APIC(4) BSD Kernel Interfaces Manual APIC(4)NAME
apic -- Advanced Programmable Interrupt Controller (APIC) driver
SYNOPSIS
This driver is a mandatory part of amd64 kernel. To compile this driver into i386 or pc98 kernel, place the following line in your kernel
configuration file:
device apic
The following tunable is settable from the loader(8):
hint.apic.X.clock
controls event timers functionality support. Setting to 0, disables it. Default value is 1.
hint.apic.X.disabled
Set this to 1 to disable APIC support, falling back to the legacy PIC.
DESCRIPTION
There are two components in the Intel APIC system, the local APIC (LAPIC) and the I/O APIC. There is one local APIC in each CPU in the sys-
tem. There is typically one I/O APIC for each peripheral bus in the system.
Local APICs manage all external interrupts for a specific processor. In addition, they are able to accept and generate inter-processor
interrupts (IPIs).
I/O APICs contain a redirection table, which is used to route the interrupts they receive from peripheral buses to one or more local APICs.
Each local APIC includes one 32-bit programmable timer. This driver uses them to supply kernel with one event timer named "LAPIC". Event
timer provided by the driver supports both one-shot an periodic modes. Because of local APIC nature it is per-CPU. The timer frequency is
not reported by the platform and so automatically measured by the driver on the first use. Depending on CPU model this timer may stop in C3
and deeper CPU sleep states. Driver automatically adjusts event timer priority and reports it to prevent entering dangerous sleep states
when it is used.
SEE ALSO atrtc(4), attimer(4), eventtimers(4), hpet(4)BSD December 20, 2011 BSD
Check Out this Related Man Page
HPET(4) BSD Kernel Interfaces Manual HPET(4)NAME
hpet -- High Precision Event Timer driver
SYNOPSIS
To compile this driver into the kernel, place the following lines in your kernel configuration file:
device acpi
The following tunables are settable from the loader(8):
hint.hpet.X.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.
hint.hpet.X.clock
controls event timers functionality support. Setting to 0, disables it. Default value is 1.
hint.hpet.X.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:
hint.attimer.0.clock=0
hint.atrtc.0.clock=0
Default value is 0.
hint.hpet.X.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.
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 "Lega-
cyReplacement 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 man-
ually via device hints.
Event timers provided by the driver support both one-shot an periodic modes and irrelevant to CPU power states.
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 possi-
ble only when each of these comparators has own unsharable IRQ.
SEE ALSO acpi(4), apic(4), atrtc(4), attimer(4), eventtimers(4), timecounters(4)HISTORY
The hpet driver first appeared in FreeBSD 6.3. Support for event timers was added in FreeBSD 9.0.
BSD September 14, 2010 BSD