drivers/hwmon/max6650.c

   1 /*
   2  * max6650.c - Part of lm_sensors, Linux kernel modules for hardware
   3  *             monitoring.
   4  *
   5  * (C) 2007 by Hans J. Koch <hjk@hansjkoch.de>
   6  *
   7  * based on code written by John Morris <john.morris@spirentcom.com>
   8  * Copyright (c) 2003 Spirent Communications
   9  * and Claus Gindhart <claus.gindhart@kontron.com>
  10  *
  11  * This module has only been tested with the MAX6650 chip. It should
  12  * also work with the MAX6651. It does not distinguish max6650 and max6651
  13  * chips.
  14  *
  15  * The datasheet was last seen at:
  16  *
  17  *        http://pdfserv.maxim-ic.com/en/ds/MAX6650-MAX6651.pdf
  18  *
  19  * This program is free software; you can redistribute it and/or modify
  20  * it under the terms of the GNU General Public License as published by
  21  * the Free Software Foundation; either version 2 of the License, or
  22  * (at your option) any later version.
  23  *
  24  * This program is distributed in the hope that it will be useful,
  25  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  26  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  27  * GNU General Public License for more details.
  28  *
  29  * You should have received a copy of the GNU General Public License
  30  * along with this program; if not, write to the Free Software
  31  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  32  */
  33
  34 #include <linux/module.h>
  35 #include <linux/init.h>
  36 #include <linux/slab.h>
  37 #include <linux/jiffies.h>
  38 #include <linux/i2c.h>
  39 #include <linux/hwmon.h>
  40 #include <linux/hwmon-sysfs.h>
  41 #include <linux/err.h>
  42
  43 /*
  44  * Insmod parameters
  45  */
  46
  47 /* fan_voltage: 5=5V fan, 12=12V fan, 0=don't change */
  48 static int fan_voltage;
  49 /* prescaler: Possible values are 1, 2, 4, 8, 16 or 0 for don't change */
  50 static int prescaler;
  51 /* clock: The clock frequency of the chip the driver should assume */
  52 static int clock = 254000;
  53
  54 module_param(fan_voltage, int, S_IRUGO);
  55 module_param(prescaler, int, S_IRUGO);
  56 module_param(clock, int, S_IRUGO);
  57
  58 /*
  59  * MAX 6650/6651 registers
  60  */
  61
  62 #define MAX6650_REG_SPEED       0x00
  63 #define MAX6650_REG_CONFIG      0x02
  64 #define MAX6650_REG_GPIO_DEF    0x04
  65 #define MAX6650_REG_DAC         0x06
  66 #define MAX6650_REG_ALARM_EN    0x08
  67 #define MAX6650_REG_ALARM       0x0A
  68 #define MAX6650_REG_TACH0       0x0C
  69 #define MAX6650_REG_TACH1       0x0E
  70 #define MAX6650_REG_TACH2       0x10
  71 #define MAX6650_REG_TACH3       0x12
  72 #define MAX6650_REG_GPIO_STAT   0x14
  73 #define MAX6650_REG_COUNT       0x16
  74
  75 /*
  76  * Config register bits
  77  */
  78
  79 #define MAX6650_CFG_V12                 0x08
  80 #define MAX6650_CFG_PRESCALER_MASK      0x07
  81 #define MAX6650_CFG_PRESCALER_2         0x01
  82 #define MAX6650_CFG_PRESCALER_4         0x02
  83 #define MAX6650_CFG_PRESCALER_8         0x03
  84 #define MAX6650_CFG_PRESCALER_16        0x04
  85 #define MAX6650_CFG_MODE_MASK           0x30
  86 #define MAX6650_CFG_MODE_ON             0x00
  87 #define MAX6650_CFG_MODE_OFF            0x10
  88 #define MAX6650_CFG_MODE_CLOSED_LOOP    0x20
  89 #define MAX6650_CFG_MODE_OPEN_LOOP      0x30
  90 #define MAX6650_COUNT_MASK              0x03
  91
  92 /*
  93  * Alarm status register bits
  94  */
  95
  96 #define MAX6650_ALRM_MAX        0x01
  97 #define MAX6650_ALRM_MIN        0x02
  98 #define MAX6650_ALRM_TACH       0x04
  99 #define MAX6650_ALRM_GPIO1      0x08
 100 #define MAX6650_ALRM_GPIO2      0x10
 101
 102 /* Minimum and maximum values of the FAN-RPM */
 103 #define FAN_RPM_MIN 240
 104 #define FAN_RPM_MAX 30000
