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Diffstat (limited to 'kernel/Documentation/thermal/exynos_thermal')
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diff --git a/kernel/Documentation/thermal/exynos_thermal b/kernel/Documentation/thermal/exynos_thermal new file mode 100644 index 000000000..9010c4416 --- /dev/null +++ b/kernel/Documentation/thermal/exynos_thermal @@ -0,0 +1,77 @@ +Kernel driver exynos_tmu +================= + +Supported chips: +* ARM SAMSUNG EXYNOS4, EXYNOS5 series of SoC + Datasheet: Not publicly available + +Authors: Donggeun Kim <dg77.kim@samsung.com> +Authors: Amit Daniel <amit.daniel@samsung.com> + +TMU controller Description: +--------------------------- + +This driver allows to read temperature inside SAMSUNG EXYNOS4/5 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 EXYNOS4/5 generates interrupt +when temperature exceeds pre-defined levels. +The maximum number of configurable threshold is five. +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 exynos_report_trigger. +Although an interrupt condition for level_0 can be set, +it can be used to synchronize the cooling action. + +TMU driver description: +----------------------- + +The exynos thermal driver is structured as, + + Kernel Core thermal framework + (thermal_core.c, step_wise.c, cpu_cooling.c) + ^ + | + | +TMU configuration data -------> TMU Driver <------> Exynos Core thermal wrapper +(exynos_tmu_data.c) (exynos_tmu.c) (exynos_thermal_common.c) +(exynos_tmu_data.h) (exynos_tmu.h) (exynos_thermal_common.h) + +a) TMU configuration data: This consist of TMU register offsets/bitfields + described through structure exynos_tmu_registers. Also several + other platform data (struct exynos_tmu_platform_data) members + are used to configure the TMU. +b) TMU driver: This component initialises the TMU controller and sets different + thresholds. It invokes core thermal implementation with the call + exynos_report_trigger. +c) Exynos Core thermal wrapper: This provides 3 wrapper function to use the + Kernel core thermal framework. They are exynos_unregister_thermal, + exynos_register_thermal and exynos_report_trigger. |