f8420b5828
settings and is an older version of the same design used for ICH SpeedStep. It is only known to be available on PIIX4 chipsets. Many thanks to Bruno Ducrot for writing the driver and Jon Noack for testing. Submitted by: Bruno Ducrot
296 lines
8.4 KiB
Groff
296 lines
8.4 KiB
Groff
.\" Copyright (c) 2005 Nate Lawson
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd April 10, 2005
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.Dt CPUFREQ 4
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.Os
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.Sh NAME
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.Nm cpufreq
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.Nd CPU frequency control framework
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.Sh SYNOPSIS
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.Cd "device cpufreq"
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.Pp
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.In sys/cpu.h
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.Ft int
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.Fn cpufreq_levels "device_t dev" "struct cf_level *levels" "int *count"
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.Ft int
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.Fn cpufreq_set "device_t dev" "const struct cf_level *level" "int priority"
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.Ft int
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.Fn cpufreq_get "device_t dev" "struct cf_level *level"
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.Ft int
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.Fo cpufreq_drv_settings
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.Fa "device_t dev"
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.Fa "struct cf_setting *sets"
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.Fa "int *count"
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.Fc
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.Ft int
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.Fn cpufreq_drv_type "device_t dev" "int *type"
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.Ft int
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.Fn cpufreq_drv_set "device_t dev" "const struct cf_setting *set"
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.Ft int
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.Fn cpufreq_drv_get "device_t dev" "struct cf_setting *set"
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.Sh DESCRIPTION
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The
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.Nm
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driver provides a unified kernel and user interface to CPU frequency
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control drivers.
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It combines multiple drivers offering different settings into a single
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interface of all possible levels.
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Users can access this interface directly via
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.Xr sysctl 8
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or by indicating to
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.Pa power_profile
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that it should switch settings when the AC line state changes via
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.Xr rc.conf 5 .
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.Sh SYSCTLS
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These settings may be overridden by kernel drivers requesting alternate
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settings.
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If this occurs, the original values will be restored once the condition
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has passed (e.g., the system has cooled sufficiently).
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If a sysctl cannot be set due to an override condition, it will return
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.Er EPERM .
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.Bl -tag -width indent
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.It Va dev.cpu.%d.freq
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Current active CPU frequency in MHz.
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.It Va dev.cpu.%d.freq_levels
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Currently available levels for the CPU (frequency/power usage).
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Values are in units of MHz and milliwatts.
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.It Va dev.DEVICE.%d.freq_settings
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Currently available settings for the driver (frequency/power usage).
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Values are in units of MHz and milliwatts.
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This is helpful for understanding which settings are offered by which
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driver for debugging purposes.
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.It Va debug.cpufreq.lowest
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Lowest CPU frequency in MHz to offer to users.
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This setting is also accessible via a tunable with the same name.
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This can be used to disable very low levels that may be unusable on
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some systems.
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.It Va debug.cpufreq.verbose
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Print verbose messages.
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This setting is also accessible via a tunable with the same name.
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.El
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.Sh SUPPORTED DRIVERS
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The following device drivers offer absolute frequency control via the
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.Nm
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interface.
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Usually, only one of these can be active at a time.
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.Pp
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.Bl -tag -compact -width ".Pa acpi_perf"
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.It Pa acpi_perf
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ACPI CPU performance states
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.It Pa est
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Intel Enhanced SpeedStep
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.It Pa ichss
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Intel SpeedStep for ICH
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.It Pa powernow
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AMD PowerNow! for K7 and K8
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.It Pa smist
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Intel SMI-based SpeedStep for PIIX4
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.El
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.Pp
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The following device drivers offer relative frequency control and
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have an additive effect:
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.Pp
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.Bl -tag -compact -width ".Pa acpi_throttle"
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.It Pa acpi_throttle
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ACPI CPU throttling
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.It Pa p4tcc
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Pentium 4 Thermal Control Circuitry
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.El
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.Sh KERNEL INTERFACE
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Kernel components can query and set CPU frequencies through the
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.Nm
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kernel interface.
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This involves obtaining a
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.Nm
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device, calling
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.Fn cpufreq_levels
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to get the currently available frequency levels,
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checking the current level with
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.Fn cpufreq_get ,
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and setting a new one from the list with
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.Fn cpufreq_set .
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Each level may actually reference more than one
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.Nm
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driver but kernel components do not need to be aware of this.
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The
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.Va total_set
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element of
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.Vt "struct cf_level"
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provides a summary of the frequency and power for this level.
