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41 lines
1.3 KiB
ReStructuredText
41 lines
1.3 KiB
ReStructuredText
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Kernel driver g760a
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===================
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Supported chips:
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* Global Mixed-mode Technology Inc. G760A
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Prefix: 'g760a'
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Datasheet: Publicly available at the GMT website
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http://www.gmt.com.tw/product/datasheet/EDS-760A.pdf
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Author: Herbert Valerio Riedel <hvr@gnu.org>
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Description
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-----------
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The GMT G760A Fan Speed PWM Controller is connected directly to a fan
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and performs closed-loop control of the fan speed.
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The fan speed is programmed by setting the period via 'pwm1' of two
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consecutive speed pulses. The period is defined in terms of clock
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cycle counts of an assumed 32kHz clock source.
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Setting a period of 0 stops the fan; setting the period to 255 sets
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fan to maximum speed.
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The measured fan rotation speed returned via 'fan1_input' is derived
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from the measured speed pulse period by assuming again a 32kHz clock
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source and a 2 pulse-per-revolution fan.
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The 'alarms' file provides access to the two alarm bits provided by
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the G760A chip's status register: Bit 0 is set when the actual fan
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speed differs more than 20% with respect to the programmed fan speed;
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bit 1 is set when fan speed is below 1920 RPM.
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The g760a driver will not update its values more frequently than every
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other second; reading them more often will do no harm, but will return
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'old' values.
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