don't want to block the net */
 164                         DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x, timeout at bit #%d\n", c&0xff, i));
 165                         return -ETIMEDOUT;
 166                 };
 167                 /* do arbitration here:
 168                  * if ( sb && ! getsda(adap) ) -> ouch! Get out of here.
 169                  */
 170                 setscl(adap, 0 );
 171                 udelay(adap->udelay);
 172         }
 173         sdahi(adap);
 174         if (sclhi(adap)<0){ /* timeout */
 175             DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x, timeout at ack\n", c&0xff));
 176             return -ETIMEDOUT;
 177         };
 178         /* read ack: SDA should be pulled down by slave */
 179         ack=getsda(adap);       /* ack: sda is pulled low ->success.     */
 180         DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x , getsda() = %d\n", c & 0xff, ack));
 181
 182         DEBPROTO( printk(KERN_DEBUG "[%2.2x]",c&0xff) );
 183         DEBPROTO(if (0==ack){ printk(KERN_DEBUG " A ");} else printk(KERN_DEBUG " NA ") );
 184         scllo(adap);
 185         return 0==ack;          /* return 1 if device acked      */
 186         /* assert: scl is low (sda undef) */
 187 }
 188
 189
 190 static int i2c_inb(struct i2c_adapter *i2c_adap)
 191 {
 192         /* read byte via i2c port, without start/stop sequence  */
 193         /* acknowledge is sent in i2c_read.                     */
 194         int i;
 195         unsigned char indata=0;
 196         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 197
 198         /* assert: scl is low */
 199         sdahi(adap);
 200         for (i=0;i<8;i++) {
 201                 if (sclhi(adap)<0) { /* timeout */
 202                         DEB2(printk(KERN_DEBUG " i2c_inb: timeout at bit #%d\n", 7-i));
 203                         return -ETIMEDOUT;
 204                 };
 205                 indata *= 2;
 206                 if ( getsda(adap) )
 207                         indata |= 0x01;
 208                 scllo(adap);
 209         }
 210         /* assert: scl is low */
 211         DEB2(printk(KERN_DEBUG "i2c_inb: 0x%02x\n", indata & 0xff));
 212
 213         DEBPROTO(printk(KERN_DEBUG " 0x%02x", indata & 0xff));
 214         return (int) (indata & 0xff);
 215 }
 216
 217 /*
 218  * Sanity check for the adapter hardware - check the reaction of
 219  * the bus lines only if it seems to be idle.
 220  */
 221 static int test_bus(struct i2c_algo_bit_data *adap, char* name) {
 222         int scl,sda;
 223
 224         if (adap->getscl==NULL)
 225                 printk(KERN_INFO "i2c-algo-bit.o: Testing SDA only, "
 226                         "SCL is not readable.\n");
 227
 228         sda=getsda(adap);
 229         scl=(adap->getscl==NULL?1:getscl(adap));
 230         printk(KERN_DEBUG "i2c-algo-bit.o: (0) scl=%d, sda=%d\n",scl,sda);
 231         if (!scl || !sda ) {
 232                 printk(KERN_WARNING "i2c-algo-bit.o: %s seems to be busy.\n", name);
 233                 goto bailout;
 234         }
 235
 236         sdalo(adap);
 237         sda=getsda(adap);
 238         scl=(adap->getscl==NULL?1:getscl(adap));
 239         printk(KERN_DEBUG "i2c-algo-bit.o: (1) scl=%d, sda=%d\n",scl,sda);
 240         if ( 0 != sda ) {
 241                 printk(KERN_WARNING "i2c-algo-bit.o: SDA stuck high!\n");
 242                 goto bailout;
 243         }
 244         if ( 0 == scl ) {
 245                 printk(KERN_WARNING "i2c-algo-bit.o: SCL unexpected low "
 246                         "while pulling SDA low!\n");
 247                 goto bailout;
 248         }
 249
 250         sdahi(adap);
 251         sda=getsda(adap);
 252         scl=(adap->getscl==NULL?1:getscl(adap));
 253         printk(KERN_DEBUG "i2c-algo-bit.o: (2) scl=%d, sda=%d\n",scl,sda);
 254         if ( 0 == sda ) {
 255                 printk(KERN_WARNING "i2c-algo-bit.o: SDA stuck low!\n");
 256                 goto bailout;
