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