 105
 106 #define DIV_FROM_REG(reg) (1 << (reg & 7))
 107
 108 static int max6650_probe(struct i2c_client *client,
 109                          const struct i2c_device_id *id);
 110 static int max6650_init_client(struct i2c_client *client);
 111 static int max6650_remove(struct i2c_client *client);
 112 static struct max6650_data *max6650_update_device(struct device *dev);
 113
 114 /*
 115  * Driver data (common to all clients)
 116  */
 117
 118 static const struct i2c_device_id max6650_id[] = {
 119         { "max6650", 1 },
 120         { "max6651", 4 },
 121         { }
 122 };
 123 MODULE_DEVICE_TABLE(i2c, max6650_id);
 124
 125 static struct i2c_driver max6650_driver = {
 126         .driver = {
 127                 .name   = "max6650",
 128         },
 129         .probe          = max6650_probe,
 130         .remove         = max6650_remove,
 131         .id_table       = max6650_id,
 132 };
 133
 134 /*
 135  * Client data (each client gets its own)
 136  */
 137
 138 struct max6650_data {
 139         struct device *hwmon_dev;
 140         struct mutex update_lock;
 141         int nr_fans;
 142         char valid; /* zero until following fields are valid */
 143         unsigned long last_updated; /* in jiffies */
 144
 145         /* register values */
 146         u8 speed;
 147         u8 config;
 148         u8 tach[4];
 149         u8 count;
 150         u8 dac;
 151         u8 alarm;
 152 };
 153
 154 static ssize_t get_fan(struct device *dev, struct device_attribute *devattr,
 155                        char *buf)
 156 {
 157         struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
 158         struct max6650_data *data = max6650_update_device(dev);
 159         int rpm;
 160
 161         /*
 162          * Calculation details:
 163          *
 164          * Each tachometer counts over an interval given by the "count"
 165          * register (0.25, 0.5, 1 or 2 seconds). This module assumes
 166          * that the fans produce two pulses per revolution (this seems
 167          * to be the most common).
 168          */
 169
 170         rpm = ((data->tach[attr->index] * 120) / DIV_FROM_REG(data->count));
 171         return sprintf(buf, "%d\n", rpm);
 172 }
 173
 174 /*
 175  * Set the fan speed to the specified RPM (or read back the RPM setting).
 176  * This works in closed loop mode only. Use pwm1 for open loop speed setting.
 177  *
 178  * The MAX6650/1 will automatically control fan speed when in closed loop
 179  * mode.
 180  *
 181  * Assumptions:
 182  *
 183  * 1) The MAX6650/1 internal 254kHz clock frequency is set correctly. Use
 184  *    the clock module parameter if you need to fine tune this.
 185  *
 186  * 2) The prescaler (low three bits of the config register) has already
 187  *    been set to an appropriate value. Use the prescaler module parameter
 188  *    if your BIOS doesn't initialize the chip properly.
 189  *
 190  * The relevant equations are given on pages 21 and 22 of the datasheet.
 191  *
 192  * From the datasheet, the relevant equation when in regulation is:
 193  *
 194  *    [fCLK / (128 x (KTACH + 1))] = 2 x FanSpeed / KSCALE
 195  *
 196  * where:
 197  *
 198  *    fCLK is the oscillator frequency (either the 254kHz internal
 199  *         oscillator or the externally applied clock)
 200  *
 201  *    KTACH is the value in the speed register
 202  *
 203  *    FanSpeed is the speed of the fan in rps
 204  *
 205  *    KSCALE is the prescaler value (1, 2, 4, 8, or 16)
 206  *
 207  * When reading, we need to solve for FanSpeed. When writing, we need to
 208  * solve for KTACH.
 209  *
 210  * Note: this tachometer is completely separate from the tachometers
 211  * used to measure the fan speeds. Only one fan's speed (fan1) is
 212  * controlled.
