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diff --git a/share/man/man4/hpet.4 b/share/man/man4/hpet.4 new file mode 100644 index 0000000..cd1b766 --- /dev/null +++ b/share/man/man4/hpet.4 @@ -0,0 +1,108 @@ +.\" Copyright (c) 2010 Alexander Motin <mav@FreeBSD.org> +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" $FreeBSD$ +.\" +.Dd September 14, 2010 +.Dt HPET 4 +.Os +.Sh NAME +.Nm hpet +.Nd High Precision Event Timer 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 acpi" +.Ed +.Pp +The following tunables are settable from the +.Xr loader 8 : +.Bl -ohang +.It Va hint.hpet. Ns Ar X Ns Va .allowed_irqs +is a 32bit mask. Each set bit allows driver to use respective IRQ, +if BIOS also set respective capability bit in comparator's configuration +register. +Default value is 0xffff0000, except some known broken hardware. +.It Va hint.hpet. Ns Ar X Ns Va .clock +controls event timers functionality support. Setting to 0, disables it. +Default value is 1. +.It Va hint.hpet. Ns Ar X Ns Va .legacy_route +controls "LegacyReplacement Route" mode. If enabled, HPET will steal IRQ0 of +i8254 timer and IRQ8 of RTC. Before using it, make sure that respective +drivers are not using interrupts, by setting also: +.Bd -literal +hint.attimer.0.clock=0 +hint.atrtc.0.clock=0 +.Ed +Default value is 0. +.It Va hint.hpet. Ns Ar X Ns Va .per_cpu +controls how much per-CPU event timers should driver attempt to register. +This functionality requires every comparator in a group to have own unshared +IRQ, so it depends on hardware capabilities and interrupts configuration. +Default value is 1. +.El +.Sh DESCRIPTION +This driver uses High Precision Event Timer hardware (part of the chipset, +usually enumerated via ACPI) to supply kernel with one time counter and +several (usually from 3 to 8) event timers. +This hardware includes single main counter with known increment frequency +(10MHz or more), and several programmable comparators (optionally with +automatic reload feature). +When value of the main counter matches current value of any comparator, +interrupt can be generated. +Depending on hardware capabilities and configuration, interrupt can be +delivered as regular I/O APIC interrupt (ISA or PCI) in range from 0 to 31, +or as Front Side Bus interrupt, alike to PCI MSI interrupts, or in so called +"LegacyReplacement Route" HPET can steal IRQ0 of i8254 and IRQ8 of the RTC. +Interrupt can be either edge- or level-triggered. In last case they could be +safely shared with PCI IRQs. +Driver prefers to use FSB interrupts, if supported, to avoid sharing. +If it is not possible, it uses single sharable IRQ from PCI range. +Other modes (LegacyReplacement and ISA IRQs) require special care to setup, +but could be configured manually via device hints. +.Pp +Event timers provided by the driver support both one-shot an periodic modes +and irrelevant to CPU power states. +.Pp +Depending on hardware capabilities and configuration, driver can expose each +comparator as separate event timer or group them into one or several per-CPU +event timers. In last case interrupt of every of those comparators within +group is bound to specific CPU core. This is possible only when each +of these comparators has own unsharable IRQ. +.Sh SEE ALSO +.Xr acpi 4 , +.Xr apic 4 , +.Xr atrtc 4 , +.Xr attimer 4 , +.Xr eventtimers 4 , +.Xr timecounters 4 +.Sh HISTORY +The +.Nm +driver first appeared in +.Fx 6.3 . +Support for event timers was added in +.Fx 9.0 . |
