Copyright (c) 2025 Brad Spencer <brad (at] anduin.eldar.org>
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.Dd Feburary 19, 2025 .Dt EMCFAN 4 .Os .Sh NAME .Nm emcfan .Nd Driver for the Microchip Technology EMC210x and EMC230x fan controllers via I2C bus .Sh SYNOPSIS .Cd "emcfan* at iic? addr 0x2c" .Cd "emcfan* at iic? addr 0x2d" .Cd "emcfan* at iic? addr 0x2e" .Cd "emcfan* at iic? addr 0x2f" .Cd "emcfan* at iic? addr 0x4c" .Cd "emcfan* at iic? addr 0x4d" .Sh DESCRIPTION The .Nm driver support the EMC210x family with the following models: EMC2101, EMC2101-R, EMC2103-1, EMC2103-2, EMC2103-4, EMC2104, and EMC2106 and for the EMC230x family with the following models: EMC2301, EMC2302, EMC2303, and EMC2305. All chips have one or more tachometers, and some of the chips have a number of temperature sensors and GPIO. The .Nm driver provides .Xr envsys 4 framework measurements for the RPM as determined by the tachometers. If the chip has temperature sensors, the .Xr envsys 4 framework will provide an entry for every possible temperature sensor that a particular chip can support. GPIO support is provided by .Xr gpio 4 framework and the pins can be accessed with the .Xr gpioctl 8 command.
p The EMC fan controllers are arranged as a set of registers. These registers are accessed by a /dev device per attached chip. The program .Xr emcfanctl 8 makes use of this device and allows all valid registers for particular chip to be read or written and provides some higher level commands that allow the drive level and frequency divider for a particular fan to be adjusted. .Sh GPIO The EMC2103-2, EMC2103-4, EMC2104 and EMC2106 chips have gpio pins. For the EMC2103-2 and EMC2103-4, these pins are only gpio and are not shared with any other function. For the EMC2104 and EMC2106, the following is how the pins maps to the altN flags in the .Xr gpio 4 framework.
| Pin:ALT0:ALT1 |
| GPIO1:CLK_IN: - |
| GPIO2:TACH2: - |
| GPIO3:PWM2: - |
| GPIO4:OVERT2#:PWM3 |
| GPIO5:OVERT3#:PWM4 |
p .Sh SYSCTL VARIABLES The following .Xr sysctl 8 variables are provided: l -tag -width Li t Li hw.emcfan0.debug If the driver is compiled with .Dv EMCFAN_DEBUG , this node will appear and can be used to set the debugging level. t Li hw.emcfan0.poles<n> For a number of the chips in the two chip families, the tachometer calcuation algorithm needs to know the number of poles that the tachometer has in order to calculate the RPM correctly. Usually this will be 2, but if the situation is otherwise, set this node to the number of poles that the particular fan has. The calculation is also effected by the number of edges present in the tachometer signal. The number of edges is set with the .Xr emcfanctl 8 command. t Li hw.emcfan0.ftach Many of the chips in the two famlies have a pin that can be used to drive an alternative 32.767khz clock for the tachometers. The EMC2103-1, EMC2103-2 and EMC2103-4 does not have this alternative clock pin, and while it is likely that the chip is running at the default 32.000khz, it might not be. This variable lets one set an alternative clock. The units for this node are in hz. t Li hw.emcfan0.vin4_temp_zone The EMC2104 and EMC2106 have a special temperature sensor pin called VIN4, if this sensor is wired up, then this variable can be set to 1 and meaningful values will appear in the .Xr envsys 4 framework. .El .Sh FILES l -tag -width Pa -compact t Pa /dev/emcfan Ns Ar u The device unit .Ar u file. .El .Sh SEE ALSO .Xr emcfanctl 8 , .Xr envsys 4 , .Xr iic 4 , .Xr envstat 8 , .Xr sysctl 8 .Sh HISTORY The .Nm driver first appeared in .Nx 11.0 . .Sh AUTHORS .An -nosplit The .Nm driver was written by .An Brad Spencer Aq Mt brad (at] anduin.eldar.org . .Sh BUGS The driver does not support the EMC2105 chip.
p While not exactly a bug, the driver does nothing with the alert interrupts that can be generated from many of the chips. It would be more typical for this to be tied to a GPIO pin which can interrupt using CPU interrupts.
Indexes created Mon Oct 20 20:10:13 GMT 2025