 213  */
 214
 215 static ssize_t get_target(struct device *dev, struct device_attribute *devattr,
 216                          char *buf)
 217 {
 218         struct max6650_data *data = max6650_update_device(dev);
 219         int kscale, ktach, rpm;
 220
 221         /*
 222          * Use the datasheet equation:
 223          *
 224          *    FanSpeed = KSCALE x fCLK / [256 x (KTACH + 1)]
 225          *
 226          * then multiply by 60 to give rpm.
 227          */
 228
 229         kscale = DIV_FROM_REG(data->config);
 230         ktach = data->speed;
 231         rpm = 60 * kscale * clock / (256 * (ktach + 1));
 232         return sprintf(buf, "%d\n", rpm);
 233 }
 234
 235 static ssize_t set_target(struct device *dev, struct device_attribute *devattr,
 236                          const char *buf, size_t count)
 237 {
 238         struct i2c_client *client = to_i2c_client(dev);
 239         struct max6650_data *data = i2c_get_clientdata(client);
 240         int kscale, ktach;
 241         unsigned long rpm;
 242         int err;
 243
 244         err = kstrtoul(buf, 10, &rpm);
 245         if (err)
 246                 return err;
 247
 248         rpm = clamp_val(rpm, FAN_RPM_MIN, FAN_RPM_MAX);
 249
 250         /*
 251          * Divide the required speed by 60 to get from rpm to rps, then
 252          * use the datasheet equation:
 253          *
 254          *     KTACH = [(fCLK x KSCALE) / (256 x FanSpeed)] - 1
 255          */
 256
 257         mutex_lock(&data->update_lock);
 258
 259         kscale = DIV_FROM_REG(data->config);
 260         ktach = ((clock * kscale) / (256 * rpm / 60)) - 1;
 261         if (ktach < 0)
 262                 ktach = 0;
 263         if (ktach > 255)
 264                 ktach = 255;
 265         data->speed = ktach;
 266
 267         i2c_smbus_write_byte_data(client, MAX6650_REG_SPEED, data->speed);
 268
 269         mutex_unlock(&data->update_lock);
 270
 271         return count;
 272 }
 273
 274 /*
 275  * Get/set the fan speed in open loop mode using pwm1 sysfs file.
 276  * Speed is given as a relative value from 0 to 255, where 255 is maximum
 277  * speed. Note that this is done by writing directly to the chip's DAC,
 278  * it won't change the closed loop speed set by fan1_target.
 279  * Also note that due to rounding errors it is possible that you don't read
 280  * back exactly the value you have set.
 281  */
 282
 283 static ssize_t get_pwm(struct device *dev, struct device_attribute *devattr,
 284                        char *buf)
 285 {
 286         int pwm;
 287         struct max6650_data *data = max6650_update_device(dev);
 288
 289         /*
 290          * Useful range for dac is 0-180 for 12V fans and 0-76 for 5V fans.
 291          * Lower DAC values mean higher speeds.
 292          */
 293         if (data->config & MAX6650_CFG_V12)
 294                 pwm = 255 - (255 * (int)data->dac)/180;
 295         else
 296                 pwm = 255 - (255 * (int)data->dac)/76;
 297
 298         if (pwm < 0)
 299                 pwm = 0;
 300
 301         return sprintf(buf, "%d\n", pwm);
 302 }
 303
 304 static ssize_t set_pwm(struct device *dev, struct device_attribute *devattr,
 305                         const char *buf, size_t count)
 306 {
 307         struct i2c_client *client = to_i2c_client(dev);
 308         struct max6650_data *data = i2c_get_clientdata(client);
 309         unsigned long pwm;
 310         int err;
 311
 312         err = kstrtoul(buf, 10, &pwm);
 313         if (err)
 314                 return err;
 315
 316         pwm = clamp_val(pwm, 0, 255);
 317
 318         mutex_lock(&data->update_lock);
 319
 320         if (data->config & MAX6650_CFG_V12)
 321                 data->dac = 180 - (180 * pwm)/255;
 322         else
 323                 data->dac = 76 - (76 * pwm)/255;
 324
 325         i2c_smbus_write_byte_data(client, MAX6650_REG_DAC, data->dac);
 326
 327         mutex_unlock(&data->update_lock);
 328
 329         return count;
 330 }
 331
 332 /*
 333  * Get/Set controller mode:
 334  * Possible values:
 335  * 0 = Fan always on
 336  * 1 = Open loop, Voltage is set according to speed, not regulated.