 257         }
 258         if ( 0 == scl ) {
 259                 printk(KERN_WARNING "i2c-algo-bit.o: SCL unexpected low "
 260                         "while pulling SDA high!\n");
 261                 goto bailout;
 262         }
 263
 264         scllo(adap);
 265         sda=getsda(adap);
 266         scl=(adap->getscl==NULL?0:getscl(adap));
 267         printk(KERN_DEBUG "i2c-algo-bit.o: (3) scl=%d, sda=%d\n",scl,sda);
 268         if ( 0 != scl ) {
 269                 printk(KERN_WARNING "i2c-algo-bit.o: SCL stuck high!\n");
 270                 goto bailout;
 271         }
 272         if ( 0 == sda ) {
 273                 printk(KERN_WARNING "i2c-algo-bit.o: SDA unexpected low "
 274                         "while pulling SCL low!\n");
 275                 goto bailout;
 276         }
 277
 278         sclhi(adap);
 279         sda=getsda(adap);
 280         scl=(adap->getscl==NULL?1:getscl(adap));
 281         printk(KERN_DEBUG "i2c-algo-bit.o: (4) scl=%d, sda=%d\n",scl,sda);
 282         if ( 0 == scl ) {
 283                 printk(KERN_WARNING "i2c-algo-bit.o: SCL stuck low!\n");
 284                 goto bailout;
 285         }
 286         if ( 0 == sda ) {
 287                 printk(KERN_WARNING "i2c-algo-bit.o: SDA unexpected low "
 288                         "while pulling SCL high!\n");
 289                 goto bailout;
 290         }
 291         printk(KERN_INFO "i2c-algo-bit.o: %s passed test.\n",name);
 292         return 0;
 293 bailout:
 294         sdahi(adap);
 295         sclhi(adap);
 296         return -ENODEV;
 297 }
 298
 299 /* ----- Utility functions
 300  */
 301
 302 /* try_address tries to contact a chip for a number of
 303  * times before it gives up.
 304  * return values:
 305  * 1 chip answered
 306  * 0 chip did not answer
 307  * -x transmission error
 308  */
 309 static inline int try_address(struct i2c_adapter *i2c_adap,
 310                        unsigned char addr, int retries)
 311 {
 312         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 313         int i,ret = -1;
 314         for (i=0;i<=retries;i++) {
 315                 ret = i2c_outb(i2c_adap,addr);
 316                 if (ret==1)
 317                         break;  /* success! */
 318                 i2c_stop(adap);
 319                 udelay(5/*adap->udelay*/);
 320                 if (i==retries)  /* no success */
 321                         break;
 322                 i2c_start(adap);
 323                 udelay(adap->udelay);
 324         }
 325         DEB2(if (i)
 326              printk(KERN_DEBUG "i2c-algo-bit.o: Used %d tries to %s client at 0x%02x : %s\n",
 327                     i+1, addr & 1 ? "read" : "write", addr>>1,
 328                     ret==1 ? "success" : ret==0 ? "no ack" : "failed, timeout?" )
 329             );
 330         return ret;
 331 }
 332
 333 static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 334 {
 335         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 336         char c;
 337         const char *temp = msg->buf;
 338         int count = msg->len;
 339         unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
 340         int retval;
 341         int wrcount=0;
 342
 343         while (count > 0) {
 344                 c = *temp;
 345                 DEB2(dev_dbg(&i2c_adap->dev, "sendbytes: writing %2.2X\n", c&0xff));
 346                 retval = i2c_outb(i2c_adap,c);
 347                 if ((retval>0) || (nak_ok && (retval==0)))  { /* ok or ignored NAK */
 348                         count--;
 349                         temp++;
 350                         wrcount++;
 351                 } else { /* arbitration or no acknowledge */
 352                         dev_err(&i2c_adap->dev, "sendbytes: error - bailout.\n");
 353                         i2c_stop(adap);
 354                         return (retval<0)? retval : -EFAULT;
 355                                 /* got a better one ?? */
 356                 }
 357 #if 0
