112 lines
3.8 KiB
Groff
112 lines
3.8 KiB
Groff
.\" Copyright (c) 2003 Poul-Henning Kamp <phk@FreeBSD.org>
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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 REGENTS 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 REGENTS 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 November 23, 2003
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.Dt CPU_ELAN 4
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.Os
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.Sh NAME
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.Nm CPU_ELAN
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.Nd AMD Elan 520 CPU support
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.Sh SYNOPSIS
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.Cd options CPU_ELAN
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.Cd options CPU_ELAN_PPS
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.Cd options CPU_ELAN_XTAL
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.Cd sysctl machdep.elan_gpio_config
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.Cd sysctl machdep.elan_freq
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.Cd options CPU_SOEKRIS
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.Sh DESCRIPTION
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.Cd options CPU_ELAN
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Enables support for the AMD Elan 520 CPU.
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.Pp
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A device "/dev/elan-mmcr" exports the MMCR register bank to userland
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using
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.Xr mmap 2 .
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.Pp
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The "i8254" timer will be adjusted to the slightly unorthodox
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frequency 1189161Hz (32768 * 45 * 25 / 31) employed by the Elan.
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.Pp
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A timecounter named "ELAN" is implemented using the general purpose timer 2,
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but it will not be usable unless HZ is configured at 150 or higher.
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This timecounter is much better than the "i8254" timecounter and should be
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used at all times.
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.Pp
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The
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.Cd sysctl machdep.elan_gpio_config
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enables configuration of the GPIO pins of the CPU.
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The string must be exactly 32 characters long.
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A '-' means the GPIO is unavailable.
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A 'l' (lower-case L) configures a
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.Xr led 4
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device (active low).
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A 'L' configures a
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.Xr led 4
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device (active higH).
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A '.' means no configuration for this GPIO.
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These
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.Xr led 4
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devices will be named "/dev/led/gpio%d".
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For meaning of 'P', 'e' and 'E', see under
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.Cd options CPU_ELAN_PPS .
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.Pp
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The
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.Cd options CPU_ELAN_XTAL
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and
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.Cd sysctl machdep.elan_freq
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can be used to set the CPU clock crystal frequency in Hz.
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The default is 33333333 Hz.
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.Pp
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The
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.Cd options CPU_ELAN_PPS
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enables precision timestamping using the RFC2783 PPS-API via the
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"/dev/elan-mmcr" device.
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The resolution will be approx 125nsec and the precision \(+- 125nsec.
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(for 125 nsec read "4 / CPU clock crystal frequency")
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.Pp
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The input signal must be connected to the TMR1IN pin and
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a GPIO pin.
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The GPIO pin must be configured with a 'P' in
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.Cd sysctl machdep.elan_gpio_config .
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.Pp
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In addition one GPIO pin can be configured with either 'e' (active low)
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or 'E' (active high) to become a "echo" output of the input signal.
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Please notice that this signal is not suitable for calibration.
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.Pp
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If the
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.Cd options CPU_SOEKRIS
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option is given, the support will additionally be tailored to the
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Soekris Engineering 45xx series of embedded computers.
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The "error" led will be configured (as "/dev/led/error") and the GPIO pins which are not
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available will be disabled.
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.Sh SEE ALSO
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.Xr sysctl 8 ,
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.Sh HISTORY
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The
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.Nm
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code first appeared in
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.Fx 5.x .
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.Sh AUTHORS
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.An "Poul-Henning Kamp" Aq phk@FreeBSD.org
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