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The MAX31790 has two sets of registers for pwm duty cycles, one to request a duty cycle and one to read the actual current duty cycle. Both do not have to be the same. When reporting the pwm duty cycle to the user, the actual pwm duty cycle from pwm duty cycle registers needs to be reported. When setting it, the pwm target duty cycle needs to be written. Since we don't know the actual pwm duty cycle after a target pwm duty cycle has been written, set the valid flag to false to indicate that actual pwm duty cycle should be read from the chip instead of using cached values. Cc: Jan Kundrát <jan.kundrat@cesnet.cz> Cc: Václav Kubernát <kubernat@cesnet.cz> Signed-off-by: Guenter Roeck <linux@roeck-us.net> Tested-by: Václav Kubernát <kubernat@ceesnet.cz> Reviewed-by: Jan Kundrát <jan.kundrat@cesnet.cz> Link: https://lore.kernel.org/r/20210526154022.3223012-3-linux@roeck-us.net
45 lines
1.4 KiB
ReStructuredText
45 lines
1.4 KiB
ReStructuredText
Kernel driver max31790
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======================
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Supported chips:
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* Maxim MAX31790
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Prefix: 'max31790'
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Addresses scanned: -
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Datasheet: https://pdfserv.maximintegrated.com/en/ds/MAX31790.pdf
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Author: Il Han <corone.il.han@gmail.com>
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Description
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-----------
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This driver implements support for the Maxim MAX31790 chip.
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The MAX31790 controls the speeds of up to six fans using six independent
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PWM outputs. The desired fan speeds (or PWM duty cycles) are written
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through the I2C interface. The outputs drive "4-wire" fans directly,
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or can be used to modulate the fan's power terminals using an external
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pass transistor.
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Tachometer inputs monitor fan tachometer logic outputs for precise (+/-1%)
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monitoring and control of fan RPM as well as detection of fan failure.
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Six pins are dedicated tachometer inputs. Any of the six PWM outputs can
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also be configured to serve as tachometer inputs.
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Sysfs entries
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-------------
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================== === =======================================================
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fan[1-12]_input RO fan tachometer speed in RPM
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fan[1-12]_fault RO fan experienced fault
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fan[1-6]_target RW desired fan speed in RPM
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pwm[1-6]_enable RW regulator mode, 0=disabled, 1=manual mode, 2=rpm mode
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pwm[1-6] RW read: current pwm duty cycle,
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write: target pwm duty cycle (0-255)
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================== === =======================================================
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