 358                 /* from asm/delay.h */
 359                 __delay(adap->mdelay * (loops_per_sec / 1000) );
 360 #endif
 361         }
 362         return wrcount;
 363 }
 364
 365 static inline int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 366 {
 367         int inval;
 368         int rdcount=0;          /* counts bytes read */
 369         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 370         char *temp = msg->buf;
 371         int count = msg->len;
 372
 373         while (count > 0) {
 374                 inval = i2c_inb(i2c_adap);
 375                 if (inval>=0) {
 376                         *temp = inval;
 377                         rdcount++;
 378                 } else {   /* read timed out */
 379                         printk(KERN_ERR "i2c-algo-bit.o: readbytes: i2c_inb timed out.\n");
 380                         break;
 381                 }
 382
 383                 temp++;
 384                 count--;
 385
 386                 if (msg->flags & I2C_M_NO_RD_ACK)
 387                         continue;
 388
 389                 if ( count > 0 ) {              /* send ack */
 390                         sdalo(adap);
 391                         DEBPROTO(printk(" Am "));
 392                 } else {
 393                         sdahi(adap);    /* neg. ack on last byte */
 394                         DEBPROTO(printk(" NAm "));
 395                 }
 396                 if (sclhi(adap)<0) {    /* timeout */
 397                         sdahi(adap);
 398                         printk(KERN_ERR "i2c-algo-bit.o: readbytes: Timeout at ack\n");
 399                         return -ETIMEDOUT;
 400                 };
 401                 scllo(adap);
 402                 sdahi(adap);
 403         }
 404         return rdcount;
 405 }
 406
 407 /* doAddress initiates the transfer by generating the start condition (in
 408  * try_address) and transmits the address in the necessary format to handle
 409  * reads, writes as well as 10bit-addresses.
 410  * returns:
 411  *  0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
 412  * -x an error occurred (like: -EREMOTEIO if the device did not answer, or
 413  *      -ETIMEDOUT, for example if the lines are stuck...)
 414  */
 415 static inline int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 416 {
 417         unsigned short flags = msg->flags;
 418         unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
 419         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 420
 421         unsigned char addr;
 422         int ret, retries;
 423
 424         retries = nak_ok ? 0 : i2c_adap->retries;
 425
 426         if ( (flags & I2C_M_TEN)  ) {
 427                 /* a ten bit address */
 428                 addr = 0xf0 | (( msg->addr >> 7) & 0x03);
 429                 DEB2(printk(KERN_DEBUG "addr0: %d\n",addr));
 430                 /* try extended address code...*/
 431                 ret = try_address(i2c_adap, addr, retries);
 432                 if ((ret != 1) && !nak_ok)  {
 433                         printk(KERN_ERR "died at extended address code.\n");
 434                         return -EREMOTEIO;
 435                 }
 436                 /* the remaining 8 bit address */
 437                 ret = i2c_outb(i2c_adap,msg->addr & 0x7f);
 438                 if ((ret != 1) && !nak_ok) {
 439                         /* the chip did not ack / xmission error occurred */
 440                         printk(KERN_ERR "died at 2nd address code.\n");
 441                         return -EREMOTEIO;
 442                 }
 443                 if ( flags & I2C_M_RD ) {
 444                         i2c_repstart(adap);
 445                         /* okay, now switch into reading mode */
 446                         addr |= 0x01;
 447                         ret = try_address(i2c_adap, addr, retries);
 448                         if ((ret!=1) && !nak_ok) {
 449                                 printk(KERN_ERR "died at extended address code.\n");
