1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 1998, 2001 Nicolas Souchu 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #include <sys/cdefs.h> 30 /* 31 * Generic I2C bit-banging code 32 * 33 * Example: 34 * 35 * iicbus 36 * / \ 37 * iicbb pcf 38 * | \ 39 * bti2c lpbb 40 * 41 * From Linux I2C generic interface 42 * (c) 1998 Gerd Knorr <kraxel@cs.tu-berlin.de> 43 * 44 */ 45 46 #include "opt_platform.h" 47 48 #include <sys/param.h> 49 #include <sys/kernel.h> 50 #include <sys/systm.h> 51 #include <sys/module.h> 52 #include <sys/bus.h> 53 #include <sys/sysctl.h> 54 #include <sys/uio.h> 55 #include <machine/cpu.h> 56 57 #ifdef FDT 58 #include <dev/ofw/ofw_bus.h> 59 #include <dev/ofw/ofw_bus_subr.h> 60 #include <dev/fdt/fdt_common.h> 61 #endif 62 63 #include <dev/iicbus/iiconf.h> 64 #include <dev/iicbus/iicbus.h> 65 66 #include <dev/smbus/smbconf.h> 67 68 #include "iicbus_if.h" 69 #include "iicbb_if.h" 70 71 /* Based on the SMBus specification. */ 72 #define DEFAULT_SCL_LOW_TIMEOUT (25 * 1000) 73 74 struct iicbb_softc { 75 device_t iicbus; 76 u_int udelay; /* signal toggle delay in usec */ 77 u_int io_latency; /* approximate pin toggling latency */ 78 u_int scl_low_timeout; 79 }; 80 81 static int iicbb_attach(device_t); 82 static void iicbb_child_detached(device_t, device_t); 83 static int iicbb_print_child(device_t, device_t); 84 static int iicbb_probe(device_t); 85 86 static int iicbb_callback(device_t, int, caddr_t); 87 static int iicbb_start(device_t, u_char, int); 88 static int iicbb_repstart(device_t, u_char, int); 89 static int iicbb_stop(device_t); 90 static int iicbb_write(device_t, const char *, int, int *, int); 91 static int iicbb_read(device_t, char *, int, int *, int, int); 92 static int iicbb_reset(device_t, u_char, u_char, u_char *); 93 static int iicbb_transfer(device_t dev, struct iic_msg *msgs, uint32_t nmsgs); 94 static void iicbb_set_speed(struct iicbb_softc *sc, u_char); 95 #ifdef FDT 96 static phandle_t iicbb_get_node(device_t, device_t); 97 #endif 98 99 static device_method_t iicbb_methods[] = { 100 /* device interface */ 101 DEVMETHOD(device_probe, iicbb_probe), 102 DEVMETHOD(device_attach, iicbb_attach), 103 DEVMETHOD(device_detach, bus_generic_detach), 104 105 /* bus interface */ 106 DEVMETHOD(bus_child_detached, iicbb_child_detached), 107 DEVMETHOD(bus_print_child, iicbb_print_child), 108 109 /* iicbus interface */ 110 DEVMETHOD(iicbus_callback, iicbb_callback), 111 DEVMETHOD(iicbus_start, iicbb_start), 112 DEVMETHOD(iicbus_repeated_start, iicbb_repstart), 113 DEVMETHOD(iicbus_stop, iicbb_stop), 114 DEVMETHOD(iicbus_write, iicbb_write), 115 DEVMETHOD(iicbus_read, iicbb_read), 116 DEVMETHOD(iicbus_reset, iicbb_reset), 117 DEVMETHOD(iicbus_transfer, iicbb_transfer), 118 119 #ifdef FDT 120 /* ofw_bus interface */ 121 DEVMETHOD(ofw_bus_get_node, iicbb_get_node), 122 #endif 123 124 { 0, 0 } 125 }; 126 127 driver_t iicbb_driver = { 128 "iicbb", 129 iicbb_methods, 130 sizeof(struct iicbb_softc), 131 }; 132 133 static int 134 iicbb_probe(device_t dev) 135 { 136 device_set_desc(dev, "I2C bit-banging driver"); 137 138 return (0); 139 } 140 141 static int 142 iicbb_attach(device_t dev) 143 { 144 struct iicbb_softc *sc = (struct iicbb_softc *)device_get_softc(dev); 145 146 sc->iicbus = device_add_child(dev, "iicbus", DEVICE_UNIT_ANY); 147 if (!sc->iicbus) 148 return (ENXIO); 149 150 sc->scl_low_timeout = DEFAULT_SCL_LOW_TIMEOUT; 151 152 SYSCTL_ADD_UINT(device_get_sysctl_ctx(dev), 153 SYSCTL_CHILDREN(device_get_sysctl_tree(dev)), OID_AUTO, 154 "delay", CTLFLAG_RD, &sc->udelay, 155 0, "Signal change delay controlled by bus frequency, microseconds"); 156 157 SYSCTL_ADD_UINT(device_get_sysctl_ctx(dev), 158 SYSCTL_CHILDREN(device_get_sysctl_tree(dev)), OID_AUTO, 159 "scl_low_timeout", CTLFLAG_RWTUN, &sc->scl_low_timeout, 160 0, "SCL low timeout, microseconds"); 161 SYSCTL_ADD_UINT(device_get_sysctl_ctx(dev), 162 SYSCTL_CHILDREN(device_get_sysctl_tree(dev)), OID_AUTO, 163 "io_latency", CTLFLAG_RWTUN, &sc->io_latency, 164 0, "Estimate of pin toggling latency, microseconds"); 165 166 bus_attach_children(dev); 167 return (0); 168 } 169 170 #ifdef FDT 171 static phandle_t 172 iicbb_get_node(device_t bus, device_t dev) 173 { 174 175 /* We only have one child, the I2C bus, which needs our own node. */ 176 return (ofw_bus_get_node(bus)); 177 } 178 #endif 179 180 static void 181 iicbb_child_detached( device_t dev, device_t child ) 182 { 183 struct iicbb_softc *sc = (struct iicbb_softc *)device_get_softc(dev); 184 185 if (child == sc->iicbus) 186 sc->iicbus = NULL; 187 } 188 189 static int 190 iicbb_print_child(device_t bus, device_t dev) 191 { 192 int error; 193 int retval = 0; 194 u_char oldaddr; 195 196 retval += bus_print_child_header(bus, dev); 197 /* retrieve the interface I2C address */ 198 error = IICBB_RESET(device_get_parent(bus), IIC_FASTEST, 0, &oldaddr); 199 if (error == IIC_ENOADDR) { 200 retval += printf(" on %s master-only\n", 201 device_get_nameunit(bus)); 202 } else { 203 /* restore the address */ 204 IICBB_RESET(device_get_parent(bus), IIC_FASTEST, oldaddr, NULL); 205 206 retval += printf(" on %s addr 0x%x\n", 207 device_get_nameunit(bus), oldaddr & 0xff); 208 } 209 210 return (retval); 211 } 212 213 #define IICBB_DEBUG 214 #ifdef IICBB_DEBUG 215 static int i2c_debug = 0; 216 217 SYSCTL_DECL(_hw_i2c); 218 SYSCTL_INT(_hw_i2c, OID_AUTO, iicbb_debug, CTLFLAG_RWTUN, 219 &i2c_debug, 0, "Enable i2c bit-banging driver debug"); 220 221 #define I2C_DEBUG(x) do { \ 222 if (i2c_debug) (x); \ 223 } while (0) 224 #else 225 #define I2C_DEBUG(x) 226 #endif 227 228 #define I2C_GETSDA(dev) (IICBB_GETSDA(device_get_parent(dev))) 229 #define I2C_SETSDA(dev, x) (IICBB_SETSDA(device_get_parent(dev), x)) 230 #define I2C_GETSCL(dev) (IICBB_GETSCL(device_get_parent(dev))) 231 #define