doc/hardware/peripherals/i3c.rst - third_party/github/zephyrproject-rtos/zephyr - Git at Google

 .. _i3c_api:

 Improved Inter-Integrated Circuit (I3C) Bus
 ###########################################

 I3C (Improved Inter-Integrated Circuit) is a two-signal shared
 peripheral interface bus.  Devices on the bus can operate in
 two roles: as a "controller" that initiates transactions and
 controls the clock, or as a "target" that responds to transaction
 commands.

 Currently, the API is based on `I3C Specification`_ version 1.1.1.

 .. contents::
     :local:
     :depth: 2

 .. _i3c-controller-api:

 I3C Controller API
 ******************

 Zephyr's I3C controller API is used when an I3C controller controls
 the bus, in particularly the start and stop conditions and the clock.
 This is the most common mode, used to interact with I3C target
 devices such as sensors.

 Due to the nature of the I3C, there are devices on the bus where
 they may not have addresses when powered on. Therefore, an additional
 dynamic address assignment needs to be carried out by the I3C
 controller. Because of this, the controller needs to maintain
 separate structures to keep track of device status. This can be done
 at build time, for example, by creating arrays of device descriptors
 for both I3C and I\ :sup:`2`\ C devices:

 .. code-block:: c

    static struct i3c_device_desc i3c_device_array[] = I3C_DEVICE_ARRAY_DT_INST(inst);
    static struct i3c_i2c_device_desc i2c_device_array[] = I3C_I2C_DEVICE_ARRAY_DT_INST(inst);

 The macros :c:macro:`I3C_DEVICE_ARRAY_DT_INST` and
 :c:macro:`I3C_I2C_DEVICE_ARRAY_DT_INST` are helper macros to aid in
 create arrays of device descriptors corresponding to the devicetree
 nodes under the I3C controller.

 Here is a list of generic steps for initializing the I3C
 controller and the I3C bus inside the device driver
 initialization function:

 #. Initialize the data structure of the I3C controller device
    driver instance. The usual device defining macros such as
    :c:macro:`DEVICE_DT_INST_DEFINE` can be used, and the initialization
    function provided as a parameter to the macro.

    * The :c:struct:`i3c_addr_slots` and :c:struct:`i3c_dev_list` are
      structures to aid in address assignments and device list management.
      If this is being used, this struct needs to be initialized by calling
      :c:func:`i3c_addr_slots_init`. These two structures can also be used
      with various helper functions.

    * Initialize the device descriptors if needed by the controller
      driver.

 #. Initialize the hardware, including but not limited to:

    * Setup pin mux and directions.

    * Setup the clock for the controller.

    * Power on the hardware.

    * Configure the hardware (e.g. SCL clock frequency).

 #. Perform bus initialization. There is a generic helper function,
    :c:func:`i3c_bus_init`, which performs the following steps.
    This function can be used if the controller does not require
    any special handling during bus initialization.

    #. Do ``RSTDAA`` to reset dynamic addresses of connected devices.
       If any connected devices have already been assigned an address,
       the bookkeeping data structures do not have records of these,
       for example, at power-on. So it is a good idea to reset and
       assign them new addresses.

    #. Do ``DISEC`` to disable any events from devices.

    #. Do ``SETDASA`` to use static addresses as dynamic address
       if so desired.

       * ``SETAASA`` may not be supported for all connected devices
         to assign static addresses as dynamic addresses.

       * BCR and DCR need to be obtained separately to populate
         the relevant fields in the I3C target device descriptor
         struct.

    #. Do ``ENTDAA`` to start dynamic address assignment, if there are
       still devices without addresses.

       * If there is a device waiting for address, it will send
         its Provisioned ID, BCR, and DCR back. Match the received
         Provisioned ID to the list of registered I3C devices.

         * If there is a match, assign an address (either from
           the stated static address if ``SETDASA`` has not been
           done, or use a free address).

           * Also, set the BCR and DCR fields in the device descriptor
             struct.