 337  * 2 = Closed loop, RPM for all fans regulated by fan1 tachometer
 338  */
 339
 340 static ssize_t get_enable(struct device *dev, struct device_attribute *devattr,
 341                           char *buf)
 342 {
 343         struct max6650_data *data = max6650_update_device(dev);
 344         int mode = (data->config & MAX6650_CFG_MODE_MASK) >> 4;
 345         int sysfs_modes[4] = {0, 1, 2, 1};
 346
 347         return sprintf(buf, "%d\n", sysfs_modes[mode]);
 348 }
 349
 350 static ssize_t set_enable(struct device *dev, struct device_attribute *devattr,
 351                           const char *buf, size_t count)
 352 {
 353         struct i2c_client *client = to_i2c_client(dev);
 354         struct max6650_data *data = i2c_get_clientdata(client);
 355         int max6650_modes[3] = {0, 3, 2};
 356         unsigned long mode;
 357         int err;
 358
 359         err = kstrtoul(buf, 10, &mode);
 360         if (err)
 361                 return err;
 362
 363         if (mode > 2)
 364                 return -EINVAL;
 365
 366         mutex_lock(&data->update_lock);
 367
 368         data->config = i2c_smbus_read_byte_data(client, MAX6650_REG_CONFIG);
 369         data->config = (data->config & ~MAX6650_CFG_MODE_MASK)
 370                        | (max6650_modes[mode] << 4);
 371
 372         i2c_smbus_write_byte_data(client, MAX6650_REG_CONFIG, data->config);
 373
 374         mutex_unlock(&data->update_lock);
 375
 376         return count;
 377 }
 378
 379 /*
 380  * Read/write functions for fan1_div sysfs file. The MAX6650 has no such
 381  * divider. We handle this by converting between divider and counttime:
 382  *
 383  * (counttime == k) <==> (divider == 2^k), k = 0, 1, 2, or 3
 384  *
 385  * Lower values of k allow to connect a faster fan without the risk of
 386  * counter overflow. The price is lower resolution. You can also set counttime
 387  * using the module parameter. Note that the module parameter "prescaler" also
 388  * influences the behaviour. Unfortunately, there's no sysfs attribute
 389  * defined for that. See the data sheet for details.
 390  */
 391
 392 static ssize_t get_div(struct device *dev, struct device_attribute *devattr,
 393                        char *buf)
 394 {
 395         struct max6650_data *data = max6650_update_device(dev);
 396
 397         return sprintf(buf, "%d\n", DIV_FROM_REG(data->count));
 398 }
 399
 400 static ssize_t set_div(struct device *dev, struct device_attribute *devattr,
 401                        const char *buf, size_t count)
 402 {
 403         struct i2c_client *client = to_i2c_client(dev);
 404         struct max6650_data *data = i2c_get_clientdata(client);
 405         unsigned long div;
 406         int err;
 407
 408         err = kstrtoul(buf, 10, &div);
 409         if (err)
 410                 return err;
 411
 412         mutex_lock(&data->update_lock);
 413         switch (div) {
 414         case 1:
 415                 data->count = 0;
 416                 break;
 417         case 2:
 418                 data->count = 1;
 419                 break;
 420         case 4:
 421                 data->count = 2;
 422                 break;
 423         case 8:
 424                 data->count = 3;
 425                 break;
 426         default:
 427                 mutex_unlock(&data->update_lock);
 428                 return -EINVAL;
 429         }
 430
 431         i2c_smbus_write_byte_data(client, MAX6650_REG_COUNT, data->count);
 432         mutex_unlock(&data->update_lock);
 433
 434         return count;
 435 }
 436
 437 /*
 438  * Get alarm stati:
 439  * Possible values:
 440  * 0 = no alarm
 441  * 1 = alarm
 442  */
 443
 444 static ssize_t get_alarm(struct device *dev, struct device_attribute *devattr,
 445                          char *buf)
 446 {
 447         struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
 448         struct max6650_data *data = max6650_update_device(dev);
 449         struct i2c_client *client = to_i2c_client(dev);
 450         int alarm = 0;
 451
 452         if (data->alarm & attr->index) {
 453                 mutex_lock(&data->update_lock);
 454                 alarm = 1;
