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diff --git a/Documentation/driver-api/thermal/exynos_thermal_emulation.rst b/Documentation/driver-api/thermal/exynos_thermal_emulation.rst new file mode 100644 index 000000000000..c21d10838bc5 --- /dev/null +++ b/Documentation/driver-api/thermal/exynos_thermal_emulation.rst @@ -0,0 +1,61 @@ +===================== +Exynos Emulation Mode +===================== + +Copyright (C) 2012 Samsung Electronics + +Written by Jonghwa Lee <jonghwa3.lee@samsung.com> + +Description +----------- + +Exynos 4x12 (4212, 4412) and 5 series provide emulation mode for thermal +management unit. Thermal emulation mode supports software debug for +TMU's operation. User can set temperature manually with software code +and TMU will read current temperature from user value not from sensor's +value. + +Enabling CONFIG_THERMAL_EMULATION option will make this support +available. When it's enabled, sysfs node will be created as +/sys/devices/virtual/thermal/thermal_zone'zone id'/emul_temp. + +The sysfs node, 'emul_node', will contain value 0 for the initial state. +When you input any temperature you want to update to sysfs node, it +automatically enable emulation mode and current temperature will be +changed into it. + +(Exynos also supports user changeable delay time which would be used to +delay of changing temperature. However, this node only uses same delay +of real sensing time, 938us.) + +Exynos emulation mode requires synchronous of value changing and +enabling. It means when you want to update the any value of delay or +next temperature, then you have to enable emulation mode at the same +time. (Or you have to keep the mode enabling.) If you don't, it fails to +change the value to updated one and just use last succeessful value +repeatedly. That's why this node gives users the right to change +termerpature only. Just one interface makes it more simply to use. + +Disabling emulation mode only requires writing value 0 to sysfs node. + +:: + + + TEMP 120 | + | + 100 | + | + 80 | + | +----------- + 60 | | | + | +-------------| | + 40 | | | | + | | | | + 20 | | | +---------- + | | | | | + 0 |______________|_____________|__________|__________|_________ + A A A A TIME + |<----->| |<----->| |<----->| | + | 938us | | | | | | + emulation : 0 50 | 70 | 20 | 0 + current temp: sensor 50 70 20 sensor |