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Unknown or irrelevant values are set to
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.Dv CPUFREQ_VAL_UNKNOWN .
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.Pp
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The
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.Fn cpufreq_levels
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method takes a
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.Nm
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device and an empty array of
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.Fa levels .
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The
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.Fa count
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value should be set to the number of levels available and after the
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function completes, will be set to the actual number of levels returned.
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If there are more levels than
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.Fa count
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will allow, it should return
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.Er E2BIG .
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.Pp
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The
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.Fn cpufreq_get
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method takes a pointer to space to store a
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.Fa level .
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After successful completion, the output will be the current active level
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and is equal to one of the levels returned by
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.Fn cpufreq_levels .
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.Pp
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The
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.Fn cpufreq_set
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method takes a pointer a
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.Fa level
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and attempts to activate it.
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The
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.Fa priority
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(i.e.,
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.Dv CPUFREQ_PRIO_KERN )
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tells
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.Nm
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whether to override previous settings while activating this level.
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If
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.Fa priority
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is higher than the current active level, that level will be saved and
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overridden with the new level.
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If a level is already saved, the new level is set without overwriting
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the older saved level.
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If
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.Fn cpufreq_set
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is called with a
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.Dv NULL
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.Fa level ,
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the saved level will be restored.
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If there is no saved level,
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.Fn cpufreq_set
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will return
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.Er ENXIO .
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If
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.Fa priority
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is lower than the current active level's priority, this method returns
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.Er EPERM .
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.Sh DRIVER INTERFACE
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Kernel drivers offering hardware-specific CPU frequency control export
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their individual settings through the
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.Nm
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driver interface.
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This involves implementing these methods:
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.Fn cpufreq_drv_settings ,
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.Fn cpufreq_drv_type ,
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.Fn cpufreq_drv_set ,
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and
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.Fn cpufreq_drv_get .
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Additionally, the driver must attach a device as a child of a CPU
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device so that these methods can be called by the
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.Nm
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framework.
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.Pp
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The
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.Fn cpufreq_drv_settings
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method returns an array of currently available settings, each of type
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.Vt "struct cf_setting" .
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The driver should set unknown or irrelevant values to
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.Dv CPUFREQ_VAL_UNKNOWN .
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All the following elements for each setting should be returned:
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.Bd -literal
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struct cf_setting {
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int freq; /* CPU clock in Mhz or 100ths of a percent. */
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int volts; /* Voltage in mV. */
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int power; /* Power consumed in mW. */
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int lat; /* Transition latency in us. */
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device_t dev; /* Driver providing this setting. */
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};
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.Ed
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.Pp
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On entry to this method,
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.Fa count
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contains the number of settings that can be returned.
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On successful completion, the driver sets it to the actual number of
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settings returned.
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If the driver offers more settings than
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.Fa count
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will allow, it should return
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.Er E2BIG .
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.Pp
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The
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.Fn cpufreq_drv_type
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method indicates the type of settings it offers, either
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.Dv CPUFREQ_TYPE_ABSOLUTE
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or
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.Dv CPUFREQ_TYPE_RELATIVE .
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Additionally, the driver may set the
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.Dv CPUFREQ_FLAG_INFO_ONLY
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flag if the settings it provides are information for other drivers only
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and cannot be passed to
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.Fn cpufreq_drv_set
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to activate them.
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.Pp
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The
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.Fn cpufreq_drv_set
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method takes a driver setting and makes it active.
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If the setting is invalid or not currently available, it should return
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.Er EINVAL .
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.Pp
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The
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.Fn cpufreq_drv_get
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method returns the currently-active driver setting.
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The
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.Vt "struct cf_setting"
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returned must be valid for passing to
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.Fn cpufreq_drv_set ,
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including all elements being filled out correctly.
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If the driver cannot infer the current setting
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(even by estimating it with
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.Fn cpu_est_clockrate )
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then it should set all elements to
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.Dv CPUFREQ_VAL_UNKNOWN .
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.Sh SEE ALSO
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.Xr acpi 4 ,
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.Xr sysctl 8
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.Sh AUTHORS
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.An Nate Lawson
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.An Bruno Ducrot
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contributed the
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.Pa powernow
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driver.
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.Sh BUGS
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The following drivers have not yet been converted to the
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.Nm
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interface:
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.Xr longrun 4 .
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.Pp
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Notification of CPU and bus frequency changes is not implemented yet.
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.Pp
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When multiple CPUs offer frequency control, they cannot be set to different
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levels and must all offer the same frequency settings.
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