         * If there is no match, depending on policy, it can be
           assigned a free address, or the device driver can stop
           the assignment process and errors out.

           * Note that the I3C API requires device descriptor to
             function. A device without a device descriptor cannot be
             accessed through the API.

       * This step can be skipped if there is no connected devices
         requiring DAA.

    #. These are optional but highly recommended:

       * Do ``GETMRL`` and ``GETMWL`` to get maximum read/write
         length.

       * Do ``GETMXDS`` to get maximum read/write speed and maximum
         read turnaround time.

       * The helper function, :c:func:`i3c_bus_init`, would retrieve
         basic device information such as BCR, DCR, MRL and MWL.

    #. Do ``ENEC`` to re-enable events from devices.

       * The helper function, :c:func:`i3c_bus_init`, only re-enables
         hot-join events. IBI event should only be enabled when
         enabling IBI of a device.

 In-Band Interrupt (IBI)
 =======================

 If a target device can generate In-Band Interrupt (IBI),
 the controller needs to be made aware of it.

 * :c:func:`i3c_ibi_enable` to enable IBI of a target device.

   * Some controller hardware have IBI slots which need to be
     programmed so that the controller can recognize incoming IBIs
     from a particular target device.

     * If the hardware has IBI slots, :c:func:`i3c_ibi_enable`
       needs to program those IBI slots.

     * Note that there are usually limited IBI slots on
       the controller so this operation may fail.

   * The implementation in driver should also send the ``ENEC`` command
     to enable interrupt of this target device.

 * :c:func:`i3c_ibi_disable` to disable IBI of a target device.

   * If controller hardware makes use of IBI slots, this will remove
     description of the target device from the slots.

   * The implementation in driver should also send the ``DISEC`` command
     to disable interrupt of this target device.

 Device Tree
 ===========

 Here is an example for defining a I3C controller in device tree:

 .. code-block:: devicetree

    i3c0: i3c@10000 {
            compatible = "vendor,i3c";

            #address-cells = < 0x3 >;
            #size-cells = < 0x0 >;

            reg = < 0x10000 0x1000 >;
            interrupts = < 0x1F 0x0 >;

            pinctrl-0 = < &pinmux-i3c >;
            pinctrl-names = "default";

            i2c-scl-hz = < 400000 >;

            i3c-scl-hz = < 12000000 >;

            status = "okay";

            i3c-dev0: i3c-dev0@420000ABCD12345678 {
                    compatible = "vendor,i3c-dev";

                    reg = < 0x42 0xABCD 0x12345678 >;

                    status = "okay";
            };

            i2c-dev0: i2c-dev0@380000000000000050 {
                    compatible = "vendor-i2c-dev";

                    reg = < 0x38 0x0 0x50 >;

                    status = "okay";
            };
    };

 I3C Devices
 -----------

 For I3C devices, the ``reg`` property has 3 elements:

 * The first one is the static address of the device.

   * Can be zero if static address is not used. Address will be
     assigned during DAA (Dynamic Address Assignment).

   * If non-zero and property ``assigned-address`` is not set,
     this will be the address of the device after SETDASA
     (Set Dynamic Address from Static Address) is issued.

 * Second element is the upper 16-bit of the Provisioned ID (PID)
   which contains the manufacturer ID left-shifted by 1. This is
   the bits 33-47 (zero-based) of the 48-bit Provisioned ID.

 * Third element contains the lower 32-bit of the Provisioned ID
   which is a combination of the part ID (left-shifted by 16,
   bits 16-31 of the PID) and the instance ID (left-shifted by 12,
   bits 12-15 of the PID).

 Note that the unit-address (the part after ``@``) must match
 the ``reg`` property fully where each element is treated as
 32-bit integer, combining to form a 96-bit integer. This is
 required for properly generating device tree macros.

