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1========================2Kernel driver exynos_tmu3========================4 5Supported chips:6 7* ARM Samsung Exynos4, Exynos5 series of SoC8 9 Datasheet: Not publicly available10 11Authors: Donggeun Kim <dg77.kim@samsung.com>12Authors: Amit Daniel <amit.daniel@samsung.com>13 14TMU controller Description:15---------------------------16 17This driver allows to read temperature inside Samsung Exynos4/5 series of SoC.18 19The chip only exposes the measured 8-bit temperature code value20through a register.21Temperature can be taken from the temperature code.22There are three equations converting from temperature to temperature code.23 24The three equations are:25 1. Two point trimming::26 27 Tc = (T - 25) * (TI2 - TI1) / (85 - 25) + TI128 29 2. One point trimming::30 31 Tc = T + TI1 - 2532 33 3. No trimming::34 35 Tc = T + 5036 37 Tc:38 Temperature code, T: Temperature,39 TI1:40 Trimming info for 25 degree Celsius (stored at TRIMINFO register)41 Temperature code measured at 25 degree Celsius which is unchanged42 TI2:43 Trimming info for 85 degree Celsius (stored at TRIMINFO register)44 Temperature code measured at 85 degree Celsius which is unchanged45 46TMU(Thermal Management Unit) in Exynos4/5 generates interrupt47when temperature exceeds pre-defined levels.48The maximum number of configurable threshold is five.49The threshold levels are defined as follows::50 51 Level_0: current temperature > trigger_level_0 + threshold52 Level_1: current temperature > trigger_level_1 + threshold53 Level_2: current temperature > trigger_level_2 + threshold54 Level_3: current temperature > trigger_level_3 + threshold55 56The threshold and each trigger_level are set57through the corresponding registers.58 59When an interrupt occurs, this driver notify kernel thermal framework60with the function exynos_report_trigger.61Although an interrupt condition for level_0 can be set,62it can be used to synchronize the cooling action.63 64TMU driver description:65-----------------------66 67The exynos thermal driver is structured as::68 69 Kernel Core thermal framework70 (thermal_core.c, step_wise.c, cpufreq_cooling.c)71 ^72 |73 |74 TMU configuration data -----> TMU Driver <----> Exynos Core thermal wrapper75 (exynos_tmu_data.c) (exynos_tmu.c) (exynos_thermal_common.c)76 (exynos_tmu_data.h) (exynos_tmu.h) (exynos_thermal_common.h)77 78a) TMU configuration data:79 This consist of TMU register offsets/bitfields80 described through structure exynos_tmu_registers. Also several81 other platform data (struct exynos_tmu_platform_data) members82 are used to configure the TMU.83b) TMU driver:84 This component initialises the TMU controller and sets different85 thresholds. It invokes core thermal implementation with the call86 exynos_report_trigger.87c) Exynos Core thermal wrapper:88 This provides 3 wrapper function to use the89 Kernel core thermal framework. They are exynos_unregister_thermal,90 exynos_register_thermal and exynos_report_trigger.91