I2C_SETSCL(dev, x) (IICBB_SETSCL(device_get_parent(dev), x)) 232 233 static int 234 iicbb_waitforscl(device_t dev) 235 { 236 struct iicbb_softc *sc = device_get_softc(dev); 237 sbintime_t fast_timeout; 238 sbintime_t now, timeout; 239 240 /* Spin for up to 1 ms, then switch to pause. */ 241 now = sbinuptime(); 242 fast_timeout = now + SBT_1MS; 243 timeout = now + sc->scl_low_timeout * SBT_1US; 244 do { 245 if (I2C_GETSCL(dev)) 246 return (0); 247 cpu_spinwait(); 248 now = sbinuptime(); 249 } while (now < fast_timeout); 250 do { 251 I2C_DEBUG(printf(".")); 252 pause_sbt("iicbb-scl-low", SBT_1MS, 0, C_PREL(2)); 253 if (I2C_GETSCL(dev)) 254 return (0); 255 now = sbinuptime(); 256 } while (now < timeout); 257 258 I2C_DEBUG(printf("*")); 259 return (IIC_ETIMEOUT); 260 } 261 262 /* Start the high phase of the clock. */ 263 static int 264 iicbb_clockin(device_t dev, int sda) 265 { 266 267 /* 268 * Precondition: SCL is low. 269 * Action: 270 * - set SDA to the value; 271 * - release SCL and wait until it's high. 272 * The caller is responsible for keeping SCL high for udelay. 273 * 274 * There should be a data set-up time, 250 ns minimum, between setting 275 * SDA and raising SCL. It's expected that the I/O access latency will 276 * naturally provide that delay. 277 */ 278 I2C_SETSDA(dev, sda); 279 I2C_SETSCL(dev, 1); 280 return (iicbb_waitforscl(dev)); 281 } 282 283 /* 284 * End the high phase of the clock and wait out the low phase 285 * as nothing interesting happens during it anyway. 286 */ 287 static void 288 iicbb_clockout(device_t dev) 289 { 290 struct iicbb_softc *sc = device_get_softc(dev); 291 292 /* 293 * Precondition: SCL is high. 294 * Action: 295 * - pull SCL low and hold for udelay. 296 */ 297 I2C_SETSCL(dev, 0); 298 DELAY(sc->udelay); 299 } 300 301 static int 302 iicbb_sendbit(device_t dev, int bit) 303 { 304 struct iicbb_softc *sc = device_get_softc(dev); 305 int err; 306 307 err = iicbb_clockin(dev, bit); 308 if (err != 0) 309 return (err); 310 DELAY(sc->udelay); 311 iicbb_clockout(dev); 312 return (0); 313 } 314 315 /* 316 * Waiting for ACKNOWLEDGE. 317 * 318 * When a chip is being addressed or has received data it will issue an 319 * ACKNOWLEDGE pulse. Therefore the MASTER must release the DATA line 320 * (set it to high level) and then release the CLOCK line. 321 * Now it must wait for the SLAVE to pull the DATA line low. 322 * Actually on the bus this looks like a START condition so nothing happens 323 * because of the fact that the IC's that have not been addressed are doing 324 * nothing. 