linux/Documentation/hwmon/exynos4_tmu
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   1Kernel driver exynos4_tmu
   2=================
   3
   4Supported chips:
   5* ARM SAMSUNG EXYNOS4 series of SoC
   6  Prefix: 'exynos4-tmu'
   7  Datasheet: Not publicly available
   8
   9Authors: Donggeun Kim <dg77.kim@samsung.com>
  10
  11Description
  12-----------
  13
  14This driver allows to read temperature inside SAMSUNG EXYNOS4 series of SoC.
  15
  16The chip only exposes the measured 8-bit temperature code value
  17through a register.
  18Temperature can be taken from the temperature code.
  19There are three equations converting from temperature to temperature code.
  20
  21The three equations are:
  22  1. Two point trimming
  23        Tc = (T - 25) * (TI2 - TI1) / (85 - 25) + TI1
  24
  25  2. One point trimming
  26        Tc = T + TI1 - 25
  27
  28  3. No trimming
  29        Tc = T + 50
  30
  31  Tc: Temperature code, T: Temperature,
  32  TI1: Trimming info for 25 degree Celsius (stored at TRIMINFO register)
  33       Temperature code measured at 25 degree Celsius which is unchanged
  34  TI2: Trimming info for 85 degree Celsius (stored at TRIMINFO register)
  35       Temperature code measured at 85 degree Celsius which is unchanged
  36
  37TMU(Thermal Management Unit) in EXYNOS4 generates interrupt
  38when temperature exceeds pre-defined levels.
  39The maximum number of configurable threshold is four.
  40The threshold levels are defined as follows:
  41  Level_0: current temperature > trigger_level_0 + threshold
  42  Level_1: current temperature > trigger_level_1 + threshold
  43  Level_2: current temperature > trigger_level_2 + threshold
  44  Level_3: current temperature > trigger_level_3 + threshold
  45
  46  The threshold and each trigger_level are set
  47  through the corresponding registers.
  48
  49When an interrupt occurs, this driver notify user space of
  50one of four threshold levels for the interrupt
  51through kobject_uevent_env and sysfs_notify functions.
  52Although an interrupt condition for level_0 can be set,
  53it is not notified to user space through sysfs_notify function.
  54
  55Sysfs Interface
  56---------------
  57name            name of the temperature sensor
  58                RO
  59
  60temp1_input     temperature
  61                RO
  62
  63temp1_max       temperature for level_1 interrupt
  64                RO
  65
  66temp1_crit      temperature for level_2 interrupt
  67                RO
  68
  69temp1_emergency temperature for level_3 interrupt
  70                RO
  71
  72temp1_max_alarm alarm for level_1 interrupt
  73                RO
  74
  75temp1_crit_alarm
  76                alarm for level_2 interrupt
  77                RO
  78
  79temp1_emergency_alarm
  80                alarm for level_3 interrupt
  81                RO
  82
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