146 lines
4.5 KiB
Groff
146 lines
4.5 KiB
Groff
.\"-
|
|
.\" SPDX-License-Identifier: BSD-2-Clause
|
|
.\"
|
|
.\" Copyright (c) 2019 Ian Lepore <ian@freebsd.org>
|
|
.\"
|
|
.\" 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 2, 2020
|
|
.Dt LTC430X 4
|
|
.Os
|
|
.Sh NAME
|
|
.Nm ltc430x
|
|
.Nd driver for LTC4305 and LTC4306 I2C mux chips
|
|
.Sh SYNOPSIS
|
|
To compile this driver into the kernel,
|
|
place the following line in your
|
|
kernel configuration file:
|
|
.Bd -ragged -offset indent
|
|
.Cd "device ltc430x"
|
|
.Ed
|
|
.Pp
|
|
Alternatively, to load the driver as a
|
|
module at boot time, place the following line in
|
|
.Xr loader.conf 5 :
|
|
.Bd -literal -offset indent
|
|
ltc430x_load="YES"
|
|
.Ed
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
driver supports the LTC4305 and LTC4306 I2C bus multiplexer (mux) chips.
|
|
It automatically connects an upstream I2C bus to one of several downstream
|
|
buses as needed when slave devices on the downstream buses initiate I/O.
|
|
More information on the automatic switching behavior is available in
|
|
.Xr iicmux 4 .
|
|
.Sh FDT CONFIGURATION
|
|
On an
|
|
.Xr fdt 4
|
|
based system, an
|
|
.Nm
|
|
device node is defined as a child node of its upstream i2c bus.
|
|
The children of the
|
|
.Nm
|
|
node are additional i2c buses, which will have their own i2c slave
|
|
devices described in their child nodes.
|
|
.Pp
|
|
The
|
|
.Nm
|
|
driver conforms to the standard
|
|
.Bk -words
|
|
.Li i2c/i2c-mux-ltc4306.txt
|
|
.Ek
|
|
bindings document, except that the following optional properties
|
|
are not currently supported and will be ignored if present:
|
|
.Bl -bullet -compact -inset -offset indent
|
|
.It
|
|
enable-gpios
|
|
.It
|
|
gpio-controller
|
|
.It
|
|
#gpio-cells
|
|
.It
|
|
ltc,downstream-accelerators-enable
|
|
.It
|
|
ltc,upstream-accelerators-enable
|
|
.El
|
|
.Pp
|
|
In addition, the following additional property is supported:
|
|
.Bl -tag -offset indent -width indent
|
|
.It Va freebsd,ctlreg2
|
|
A value to store into the chip's control register 2 during initialization.
|
|
Consult the chip datasheet for the meaning of the various bits in
|
|
the register.
|
|
.El
|
|
.Sh HINTS CONFIGURATION
|
|
On a
|
|
.Xr device.hints 5
|
|
based system, the following hints are required:
|
|
.Bl -tag -offset indent -width indent
|
|
.It Va hint.ltc430x.<unit>.at
|
|
The upstream
|
|
.Xr iicbus 4
|
|
the
|
|
.Nm
|
|
instance is attached to.
|
|
.It Va hint.ltc430x.<unit>.addr
|
|
The slave address of the
|
|
.Nm
|
|
instance on the upstream bus.
|
|
.It Va hint.ltc430x.<unit>.chip_type
|
|
The type of chip the driver is controlling.
|
|
Valid values are
|
|
.Dq ltc4305
|
|
and
|
|
.Dq ltc4306 .
|
|
.El
|
|
.Pp
|
|
The following hints are optional:
|
|
.Bl -tag -offset indent -width indent
|
|
.It Va hint.ltc430x.<unit>.ctlreg2
|
|
A value to store into the chip's control register 2 during initialization.
|
|
Consult the chip datasheet for the meaning of the various bits in
|
|
the register.
|
|
This hint is optional; when missing, the driver does not update control
|
|
register 2.
|
|
.It Va hint.ltc430x.<unit>.idle_disconnect
|
|
Whether to disconnect all downstream busses from the upstream bus when idle.
|
|
If set to zero, the most recently used downstream bus is left connected to
|
|
the upstream bus after IO completes.
|
|
Any non-zero value causes all downstream busses to be disconnected when idle.
|
|
This hint is optional; when missing, the driver behaves as if it were zero.
|
|
.El
|
|
.Pp
|
|
When configured via hints, the driver automatically adds an iicbus
|
|
instance for every downstream bus supported by the chip.
|
|
There is currently no way to indicate used versus unused downstream channels.
|
|
.Sh SEE ALSO
|
|
.Xr iicbus 4 ,
|
|
.Xr iicmux 4
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
driver first appeared in
|
|
.Fx 13.0 .
|