1.\"- 2.\" SPDX-License-Identifier: BSD-2-Clause 3.\" 4.\" Copyright (c) 2019 Ian Lepore <ian@freebsd.org> 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25.\" SUCH DAMAGE. 26.\" 27.Dd September 2, 2020 28.Dt LTC430X 4 29.Os 30.Sh NAME 31.Nm ltc430x 32.Nd driver for LTC4305 and LTC4306 I2C mux chips 33.Sh SYNOPSIS 34To compile this driver into the kernel, 35place the following line in your 36kernel configuration file: 37.Bd -ragged -offset indent 38.Cd "device ltc430x" 39.Ed 40.Pp 41Alternatively, to load the driver as a 42module at boot time, place the following line in 43.Xr loader.conf 5 : 44.Bd -literal -offset indent 45ltc430x_load="YES" 46.Ed 47.Sh DESCRIPTION 48The 49.Nm 50driver supports the LTC4305 and LTC4306 I2C bus multiplexer (mux) chips. 51It automatically connects an upstream I2C bus to one of several downstream 52buses as needed when slave devices on the downstream buses initiate I/O. 53More information on the automatic switching behavior is available in 54.Xr iicmux 4 . 55.Sh FDT CONFIGURATION 56On an 57.Xr fdt 4 58based system, an 59.Nm 60device node is defined as a child node of its upstream i2c bus. 61The children of the 62.Nm 63node are additional i2c buses, which will have their own i2c slave 64devices described in their child nodes. 65.Pp 66The 67.Nm 68driver conforms to the standard 69.Bk -words 70.Li i2c/i2c-mux-ltc4306.txt 71.Ek 72bindings document, except that the following optional properties 73are not currently supported and will be ignored if present: 74.Bl -bullet -compact -inset -offset indent 75.It 76enable-gpios 77.It 78gpio-controller 79.It 80#gpio-cells 81.It 82ltc,downstream-accelerators-enable 83.It 84ltc,upstream-accelerators-enable 85.El 86.Pp 87In addition, the following additional property is supported: 88.Bl -tag -offset indent -width indent 89.It Va freebsd,ctlreg2 90A value to store into the chip's control register 2 during initialization. 91Consult the chip datasheet for the meaning of the various bits in 92the register. 93.El 94.Sh HINTS CONFIGURATION 95On a 96.Xr device.hints 5 97based system, the following hints are required: 98.Bl -tag -offset indent -width indent 99.It Va hint.ltc430x.<unit>.at 100The upstream 101.Xr iicbus 4 102the 103.Nm 104instance is attached to. 105.It Va hint.ltc430x.<unit>.addr 106The slave address of the 107.Nm 108instance on the upstream bus. 109.It Va hint.ltc430x.<unit>.chip_type 110The type of chip the driver is controlling. 111Valid values are 112.Dq ltc4305 113and 114.Dq ltc4306 . 115.El 116.Pp 117The following hints are optional: 118.Bl -tag -offset indent -width indent 119.It Va hint.ltc430x.<unit>.ctlreg2 120A value to store into the chip's control register 2 during initialization. 121Consult the chip datasheet for the meaning of the various bits in 122the register. 123This hint is optional; when missing, the driver does not update control 124register 2. 125.It Va hint.ltc430x.<unit>.idle_disconnect 126Whether to disconnect all downstream busses from the upstream bus when idle. 127If set to zero, the most recently used downstream bus is left connected to 128the upstream bus after IO completes. 129Any non-zero value causes all downstream busses to be disconnected when idle. 130This hint is optional; when missing, the driver behaves as if it were zero. 131.El 132.Pp 133When configured via hints, the driver automatically adds an iicbus 134instance for every downstream bus supported by the chip. 135There is currently no way to indicate used versus unused downstream channels. 136.Sh SEE ALSO 137.Xr iicbus 4 , 138.Xr iicmux 4 139.Sh HISTORY 140The 141.Nm 142driver first appeared in 143.Fx 13.0 . 144