Add support for i2c bus mux hardware.
An i2c bus can be divided into segments which can be selectively connected
and disconnected from the main bus. This is usually done to enable using
multiple slave devices having the same address, by isolating the devices
onto separate bus segments, only one of which is connected to the main bus
at once.
There are several types of i2c bus muxes, which break down into two general
categories...
- Muxes which are themselves i2c slaves. These devices respond to i2c
commands on their upstream bus, and based on those commands, connect
various downstream buses to the upstream. In newbus terms, they are both
a child of an iicbus and the parent of one or more iicbus instances.
- Muxes which are not i2c devices themselves. Such devices are part of the
i2c bus electrically, but in newbus terms their parent is some other
bus. The association with the upstream bus must be established by
separate metadata (such as FDT data).
In both cases, the mux driver has one or more iicbus child instances
representing the downstream buses. The mux driver implements the iicbus_if
interface, as if it were an iichb host bridge/i2c controller driver. It
services the IO requests sent to it by forwarding them to the iicbus
instance representing the upstream bus, after electrically connecting the
upstream bus to the downstream bus that hosts the i2c slave device which
made the IO request.
The net effect is automatic mux switching which is transparent to slaves on
the downstream buses. They just do i2c IO they way they normally do, and the
bus is electrically connected for the duration of the IO and then idled when
it is complete.
The existing iicbus_if callback() method is enhanced so that the parameter
passed to it can be a struct which contains a device_t for the requesting
bus and slave devices. This change is done by adding a flag that indicates
the extra values are present, and making the flags field the first field of
a new args struct. If the flag is set, the iichb or mux driver can recast
the pointer-to-flags into a pointer-to-struct and access the extra
fields. Thus abi compatibility with older drivers is retained (but a mux
cannot exist on the bus with the older iicbus driver in use.)
A new set of core support routines exists in iicbus.c. This code will help
implement mux drivers for any type of mux hardware by supplying all the
boilerplate code that forwards IO requests upstream. It also has code for
parsing metadata and instantiating the child iicbus instances based on it.
Two new hardware mux drivers are added. The ltc430x driver supports the
LTC4305/4306 mux chips which are controlled via i2c commands. The
iic_gpiomux driver supports any mux hardware which is controlled by
manipulating the state of one or more gpio pins. Test Plan
Tested locally using a variety of mux'd bus configurations involving both
ltc4305 and a homebrew gpio-controlled mux. Tested configurations included
cascaded muxes (unlikely in the real world, but useful to prove that 'it all
just works' in terms of the automatic switching and upstream forwarding of
IO requests).
2020-01-02 17:51:49 +00:00
|
|
|
.\"-
|
|
|
|
|
.\" 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.
|
|
|
|
|
.\"
|
|
|
|
|
.\" $FreeBSD$
|
|
|
|
|
.\"
|
2020-09-02 19:37:47 +00:00
|
|
|
.Dd September 2, 2020
|
Add support for i2c bus mux hardware.
An i2c bus can be divided into segments which can be selectively connected
and disconnected from the main bus. This is usually done to enable using
multiple slave devices having the same address, by isolating the devices
onto separate bus segments, only one of which is connected to the main bus
at once.
There are several types of i2c bus muxes, which break down into two general
categories...
- Muxes which are themselves i2c slaves. These devices respond to i2c
commands on their upstream bus, and based on those commands, connect
various downstream buses to the upstream. In newbus terms, they are both
a child of an iicbus and the parent of one or more iicbus instances.
- Muxes which are not i2c devices themselves. Such devices are part of the
i2c bus electrically, but in newbus terms their parent is some other
bus. The association with the upstream bus must be established by
separate metadata (such as FDT data).
In both cases, the mux driver has one or more iicbus child instances
representing the downstream buses. The mux driver implements the iicbus_if
interface, as if it were an iichb host bridge/i2c controller driver. It
services the IO requests sent to it by forwarding them to the iicbus
instance representing the upstream bus, after electrically connecting the
upstream bus to the downstream bus that hosts the i2c slave device which
made the IO request.
The net effect is automatic mux switching which is transparent to slaves on
the downstream buses. They just do i2c IO they way they normally do, and the
bus is electrically connected for the duration of the IO and then idled when
it is complete.
