Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 144 insertions, 0 deletions

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+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.
+	Examples of features are SMBusHostNotify and SMBusAlert. Examples of
+	restrictions are more reserved addresses and timeout definitions.
+
+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.