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Language cleanup.

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Reviewed by:	mav, bcr, wblock
MFC after:	1 week
This commit is contained in:
Christian Brueffer 2014-05-26 19:02:34 +00:00
parent 6303b65d35
commit 9bb8172b56
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=266709
1 changed files with 26 additions and 16 deletions
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42
share/man/man4/attimer.4
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@ -24,7 +24,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd September 14, 2010
.Dd May 26, 2014
.Dt ATTIMER 4
.Os
.Sh NAME
@ -37,38 +37,48 @@ The following tunables are settable from the
.Xr loader 8 :
.Bl -ohang
.It Va hint.attimer. Ns Ar X Ns Va .clock
controls event timers functionality support. Setting to 0, disables it.
Default value is 1.
controls support for the event timer functionality.
Setting this value to
.Dv 0
disables it.
The default value is
.Dv 1 .
.It Va hint.attimer. Ns Ar X Ns Va .timecounter
controls time counter functionality support. Setting to 0, disables it.
Default value is 1.
controls support for the time counter functionality.
Setting this value to
.Dv 0
disables it.
The default value is
.Dv 1 .
.It Va hw.i8254.freq
allows to override default counter frequency.
The same value is also available in run-time via
allows overriding the default counter frequency.
The same value is also available at run-time via the
.Va machdep.i8254_freq
sysctl.
.El
.Sh DESCRIPTION
This driver uses i8254 Programmable Interval Timer (AT Timer) hardware
to supply kernel with one time counter and one event timer, and generate
sound tones for system speaker.
to supply the kernel with one timecounter and one event timer, and to generate
sound tones for the system speaker.
This hardware includes three channels.
Each channel includes 16bit counter, counting down with known,
Each channel includes a 16 bit counter which decreases with a known,
platform-dependent frequency.
Counters can operate in several different modes, including periodic and
one-shot.
Output of each channel has platform-defined wiring: one channel is wired
The output of each channel has platform-defined wiring: one channel is wired
to the interrupt controller and may be used as event timer, one channel is
wired to speaker and used to generate sound tones, and one timer is reserved
wired to the speaker and used to generate sound tones, and one timer is reserved
for platform purposes.
.Pp
Driver uses single hardware channel to provide both time counter and event
The
.Nm
driver uses a single hardware channel to provide both time counter and event
timer functionality.
To make it possible, respective counter must be running in periodic more.
As result, one-shot event timer mode supported only when time counter
To make this possible, the respective counter must be running in periodic mode.
As a result, the one-shot event timer mode is supported only when time counter
functionality is disabled.
.Pp
Event timer provided by the driver is irrelevant to CPU power states.
The event timer provided by the driver is irrelevant to CPU power states.
.Sh SEE ALSO
.Xr apic 4 ,
.Xr atrtc 4 ,