1 /* 2 * sht15.c - support for the SHT15 Temperature and Humidity Sensor 3 * 4 * Copyright (c) 2009 Jonathan Cameron 5 * 6 * Copyright (c) 2007 Wouter Horre 7 * 8 * This program is free software; you can redistribute it and/or modify 9 * it under the terms of the GNU General Public License version 2 as 10 * published by the Free Software Foundation. 11 * 12 * Currently ignoring checksum on readings. 13 * Default resolution only (14bit temp, 12bit humidity) 14 * Ignoring battery status. 15 * Heater not enabled. 16 * Timings are all conservative. 17 * 18 * Data sheet available (1/2009) at 19 * http://www.sensirion.ch/en/pdf/product_information/Datasheet-humidity-sensor-SHT1x.pdf 20 * 21 * Regulator supply name = vcc 22 */ 23 24 #include <linux/interrupt.h> 25 #include <linux/irq.h> 26 #include <linux/gpio.h> 27 #include <linux/module.h> 28 #include <linux/init.h> 29 #include <linux/hwmon.h> 30 #include <linux/hwmon-sysfs.h> 31 #include <linux/mutex.h> 32 #include <linux/platform_device.h> 33 #include <linux/sched.h> 34 #include <linux/delay.h> 35 #include <linux/jiffies.h> 36 #include <linux/err.h> 37 #include <linux/sht15.h> 38 #include <linux/regulator/consumer.h> 39 #include <linux/slab.h> 40 #include <asm/atomic.h> 41 42 #define SHT15_MEASURE_TEMP 3 43 #define SHT15_MEASURE_RH 5 44 45 #define SHT15_READING_NOTHING 0 46 #define SHT15_READING_TEMP 1 47 #define SHT15_READING_HUMID 2 48 49 /* Min timings in nsecs */ 50 #define SHT15_TSCKL 100 /* clock low */ 51 #define SHT15_TSCKH 100 /* clock high */ 52 #define SHT15_TSU 150 /* data setup time */ 53 54 /** 55 * struct sht15_temppair - elements of voltage dependant temp calc 56 * @vdd: supply voltage in microvolts 57 * @d1: see data sheet 58 */ 59 struct sht15_temppair { 60 int vdd; /* microvolts */ 61 int d1; 62 }; 63 64 /* Table 9 from data sheet - relates temperature calculation 65 * to supply voltage. 66 */ 67 static const struct sht15_temppair temppoints[] = { 68 { 2500000, -39400 }, 69 { 3000000, -39600 }, 70 { 3500000, -39700 }, 71 { 4000000, -39800 }, 72 { 5000000, -40100 }, 73 }; 74 75 /** 76 * struct sht15_data - device instance specific data 77 * @pdata: platform data (gpio's etc) 78 * @read_work: bh of interrupt handler 79 * @wait_queue: wait queue for getting values from device 80 * @val_temp: last temperature value read from device 81 * @val_humid: last humidity value read from device 82 * @flag: status flag used to identify what the last request was 83 * @valid: are the current stored values valid (start condition) 84 * @last_updat: time of last update 85 * @read_lock: mutex to ensure only one read in progress 86 * at a time. 87 * @dev: associate device structure 88 * @hwmon_dev: device associated with hwmon subsystem 89 * @reg: associated regulator (if specified) 90 * @nb: notifier block to handle notifications of voltage changes 91 * @supply_uV: local copy of supply voltage used to allow 92 * use of regulator consumer if available 93 * @supply_uV_valid: indicates that an updated value has not yet 94 * been obtained from the regulator and so any calculations 95 * based upon it will be invalid. 