Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.
1 Kernel driver exynos_tmu 2 ================= 3 4 Supported chips: 5 * ARM SAMSUNG EXYNOS4, EXYNOS5 series of SoC 6 Datasheet: Not publicly available 7 8 Authors: Donggeun Kim <dg77.kim@samsung.com> 9 Authors: Amit Daniel <amit.daniel@samsung.com> 10 11 TMU controller Description: 12 --------------------------- 13 14 This driver allows to read temperature inside SAMSUNG EXYNOS4/5 series of SoC. 15 16 The chip only exposes the measured 8-bit temperature code value 17 through a register. 18 Temperature can be taken from the temperature code. 19 There are three equations converting from temperature to temperature code. 20 21 The three equations are: 22 1. Two point trimming 23 Tc = (T - 25) * (TI2 - TI1) / (85 - 25) + TI1 24 25 2. One point trimming 26 Tc = T + TI1 - 25 27 28 3. No trimming 29 Tc = T + 50 30 31 Tc: Temperature code, T: Temperature, 32 TI1: Trimming info for 25 degree Celsius (stored at TRIMINFO register) 33 Temperature code measured at 25 degree Celsius which is unchanged 34 TI2: Trimming info for 85 degree Celsius (stored at TRIMINFO register) 35 Temperature code measured at 85 degree Celsius which is unchanged 36 37 TMU(Thermal Management Unit) in EXYNOS4/5 generates interrupt 38 when temperature exceeds pre-defined levels. 39 The maximum number of configurable threshold is five. 40 The threshold levels are defined as follows: 41 Level_0: current temperature > trigger_level_0 + threshold 42 Level_1: current temperature > trigger_level_1 + threshold 43 Level_2: current temperature > trigger_level_2 + threshold 44 Level_3: current temperature > trigger_level_3 + threshold 45 46 The threshold and each trigger_level are set 47 through the corresponding registers. 48 49 When an interrupt occurs, this driver notify kernel thermal framework 50 with the function exynos_report_trigger. 51 Although an interrupt condition for level_0 can be set, 52 it can be used to synchronize the cooling action. 53 54 TMU driver description: 55 ----------------------- 56 57 The exynos thermal driver is structured as, 58 59 Kernel Core thermal framework 60 (thermal_core.c, step_wise.c, cpu_cooling.c) 61 ^ 62 | 63 | 64 TMU configuration data -------> TMU Driver <------> Exynos Core thermal wrapper 65 (exynos_tmu_data.c) (exynos_tmu.c) (exynos_thermal_common.c) 66 (exynos_tmu_data.h) (exynos_tmu.h) (exynos_thermal_common.h) 67 68 a) TMU configuration data: This consist of TMU register offsets/bitfields 69 described through structure exynos_tmu_registers. Also several 70 other platform data (struct exynos_tmu_platform_data) members 71 are used to configure the TMU. 72 b) TMU driver: This component initialises the TMU controller and sets different 73 thresholds. It invokes core thermal implementation with the call 74 exynos_report_trigger. 75 c) Exynos Core thermal wrapper: This provides 3 wrapper function to use the 76 Kernel core thermal framework. They are exynos_unregister_thermal, 77 exynos_register_thermal and exynos_report_trigger.