1======================== 2Kernel driver exynos_tmu 3======================== 4 5Supported chips: 6 7* ARM Samsung Exynos4, Exynos5 series of SoC 8 9 Datasheet: Not publicly available 10 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 value 20through 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) + TI1 28 29 2. One point trimming:: 30 31 Tc = T + TI1 - 25 32 33 3. No trimming:: 34 35 Tc = T + 50 36 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 unchanged 42 TI2: 43 Trimming info for 85 degree Celsius (stored at TRIMINFO register) 44 Temperature code measured at 85 degree Celsius which is unchanged 45 46TMU(Thermal Management Unit) in Exynos4/5 generates interrupt 47when 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 + threshold 52 Level_1: current temperature > trigger_level_1 + threshold 53 Level_2: current temperature > trigger_level_2 + threshold 54 Level_3: current temperature > trigger_level_3 + threshold 55 56The threshold and each trigger_level are set 57through the corresponding registers. 58 59When an interrupt occurs, this driver notify kernel thermal framework 60with 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 framework 70 (thermal_core.c, step_wise.c, cpufreq_cooling.c) 71 ^ 72 | 73 | 74 TMU configuration data -----> TMU Driver <----> Exynos Core thermal wrapper 75 (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/bitfields 80 described through structure exynos_tmu_registers. Also several 81 other platform data (struct exynos_tmu_platform_data) members 82 are used to configure the TMU. 83b) TMU driver: 84 This component initialises the TMU controller and sets different 85 thresholds. It invokes core thermal implementation with the call 86 exynos_report_trigger. 87c) Exynos Core thermal wrapper: 88 This provides 3 wrapper function to use the 89 Kernel core thermal framework. They are exynos_unregister_thermal, 90 exynos_register_thermal and exynos_report_trigger. 91