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 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)
  87                 goto done;
  88
  89         start=jiffies;
  90         while (! getscl(adap) ) {
  91                 /* the hw knows how to read the clock line,
  92                  * so we wait until it actually gets high.
  93                  * This is safer as some chips may hold it low
  94                  * while they are processing data internally.
  95                  */
  96                 if (time_after_eq(jiffies, start+adap->timeout)) {
  97                         return -ETIMEDOUT;
  98                 }
  99                 cond_resched();
 100         }
 101         DEBSTAT(printk(KERN_DEBUG "needed %ld jiffies\n", jiffies-start));
 102
 103 done:
 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
 125         sdalo(adap);
 126         scllo(adap);
 127 }
 128
 129
 130 static void i2c_stop(struct i2c_algo_bit_data *adap)
 131 {
 132         DEBPROTO(printk("P\n"));
 133         /* assert: scl is low */
 134         sdalo(adap);
 135         sclhi(adap);
 136         sdahi(adap);
 137 }
 138
 139
 140
 141 /* send a byte without start cond., look for arbitration,
 142    check ackn. from slave */
 143 /* returns:
 144  * 1 if the device acknowledged
 145  * 0 if the device did not ack
 146  * -ETIMEDOUT if an error occurred (while raising the scl line)
 147  */
 148 static int i2c_outb(struct i2c_adapter *i2c_adap, char c)
 149 {
 150         int i;
 151         int sb;
 152         int ack;
 153         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 154
 155         /* assert: scl is low */
 156         for ( i=7 ; i>=0 ; i-- ) {
 157                 sb = c & ( 1 << i );
 158                 setsda(adap,sb);
 159                 udelay(adap->udelay);
 160                 DEBPROTO(printk(KERN_DEBUG "%d",sb!=0));
 161                 if (sclhi(adap)<0) { /* timed out */
 162                         sdahi(adap); /* we don't want to block the net */
 163                         DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x, timeout at bit #%d\n", c&0xff, i));
 164                         return -ETIMEDOUT;
 165                 };
 166                 /* do arbitration here:
 167                  * if ( sb && ! getsda(adap) ) -> ouch! Get out of here.
 168                  */
 169                 setscl(adap, 0 );
 170                 udelay(adap->udelay);
 171         }
 172         sdahi(adap);
 173         if (sclhi(adap)<0){ /* timeout */
 174             DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x, timeout at ack\n", c&0xff));
 175             return -ETIMEDOUT;
 176         };
 177         /* read ack: SDA should be pulled down by slave */
 178         ack=getsda(adap);       /* ack: sda is pulled low ->success.     */
 179         DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x , getsda() = %d\n", c & 0xff, ack));
 180
 181         DEBPROTO( printk(KERN_DEBUG "[%2.2x]",c&0xff) );
 182         DEBPROTO(if (0==ack){ printk(KERN_DEBUG " A ");} else printk(KERN_DEBUG " NA ") );
 183         scllo(adap);
 184         return 0==ack;          /* return 1 if device acked      */
 185         /* assert: scl is low (sda undef) */
 186 }
 187
 188
 189 static int i2c_inb(struct i2c_adapter *i2c_adap)
 190 {
 191         /* read byte via i2c port, without start/stop sequence  */
 192         /* acknowledge is sent in i2c_read.                     */
 193         int i;
 194         unsigned char indata=0;
 195         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 196
 197         /* assert: scl is low */
 198         sdahi(adap);
 199         for (i=0;i<8;i++) {
 200                 if (sclhi(adap)<0) { /* timeout */
 201                         DEB2(printk(KERN_DEBUG " i2c_inb: timeout at bit #%d\n", 7-i));
 202                         return -ETIMEDOUT;
 203                 };
 204                 indata *= 2;
 205                 if ( getsda(adap) )
 206                         indata |= 0x01;
 207                 scllo(adap);
 208         }
 209         /* assert: scl is low */
 210         DEB2(printk(KERN_DEBUG "i2c_inb: 0x%02x\n", indata & 0xff));
 211
 212         DEBPROTO(printk(KERN_DEBUG " 0x%02x", indata & 0xff));
 213         return (int) (indata & 0xff);
 214 }
 215
 216 /*
 217  * Sanity check for the adapter hardware - check the reaction of
 218  * the bus lines only if it seems to be idle.