96 * @update_supply_work: work struct that is used to update the supply_uV 97 * @interrupt_handled: flag used to indicate a hander has been scheduled 98 */ 99 struct sht15_data { 100 struct sht15_platform_data *pdata; 101 struct work_struct read_work; 102 wait_queue_head_t wait_queue; 103 uint16_t val_temp; 104 uint16_t val_humid; 105 u8 flag; 106 u8 valid; 107 unsigned long last_updat; 108 struct mutex read_lock; 109 struct device *dev; 110 struct device *hwmon_dev; 111 struct regulator *reg; 112 struct notifier_block nb; 113 int supply_uV; 114 int supply_uV_valid; 115 struct work_struct update_supply_work; 116 atomic_t interrupt_handled; 117 }; 118 119 /** 120 * sht15_connection_reset() - reset the comms interface 121 * @data: sht15 specific data 122 * 123 * This implements section 3.4 of the data sheet 124 */ 125 static void sht15_connection_reset(struct sht15_data *data) 126 { 127 int i; 128 gpio_direction_output(data->pdata->gpio_data, 1); 129 ndelay(SHT15_TSCKL); 130 gpio_set_value(data->pdata->gpio_sck, 0); 131 ndelay(SHT15_TSCKL); 132 for (i = 0; i < 9; ++i) { 133 gpio_set_value(data->pdata->gpio_sck, 1); 134 ndelay(SHT15_TSCKH); 135 gpio_set_value(data->pdata->gpio_sck, 0); 136 ndelay(SHT15_TSCKL); 137 } 138 } 139 /** 140 * sht15_send_bit() - send an individual bit to the device 141 * @data: device state data 142 * @val: value of bit to be sent 143 **/ 144 static inline void sht15_send_bit(struct sht15_data *data, int val) 145 { 146 147 gpio_set_value(data->pdata->gpio_data, val); 148 ndelay(SHT15_TSU); 149 gpio_set_value(data->pdata->gpio_sck, 1); 150 ndelay(SHT15_TSCKH); 151 gpio_set_value(data->pdata->gpio_sck, 0); 152 ndelay(SHT15_TSCKL); /* clock low time */ 153 } 154 155 /** 156 * sht15_transmission_start() - specific sequence for new transmission 157 * 158 * @data: device state data 159 * Timings for this are not documented on the data sheet, so very 160 * conservative ones used in implementation. This implements 161 * figure 12 on the data sheet. 162 **/ 163 static void sht15_transmission_start(struct sht15_data *data) 164 { 165 /* ensure data is high and output */ 166 gpio_direction_output(data->pdata->gpio_data, 1); 167 ndelay(SHT15_TSU); 168 gpio_set_value(data->pdata->gpio_sck, 0); 169 ndelay(SHT15_TSCKL); 170 gpio_set_value(data->pdata->gpio_sck, 1); 171 ndelay(SHT15_TSCKH); 172 gpio_set_value(data->pdata->gpio_data, 0); 173 ndelay(SHT15_TSU); 174 gpio_set_value(data->pdata->gpio_sck, 0); 175 ndelay(SHT15_TSCKL); 176 gpio_set_value(data->pdata->gpio_sck, 1); 177 ndelay(SHT15_TSCKH); 178 gpio_set_value(data->pdata->gpio_data, 1); 179 ndelay(SHT15_TSU); 180 gpio_set_value(data->pdata->gpio_sck, 0); 181 ndelay(SHT15_TSCKL); 182 } 183 /** 184 * sht15_send_byte() - send a single byte to the device 185 * @data: device state 186 * @byte: value to be sent 187 **/ 188 static void sht15_send_byte(struct sht15_data *data, u8 byte) 189 { 190 int i; 191 for (i = 0; i < 8; i++) { 192 sht15_send_bit(data, !!(byte & 0x80)); 193 byte <<= 1; 194 } 195 } 196 /** 197 * sht15_wait_for_response() - checks for ack from device 198 * @data: device state 199 **/ 200 static int sht15_wait_for_response(struct sht15_data *data) 201 { 202 gpio_direction_input(data->pdata->gpio_data); 203 gpio_set_value(data->pdata->gpio_sck, 1); 204 ndelay(SHT15_TSCKH); 205 if (gpio_get_value(data->pdata->gpio_data)) { 206 gpio_set_value(data->pdata->gpio_sck, 0); 207 dev_err(data->dev, "Command not acknowledged\n"); 208 sht15_connection_reset(data); 209 return -EIO; 210 } 211 gpio_set_value(data->pdata->gpio_sck, 0); 212 ndelay(SHT15_TSCKL); 213 return 0; 214 } 215 216 /** 217 * sht15_send_cmd() - Sends a command to the device. 218 * @data: device state 219 * @cmd: command byte to be sent 220 * 221 * On entry, sck is output low, data is output pull high 222 * and the interrupt disabled. 