325 * 326 * When the SLAVE has pulled this line low the MASTER will take the CLOCK 327 * line low and then the SLAVE will release the SDA (data) line. 328 */ 329 static int 330 iicbb_getack(device_t dev) 331 { 332 struct iicbb_softc *sc = device_get_softc(dev); 333 int noack, err; 334 int t; 335 336 /* Release SDA so that the slave can drive it. */ 337 err = iicbb_clockin(dev, 1); 338 if (err != 0) { 339 I2C_DEBUG(printf("! ")); 340 return (err); 341 } 342 343 /* Sample SDA until ACK (low) or udelay runs out. */ 344 for (t = 0; t < sc->udelay; t++) { 345 noack = I2C_GETSDA(dev); 346 if (!noack) 347 break; 348 DELAY(1); 349 } 350 351 DELAY(sc->udelay - t); 352 iicbb_clockout(dev); 353 354 I2C_DEBUG(printf("%c ", noack ? '-' : '+')); 355 return (noack ? IIC_ENOACK : 0); 356 } 357 358 static int 359 iicbb_sendbyte(device_t dev, uint8_t data) 360 { 361 int err, i; 362 363 for (i = 7; i >= 0; i--) { 364 err = iicbb_sendbit(dev, (data & (1 << i)) != 0); 365 if (err != 0) { 366 I2C_DEBUG(printf("w!")); 367 return (err); 368 } 369 } 370 I2C_DEBUG(printf("w%02x", data)); 371 return (0); 372 } 373 374 static int 375 iicbb_readbyte(device_t dev, bool last, uint8_t *data) 376 { 377 struct iicbb_softc *sc = device_get_softc(dev); 378 int i, err; 379 380 /* 381 * Release SDA so that the slave can drive it. 382 * We do not use iicbb_clockin() here because we need to release SDA 383 * only once and then we just pulse the SCL. 384 */ 385 *data = 0; 386 I2C_SETSDA(dev, 1); 387 for (i = 7; i >= 0; i--) { 388 I2C_SETSCL(dev, 1); 389 err = iicbb_waitforscl(dev); 390 if (err != 0) { 391 I2C_DEBUG(printf("r! ")); 392 return (err); 393 } 394 DELAY((sc->udelay + 1) / 2); 395 if (I2C_GETSDA(dev)) 396 *data |= 1 << i; 397 DELAY((sc->udelay + 1) / 2); 398 iicbb_clockout(dev); 399 } 400 401 /* 402 * Send master->slave ACK (low) for more data, 403 * NoACK (high) otherwise. 404 */ 405 iicbb_sendbit(dev, last); 406 I2C_DEBUG(printf("r%02x%c ", *data, last ? '-' : '+')); 407 return (0); 408 } 409 410 static int 411 iicbb_callback(device_t dev, int index, caddr_t data) 412 { 413 return (IICBB_CALLBACK(device_get_parent(dev), index, data)); 414 } 415 416 static int 417 iicbb_reset(device_t dev, u_char speed, u_char addr, u_char *oldaddr) 418 { 419 iicbb_set_speed(device_get_softc(dev), speed); 420 return (IICBB_RESET(device_get_parent(dev), speed, addr, oldaddr)); 421 } 422 423 static int 424 iicbb_start_impl(device_t dev, u_char slave, bool repstart) 425 { 426 struct iicbb_softc *sc = device_get_softc(dev); 427 int error; 428 429 if (!repstart) { 430 I2C_DEBUG(printf("<<")); 431 432 /* SCL must be high on the idle bus. */ 433 if (iicbb_waitforscl(dev) != 0) { 434 I2C_DEBUG(printf("C!\n")); 435 return (IIC_EBUSERR); 436 } 437 } else { 438 I2C_DEBUG(printf("<")); 439 error = iicbb_clockin(dev, 1); 440 if (error != 0) 441 return (error); 442 443 /* SDA will go low in the middle of the SCL high phase. */ 444 DELAY((sc->udelay + 1) / 2); 445 } 446 447 /* 448 * SDA must be high after the earlier stop condition or the end 449 * of Ack/NoAck pulse. 450 */ 451 if (!I2C_GETSDA(dev)) { 452 I2C_DEBUG(printf("D!