91 lines
2.9 KiB
ReStructuredText
91 lines
2.9 KiB
ReStructuredText
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Kernel driver exynos_tmu
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========================
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Supported chips:
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* ARM Samsung Exynos4, Exynos5 series of SoC
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Datasheet: Not publicly available
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Authors: Donggeun Kim <dg77.kim@samsung.com>
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Authors: Amit Daniel <amit.daniel@samsung.com>
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TMU controller Description:
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---------------------------
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This driver allows to read temperature inside Samsung Exynos4/5 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:
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Temperature code, T: Temperature,
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TI1:
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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:
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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 Exynos4/5 generates interrupt
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when temperature exceeds pre-defined levels.
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The maximum number of configurable threshold is five.
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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 exynos_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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TMU driver description:
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-----------------------
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The exynos thermal driver is structured as::
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Kernel Core thermal framework
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(thermal_core.c, step_wise.c, cpufreq_cooling.c)
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^
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TMU configuration data -----> TMU Driver <----> Exynos Core thermal wrapper
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(exynos_tmu_data.c) (exynos_tmu.c) (exynos_thermal_common.c)
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(exynos_tmu_data.h) (exynos_tmu.h) (exynos_thermal_common.h)
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a) TMU configuration data:
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This consist of TMU register offsets/bitfields
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described through structure exynos_tmu_registers. Also several
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other platform data (struct exynos_tmu_platform_data) members
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are used to configure the TMU.
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b) TMU driver:
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This component initialises the TMU controller and sets different
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thresholds. It invokes core thermal implementation with the call
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exynos_report_trigger.
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c) Exynos Core thermal wrapper:
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This provides 3 wrapper function to use the
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Kernel core thermal framework. They are exynos_unregister_thermal,
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exynos_register_thermal and exynos_report_trigger.
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