1Kernel driver exynos4_tmu 2================= 3 4Supported chips: 5* ARM SAMSUNG EXYNOS4 series of SoC 6 Prefix: 'exynos4-tmu' 7 Datasheet: Not publicly available 8 9Authors: Donggeun Kim <dg77.kim@samsung.com> 10 11Description 12----------- 13 14This driver allows to read temperature inside SAMSUNG EXYNOS4 series of SoC. 15 16The chip only exposes the measured 8-bit temperature code value 17through a register. 18Temperature can be taken from the temperature code. 19There are three equations converting from temperature to temperature code. 20 21The 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 37TMU(Thermal Management Unit) in EXYNOS4 generates interrupt 38when temperature exceeds pre-defined levels. 39The maximum number of configurable threshold is four. 40The 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 49When an interrupt occurs, this driver notify kernel thermal framework 50with the function exynos4_report_trigger. 51Although an interrupt condition for level_0 can be set, 52it can be used to synchronize the cooling action. 53