linux/Documentation/thermal/exynos_thermal
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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 kernel thermal framework
  50with the function exynos4_report_trigger.
  51Although an interrupt condition for level_0 can be set,
  52it can be used to synchronize the cooling action.
  53
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