223 **/ 224 static int sht15_send_cmd(struct sht15_data *data, u8 cmd) 225 { 226 int ret = 0; 227 sht15_transmission_start(data); 228 sht15_send_byte(data, cmd); 229 ret = sht15_wait_for_response(data); 230 return ret; 231 } 232 /** 233 * sht15_update_single_val() - get a new value from device 234 * @data: device instance specific data 235 * @command: command sent to request value 236 * @timeout_msecs: timeout after which comms are assumed 237 * to have failed are reset. 238 **/ 239 static inline int sht15_update_single_val(struct sht15_data *data, 240 int command, 241 int timeout_msecs) 242 { 243 int ret; 244 ret = sht15_send_cmd(data, command); 245 if (ret) 246 return ret; 247 248 gpio_direction_input(data->pdata->gpio_data); 249 atomic_set(&data->interrupt_handled, 0); 250 251 enable_irq(gpio_to_irq(data->pdata->gpio_data)); 252 if (gpio_get_value(data->pdata->gpio_data) == 0) { 253 disable_irq_nosync(gpio_to_irq(data->pdata->gpio_data)); 254 /* Only relevant if the interrupt hasn't occured. */ 255 if (!atomic_read(&data->interrupt_handled)) 256 schedule_work(&data->read_work); 257 } 258 ret = wait_event_timeout(data->wait_queue, 259 (data->flag == SHT15_READING_NOTHING), 260 msecs_to_jiffies(timeout_msecs)); 261 if (ret == 0) {/* timeout occurred */ 262 disable_irq_nosync(gpio_to_irq(data->pdata->gpio_data)); 263 sht15_connection_reset(data); 264 return -ETIME; 265 } 266 return 0; 267 } 268 269 /** 270 * sht15_update_vals() - get updated readings from device if too old 271 * @data: device state 272 **/ 273 static int sht15_update_vals(struct sht15_data *data) 274 { 275 int ret = 0; 276 int timeout = HZ; 277 278 mutex_lock(&data->read_lock); 279 if (time_after(jiffies, data->last_updat + timeout) 280 || !data->valid) { 281 data->flag = SHT15_READING_HUMID; 282 ret = sht15_update_single_val(data, SHT15_MEASURE_RH, 160); 283 if (ret) 284 goto error_ret; 285 data->flag = SHT15_READING_TEMP; 286 ret = sht15_update_single_val(data, SHT15_MEASURE_TEMP, 400); 287 if (ret) 288 goto error_ret; 289 data->valid = 1; 290 data->last_updat = jiffies; 291 } 292 error_ret: 293 mutex_unlock(&data->read_lock); 294 295 return ret; 296 } 297 298 /** 299 * sht15_calc_temp() - convert the raw reading to a temperature 300 * @data: device state 301 * 302 * As per section 4.3 of the data sheet. 303 **/ 304 static inline int sht15_calc_temp(struct sht15_data *data) 305 { 306 int d1 = temppoints[0].d1; 307 int i; 308 309 for (i = ARRAY_SIZE(temppoints) - 1; i > 0; i--) 310 /* Find pointer to interpolate */ 311 if (data->supply_uV > temppoints[i - 1].vdd) { 312 d1 = (data->supply_uV - temppoints[i - 1].vdd) 313 * (temppoints[i].d1 - temppoints[i - 1].d1) 314 / (temppoints[i].vdd - temppoints[i - 1].vdd) 315 + temppoints[i - 1].d1; 316 break; 317 } 318 319 return data->val_temp*10 + d1; 320 } 321 322 /** 323 * sht15_calc_humid() - using last temperature convert raw to humid 324 * @data: device state 325 * 326 * This is the temperature compensated version as per section 4.2 of 327 * the data sheet. 