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.\" $FreeBSD$ 28.\" 29.Dd September 2, 2020 30.Dt LTC430X 4 31.Os 32.Sh NAME 33.Nm ltc430x 34.Nd driver for LTC4305 and LTC4306 I2C mux chips 35.Sh SYNOPSIS 36To compile this driver into the kernel, 37place the following line in your 38kernel configuration file: 39.Bd -ragged -offset indent 40.Cd "device ltc430x" 41.Ed 42.Pp 43Alternatively, to load the driver as a 44module at boot time, place the following line in 45.Xr loader.conf 5 : 46.Bd -literal -offset indent 47ltc430x_load="YES" 48.Ed 49.Sh DESCRIPTION 50The 51.Nm 52driver supports the LTC4305 and LTC4306 I2C bus multiplexer (mux) chips. 53It automatically connects an upstream I2C bus to one of several downstream 54buses as needed when slave devices on the downstream buses initiate I/O. 55More information on the automatic switching behavior is available in 56.Xr iicmux 4 . 57.Sh FDT CONFIGURATION 58On an 59.Xr fdt 4 60based system, an 61.Nm 62device node is defined as a child node of its upstream i2c bus. 63The children of the 64.Nm 65node are additional i2c buses, which will have their own i2c slave 66devices described in their child nodes. 67.Pp 68The 69.Nm 70driver conforms to the standard 71.Bk -words 72.Li i2c/i2c-mux-ltc4306.txt 73.Ek 74bindings document, except that the following optional properties 75are not currently supported and will be ignored if present: 76.Bl -bullet -compact -inset -offset indent 77.It 78enable-gpios 79.It 80gpio-controller 81.It 82#gpio-cells 83.It 84ltc,downstream-accelerators-enable 85.It 86ltc,upstream-accelerators-enable 87.El 88.Pp 89In addition, the following additional property is supported: 90.Bl -tag -offset indent -width indent 91.It Va freebsd,ctlreg2 92A value to store into the chip's control register 2 during initialization. 93Consult the chip datasheet for the meaning of the various bits in 94the register. 95.El 96.Sh HINTS CONFIGURATION 97On a 98.Xr device.hints 5 99based system, the following hints are required: 100.Bl -tag -offset indent -width indent 101.It Va hint.ltc430x.<unit>.at 102The upstream 103.Xr iicbus 4 104the 105.Nm 106instance is attached to. 107.It Va hint.ltc430x.<unit>.addr 108The slave address of the 109.Nm 110instance on the upstream bus. 111.It Va hint.ltc430x.<unit>.chip_type 112The type of chip the driver is controlling. 113Valid values are 114.Dq ltc4305 115and 116.Dq ltc4306 . 117.El 118.Pp 119The following hints are optional: 120.Bl -tag -offset indent -width indent 121.It Va hint.ltc430x.<unit>.ctlreg2 122A value to store into the chip's control register 2 during initialization. 123Consult the chip datasheet for the meaning of the various bits in 124the register. 125This hint is optional; when missing, the driver does not update control 126register 2. 127.It Va hint.ltc430x.<unit>.idle_disconnect 128Whether to disconnect all downstream busses from the upstream bus when idle. 129If set to zero, the most recently used downstream bus is left connected to 130the upstream bus after IO completes. 131Any non-zero value causes all downstream busses to be disconnected when idle. 132This hint is optional; when missing, the driver behaves as if it were zero. 133.El 134.Pp 135When configured via hints, the driver automatically adds an iicbus 136instance for every downstream bus supported by the chip. 137There is currently no way to indicate used versus unused downstream channels. 138.Sh SEE ALSO 139.Xr iicbus 4 , 140.Xr iicmux 4 , 141.Sh HISTORY 142The 143.Nm 144driver first appeared in 145.Fx 13.0 . 146