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- Kernel driver exynos_tmu
- =================
- Supported chips:
- * ARM SAMSUNG EXYNOS4, EXYNOS5 series of SoC
- Datasheet: Not publicly available
- Authors: Donggeun Kim <dg77.kim@samsung.com>
- Authors: Amit Daniel <amit.daniel@samsung.com>
- TMU controller Description:
- ---------------------------
- This driver allows to read temperature inside SAMSUNG EXYNOS4/5 series of SoC.
- The chip only exposes the measured 8-bit temperature code value
- through a register.
- Temperature can be taken from the temperature code.
- There are three equations converting from temperature to temperature code.
- The three equations are:
- 1. Two point trimming
- Tc = (T - 25) * (TI2 - TI1) / (85 - 25) + TI1
- 2. One point trimming
- Tc = T + TI1 - 25
- 3. No trimming
- Tc = T + 50
- Tc: Temperature code, T: Temperature,
- TI1: Trimming info for 25 degree Celsius (stored at TRIMINFO register)
- Temperature code measured at 25 degree Celsius which is unchanged
- TI2: Trimming info for 85 degree Celsius (stored at TRIMINFO register)
- Temperature code measured at 85 degree Celsius which is unchanged
- TMU(Thermal Management Unit) in EXYNOS4/5 generates interrupt
- when temperature exceeds pre-defined levels.
- The maximum number of configurable threshold is five.
- The threshold levels are defined as follows:
- Level_0: current temperature > trigger_level_0 + threshold
- Level_1: current temperature > trigger_level_1 + threshold
- Level_2: current temperature > trigger_level_2 + threshold
- Level_3: current temperature > trigger_level_3 + threshold
- The threshold and each trigger_level are set
- through the corresponding registers.
- When an interrupt occurs, this driver notify kernel thermal framework
- with the function exynos_report_trigger.
- Although an interrupt condition for level_0 can be set,
- it can be used to synchronize the cooling action.
- TMU driver description:
- -----------------------
- The exynos thermal driver is structured as,
- Kernel Core thermal framework
- (thermal_core.c, step_wise.c, cpu_cooling.c)
- ^
- |
- |
- TMU configuration data -------> TMU Driver <------> Exynos Core thermal wrapper
- (exynos_tmu_data.c) (exynos_tmu.c) (exynos_thermal_common.c)
- (exynos_tmu_data.h) (exynos_tmu.h) (exynos_thermal_common.h)
- a) TMU configuration data: This consist of TMU register offsets/bitfields
- described through structure exynos_tmu_registers. Also several
- other platform data (struct exynos_tmu_platform_data) members
- are used to configure the TMU.
- b) TMU driver: This component initialises the TMU controller and sets different
- thresholds. It invokes core thermal implementation with the call
- exynos_report_trigger.
- c) Exynos Core thermal wrapper: This provides 3 wrapper function to use the
- Kernel core thermal framework. They are exynos_unregister_thermal,
- exynos_register_thermal and exynos_report_trigger.
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