forked from Minki/linux
0f614d834b
Some I2C devices have multiple addresses assigned, for example each address corresponding to a different internal register map page of the device. So far drivers which need support for this have handled this with a driver specific and non-generic implementation, e.g. passing the additional address via platform data. This patch provides a new helper function called i2c_new_secondary_device() which is intended to provide a generic way to get the secondary address as well as instantiate a struct i2c_client for the secondary address. The function expects a pointer to the primary i2c_client, a name for the secondary address and an optional default address. The name is used as a handle to specify which secondary address to get. The default address is used as a fallback in case no secondary address was explicitly specified. In case no secondary address and no default address were specified the function returns NULL. For now the function only supports look-up of the secondary address from devicetree, but it can be extended in the future to for example support board files and/or ACPI. Signed-off-by: Jean-Michel Hautbois <jean-michel.hautbois@veo-labs.com> Acked-by: Rob Herring <robh@kernel.org> Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com> Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
79 lines
2.7 KiB
Plaintext
79 lines
2.7 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 in a device tree.
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Required properties
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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 following generic names
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recommended practice.
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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. This is usually a 7 bit address. However,
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flags can be attached to the address. I2C_TEN_BIT_ADDRESS is used to mark a 10
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bit address. It is needed to avoid the ambiguity between e.g. a 7 bit address
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of 0x50 and a 10 bit address of 0x050 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 listen to
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be devices ourselves.
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Optional properties
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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 the bindings below.
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- clock-frequency
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frequency of bus clock in Hz.
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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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- interrupts
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interrupts used by the device.
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- interrupt-names
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"irq" and "wakeup" names are recognized by I2C core, other names are
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left to individual drivers.
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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.
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- wakeup-source
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device can be used as a wakeup source.
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- reg
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I2C slave addresses
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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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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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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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