EXYNOS EMULATION MODE
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Copyright (C) 2012 Samsung Electronics
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Written by Jonghwa Lee <jonghwa3.lee@samsung.com>
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Description
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Exynos 4x12 (4212, 4412) and 5 series provide emulation mode for thermal management unit.
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Thermal emulation mode supports software debug for TMU's operation. User can set temperature
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manually with software code and TMU will read current temperature from user value not from
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sensor's value.
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Enabling CONFIG_THERMAL_EMULATION option will make this support available.
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When it's enabled, sysfs node will be created as
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/sys/devices/virtual/thermal/thermal_zone'zone id'/emul_temp.
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The sysfs node, 'emul_node', will contain value 0 for the initial state. When you input any
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temperature you want to update to sysfs node, it automatically enable emulation mode and
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current temperature will be changed into it.
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(Exynos also supports user changeable delay time which would be used to delay of
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changing temperature. However, this node only uses same delay of real sensing time, 938us.)
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Exynos emulation mode requires synchronous of value changing and enabling. It means when you
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want to update the any value of delay or next temperature, then you have to enable emulation
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mode at the same time. (Or you have to keep the mode enabling.) If you don't, it fails to
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change the value to updated one and just use last succeessful value repeatedly. That's why
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this node gives users the right to change termerpature only. Just one interface makes it more
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simply to use.
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Disabling emulation mode only requires writing value 0 to sysfs node.
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TEMP 120 |
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100 |
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80 |
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60 | | |
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40 | | | |
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20 | | | +----------
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0 |______________|_____________|__________|__________|_________
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A A A A TIME
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|<----->| |<----->| |<----->| |
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| 938us | | | | | |
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emulation : 0 50 | 70 | 20 | 0
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current temp : sensor 50 70 20 sensor
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