 455                 data->alarm &= ~attr->index;
 456                 data->alarm |= i2c_smbus_read_byte_data(client,
 457                                                         MAX6650_REG_ALARM);
 458                 mutex_unlock(&data->update_lock);
 459         }
 460
 461         return sprintf(buf, "%d\n", alarm);
 462 }
 463
 464 static SENSOR_DEVICE_ATTR(fan1_input, S_IRUGO, get_fan, NULL, 0);
 465 static SENSOR_DEVICE_ATTR(fan2_input, S_IRUGO, get_fan, NULL, 1);
 466 static SENSOR_DEVICE_ATTR(fan3_input, S_IRUGO, get_fan, NULL, 2);
 467 static SENSOR_DEVICE_ATTR(fan4_input, S_IRUGO, get_fan, NULL, 3);
 468 static DEVICE_ATTR(fan1_target, S_IWUSR | S_IRUGO, get_target, set_target);
 469 static DEVICE_ATTR(fan1_div, S_IWUSR | S_IRUGO, get_div, set_div);
 470 static DEVICE_ATTR(pwm1_enable, S_IWUSR | S_IRUGO, get_enable, set_enable);
 471 static DEVICE_ATTR(pwm1, S_IWUSR | S_IRUGO, get_pwm, set_pwm);
 472 static SENSOR_DEVICE_ATTR(fan1_max_alarm, S_IRUGO, get_alarm, NULL,
 473                           MAX6650_ALRM_MAX);
 474 static SENSOR_DEVICE_ATTR(fan1_min_alarm, S_IRUGO, get_alarm, NULL,
 475                           MAX6650_ALRM_MIN);
 476 static SENSOR_DEVICE_ATTR(fan1_fault, S_IRUGO, get_alarm, NULL,
 477                           MAX6650_ALRM_TACH);
 478 static SENSOR_DEVICE_ATTR(gpio1_alarm, S_IRUGO, get_alarm, NULL,
 479                           MAX6650_ALRM_GPIO1);
 480 static SENSOR_DEVICE_ATTR(gpio2_alarm, S_IRUGO, get_alarm, NULL,
 481                           MAX6650_ALRM_GPIO2);
 482
 483 static umode_t max6650_attrs_visible(struct kobject *kobj, struct attribute *a,
 484                                     int n)
 485 {
 486         struct device *dev = container_of(kobj, struct device, kobj);
 487         struct i2c_client *client = to_i2c_client(dev);
 488         u8 alarm_en = i2c_smbus_read_byte_data(client, MAX6650_REG_ALARM_EN);
 489         struct device_attribute *devattr;
 490
 491         /*
 492          * Hide the alarms that have not been enabled by the firmware
 493          */
 494
 495         devattr = container_of(a, struct device_attribute, attr);
 496         if (devattr == &sensor_dev_attr_fan1_max_alarm.dev_attr
 497          || devattr == &sensor_dev_attr_fan1_min_alarm.dev_attr
 498          || devattr == &sensor_dev_attr_fan1_fault.dev_attr
 499          || devattr == &sensor_dev_attr_gpio1_alarm.dev_attr
 500          || devattr == &sensor_dev_attr_gpio2_alarm.dev_attr) {
 501                 if (!(alarm_en & to_sensor_dev_attr(devattr)->index))
 502                         return 0;
 503         }
 504
 505         return a->mode;
 506 }
 507
 508 static struct attribute *max6650_attrs[] = {
 509         &sensor_dev_attr_fan1_input.dev_attr.attr,
 510         &dev_attr_fan1_target.attr,
 511         &dev_attr_fan1_div.attr,
 512         &dev_attr_pwm1_enable.attr,
 513         &dev_attr_pwm1.attr,
 514         &sensor_dev_attr_fan1_max_alarm.dev_attr.attr,
 515         &sensor_dev_attr_fan1_min_alarm.dev_attr.attr,
 516         &sensor_dev_attr_fan1_fault.dev_attr.attr,
 517         &sensor_dev_attr_gpio1_alarm.dev_attr.attr,
 518         &sensor_dev_attr_gpio2_alarm.dev_attr.attr,
 519         NULL
 520 };
 521
 522 static struct attribute_group max6650_attr_grp = {
 523         .attrs = max6650_attrs,
 524         .is_visible = max6650_attrs_visible,
 525 };
 526
 527 static struct attribute *max6651_attrs[] = {
 528         &sensor_dev_attr_fan2_input.dev_attr.attr,
 529         &sensor_dev_attr_fan3_input.dev_attr.attr,
 530         &sensor_dev_attr_fan4_input.dev_attr.attr,
 531         NULL
 532 };
 533
 534 static const struct attribute_group max6651_attr_grp = {
 535         .attrs = max6651_attrs,
 536 };
 537
 538 /*
 539  * Real code
 540  */
 541
 542 static int max6650_probe(struct i2c_client *client,
 543                          const struct i2c_device_id *id)
 544 {
 545         struct max6650_data *data;
 546         int err;
 547
 548         data = devm_kzalloc(&client->dev, sizeof(struct max6650_data),
 549                             GFP_KERNEL);
 550         if (!data) {
 551                 dev_err(&client->dev, "out of memory.\n");