\n")); 453 return (IIC_EBUSERR); 454 } 455 456 /* Start: SDA high->low. */ 457 I2C_SETSDA(dev, 0); 458 459 /* Wait the second half of the SCL high phase. */ 460 DELAY((sc->udelay + 1) / 2); 461 462 /* Pull SCL low to keep the bus reserved. */ 463 iicbb_clockout(dev); 464 465 /* send address */ 466 error = iicbb_sendbyte(dev, slave); 467 468 /* check for ack */ 469 if (error == 0) 470 error = iicbb_getack(dev); 471 if (error != 0) 472 (void)iicbb_stop(dev); 473 return (error); 474 } 475 476 /* NB: the timeout is ignored. */ 477 static int 478 iicbb_start(device_t dev, u_char slave, int timeout) 479 { 480 return (iicbb_start_impl(dev, slave, false)); 481 } 482 483 /* NB: the timeout is ignored. */ 484 static int 485 iicbb_repstart(device_t dev, u_char slave, int timeout) 486 { 487 return (iicbb_start_impl(dev, slave, true)); 488 } 489 490 static int 491 iicbb_stop(device_t dev) 492 { 493 struct iicbb_softc *sc = device_get_softc(dev); 494 int err = 0; 495 496 /* 497 * Stop: SDA goes from low to high in the middle of the SCL high phase. 498 */ 499 err = iicbb_clockin(dev, 0); 500 if (err != 0) 501 return (err); 502 DELAY((sc->udelay + 1) / 2); 503 I2C_SETSDA(dev, 1); 504 DELAY((sc->udelay + 1) / 2); 505 506 I2C_DEBUG(printf("%s>>", err != 0 ? "!" : "")); 507 I2C_DEBUG(printf("\n")); 508 return (err); 509 } 510 511 /* NB: the timeout is ignored. */ 512 static int 513 iicbb_write(device_t dev, const char *buf, int len, int *sent, int timeout) 514 { 515 int bytes, error = 0; 516 517 bytes = 0; 518 while (len > 0) { 519 /* send byte */ 520 iicbb_sendbyte(dev, (uint8_t)*buf++); 521 522 /* check for ack */ 523 error = iicbb_getack(dev); 524 if (error != 0) 525 break; 526 bytes++; 527 len--; 528 } 529 530 *sent = bytes; 531 return (error); 532 } 533 534 /* NB: whatever delay is, it's ignored. */ 535 static int 536 iicbb_read(device_t dev, char *buf, int len, int *read, int last, int delay) 537 { 538 int bytes = 0; 539 int err = 0; 540 541 while (len > 0) { 542 err = iicbb_readbyte(dev, (len == 1) ? last : 0, 543 (uint8_t *)buf); 544 if (err != 0) 545 break; 546 buf++; 547 bytes++; 548 len--; 549 } 550 551 *read = bytes; 552 return (err); 553 } 554 555 static int 556 iicbb_transfer(device_t dev, struct iic_msg *msgs, uint32_t nmsgs) 557 { 558 int error; 559 560 error = IICBB_PRE_XFER(device_get_parent(dev)); 561 if (error) 562 return (error); 563 564 error = iicbus_transfer_gen(dev, msgs, nmsgs); 565 566 IICBB_POST_XFER(device_get_parent(dev)); 567 return (error); 568 } 569 570 static void 571 iicbb_set_speed(struct iicbb_softc *sc, u_char speed) 572 { 573 u_int busfreq; 574 int period; 575 576 /* 577 * udelay is half a period, the clock is held high or low for this long. 578 */ 579 busfreq = IICBUS_GET_FREQUENCY(sc->iicbus, speed); 580 period = 1000000 / 2 / busfreq; /* Hz -> uS */ 581 period -= sc->io_latency; 582 sc->udelay = MAX(period, 1); 583 } 584 585 DRIVER_MODULE(iicbus, iicbb, iicbus_driver, 0, 0); 586 587 MODULE_DEPEND(iicbb, iicbus, IICBUS_MINVER, IICBUS_PREFVER, IICBUS_MAXVER); 588 MODULE_VERSION(iicbb, IICBB_MODVER); 589