 I\ :sup:`2`\ C Devices
 ----------------------

 For I\ :sup:`2`\ C devices where the device driver has support for
 working under I3C bus, the device node can be described as
 a child of the I3C controller. If the device driver is written to
 only work with I\ :sup:`2`\ C controllers, define the node under
 the I\ :sup:`2`\ C virtual controller as described below.
 Otherwise, the ``reg`` property, similar to I3C devices,
 has 3 elements:

 * The first one is the static address of the device. This must be
   a valid address as I\ :sup:`2`\ C devices do not support
   dynamic address assignment.

 * Second element is always zero.

   * This is used by various helper macros to determine whether
     the device tree entry corresponds to a I\ :sup:`2`\ C device.

 * Third element is the LVR (Legacy Virtual Register):

   * bit[31:8] are unused.

   * bit[7:5] are the I\ :sup:`2`\ C device index:

     * Index ``0``

       * I3C device has a 50 ns spike filter where it is not
         affected by high frequency on SCL.

     * Index ``1``

       * I\ :sup:`2`\ C device does not have a 50 ns spike filter but
         can work with high frequency on SCL.

     * Index ``2``

       * I3C device does not have a 50 ns spike filter and
         cannot work with high frequency on SCL.

   * bit[4] is the I\ :sup:`2`\ C mode indicator:

     * ``0`` is FM+ mode.

     * ``1`` is FM mode.

 Similar to I3C devices, the unit-address must match the ``reg``
 property fully where each element is treated as 32-bit integer,
 combining to form a 96-bit integer.

 Device Drivers for I3C Devices
 ==============================

 All of the transfer functions of I3C controller API require
 the use of device descriptors, :c:struct:`i3c_device_desc`.
 This struct contains runtime information about a I3C device,
 such as, its dynamic address, BCR, DCR, MRL and MWL. Therefore,
 the device driver of a I3C device should grab a pointer to
 this device descriptor from the controller using
 :c:func:`i3c_device_find`. This function takes an ID parameter
 of type :c:struct:`i3c_device_id` for matching. The returned
 pointer can then be used in subsequent API calls to
 the controller.

 I\ :sup:`2`\ C Devices under I3C Bus
 ====================================

 Since I3C is backward compatible with I\ :sup:`2`\ C, the I3C controller
 API can accommodate I2C API calls without modifications if the controller
 device driver implements the I2C API. This has the advantage of using
 existing I2C devices without any modifications to their device drivers.
 However, since the I3C controller API works on device descriptors,
 any calls to I2C API will need to look up the corresponding device
 descriptor from the I2C device address. This adds a bit of processing
 cost to any I2C API calls.

 On the other hand, a device driver can be extended to utilize native
 I2C device support via the I3C controller API. During device
 initialization, :c:func:`i3c_i2c_device_find` needs to be called to
 retrieve the pointer to the device descriptor. This pointer can be used
 in subsequent API calls.

 Note that, with either methods mentioned above, the devicetree node of
 the I2C device must be declared according to I3C standard:

 The I\ :sup:`2`\ C virtual controller device driver provides a way to
 interface I\ :sup:`2`\ C devices on the I3C bus where the associated
 device drivers can be used as-is without modifications. This requires
 adding an intermediate node in the device tree:

 .. code-block:: devicetree

    i3c0: i3c@10000 {
            <... I3C controller related properties ...>
            <... Nodes of I3C devices, if any ...>

            i2c-dev0: i2c-dev0@420000000000000050 {
                    compatible = "vendor-i2c-dev";

                    reg = < 0x42 0x0 0x50 >;

                    status = "okay";
            };
    };

 Configuration Options
 *********************

 Related configuration options:

 * :kconfig:option:`CONFIG_I3C`
 * :kconfig:option:`CONFIG_I3C_USE_GROUP_ADDR`
 * :kconfig:option:`CONFIG_I3C_USE_IBI`
 * :kconfig:option:`CONFIG_I3C_IBI_MAX_PAYLOAD_SIZE`
 * :kconfig:option:`CONFIG_I3C_CONTROLLER_INIT_PRIORITY`

 API Reference
 *************

 .. doxygengroup:: i3c_interface
 .. doxygengroup:: i3c_ccc
 .. doxygengroup:: i3c_addresses
 .. doxygengroup:: i3c_target_device

 .. _I3C Specification: https://www.mipi.org/specifications/i3c-sensor-specification
	.. _i3c_api:

	Improved Inter-Integrated Circuit (I3C) Bus
	###########################################

	I3C (Improved Inter-Integrated Circuit) is a two-signal shared
	peripheral interface bus. Devices on the bus can operate in
	two roles: as a "controller" that initiates transactions and
	controls the clock, or as a "target" that responds to transaction
	commands.