 552                 return -ENOMEM;
 553         }
 554
 555         i2c_set_clientdata(client, data);
 556         mutex_init(&data->update_lock);
 557         data->nr_fans = id->driver_data;
 558
 559         /*
 560          * Initialize the max6650 chip
 561          */
 562         err = max6650_init_client(client);
 563         if (err)
 564                 return err;
 565
 566         err = sysfs_create_group(&client->dev.kobj, &max6650_attr_grp);
 567         if (err)
 568                 return err;
 569         /* 3 additional fan inputs for the MAX6651 */
 570         if (data->nr_fans == 4) {
 571                 err = sysfs_create_group(&client->dev.kobj, &max6651_attr_grp);
 572                 if (err)
 573                         goto err_remove;
 574         }
 575
 576         data->hwmon_dev = hwmon_device_register(&client->dev);
 577         if (!IS_ERR(data->hwmon_dev))
 578                 return 0;
 579
 580         err = PTR_ERR(data->hwmon_dev);
 581         dev_err(&client->dev, "error registering hwmon device.\n");
 582         if (data->nr_fans == 4)
 583                 sysfs_remove_group(&client->dev.kobj, &max6651_attr_grp);
 584 err_remove:
 585         sysfs_remove_group(&client->dev.kobj, &max6650_attr_grp);
 586         return err;
 587 }
 588
 589 static int max6650_remove(struct i2c_client *client)
 590 {
 591         struct max6650_data *data = i2c_get_clientdata(client);
 592
 593         hwmon_device_unregister(data->hwmon_dev);
 594         if (data->nr_fans == 4)
 595                 sysfs_remove_group(&client->dev.kobj, &max6651_attr_grp);
 596         sysfs_remove_group(&client->dev.kobj, &max6650_attr_grp);
 597         return 0;
 598 }
 599
 600 static int max6650_init_client(struct i2c_client *client)
 601 {
 602         struct max6650_data *data = i2c_get_clientdata(client);
 603         int config;
 604         int err = -EIO;
 605
 606         config = i2c_smbus_read_byte_data(client, MAX6650_REG_CONFIG);
 607
 608         if (config < 0) {
 609                 dev_err(&client->dev, "Error reading config, aborting.\n");
 610                 return err;
 611         }
 612
 613         switch (fan_voltage) {
 614         case 0:
 615                 break;
 616         case 5:
 617                 config &= ~MAX6650_CFG_V12;
 618                 break;
 619         case 12:
 620                 config |= MAX6650_CFG_V12;
 621                 break;
 622         default:
 623                 dev_err(&client->dev, "illegal value for fan_voltage (%d)\n",
 624                         fan_voltage);
 625         }
 626
 627         dev_info(&client->dev, "Fan voltage is set to %dV.\n",
 628                  (config & MAX6650_CFG_V12) ? 12 : 5);
 629
 630         switch (prescaler) {
 631         case 0:
 632                 break;
 633         case 1:
 634                 config &= ~MAX6650_CFG_PRESCALER_MASK;
 635                 break;
 636         case 2:
 637                 config = (config & ~MAX6650_CFG_PRESCALER_MASK)
 638                          | MAX6650_CFG_PRESCALER_2;
 639                 break;
 640         case  4:
 641                 config = (config & ~MAX6650_CFG_PRESCALER_MASK)
 642                          | MAX6650_CFG_PRESCALER_4;
 643                 break;
 644         case  8:
 645                 config = (config & ~MAX6650_CFG_PRESCALER_MASK)
 646                          | MAX6650_CFG_PRESCALER_8;
 647                 break;
 648         case 16:
 649                 config = (config & ~MAX6650_CFG_PRESCALER_MASK)
 650                          | MAX6650_CFG_PRESCALER_16;
 651                 break;
 652         default:
 653                 dev_err(&client->dev, "illegal value for prescaler (%d)\n",
 654                         prescaler);
 655         }
 656
 657         dev_info(&client->dev, "Prescaler is set to %d.\n",
 658                  1 << (config & MAX6650_CFG_PRESCALER_MASK));
 659
 660         /*
 661          * If mode is set to "full off", we change it to "open loop" and
 662          * set DAC to 255, which has the same effect. We do this because
 663          * there's no "full off" mode defined in hwmon specifications.
