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i2c: regroup documentation of bindings

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Some bindings are for the bus master, some are for the slaves.
Regroup them and give them separate headings to make it clear.
Also, remove references to "generic names" which is for nodes and not
for compatibles.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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Wolfram Sang 2020-04-15 12:51:00 +02:00 committed by Wolfram Sang
parent 09cc9a3bce
commit 88fb09c409
1 changed files with 40 additions and 28 deletions
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68
Documentation/devicetree/bindings/i2c/i2c.txt
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@ -2,32 +2,26 @@ Generic device tree bindings for I2C busses
===========================================
This document describes generic bindings which can be used to describe I2C
busses in a device tree.
busses and their child devices in a device tree.
Required properties
-------------------
Required properties (per bus)
-----------------------------
- #address-cells - should be <1>. Read more about addresses below.
- #size-cells - should be <0>.
- compatible - name of I2C bus controller following generic names
recommended practice.
- compatible - name of I2C bus controller
For other required properties e.g. to describe register sets,
clocks, etc. check the binding documentation of the specific driver.
The cells properties above define that an address of children of an I2C bus
are described by a single value. This is usually a 7 bit address. However,
flags can be attached to the address. I2C_TEN_BIT_ADDRESS is used to mark a 10
bit address. It is needed to avoid the ambiguity between e.g. a 7 bit address
of 0x50 and a 10 bit address of 0x050 which, in theory, can be on the same bus.
Another flag is I2C_OWN_SLAVE_ADDRESS to mark addresses on which we listen to
be devices ourselves.
are described by a single value.
Optional properties
-------------------
Optional properties (per bus)
-----------------------------
These properties may not be supported by all drivers. However, if a driver
wants to support one of the below features, it should adapt the bindings below.
wants to support one of the below features, it should adapt these bindings.
- clock-frequency
frequency of bus clock in Hz.
@ -73,6 +67,35 @@ wants to support one of the below features, it should adapt the bindings below.
i2c bus clock frequency (clock-frequency).
Specified in Hz.
- multi-master
states that there is another master active on this bus. The OS can use
this information to adapt power management to keep the arbitration awake
all the time, for example.
Required properties (per child device)
--------------------------------------
- compatible
name of I2C slave device
- reg
One or many I2C slave addresses. These are usually a 7 bit addresses.
However, flags can be attached to an address. I2C_TEN_BIT_ADDRESS is
used to mark a 10 bit address. It is needed to avoid the ambiguity
between e.g. a 7 bit address of 0x50 and a 10 bit address of 0x050
which, in theory, can be on the same bus.
Another flag is I2C_OWN_SLAVE_ADDRESS to mark addresses on which we
listen to be devices ourselves.
Optional properties (per child device)
--------------------------------------
These properties may not be supported by all drivers. However, if a driver
wants to support one of the below features, it should adapt these bindings.
- host-notify
device uses SMBus host notify protocol instead of interrupt line.
- interrupts
interrupts used by the device.
@ -80,24 +103,13 @@ wants to support one of the below features, it should adapt the bindings below.
"irq", "wakeup" and "smbus_alert" names are recognized by I2C core,
other names are left to individual drivers.
- host-notify
device uses SMBus host notify protocol instead of interrupt line.
- multi-master
states that there is another master active on this bus. The OS can use
this information to adapt power management to keep the arbitration awake
all the time, for example.
- wakeup-source
device can be used as a wakeup source.
- reg
I2C slave addresses
- reg-names
Names of map programmable addresses.
It can contain any map needing another address than default one.
- wakeup-source
device can be used as a wakeup source.
Binding may contain optional "interrupts" property, describing interrupts
used by the device. I2C core will assign "irq" interrupt (or the very first
interrupt if not using interrupt names) as primary interrupt for the slave.