 219  */
 220 static int test_bus(struct i2c_algo_bit_data *adap, char* name) {
 221         int scl,sda;
 222
 223         if (adap->getscl==NULL)
 224                 printk(KERN_INFO "i2c-algo-bit.o: Testing SDA only, "
 225                         "SCL is not readable.\n");
 226
 227         sda=getsda(adap);
 228         scl=(adap->getscl==NULL?1:getscl(adap));
 229         printk(KERN_DEBUG "i2c-algo-bit.o: (0) scl=%d, sda=%d\n",scl,sda);
 230         if (!scl || !sda ) {
 231                 printk(KERN_WARNING "i2c-algo-bit.o: %s seems to be busy.\n", name);
 232                 goto bailout;
 233         }
 234
 235         sdalo(adap);
 236         sda=getsda(adap);
 237         scl=(adap->getscl==NULL?1:getscl(adap));
 238         printk(KERN_DEBUG "i2c-algo-bit.o: (1) scl=%d, sda=%d\n",scl,sda);
 239         if ( 0 != sda ) {
 240                 printk(KERN_WARNING "i2c-algo-bit.o: SDA stuck high!\n");
 241                 goto bailout;
 242         }
 243         if ( 0 == scl ) {
 244                 printk(KERN_WARNING "i2c-algo-bit.o: SCL unexpected low "
 245                         "while pulling SDA low!\n");
 246                 goto bailout;
 247         }
 248
 249         sdahi(adap);
 250         sda=getsda(adap);
 251         scl=(adap->getscl==NULL?1:getscl(adap));
 252         printk(KERN_DEBUG "i2c-algo-bit.o: (2) scl=%d, sda=%d\n",scl,sda);
 253         if ( 0 == sda ) {
 254                 printk(KERN_WARNING "i2c-algo-bit.o: SDA stuck low!\n");
 255                 goto bailout;
 256         }
 257         if ( 0 == scl ) {
 258                 printk(KERN_WARNING "i2c-algo-bit.o: SCL unexpected low "
 259                         "while pulling SDA high!\n");
 260                 goto bailout;
 261         }
 262
 263         scllo(adap);
 264         sda=getsda(adap);
 265         scl=(adap->getscl==NULL?0:getscl(adap));
 266         printk(KERN_DEBUG "i2c-algo-bit.o: (3) scl=%d, sda=%d\n",scl,sda);
 267         if ( 0 != scl ) {
 268                 printk(KERN_WARNING "i2c-algo-bit.o: SCL stuck high!\n");
 269                 goto bailout;
 270         }
 271         if ( 0 == sda ) {
 272                 printk(KERN_WARNING "i2c-algo-bit.o: SDA unexpected low "
 273                         "while pulling SCL low!\n");
 274                 goto bailout;
 275         }
 276
 277         sclhi(adap);
 278         sda=getsda(adap);
 279         scl=(adap->getscl==NULL?1:getscl(adap));
 280         printk(KERN_DEBUG "i2c-algo-bit.o: (4) scl=%d, sda=%d\n",scl,sda);
 281         if ( 0 == scl ) {
 282                 printk(KERN_WARNING "i2c-algo-bit.o: SCL stuck low!\n");
 283                 goto bailout;
 284         }
 285         if ( 0 == sda ) {
 286                 printk(KERN_WARNING "i2c-algo-bit.o: SDA unexpected low "
 287                         "while pulling SCL high!\n");
 288                 goto bailout;
 289         }
 290         printk(KERN_INFO "i2c-algo-bit.o: %s passed test.\n",name);
 291         return 0;
 292 bailout:
 293         sdahi(adap);
 294         sclhi(adap);
 295         return -ENODEV;
 296 }
 297
 298 /* ----- Utility functions
 299  */
 300
 301 /* try_address tries to contact a chip for a number of
 302  * times before it gives up.