The existing iicbus_if callback() method is enhanced so that the parameter
passed to it can be a struct which contains a device_t for the requesting
bus and slave devices. This change is done by adding a flag that indicates
the extra values are present, and making the flags field the first field of
a new args struct. If the flag is set, the iichb or mux driver can recast
the pointer-to-flags into a pointer-to-struct and access the extra
fields. Thus abi compatibility with older drivers is retained (but a mux
cannot exist on the bus with the older iicbus driver in use.)
A new set of core support routines exists in iicbus.c. This code will help
implement mux drivers for any type of mux hardware by supplying all the
boilerplate code that forwards IO requests upstream. It also has code for
parsing metadata and instantiating the child iicbus instances based on it.
Two new hardware mux drivers are added. The ltc430x driver supports the
LTC4305/4306 mux chips which are controlled via i2c commands. The
iic_gpiomux driver supports any mux hardware which is controlled by
manipulating the state of one or more gpio pins. Test Plan
Tested locally using a variety of mux'd bus configurations involving both
ltc4305 and a homebrew gpio-controlled mux. Tested configurations included
cascaded muxes (unlikely in the real world, but useful to prove that 'it all
just works' in terms of the automatic switching and upstream forwarding of
IO requests).
2020-01-02 17:51:49 +00:00
|
|
|
.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
|
2020-09-02 19:37:47 +00:00
|
|
|
.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
|
Add support for i2c bus mux hardware.
An i2c bus can be divided into segments which can be selectively connected
and disconnected from the main bus. This is usually done to enable using
multiple slave devices having the same address, by isolating the devices
onto separate bus segments, only one of which is connected to the main bus
at once.
There are several types of i2c bus muxes, which break down into two general
categories...
- Muxes which are themselves i2c slaves. These devices respond to i2c
commands on their upstream bus, and based on those commands, connect
various downstream buses to the upstream. In newbus terms, they are both
a child of an iicbus and the parent of one or more iicbus instances.
- Muxes which are not i2c devices themselves. Such devices are part of the
i2c bus electrically, but in newbus terms their parent is some other
bus. The association with the upstream bus must be established by
separate metadata (such as FDT data).
In both cases, the mux driver has one or more iicbus child instances
representing the downstream buses. The mux driver implements the iicbus_if
interface, as if it were an iichb host bridge/i2c controller driver. It
services the IO requests sent to it by forwarding them to the iicbus
instance representing the upstream bus, after electrically connecting the
upstream bus to the downstream bus that hosts the i2c slave device which
made the IO request.
The net effect is automatic mux switching which is transparent to slaves on
the downstream buses. They just do i2c IO they way they normally do, and the
bus is electrically connected for the duration of the IO and then idled when
it is complete.
The existing iicbus_if callback() method is enhanced so that the parameter
passed to it can be a struct which contains a device_t for the requesting
bus and slave devices. This change is done by adding a flag that indicates
the extra values are present, and making the flags field the first field of
a new args struct. If the flag is set, the iichb or mux driver can recast
the pointer-to-flags into a pointer-to-struct and access the extra
fields. Thus abi compatibility with older drivers is retained (but a mux
cannot exist on the bus with the older iicbus driver in use.)
A new set of core support routines exists in iicbus.c. This code will help
implement mux drivers for any type of mux hardware by supplying all the
boilerplate code that forwards IO requests upstream. It also has code for
parsing metadata and instantiating the child iicbus instances based on it.
Two new hardware mux drivers are added. The ltc430x driver supports the
LTC4305/4306 mux chips which are controlled via i2c commands. The
iic_gpiomux driver supports any mux hardware which is controlled by
manipulating the state of one or more gpio pins. Test Plan
Tested locally using a variety of mux'd bus configurations involving both
ltc4305 and a homebrew gpio-controlled mux. Tested configurations included
cascaded muxes (unlikely in the real world, but useful to prove that 'it all
just works' in terms of the automatic switching and upstream forwarding of
IO requests).
2020-01-02 17:51:49 +00:00
|
|
|
.Sh HINTS CONFIGURATION
|
|
|
|
|
On a
|
|
|
|
|
.Xr device.hints 5
|
2020-09-02 19:37:47 +00:00
|
|
|
based system, the following hints are required:
|
|
|
|
|
.Bl -tag -offset indent -width indent
|
Add support for i2c bus mux hardware.
An i2c bus can be divided into segments which can be selectively connected
and disconnected from the main bus. This is usually done to enable using
multiple slave devices having the same address, by isolating the devices
onto separate bus segments, only one of which is connected to the main bus
at once.
There are several types of i2c bus muxes, which break down into two general
categories...
