.\"-
.\" Copyright (c) 2010 Nathan Whitehorn <nwhitehorn@FreeBSD.org>
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.Dd February 22, 2010
.Dt SMU 4
.Os
.Sh NAME
.Nm smu
.Nd Apple System Management Unit Driver
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following lines in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "device smu"
.Ed
.Sh DESCRIPTION
The
.Nm
driver provides support for the System Management Unit (SMU) found in many
Apple G5 systems.
This includes most Power Macintosh G5 and all iMac G5 systems.
.Pp
The Apple SMU controller provides software power management and thermal
control functionality, and is responsible for managing system cooling
devices.
.Sh HARDWARE
Chips supported by the
.Nm
driver include:
.Pp
.Bl -bullet -compact
.It
Apple System Management Unit
.El
.Sh THERMAL MANAGEMENT
The
.Nm
driver provides basic automatic thermal management.
Without a userspace daemon providing more advanced control, the driver will
attempt to maintain system temperatures in a conservative range through
coarse-grained control of system cooling devices (see below).
Automatic kernel-level thermal control will take over if more than 3
seconds elapses between userspace cooling setting adjustments.
.Sh SYSCTL VARIABLES
The
.Nm
driver provides power management services and thermal readout through a
sysctl interface.
The following sysctls can be used to control the power management behavior
and to examine current system power and thermal conditions.
.Bl -tag -width indent
.It Va dev.smu.%d.server_mode
Restart after power failure behavior (1 causes system to reboot after power
cut, 0 causes system to remain off).
.It Va dev.smu.%d.target_temp
Target system temperature, in degrees Celsius.
The
.Nm
driver will attempt to adjust fans to maintain the temperature of the
warmest component in the system at or below this level.
.It Va dev.smu.%d.critical_temp
System critical temperature, in degrees Celsius.
If any component in the system exceeds this temperature, the machine
will be shut down within 500 ms.
.It Va dev.smu.%d.fans.%s.minrpm
Minimum allowed speed for this fan.
.It Va dev.smu.%d.fans.%s.maxrpm
Maximum allowed speed for this fan.
.It Va dev.smu.%d.fans.%s.rpm
Current speed for this fan.
The fan speed can be adjusted by changing this sysctl.
If more than 3 seconds elapses between fan speed adjustments, the kernel will
resume automatic control of the fan.
.It Va dev.smu.%d.sensors.%s
Current reading from this sensor.
Four sensor types are supported.
Temperature sensors are in units of degrees Celsius, current sensors in
milliamps, voltage sensors in millivolts, and power sensors in milliwatts.
.El
.Sh LED INTERFACE
The
.Nm
driver provides an
.Xr led 4
annunciator interface at
.Pa /dev/led/sleepled .
.Sh SEE ALSO
.Xr acpi 4 ,
.Xr led 4 ,
.Xr pmu 4
.Sh HISTORY
The
.Nm
device driver appeared in
.Fx 8.0 .
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was written by
.An Nathan Whitehorn Aq Mt nwhitehorn@FreeBSD.org .