 303  * return values:
 304  * 1 chip answered
 305  * 0 chip did not answer
 306  * -x transmission error
 307  */
 308 static int try_address(struct i2c_adapter *i2c_adap,
 309                        unsigned char addr, int retries)
 310 {
 311         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 312         int i,ret = -1;
 313         for (i=0;i<=retries;i++) {
 314                 ret = i2c_outb(i2c_adap,addr);
 315                 if (ret==1)
 316                         break;  /* success! */
 317                 i2c_stop(adap);
 318                 udelay(5/*adap->udelay*/);
 319                 if (i==retries)  /* no success */
 320                         break;
 321                 i2c_start(adap);
 322                 udelay(adap->udelay);
 323         }
 324         DEB2(if (i)
 325              printk(KERN_DEBUG "i2c-algo-bit.o: Used %d tries to %s client at 0x%02x : %s\n",
 326                     i+1, addr & 1 ? "read" : "write", addr>>1,
 327                     ret==1 ? "success" : ret==0 ? "no ack" : "failed, timeout?" )
 328             );
 329         return ret;
 330 }
 331
 332 static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 333 {
 334         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 335         char c;
 336         const char *temp = msg->buf;
 337         int count = msg->len;
 338         unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
 339         int retval;
 340         int wrcount=0;
 341
 342         while (count > 0) {
 343                 c = *temp;
 344                 DEB2(dev_dbg(&i2c_adap->dev, "sendbytes: writing %2.2X\n", c&0xff));
 345                 retval = i2c_outb(i2c_adap,c);
 346                 if ((retval>0) || (nak_ok && (retval==0)))  { /* ok or ignored NAK */
 347                         count--;
 348                         temp++;
 349                         wrcount++;
 350                 } else { /* arbitration or no acknowledge */
 351                         dev_err(&i2c_adap->dev, "sendbytes: error - bailout.\n");
 352                         i2c_stop(adap);
 353                         return (retval<0)? retval : -EFAULT;
 354                                 /* got a better one ?? */
 355                 }
 356         }
 357         return wrcount;
 358 }
 359
 360 static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
 361 {
 362         int inval;
 363         int rdcount=0;          /* counts bytes read */
 364         struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
 365         char *temp = msg->buf;
 366         int count = msg->len;
 367
 368         while (count > 0) {
 369                 inval = i2c_inb(i2c_adap);
 370                 if (inval>=0) {
 371                         *temp = inval;
 372                         rdcount++;
 373                 } else {   /* read timed out */
 374                         printk(KERN_ERR "i2c-algo-bit.o: readbytes: i2c_inb timed out.\n");
 375                         break;
 376                 }
 377
 378                 temp++;
 379                 count--;
 380
 381                 if (msg->flags & I2C_M_NO_RD_ACK)
 382                         continue;
 383
 384                 if ( count > 0 ) {              /* send ack */
 385                         sdalo(adap);
 386                         DEBPROTO(printk(" Am "));
 387                 } else {
 388                         sdahi(adap);    /* neg. ack on last byte */
 389                         DEBPROTO(printk(" NAm "));
 390                 }
 391                 if (sclhi(adap)<0) {    /* timeout */
 392                         sdahi(adap);
 393                         printk(KERN_ERR "i2c-algo-bit.o: readbytes: Timeout at ack\n");
 394                         return -ETIMEDOUT;
 395                 };
 396                 scllo(adap);
 397                 sdahi(adap);
 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 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_I2C | I2C_FUNC_SMBUS_EMUL |
 509                I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
 510 }
 511
 512
 513 /* -----exported algorithm data: -------------------------------------  */
 514
 515 static const struct i2c_algorithm i2c_bit_algo = {
 516         .master_xfer    = bit_xfer,
 517         .functionality  = bit_func,
 518 };
 519
 520 /*
 521  * registering functions to load algorithms at runtime
 522  */
 523 int i2c_bit_add_bus(struct i2c_adapter *adap)
 524 {
 525         struct i2c_algo_bit_data *bit_adap = adap->algo_data;
 526
 527         if (bit_test) {
 528                 int ret = test_bus(bit_adap, adap->name);
 529                 if (ret<0)
 530                         return -ENODEV;
 531         }
 532
 533         DEB2(dev_dbg(&adap->dev, "hw routines registered.\n"));
 534
 535         /* register new adapter to i2c module... */
 536         adap->algo = &i2c_bit_algo;
 537
 538         adap->timeout = 100;    /* default values, should       */
 539         adap->retries = 3;      /* be replaced by defines       */
 540
 541         return i2c_add_adapter(adap);
 542 }
 543 EXPORT_SYMBOL(i2c_bit_add_bus);
 544
 545 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
 546 MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
 547 MODULE_LICENSE("GPL");
 548
 549 module_param(bit_test, bool, 0);
 550 module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
 551
 552 MODULE_PARM_DESC(bit_test, "Test the lines of the bus to see if it is stuck");
 553 MODULE_PARM_DESC(i2c_debug,
 554                  "debug level - 0 off; 1 normal; 2,3 more verbose; 9 bit-protocol");