 664          */
 665
 666         if ((config & MAX6650_CFG_MODE_MASK) == MAX6650_CFG_MODE_OFF) {
 667                 dev_dbg(&client->dev, "Change mode to open loop, full off.\n");
 668                 config = (config & ~MAX6650_CFG_MODE_MASK)
 669                          | MAX6650_CFG_MODE_OPEN_LOOP;
 670                 if (i2c_smbus_write_byte_data(client, MAX6650_REG_DAC, 255)) {
 671                         dev_err(&client->dev, "DAC write error, aborting.\n");
 672                         return err;
 673                 }
 674         }
 675
 676         if (i2c_smbus_write_byte_data(client, MAX6650_REG_CONFIG, config)) {
 677                 dev_err(&client->dev, "Config write error, aborting.\n");
 678                 return err;
 679         }
 680
 681         data->config = config;
 682         data->count = i2c_smbus_read_byte_data(client, MAX6650_REG_COUNT);
 683
 684         return 0;
 685 }
 686
 687 static const u8 tach_reg[] = {
 688         MAX6650_REG_TACH0,
 689         MAX6650_REG_TACH1,
 690         MAX6650_REG_TACH2,
 691         MAX6650_REG_TACH3,
 692 };
 693
 694 static struct max6650_data *max6650_update_device(struct device *dev)
 695 {
 696         int i;
 697         struct i2c_client *client = to_i2c_client(dev);
 698         struct max6650_data *data = i2c_get_clientdata(client);
 699
 700         mutex_lock(&data->update_lock);
 701
 702         if (time_after(jiffies, data->last_updated + HZ) || !data->valid) {
 703                 data->speed = i2c_smbus_read_byte_data(client,
 704                                                        MAX6650_REG_SPEED);
 705                 data->config = i2c_smbus_read_byte_data(client,
 706                                                         MAX6650_REG_CONFIG);
 707                 for (i = 0; i < data->nr_fans; i++) {
 708                         data->tach[i] = i2c_smbus_read_byte_data(client,
 709                                                                  tach_reg[i]);
 710                 }
 711                 data->count = i2c_smbus_read_byte_data(client,
 712                                                         MAX6650_REG_COUNT);
 713                 data->dac = i2c_smbus_read_byte_data(client, MAX6650_REG_DAC);
 714
 715                 /*
 716                  * Alarms are cleared on read in case the condition that
 717                  * caused the alarm is removed. Keep the value latched here
 718                  * for providing the register through different alarm files.
 719                  */
 720                 data->alarm |= i2c_smbus_read_byte_data(client,
 721                                                         MAX6650_REG_ALARM);
 722
 723                 data->last_updated = jiffies;
 724                 data->valid = 1;
 725         }
 726
 727         mutex_unlock(&data->update_lock);
 728
 729         return data;
 730 }
 731
 732 module_i2c_driver(max6650_driver);
 733
 734 MODULE_AUTHOR("Hans J. Koch");
 735 MODULE_DESCRIPTION("MAX6650 sensor driver");
 736 MODULE_LICENSE("GPL");