	Currently, the API is based on `I3C Specification`_ version 1.1.1.

	.. contents::
	:local:
	:depth: 2

	.. _i3c-controller-api:

	I3C Controller API
	******************

	Zephyr's I3C controller API is used when an I3C controller controls
	the bus, in particularly the start and stop conditions and the clock.
	This is the most common mode, used to interact with I3C target
	devices such as sensors.

	Due to the nature of the I3C, there are devices on the bus where
	they may not have addresses when powered on. Therefore, an additional
	dynamic address assignment needs to be carried out by the I3C
	controller. Because of this, the controller needs to maintain
	separate structures to keep track of device status. This can be done
	at build time, for example, by creating arrays of device descriptors
	for both I3C and I\ :sup:`2`\ C devices:

	.. code-block:: c

	static struct i3c_device_desc i3c_device_array[] = I3C_DEVICE_ARRAY_DT_INST(inst);
	static struct i3c_i2c_device_desc i2c_device_array[] = I3C_I2C_DEVICE_ARRAY_DT_INST(inst);

	The macros :c:macro:`I3C_DEVICE_ARRAY_DT_INST` and
	:c:macro:`I3C_I2C_DEVICE_ARRAY_DT_INST` are helper macros to aid in
	create arrays of device descriptors corresponding to the devicetree
	nodes under the I3C controller.

	Here is a list of generic steps for initializing the I3C
	controller and the I3C bus inside the device driver
	initialization function:

	#. Initialize the data structure of the I3C controller device
	driver instance. The usual device defining macros such as
	:c:macro:`DEVICE_DT_INST_DEFINE` can be used, and the initialization
	function provided as a parameter to the macro.

	* The :c:struct:`i3c_addr_slots` and :c:struct:`i3c_dev_list` are
	structures to aid in address assignments and device list management.
	If this is being used, this struct needs to be initialized by calling
	:c:func:`i3c_addr_slots_init`. These two structures can also be used
	with various helper functions.

	* Initialize the device descriptors if needed by the controller
	driver.

	#. Initialize the hardware, including but not limited to:

	* Setup pin mux and directions.

	* Setup the clock for the controller.

	* Power on the hardware.

	* Configure the hardware (e.g. SCL clock frequency).

	#. Perform bus initialization. There is a generic helper function,
	:c:func:`i3c_bus_init`, which performs the following steps.
	This function can be used if the controller does not require
	any special handling during bus initialization.

	#. Do ``RSTDAA`` to reset dynamic addresses of connected devices.
	If any connected devices have already been assigned an address,
	the bookkeeping data structures do not have records of these,
	for example, at power-on. So it is a good idea to reset and
	assign them new addresses.

	#. Do ``DISEC`` to disable any events from devices.

	#. Do ``SETDASA`` to use static addresses as dynamic address
	if so desired.

	* ``SETAASA`` may not be supported for all connected devices
	to assign static addresses as dynamic addresses.

	* BCR and DCR need to be obtained separately to populate
	the relevant fields in the I3C target device descriptor
	struct.

	#. Do ``ENTDAA`` to start dynamic address assignment, if there are
	still devices without addresses.

	* If there is a device waiting for address, it will send
	its Provisioned ID, BCR, and DCR back. Match the received
	Provisioned ID to the list of registered I3C devices.

	* If there is a match, assign an address (either from
	the stated static address if ``SETDASA`` has not been
	done, or use a free address).

	* Also, set the BCR and DCR fields in the device descriptor
	struct.

