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53 lines
1.7 KiB
Plaintext
53 lines
1.7 KiB
Plaintext
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Kernel driver exynos4_tmu
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=================
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Supported chips:
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* ARM SAMSUNG EXYNOS4 series of SoC
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Prefix: 'exynos4-tmu'
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Datasheet: Not publicly available
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Authors: Donggeun Kim <dg77.kim@samsung.com>
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Description
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-----------
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This driver allows to read temperature inside SAMSUNG EXYNOS4 series of SoC.
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The chip only exposes the measured 8-bit temperature code value
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through a register.
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Temperature can be taken from the temperature code.
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There are three equations converting from temperature to temperature code.
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The three equations are:
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1. Two point trimming
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Tc = (T - 25) * (TI2 - TI1) / (85 - 25) + TI1
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2. One point trimming
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Tc = T + TI1 - 25
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3. No trimming
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Tc = T + 50
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Tc: Temperature code, T: Temperature,
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TI1: Trimming info for 25 degree Celsius (stored at TRIMINFO register)
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Temperature code measured at 25 degree Celsius which is unchanged
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TI2: Trimming info for 85 degree Celsius (stored at TRIMINFO register)
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Temperature code measured at 85 degree Celsius which is unchanged
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TMU(Thermal Management Unit) in EXYNOS4 generates interrupt
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when temperature exceeds pre-defined levels.
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The maximum number of configurable threshold is four.
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The threshold levels are defined as follows:
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Level_0: current temperature > trigger_level_0 + threshold
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Level_1: current temperature > trigger_level_1 + threshold
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Level_2: current temperature > trigger_level_2 + threshold
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Level_3: current temperature > trigger_level_3 + threshold
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The threshold and each trigger_level are set
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through the corresponding registers.
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When an interrupt occurs, this driver notify kernel thermal framework
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with the function exynos4_report_trigger.
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Although an interrupt condition for level_0 can be set,
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it can be used to synchronize the cooling action.
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