328 **/ 329 static inline int sht15_calc_humid(struct sht15_data *data) 330 { 331 int RHlinear; /* milli percent */ 332 int temp = sht15_calc_temp(data); 333 334 const int c1 = -4; 335 const int c2 = 40500; /* x 10 ^ -6 */ 336 const int c3 = -28; /* x 10 ^ -7 */ 337 338 RHlinear = c1*1000 339 + c2 * data->val_humid/1000 340 + (data->val_humid * data->val_humid * c3) / 10000; 341 return (temp - 25000) * (10000 + 80 * data->val_humid) 342 / 1000000 + RHlinear; 343 } 344 345 static ssize_t sht15_show_temp(struct device *dev, 346 struct device_attribute *attr, 347 char *buf) 348 { 349 int ret; 350 struct sht15_data *data = dev_get_drvdata(dev); 351 352 /* Technically no need to read humidity as well */ 353 ret = sht15_update_vals(data); 354 355 return ret ? ret : sprintf(buf, "%d\n", 356 sht15_calc_temp(data)); 357 } 358 359 static ssize_t sht15_show_humidity(struct device *dev, 360 struct device_attribute *attr, 361 char *buf) 362 { 363 int ret; 364 struct sht15_data *data = dev_get_drvdata(dev); 365 366 ret = sht15_update_vals(data); 367 368 return ret ? ret : sprintf(buf, "%d\n", sht15_calc_humid(data)); 369 370 }; 371 static ssize_t show_name(struct device *dev, 372 struct device_attribute *attr, 373 char *buf) 374 { 375 struct platform_device *pdev = to_platform_device(dev); 376 return sprintf(buf, "%s\n", pdev->name); 377 } 378 379 static SENSOR_DEVICE_ATTR(temp1_input, 380 S_IRUGO, sht15_show_temp, 381 NULL, 0); 382 static SENSOR_DEVICE_ATTR(humidity1_input, 383 S_IRUGO, sht15_show_humidity, 384 NULL, 0); 385 static DEVICE_ATTR(name, S_IRUGO, show_name, NULL); 386 static struct attribute *sht15_attrs[] = { 387 &sensor_dev_attr_temp1_input.dev_attr.attr, 388 &sensor_dev_attr_humidity1_input.dev_attr.attr, 389 &dev_attr_name.attr, 390 NULL, 391 }; 392 393 static const struct attribute_group sht15_attr_group = { 394 .attrs = sht15_attrs, 395 }; 396 397 static irqreturn_t sht15_interrupt_fired(int irq, void *d) 398 { 399 struct sht15_data *data = d; 400 /* First disable the interrupt */ 401 disable_irq_nosync(irq); 402 atomic_inc(&data->interrupt_handled); 403 /* Then schedule a reading work struct */ 404 if (data->flag != SHT15_READING_NOTHING) 405 schedule_work(&data->read_work); 406 return IRQ_HANDLED; 407 } 408 409 /* Each byte of data is acknowledged by pulling the data line 410 * low for one clock pulse. 411 */ 412 static void sht15_ack(struct sht15_data *data) 413 { 414 gpio_direction_output(data->pdata->gpio_data, 0); 415 ndelay(SHT15_TSU); 416 gpio_set_value(data->pdata->gpio_sck, 1); 417 ndelay(SHT15_TSU); 418 gpio_set_value(data->pdata->gpio_sck, 0); 419 ndelay(SHT15_TSU); 420 gpio_set_value(data->pdata->gpio_data, 1); 421 422 gpio_direction_input(data->pdata->gpio_data); 423 } 424 /** 425 * sht15_end_transmission() - notify device of end of transmission 426 * @data: device state 427 * 428 * This is basically a NAK. (single clock pulse, data high) 429 **/ 430 static void sht15_end_transmission(struct sht15_data *data) 431 { 432 gpio_direction_output(data->pdata->gpio_data, 1); 433 ndelay(SHT15_TSU); 434 gpio_set_value(data->pdata->gpio_sck, 1); 435 ndelay(SHT15_TSCKH); 436 gpio_set_value(data->pdata->gpio_sck, 0); 437 ndelay(SHT15_TSCKL); 438 } 439 440 static void sht15_bh_read_data(struct work_struct *work_s) 441 { 442 int i; 443 uint16_t val = 0; 444 struct sht15_data *data 445 = container_of(work_s, struct sht15_data, 446 read_work); 447 /* Firstly, verify the line is low */ 448 if (gpio_get_value(data->pdata->gpio_data)) { 449 /* If not, then start the interrupt again - care 450 here as could have gone low in meantime so verify 451 it hasn't! 452 */ 453 atomic_set(&data->interrupt_handled, 0); 454 enable_irq(gpio_to_irq(data->pdata->gpio_data)); 455 /* If still not occured or another handler has been