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Diffstat (limited to 'Documentation/devicetree/bindings/i2c/i2c.txt')
| -rw-r--r-- | Documentation/devicetree/bindings/i2c/i2c.txt | 95 |
1 files changed, 67 insertions, 28 deletions
diff --git a/Documentation/devicetree/bindings/i2c/i2c.txt b/Documentation/devicetree/bindings/i2c/i2c.txt index 9a53df4243c6..fc3dd7ec0445 100644 --- a/Documentation/devicetree/bindings/i2c/i2c.txt +++ b/Documentation/devicetree/bindings/i2c/i2c.txt @@ -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. @@ -73,31 +67,76 @@ wants to support one of the below features, it should adapt the bindings below. i2c bus clock frequency (clock-frequency). Specified in Hz. -- 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. + all the time, for example. Can not be combined with 'single-master'. -- wakeup-source - device can be used as a wakeup source. +- 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 - I2C slave addresses + 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. |