27 lines
1.1 KiB
Plaintext
27 lines
1.1 KiB
Plaintext
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kernel driver gpio-tachometer:
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===================================
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To measure cpu fan/motor speed using GPIO pin, this driver can be used.
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The driver does not rely on any specific peripheral like input capture.
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Author: Vishruth Jain <vishruthj@nvidia.com>
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Description:
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------------
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In platforms where the motor speed input pin is NOT connected to input capture
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pin or any other peripheral capable of measuring the frequency of external
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signal, this driver can be used to measure motor speed.
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The driver works by using GPIO IRQ.
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Driver makes following assumptions:
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-> The pin to which is motor tach output is connected is IRQ capable.
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-> Motor speed indicator(tachometer output from motor) has default state high
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and is pulled to ground level, 1 or more times for every full rotation.
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Speed is calculated based on the number of times GPIO IRQ is triggered in a
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time window. Speed in RPM(rotations per minute) is derived from the count
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captured using IRQ.
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Optionally driver supports creating a delayed worker, which monitors the motor
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speed periodically. If the motor is stopped, indicated by speed being 0, the
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delayed worker initiates system shutdown.
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