| Kernel driver exynos4_tmu | |
| ================= | |
| Supported chips: | |
| * ARM SAMSUNG EXYNOS4 series of SoC | |
| Prefix: 'exynos4-tmu' | |
| Datasheet: Not publicly available | |
| Authors: Donggeun Kim <dg77.kim@samsung.com> | |
| Description | |
| ----------- | |
| This driver allows to read temperature inside SAMSUNG EXYNOS4 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 generates interrupt | |
| when temperature exceeds pre-defined levels. | |
| The maximum number of configurable threshold is four. | |
| 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 exynos4_report_trigger. | |
| Although an interrupt condition for level_0 can be set, | |
| it can be used to synchronize the cooling action. |