From 76cb841cb886eef6b3bee341a2266c76578724ad Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Mon, 6 May 2024 03:02:30 +0200 Subject: Adding upstream version 4.19.249. Signed-off-by: Daniel Baumann --- Documentation/devicetree/bindings/i2c/i2c.txt | 94 +++++++++++++++++++++++++++ 1 file changed, 94 insertions(+) create mode 100644 Documentation/devicetree/bindings/i2c/i2c.txt (limited to 'Documentation/devicetree/bindings/i2c/i2c.txt') diff --git a/Documentation/devicetree/bindings/i2c/i2c.txt b/Documentation/devicetree/bindings/i2c/i2c.txt new file mode 100644 index 000000000..112639824 --- /dev/null +++ b/Documentation/devicetree/bindings/i2c/i2c.txt @@ -0,0 +1,94 @@ +Generic device tree bindings for I2C busses +=========================================== + +This document describes generic bindings which can be used to describe I2C +busses in a device tree. + +Required properties +------------------- + +- #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. + +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. + +Optional properties +------------------- + +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. + +- 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. + +- 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. + +- 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. + +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. -- cgit v1.2.3