path: root/Documentation/thermal
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authorAmit Daniel Kachhap <amit.kachhap@linaro.org>2012-08-16 17:11:41 +0530
committerZhang Rui <rui.zhang@intel.com>2012-09-24 14:44:38 +0800
commitc48cbba6fee3587bdfe77ef850a1a0aa30a2a60f (patch)
tree43a342f501ce99e0b44b5a9346dd3edcf1b255d9 /Documentation/thermal
parent023614183768a7ac62898bded5ec6c0c9fecbdd9 (diff)
hwmon: exynos4: move thermal sensor driver to driver/thermal directory
This movement is needed because the hwmon entries and corresponding sysfs interface is a duplicate of utilities already provided by driver/thermal/thermal_sys.c. The goal is to place it in thermal folder and add necessary functions to use the in-kernel thermal interfaces. Signed-off-by: Amit Daniel Kachhap <amit.kachhap@linaro.org> Acked-by: Guenter Roeck <guenter.roeck@ericsson.com> Cc: SangWook Ju <sw.ju@samsung.com> Cc: Durgadoss <durgadoss.r@intel.com> Cc: Len Brown <lenb@kernel.org> Cc: Jean Delvare <khali@linux-fr.org> Cc: Kyungmin Park <kmpark@infradead.org> Cc: Kukjin Kim <kgene.kim@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Diffstat (limited to 'Documentation/thermal')
1 files changed, 52 insertions, 0 deletions
diff --git a/Documentation/thermal/exynos_thermal b/Documentation/thermal/exynos_thermal
new file mode 100644
index 000000000000..2b46f67b1ccb
--- /dev/null
+++ b/Documentation/thermal/exynos_thermal
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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>
+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.

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