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exynos4_tmu
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exynos4_tmu
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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 user space of
one of four threshold levels for the interrupt
through kobject_uevent_env and sysfs_notify functions.
Although an interrupt condition for level_0 can be set,
it is not notified to user space through sysfs_notify function.
Sysfs Interface
---------------
name name of the temperature sensor
RO
temp1_input temperature
RO
temp1_max temperature for level_1 interrupt
RO
temp1_crit temperature for level_2 interrupt
RO
temp1_emergency temperature for level_3 interrupt
RO
temp1_max_alarm alarm for level_1 interrupt
RO
temp1_crit_alarm
alarm for level_2 interrupt
RO
temp1_emergency_alarm
alarm for level_3 interrupt
RO