91 lines
2.9 KiB
ReStructuredText
91 lines
2.9 KiB
ReStructuredText
|
========================
|
||
|
|
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.
|