 450                                 return -EREMOTEIO;
 451                         }
 452                 }
 453         } else {                /* normal 7bit address  */
 454                 addr = ( msg->addr << 1 );
 455                 if (flags & I2C_M_RD )
 456                         addr |= 1;
 457                 if (flags & I2C_M_REV_DIR_ADDR )
 458                         addr ^= 1;
 459                 ret = try_address(i2c_adap, addr, retries);
 460                 if ((ret!=1) && !nak_ok)
 461                         return -EREMOTEIO;
 462         }
 463
 464         return 0;
 465 }
 466
 467 static int bit_xfer(struct i2c_adapter *i2c_adap,
 468                     struct i2c_msg msgs[], int num)
 469 {
 470         struct i2c_msg *pmsg;
 471         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 472
 473         int i,ret;
 474         unsigned short nak_ok;
 475
 476         i2c_start(adap);
 477         for (i=0;i<num;i++) {
 478                 pmsg = &msgs[i];
 479                 nak_ok = pmsg->flags & I2C_M_IGNORE_NAK;
 480                 if (!(pmsg->flags & I2C_M_NOSTART)) {
 481                         if (i) {
 482                                 i2c_repstart(adap);
 483                         }
 484                         ret = bit_doAddress(i2c_adap, pmsg);
 485                         if ((ret != 0) && !nak_ok) {
 486                             DEB2(printk(KERN_DEBUG "i2c-algo-bit.o: NAK from device addr %2.2x msg #%d\n"
 487                                         ,msgs[i].addr,i));
 488                             return (ret<0) ? ret : -EREMOTEIO;
 489                         }
 490                 }
 491                 if (pmsg->flags & I2C_M_RD ) {
 492                         /* read bytes into buffer*/
 493                         ret = readbytes(i2c_adap, pmsg);
 494                         DEB2(printk(KERN_DEBUG "i2c-algo-bit.o: read %d bytes.\n",ret));
 495                         if (ret < pmsg->len ) {
 496                                 return (ret<0)? ret : -EREMOTEIO;
 497                         }
 498                 } else {
 499                         /* write bytes from buffer */
 500                         ret = sendbytes(i2c_adap, pmsg);
 501                         DEB2(printk(KERN_DEBUG "i2c-algo-bit.o: wrote %d bytes.\n",ret));
 502                         if (ret < pmsg->len ) {
 503                                 return (ret<0) ? ret : -EREMOTEIO;
 504                         }
 505                 }
 506         }
 507         i2c_stop(adap);
 508         return num;
 509 }
 510
 511 static u32 bit_func(struct i2c_adapter *adap)
 512 {
 513         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
 514                I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
 515 }
 516
 517
 518 /* -----exported algorithm data: -------------------------------------  */
 519
 520 static struct i2c_algorithm i2c_bit_algo = {
 521         .master_xfer    = bit_xfer,
 522         .functionality  = bit_func,
 523 };
 524
 525 /*
 526  * registering functions to load algorithms at runtime
 527  */
 528 int i2c_bit_add_bus(struct i2c_adapter *adap)
 529 {
 530         struct i2c_algo_bit_data *bit_adap = adap->algo_data;
 531
 532         if (bit_test) {
 533                 int ret = test_bus(bit_adap, adap->name);
 534                 if (ret<0)
 535                         return -ENODEV;
 536         }
 537
 538         DEB2(dev_dbg(&adap->dev, "hw routines registered.\n"));
 539
 540         /* register new adapter to i2c module... */
 541         adap->algo = &i2c_bit_algo;
 542
 543         adap->timeout = 100;    /* default values, should       */
 544         adap->retries = 3;      /* be replaced by defines       */
 545
 546         return i2c_add_adapter(adap);
 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_param(bit_test, bool, 0);
 563 module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
 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");