summaryrefslogtreecommitdiffstats
path: root/kernel/Documentation/thermal/exynos_thermal
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/Documentation/thermal/exynos_thermal')
-rw-r--r--kernel/Documentation/thermal/exynos_thermal77
1 files changed, 77 insertions, 0 deletions
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.