- Muxes which are themselves i2c slaves. These devices respond to i2c
commands on their upstream bus, and based on those commands, connect
various downstream buses to the upstream. In newbus terms, they are both
a child of an iicbus and the parent of one or more iicbus instances.
- Muxes which are not i2c devices themselves. Such devices are part of the
i2c bus electrically, but in newbus terms their parent is some other
bus. The association with the upstream bus must be established by
separate metadata (such as FDT data).
In both cases, the mux driver has one or more iicbus child instances
representing the downstream buses. The mux driver implements the iicbus_if
interface, as if it were an iichb host bridge/i2c controller driver. It
services the IO requests sent to it by forwarding them to the iicbus
instance representing the upstream bus, after electrically connecting the
upstream bus to the downstream bus that hosts the i2c slave device which
made the IO request.
The net effect is automatic mux switching which is transparent to slaves on
the downstream buses. They just do i2c IO they way they normally do, and the
bus is electrically connected for the duration of the IO and then idled when
it is complete.
The existing iicbus_if callback() method is enhanced so that the parameter
passed to it can be a struct which contains a device_t for the requesting
bus and slave devices. This change is done by adding a flag that indicates
the extra values are present, and making the flags field the first field of
a new args struct. If the flag is set, the iichb or mux driver can recast
the pointer-to-flags into a pointer-to-struct and access the extra
fields. Thus abi compatibility with older drivers is retained (but a mux
cannot exist on the bus with the older iicbus driver in use.)
A new set of core support routines exists in iicbus.c. This code will help
implement mux drivers for any type of mux hardware by supplying all the
boilerplate code that forwards IO requests upstream. It also has code for
parsing metadata and instantiating the child iicbus instances based on it.
Two new hardware mux drivers are added. The ltc430x driver supports the
LTC4305/4306 mux chips which are controlled via i2c commands. The
iic_gpiomux driver supports any mux hardware which is controlled by
manipulating the state of one or more gpio pins. Test Plan
Tested locally using a variety of mux'd bus configurations involving both
ltc4305 and a homebrew gpio-controlled mux. Tested configurations included
cascaded muxes (unlikely in the real world, but useful to prove that 'it all
just works' in terms of the automatic switching and upstream forwarding of
IO requests).
2020-01-02 17:51:49 +00:00
|
|
|
.It Va hint.ltc430x.<unit>.at
|
|
|
|
|
The upstream
|
|
|
|
|
.Xr iicbus 4
|
|
|
|
|
the
|
|
|
|
|
.Nm
|
|
|
|
|
instance is attached to.
|
2020-09-01 19:06:08 +00:00
|
|
|
.It Va hint.ltc430x.<unit>.addr
|
|
|
|
|
The slave address of the
|
|
|
|
|
.Nm
|
|
|
|
|
instance on the upstream bus.
|
2020-09-02 19:37:47 +00:00
|
|
|
.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.
|
Add support for i2c bus mux hardware.
An i2c bus can be divided into segments which can be selectively connected
and disconnected from the main bus. This is usually done to enable using
multiple slave devices having the same address, by isolating the devices
onto separate bus segments, only one of which is connected to the main bus
at once.
There are several types of i2c bus muxes, which break down into two general
categories...
- Muxes which are themselves i2c slaves. These devices respond to i2c
commands on their upstream bus, and based on those commands, connect
various downstream buses to the upstream. In newbus terms, they are both
a child of an iicbus and the parent of one or more iicbus instances.
- Muxes which are not i2c devices themselves. Such devices are part of the
i2c bus electrically, but in newbus terms their parent is some other
bus. The association with the upstream bus must be established by
separate metadata (such as FDT data).
In both cases, the mux driver has one or more iicbus child instances
representing the downstream buses. The mux driver implements the iicbus_if
interface, as if it were an iichb host bridge/i2c controller driver. It
services the IO requests sent to it by forwarding them to the iicbus
instance representing the upstream bus, after electrically connecting the
upstream bus to the downstream bus that hosts the i2c slave device which
made the IO request.
The net effect is automatic mux switching which is transparent to slaves on
the downstream buses. They just do i2c IO they way they normally do, and the
bus is electrically connected for the duration of the IO and then idled when
it is complete.
