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