[linuxkernelnewbies] Re: CPU Status and temperature

Mon, 22 Mar 2010 17:36:47 -0700

David Gutierrez wrote:
Hello,
Do any one knows where I can get some tools which measure the CPU Temperature.
David


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Temperature reporting is dependent on the specific capabilities of the motherboard, see Documentation/hwmon/adm1021 for an example - this documents the temperature sensors for Intel Xeon processors.

Under the hwmon subdirectories are the implementation for the different temperature sensing for different CPUs:

In drivers/hwmon:

coretemp.c  k10temp.c  k8temp.c  via-cputemp.c

Via ACPI you can also get the temperature for the CPU, for example drivers/acpi/thermal.c:

 249 static int acpi_thermal_get_temperature(struct acpi_thermal *tz)
 250 {
 251         acpi_status status = AE_OK;
 252         unsigned long long tmp;
 253
 254         if (!tz)
 255                 return -EINVAL;
 256
 257         tz->last_temperature = tz->temperature;
 258
 259         status = acpi_evaluate_integer(tz->device->handle, "_TMP", NULL, &tmp);
 260         if (ACPI_FAILURE(status))
 261                 return -ENODEV;
 262
 263         tz->temperature = tmp;
 264         ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Temperature is %lu dK\n",
 265                           tz->temperature));
 266
 267         return 0;
 268 }

This is because ACPI specs has a requirement:

  24  *
  25  *  This driver fully implements the ACPI thermal policy as described in the
  26  *  ACPI 2.0 Specification.
  27  *
  28  *  TBD: 1. Implement passive cooling hysteresis.
  29  *       2. Enhance passive cooling (CPU) states/limit interface to support
  30  *          concepts of 'multiple limiters', upper/lower limits, etc.
  31  *
  32  */
  33
  51
  52 #define ACPI_THERMAL_CLASS              "thermal_zone"
  53 #define ACPI_THERMAL_DEVICE_NAME        "Thermal Zone"
  54 #define ACPI_THERMAL_FILE_STATE         "state"
  55 #define ACPI_THERMAL_FILE_TEMPERATURE   "temperature"
  56 #define ACPI_THERMAL_FILE_TRIP_POINTS   "trip_points"
  57 #define ACPI_THERMAL_FILE_COOLING_MODE  "cooling_mode"
  58 #define ACPI_THERMAL_FILE_POLLING_FREQ  "polling_frequency"
  59 #define ACPI_THERMAL_NOTIFY_TEMPERATURE 0x80
  60 #define ACPI_THERMAL_NOTIFY_THRESHOLDS  0x81
  61 #define ACPI_THERMAL_NOTIFY_DEVICES     0x82
  62 #define ACPI_THERMAL_NOTIFY_CRITICAL    0xF0
  63 #define ACPI_THERMAL_NOTIFY_HOT         0xF1
  64 #define ACPI_THERMAL_MODE_ACTIVE        0x00
  65
  66 #define ACPI_THERMAL_MAX_ACTIVE 10
  67 #define ACPI_THERMAL_MAX_LIMIT_STR_LEN 65
  68
  69 #define _COMPONENT              ACPI_THERMAL_COMPONENT
  70 ACPI_MODULE_NAME("thermal");
  71
  72 MODULE_AUTHOR("Paul Diefenbaugh");
  73 MODULE_DESCRIPTION("ACPI Thermal Zone Driver");
  74 MODULE_LICENSE("GPL");
  75

etc etc.

Not sure if these are enough to get you going?

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