linux/Documentation/thermal/exynos_thermal_emulation
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   1EXYNOS EMULATION MODE
   2========================
   3
   4Copyright (C) 2012 Samsung Electronics
   5
   6Written by Jonghwa Lee <jonghwa3.lee@samsung.com>
   7
   8Description
   9-----------
  10
  11Exynos 4x12 (4212, 4412) and 5 series provide emulation mode for thermal management unit.
  12Thermal emulation mode supports software debug for TMU's operation. User can set temperature
  13manually with software code and TMU will read current temperature from user value not from
  14sensor's value.
  15
  16Enabling CONFIG_THERMAL_EMULATION option will make this support available.
  17When it's enabled, sysfs node will be created as
  18/sys/devices/virtual/thermal/thermal_zone'zone id'/emul_temp.
  19
  20The sysfs node, 'emul_node', will contain value 0 for the initial state. When you input any
  21temperature you want to update to sysfs node, it automatically enable emulation mode and
  22current temperature will be changed into it.
  23(Exynos also supports user changeable delay time which would be used to delay of
  24 changing temperature. However, this node only uses same delay of real sensing time, 938us.)
  25
  26Exynos emulation mode requires synchronous of value changing and enabling. It means when you
  27want to update the any value of delay or next temperature, then you have to enable emulation
  28mode at the same time. (Or you have to keep the mode enabling.) If you don't, it fails to
  29change the value to updated one and just use last succeessful value repeatedly. That's why
  30this node gives users the right to change termerpature only. Just one interface makes it more
  31simply to use.
  32
  33Disabling emulation mode only requires writing value 0 to sysfs node.
  34
  35
  36TEMP    120 |
  37            |
  38        100 |
  39            |
  40         80 |
  41            |                            +-----------
  42         60 |                            |          |
  43            |              +-------------|          |
  44         40 |              |             |          |
  45            |              |             |          |
  46         20 |              |             |          +----------
  47            |              |             |          |          |
  48          0 |______________|_____________|__________|__________|_________
  49                   A             A          A                  A     TIME
  50                   |<----->|     |<----->|  |<----->|          |
  51                   | 938us |     |       |  |       |          |
  52emulation    :  0  50      |     70      |  20      |          0
  53current temp :   sensor   50             70         20        sensor
  54
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