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linux/Documentation/hwmon/pwm-fan.rst

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hwmon: Add pwm-fan driver The pwm-fan driver enables control of fans connected to PWM lines. This driver uses the PWM framework, so it is compatible with all PWM devices that provide drivers through the PWM framework. Signed-off-by: Kamil Debski <k.debski@samsung.com> Reviewed-by: Varka Bhadram <varkabhadram@gmail.com> Reviewed-by: Tobias Klauser <tklauser@distanz.ch> [Guenter Roeck: Last argument to devm_of_pwm_get is pointer, use NULL] Signed-off-by: Guenter Roeck <linux@roeck-us.net>
2014-07-16 19:46:42 +04:00
Kernel driver pwm-fan
=====================
This driver enables the use of a PWM module to drive a fan. It uses the
generic PWM interface thus it is hardware independent. It can be used on
many SoCs, as long as the SoC supplies a PWM line driver that exposes
the generic PWM API.
Author: Kamil Debski <k.debski@samsung.com>
Description
-----------
The driver implements a simple interface for driving a fan connected to
a PWM output. It uses the generic PWM interface, thus it can be used with
a range of SoCs. The driver exposes the fan to the user space through
the hwmon's sysfs interface.
Documentation: pwm-fan: Add description for RPM support This adds a short description for the new RPM support of the pwm-fan driver. Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com> Reviewed-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
2019-04-11 16:30:10 +03:00
The fan rotation speed returned via the optional 'fan1_input' is extrapolated
from the sampled interrupts from the tachometer signal within 1 second.
hwmon: (pwm-fan) Switch regulator dynamically This adds the enable attribute which is used to select if zero PWM duty means to switch off regulator and PWM or to keep them enabled but at inactive PWM output level. Depending on the select enable mode, turn off the regulator and PWM if the PWM duty is zero, or keep them enabled. This is especially important for fan using inverted PWM signal polarity. Having regulator supplied and PWM disabled, some PWM controllers provide the active, rather than inactive signal. With this change the shutdown as well as suspend/resume paths require modifcations as well. Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com> Link: https://lore.kernel.org/r/20220914153137.613982-6-alexander.stein@ew.tq-group.com Signed-off-by: Guenter Roeck <linux@roeck-us.net>
2022-09-14 18:31:37 +03:00
The driver provides the following sensor accesses in sysfs:
=============== ======= =======================================================
fan1_input ro fan tachometer speed in RPM
pwm1_enable rw keep enable mode, defines behaviour when pwm1=0
0 -> disable pwm and regulator
1 -> enable pwm; if pwm==0, disable pwm, keep regulator enabled
2 -> enable pwm; if pwm==0, keep pwm and regulator enabled
3 -> enable pwm; if pwm==0, disable pwm and regulator
pwm1 rw relative speed (0-255), 255=max. speed.
=============== ======= =======================================================
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