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The I2C GPIO bus recovery properties consist of two GPIOS and one extra
pinctrl state ("gpio" or "recovery"). "recovery" pinctrl state is
considered deprecated and "gpio" should be used instead.
Not all are mandatory for recovery.
Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
Reviewed-by: Rob Herring <robh@kernel.org>
[wsa: kept sorting, minor whitespace change]
Signed-off-by: Wolfram Sang <wsa@kernel.org>
140 lines
4.9 KiB
Plaintext
140 lines
4.9 KiB
Plaintext
Generic device tree bindings for I2C busses
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===========================================
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This document describes generic bindings which can be used to describe I2C
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busses and their child devices in a device tree.
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Required properties (per bus)
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-----------------------------
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- #address-cells - should be <1>. Read more about addresses below.
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- #size-cells - should be <0>.
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- compatible - name of I2C bus controller
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For other required properties e.g. to describe register sets,
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clocks, etc. check the binding documentation of the specific driver.
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The cells properties above define that an address of children of an I2C bus
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are described by a single value.
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Optional properties (per bus)
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-----------------------------
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These properties may not be supported by all drivers. However, if a driver
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wants to support one of the below features, it should adapt these bindings.
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- clock-frequency
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frequency of bus clock in Hz.
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- i2c-bus
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For I2C adapters that have child nodes that are a mixture of both I2C
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devices and non-I2C devices, the 'i2c-bus' subnode can be used for
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populating I2C devices. If the 'i2c-bus' subnode is present, only
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subnodes of this will be considered as I2C slaves. The properties,
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'#address-cells' and '#size-cells' must be defined under this subnode
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if present.
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- i2c-scl-falling-time-ns
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Number of nanoseconds the SCL signal takes to fall; t(f) in the I2C
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specification.
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- i2c-scl-internal-delay-ns
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Number of nanoseconds the IP core additionally needs to setup SCL.
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- i2c-scl-rising-time-ns
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Number of nanoseconds the SCL signal takes to rise; t(r) in the I2C
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specification.
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- i2c-sda-falling-time-ns
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Number of nanoseconds the SDA signal takes to fall; t(f) in the I2C
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specification.
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- i2c-analog-filter
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Enable analog filter for i2c lines.
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- i2c-digital-filter
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Enable digital filter for i2c lines.
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- i2c-digital-filter-width-ns
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Width of spikes which can be filtered by digital filter
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(i2c-digital-filter). This width is specified in nanoseconds.
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- i2c-analog-filter-cutoff-frequency
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Frequency that the analog filter (i2c-analog-filter) uses to distinguish
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which signal to filter. Signal with higher frequency than specified will
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be filtered out. Only lower frequency will pass (this is applicable to
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a low-pass analog filter). Typical value should be above the normal
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i2c bus clock frequency (clock-frequency).
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Specified in Hz.
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- multi-master
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states that there is another master active on this bus. The OS can use
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this information to adapt power management to keep the arbitration awake
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all the time, for example. Can not be combined with 'single-master'.
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- pinctrl
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add extra pinctrl to configure SCL/SDA pins to GPIO function for bus
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recovery, call it "gpio" or "recovery" (deprecated) state
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- scl-gpios
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specify the gpio related to SCL pin. Used for GPIO bus recovery.
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- sda-gpios
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specify the gpio related to SDA pin. Optional for GPIO bus recovery.
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- single-master
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states that there is no other master active on this bus. The OS can use
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this information to detect a stalled bus more reliably, for example.
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Can not be combined with 'multi-master'.
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Required properties (per child device)
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--------------------------------------
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- compatible
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name of I2C slave device
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- reg
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One or many I2C slave addresses. These are usually a 7 bit addresses.
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However, flags can be attached to an address. I2C_TEN_BIT_ADDRESS is
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used to mark a 10 bit address. It is needed to avoid the ambiguity
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between e.g. a 7 bit address of 0x50 and a 10 bit address of 0x050
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which, in theory, can be on the same bus.
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Another flag is I2C_OWN_SLAVE_ADDRESS to mark addresses on which we
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listen to be devices ourselves.
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Optional properties (per child device)
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--------------------------------------
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These properties may not be supported by all drivers. However, if a driver
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wants to support one of the below features, it should adapt these bindings.
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- host-notify
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device uses SMBus host notify protocol instead of interrupt line.
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- interrupts
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interrupts used by the device.
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- interrupt-names
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"irq", "wakeup" and "smbus_alert" names are recognized by I2C core,
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other names are left to individual drivers.
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- reg-names
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Names of map programmable addresses.
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It can contain any map needing another address than default one.
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- wakeup-source
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device can be used as a wakeup source.
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Binding may contain optional "interrupts" property, describing interrupts
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used by the device. I2C core will assign "irq" interrupt (or the very first
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interrupt if not using interrupt names) as primary interrupt for the slave.
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Alternatively, devices supporting SMBus Host Notify, and connected to
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adapters that support this feature, may use "host-notify" property. I2C
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core will create a virtual interrupt for Host Notify and assign it as
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primary interrupt for the slave.
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Also, if device is marked as a wakeup source, I2C core will set up "wakeup"
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interrupt for the device. If "wakeup" interrupt name is not present in the
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binding, then primary interrupt will be used as wakeup interrupt.
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