The existing iicbus_if callback() method is enhanced so that the parameter
passed to it can be a struct which contains a device_t for the requesting
bus and slave devices. This change is done by adding a flag that indicates
the extra values are present, and making the flags field the first field of
a new args struct. If the flag is set, the iichb or mux driver can recast
the pointer-to-flags into a pointer-to-struct and access the extra
fields. Thus abi compatibility with older drivers is retained (but a mux
cannot exist on the bus with the older iicbus driver in use.)
A new set of core support routines exists in iicbus.c. This code will help
implement mux drivers for any type of mux hardware by supplying all the
boilerplate code that forwards IO requests upstream. It also has code for
parsing metadata and instantiating the child iicbus instances based on it.
Two new hardware mux drivers are added. The ltc430x driver supports the
LTC4305/4306 mux chips which are controlled via i2c commands. The
iic_gpiomux driver supports any mux hardware which is controlled by
manipulating the state of one or more gpio pins. Test Plan
Tested locally using a variety of mux'd bus configurations involving both
ltc4305 and a homebrew gpio-controlled mux. Tested configurations included
cascaded muxes (unlikely in the real world, but useful to prove that 'it all
just works' in terms of the automatic switching and upstream forwarding of
IO requests).
2020-01-02 17:51:49 +00:00
|
|
|
.El
|
|
|
|
|
.Pp
|
|
|
|
|
When configured via hints, the driver automatically adds an iicbus
|
|
|
|
|
instance for every downstream bus supported by the chip.
|
2020-09-02 19:37:47 +00:00
|
|
|
There is currently no way to indicate used versus unused downstream channels.
|
Add support for i2c bus mux hardware.
An i2c bus can be divided into segments which can be selectively connected
and disconnected from the main bus. This is usually done to enable using
multiple slave devices having the same address, by isolating the devices
onto separate bus segments, only one of which is connected to the main bus
at once.
There are several types of i2c bus muxes, which break down into two general
categories...
- Muxes which are themselves i2c slaves. These devices respond to i2c
commands on their upstream bus, and based on those commands, connect
various downstream buses to the upstream. In newbus terms, they are both
a child of an iicbus and the parent of one or more iicbus instances.
- Muxes which are not i2c devices themselves. Such devices are part of the
i2c bus electrically, but in newbus terms their parent is some other
bus. The association with the upstream bus must be established by
separate metadata (such as FDT data).
In both cases, the mux driver has one or more iicbus child instances
representing the downstream buses. The mux driver implements the iicbus_if
interface, as if it were an iichb host bridge/i2c controller driver. It
services the IO requests sent to it by forwarding them to the iicbus
instance representing the upstream bus, after electrically connecting the
upstream bus to the downstream bus that hosts the i2c slave device which
made the IO request.
The net effect is automatic mux switching which is transparent to slaves on
the downstream buses. They just do i2c IO they way they normally do, and the
bus is electrically connected for the duration of the IO and then idled when
it is complete.
The existing iicbus_if callback() method is enhanced so that the parameter
passed to it can be a struct which contains a device_t for the requesting
bus and slave devices. This change is done by adding a flag that indicates
the extra values are present, and making the flags field the first field of
a new args struct. If the flag is set, the iichb or mux driver can recast
the pointer-to-flags into a pointer-to-struct and access the extra
fields. Thus abi compatibility with older drivers is retained (but a mux
cannot exist on the bus with the older iicbus driver in use.)
A new set of core support routines exists in iicbus.c. This code will help
implement mux drivers for any type of mux hardware by supplying all the
boilerplate code that forwards IO requests upstream. It also has code for
parsing metadata and instantiating the child iicbus instances based on it.
Two new hardware mux drivers are added. The ltc430x driver supports the
LTC4305/4306 mux chips which are controlled via i2c commands. The
iic_gpiomux driver supports any mux hardware which is controlled by
manipulating the state of one or more gpio pins. Test Plan
Tested locally using a variety of mux'd bus configurations involving both
ltc4305 and a homebrew gpio-controlled mux. Tested configurations included
cascaded muxes (unlikely in the real world, but useful to prove that 'it all
just works' in terms of the automatic switching and upstream forwarding of
IO requests).
2020-01-02 17:51:49 +00:00
|
|
|
.Sh SEE ALSO
|
|
|
|
|
.Xr iicbus 4 ,
|
|
|
|
|
.Xr iicmux 4 ,
|
|
|
|
|
.Sh HISTORY
|
|
|
|
|
The
|
|
|
|
|
.Nm
|
|
|
|
|
driver first appeared in
|
|
|
|
|
.Fx 13.0 .
|