+++ /dev/null
-Generic device tree bindings for I2C busses
-===========================================
-
-This document describes generic bindings which can be used to describe I2C
-busses and their child devices in a device tree.
-
-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
-
-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.
-
-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 these bindings.
-
-- clock-frequency
- frequency of bus clock in Hz.
-
-- i2c-bus
- For I2C adapters that have child nodes that are a mixture of both I2C
- devices and non-I2C devices, the 'i2c-bus' subnode can be used for
- populating I2C devices. If the 'i2c-bus' subnode is present, only
- subnodes of this will be considered as I2C slaves. The properties,
- '#address-cells' and '#size-cells' must be defined under this subnode
- if present.
-
-- i2c-scl-falling-time-ns
- Number of nanoseconds the SCL signal takes to fall; t(f) in the I2C
- specification.
-
-- i2c-scl-internal-delay-ns
- Number of nanoseconds the IP core additionally needs to setup SCL.
-
-- i2c-scl-rising-time-ns
- Number of nanoseconds the SCL signal takes to rise; t(r) in the I2C
- specification.
-
-- i2c-sda-falling-time-ns
- Number of nanoseconds the SDA signal takes to fall; t(f) in the I2C
- specification.
-
-- i2c-analog-filter
- Enable analog filter for i2c lines.
-
-- i2c-digital-filter
- Enable digital filter for i2c lines.
-
-- i2c-digital-filter-width-ns
- Width of spikes which can be filtered by digital filter
- (i2c-digital-filter). This width is specified in nanoseconds.
-
-- i2c-analog-filter-cutoff-frequency
- Frequency that the analog filter (i2c-analog-filter) uses to distinguish
- which signal to filter. Signal with higher frequency than specified will
- be filtered out. Only lower frequency will pass (this is applicable to
- a low-pass analog filter). Typical value should be above the normal
- 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. Can not be combined with 'single-master'.
-
-- pinctrl
- add extra pinctrl to configure SCL/SDA pins to GPIO function for bus
- recovery, call it "gpio" or "recovery" (deprecated) state
-
-- scl-gpios
- specify the gpio related to SCL pin. Used for GPIO bus recovery.
-
-- sda-gpios
- specify the gpio related to SDA pin. Optional for GPIO bus recovery.
-
-- single-master
- states that there is no other master active on this bus. The OS can use
- this information to detect a stalled bus more reliably, for example.
- Can not be combined with 'multi-master'.
-
-- smbus
- states that additional SMBus restrictions and features apply to this bus.
- An example of feature is SMBusHostNotify. Examples of restrictions are
- more reserved addresses and timeout definitions.
-
-- smbus-alert
- states that the optional SMBus-Alert feature apply to this bus.
-
-- mctp-controller
- indicates that the system is accessible via this bus as an endpoint for
- MCTP over I2C transport.
-
-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.
-
-- interrupt-names
- "irq", "wakeup" and "smbus_alert" names are recognized by I2C core,
- other names are left to individual drivers.
-
-- 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.
-
-Alternatively, devices supporting SMBus Host Notify, and connected to
-adapters that support this feature, may use "host-notify" property. I2C
-core will create a virtual interrupt for Host Notify and assign it as
-primary interrupt for the slave.
-
-Also, if device is marked as a wakeup source, I2C core will set up "wakeup"
-interrupt for the device. If "wakeup" interrupt name is not present in the
-binding, then primary interrupt will be used as wakeup interrupt.
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