scheduled */ 456 if (gpio_get_value(data->pdata->gpio_data) 457 || atomic_read(&data->interrupt_handled)) 458 return; 459 } 460 /* Read the data back from the device */ 461 for (i = 0; i < 16; ++i) { 462 val <<= 1; 463 gpio_set_value(data->pdata->gpio_sck, 1); 464 ndelay(SHT15_TSCKH); 465 val |= !!gpio_get_value(data->pdata->gpio_data); 466 gpio_set_value(data->pdata->gpio_sck, 0); 467 ndelay(SHT15_TSCKL); 468 if (i == 7) 469 sht15_ack(data); 470 } 471 /* Tell the device we are done */ 472 sht15_end_transmission(data); 473 474 switch (data->flag) { 475 case SHT15_READING_TEMP: 476 data->val_temp = val; 477 break; 478 case SHT15_READING_HUMID: 479 data->val_humid = val; 480 break; 481 } 482 483 data->flag = SHT15_READING_NOTHING; 484 wake_up(&data->wait_queue); 485 } 486 487 static void sht15_update_voltage(struct work_struct *work_s) 488 { 489 struct sht15_data *data 490 = container_of(work_s, struct sht15_data, 491 update_supply_work); 492 data->supply_uV = regulator_get_voltage(data->reg); 493 } 494 495 /** 496 * sht15_invalidate_voltage() - mark supply voltage invalid when notified by reg 497 * @nb: associated notification structure 498 * @event: voltage regulator state change event code 499 * @ignored: function parameter - ignored here 500 * 501 * Note that as the notification code holds the regulator lock, we have 502 * to schedule an update of the supply voltage rather than getting it directly. 503 **/ 504 static int sht15_invalidate_voltage(struct notifier_block *nb, 505 unsigned long event, 506 void *ignored) 507 { 508 struct sht15_data *data = container_of(nb, struct sht15_data, nb); 509 510 if (event == REGULATOR_EVENT_VOLTAGE_CHANGE) 511 data->supply_uV_valid = false; 512 schedule_work(&data->update_supply_work); 513 514 return NOTIFY_OK; 515 } 516 517 static int __devinit sht15_probe(struct platform_device *pdev) 518 { 519 int ret = 0; 520 struct sht15_data *data = kzalloc(sizeof(*data), GFP_KERNEL); 521 522 if (!data) { 523 ret = -ENOMEM; 524 dev_err(&pdev->dev, "kzalloc failed"); 525 goto error_ret; 526 } 527 528 INIT_WORK(&data->read_work, sht15_bh_read_data); 529 INIT_WORK(&data->update_supply_work, sht15_update_voltage); 530 platform_set_drvdata(pdev, data); 531 mutex_init(&data->read_lock); 532 data->dev = &pdev->dev; 533 init_waitqueue_head(&data->wait_queue); 534 535 if (pdev->dev.platform_data == NULL) { 536 dev_err(&pdev->dev, "no platform data supplied"); 537 goto err_free_data; 538 } 539 data->pdata = pdev->dev.platform_data; 540 data->supply_uV = data->pdata->supply_mv*1000; 541 542 /* If a regulator is available, query what the supply voltage actually is!*/ 543 data->reg = regulator_get(data->dev, "vcc"); 544 if (!IS_ERR(data->reg)) { 545 int voltage; 546 547 voltage = regulator_get_voltage(data->reg); 548 if (voltage) 549 data->supply_uV = voltage; 550 551 regulator_enable(data->reg); 552 /* setup a notifier block to update this if another device 553 * causes the voltage to change */ 554 data->nb.notifier_call = &sht15_invalidate_voltage; 555 ret = regulator_register_notifier(data->reg, &data->nb); 556 } 557 /* Try requesting the GPIOs */ 558 ret = gpio_request(data->pdata->gpio_sck, "SHT15 sck"); 559 if (ret) { 560 dev_err(&pdev->dev, "gpio request failed"); 561 goto err_free_data; 562 } 563 gpio_direction_output(data->pdata->gpio_sck, 0); 564 ret = gpio_request(data->pdata->gpio_data, "SHT15 data"); 565 if (ret) { 566 dev_err(&pdev->dev, "gpio request failed"); 567 goto err_release_gpio_sck; 568 } 569 ret = sysfs_create_group(&pdev->dev.kobj, &sht15_attr_group); 570 if (ret) { 571 dev_err(&pdev->dev, "sysfs create failed"); 572 goto err_release_gpio_data; 573 } 574 575 ret = request_irq(gpio_to_irq(data->pdata->gpio_data), 576 sht15_interrupt_fired, 577 IRQF_TRIGGER_FALLING, 578 "sht15 data", 579 data); 580 if (ret) { 581 dev_err(&pdev->dev, "failed to get irq for data line"); 582 goto err_release_gpio_data; 583 } 584 disable_irq_nosync(gpio_to_irq(data->pdata->gpio_data)); 585 sht15_connection_reset(data); 586 sht15_send_cmd(data, 0x1E); 587 588 data->hwmon_dev = hwmon_device_register(data->dev); 589 if (IS_ERR(data->hwmon_dev)) { 590 ret = PTR_ERR(data->hwmon_dev); 591 goto err_release_irq; 592 } 593 return 0; 594 595 err_release_irq: 596 free_irq(gpio_to_irq(data->pdata->gpio_data), data); 597 err_release_gpio_data: 598 gpio_free(data->pdata->gpio_data); 599 err_release_gpio_sck: 600 gpio_free(data->pdata->gpio_sck); 601 err_free_data: 602 kfree(data); 603 error_ret: 604 605 return ret; 606 } 607 608 static int __devexit sht15_remove(struct platform_device *pdev) 609 { 610 struct sht15_data *data = platform_get_drvdata(pdev); 611 612 /* Make sure any reads from the device are done and 613 * prevent new ones from beginning */ 614 mutex_lock(&data->read_lock); 615 hwmon_device_unregister(data->hwmon_dev); 616 sysfs_remove_group(&pdev->dev.kobj, &sht15_attr_group); 617 if (!IS_ERR(data->reg)) { 618 regulator_unregister_notifier(data->reg, &data->nb); 619 regulator_disable(data->reg); 620 regulator_put(data->reg); 621 } 622 623 free_irq(gpio_to_irq(data->pdata->gpio_data), data); 624 gpio_free(data->pdata->gpio_data); 625 gpio_free(data->pdata->gpio_sck); 626 mutex_unlock(&data->read_lock); 627 kfree(data); 628 return 0; 629 } 630 631 632 /* 633 * sht_drivers simultaneously refers to __devinit and __devexit function 634 * which causes spurious section mismatch warning. So use __refdata to 635 * get rid from this. 636 */ 637 static struct platform_driver __refdata sht_drivers[] = { 638 { 639 .driver = { 640 .name = "sht10", 641 .owner = THIS_MODULE, 642 }, 643 .probe = sht15_probe, 644 .remove = __devexit_p(sht15_remove), 645 }, { 646 .driver = { 647 .name = "sht11", 648 .owner = THIS_MODULE, 649 }, 650 .probe = sht15_probe, 651 .remove = __devexit_p(sht15_remove), 652 }, { 653 .driver = { 654 .name = "sht15", 655 .owner = THIS_MODULE, 656 }, 657 .probe = sht15_probe, 658 .remove = __devexit_p(sht15_remove), 659 }, { 660 .driver = { 661 .name = "sht71", 662 .owner = THIS_MODULE, 663 }, 664 .probe = sht15_probe, 665 .remove = __devexit_p(sht15_remove), 666 }, { 667 .driver = { 668 .name = "sht75", 669 .owner = THIS_MODULE, 670 }, 671 .probe = sht15_probe, 672 .remove = __devexit_p(sht15_remove), 673 }, 674 }; 675 676 677 static int __init sht15_init(void) 678 { 679 int ret; 680 int i; 681 682 for (i = 0; i < ARRAY_SIZE(sht_drivers); i++) { 683 ret = platform_driver_register(&sht_drivers[i]); 684 if (ret) 685 goto error_unreg; 686 } 687 688 return 0; 689 690 error_unreg: 691 while (--i >= 0) 692 platform_driver_unregister(&sht_drivers[i]); 693 694 return ret; 695 } 696 module_init(sht15_init); 697 698 static void __exit sht15_exit(void) 699 { 700 int i; 701 for (i = ARRAY_SIZE(sht_drivers) - 1; i >= 0; i--) 702 platform_driver_unregister(&sht_drivers[i]); 703 } 704 module_exit(sht15_exit); 705 706 MODULE_LICENSE("GPL"); 707