	* If there is no match, depending on policy, it can be
	assigned a free address, or the device driver can stop
	the assignment process and errors out.

	* Note that the I3C API requires device descriptor to
	function. A device without a device descriptor cannot be
	accessed through the API.

	* This step can be skipped if there is no connected devices
	requiring DAA.

	#. These are optional but highly recommended:

	* Do ``GETMRL`` and ``GETMWL`` to get maximum read/write
	length.

	* Do ``GETMXDS`` to get maximum read/write speed and maximum
	read turnaround time.

	* The helper function, :c:func:`i3c_bus_init`, would retrieve
	basic device information such as BCR, DCR, MRL and MWL.

	#. Do ``ENEC`` to re-enable events from devices.

	* The helper function, :c:func:`i3c_bus_init`, only re-enables
	hot-join events. IBI event should only be enabled when
	enabling IBI of a device.

	In-Band Interrupt (IBI)
	=======================

	If a target device can generate In-Band Interrupt (IBI),
	the controller needs to be made aware of it.

	* :c:func:`i3c_ibi_enable` to enable IBI of a target device.

	* Some controller hardware have IBI slots which need to be
	programmed so that the controller can recognize incoming IBIs
	from a particular target device.

	* If the hardware has IBI slots, :c:func:`i3c_ibi_enable`
	needs to program those IBI slots.

	* Note that there are usually limited IBI slots on
	the controller so this operation may fail.

	* The implementation in driver should also send the ``ENEC`` command
	to enable interrupt of this target device.

	* :c:func:`i3c_ibi_disable` to disable IBI of a target device.

	* If controller hardware makes use of IBI slots, this will remove
	description of the target device from the slots.

	* The implementation in driver should also send the ``DISEC`` command
	to disable interrupt of this target device.

	Device Tree
	===========

	Here is an example for defining a I3C controller in device tree:

	.. code-block:: devicetree

	i3c0: i3c@10000 {
	compatible = "vendor,i3c";

	#address-cells = < 0x3 >;
	#size-cells = < 0x0 >;

	reg = < 0x10000 0x1000 >;
	interrupts = < 0x1F 0x0 >;

	pinctrl-0 = < &pinmux-i3c >;
	pinctrl-names = "default";

	i2c-scl-hz = < 400000 >;

	i3c-scl-hz = < 12000000 >;

	status = "okay";

	i3c-dev0: i3c-dev0@420000ABCD12345678 {
	compatible = "vendor,i3c-dev";

	reg = < 0x42 0xABCD 0x12345678 >;

	status = "okay";
	};

	i2c-dev0: i2c-dev0@380000000000000050 {
	compatible = "vendor-i2c-dev";

	reg = < 0x38 0x0 0x50 >;

	status = "okay";
	};
	};

	I3C Devices
	-----------

	For I3C devices, the ``reg`` property has 3 elements:

	* The first one is the static address of the device.

	* Can be zero if static address is not used. Address will be
	assigned during DAA (Dynamic Address Assignment).

	* If non-zero and property ``assigned-address`` is not set,
	this will be the address of the device after SETDASA
	(Set Dynamic Address from Static Address) is issued.

	* Second element is the upper 16-bit of the Provisioned ID (PID)
	which contains the manufacturer ID left-shifted by 1. This is
	the bits 33-47 (zero-based) of the 48-bit Provisioned ID.

	* Third element contains the lower 32-bit of the Provisioned ID
	which is a combination of the part ID (left-shifted by 16,
	bits 16-31 of the PID) and the instance ID (left-shifted by 12,
	bits 12-15 of the PID).

	Note that the unit-address (the part after ``@``) must match
	the ``reg`` property fully where each element is treated as
	32-bit integer, combining to form a 96-bit integer. This is
	required for properly generating device tree macros.

	I\ :sup:`2`\ C Devices
	----------------------

	For I\ :sup:`2`\ C devices where the device driver has support for
	working under I3C bus, the device node can be described as
	a child of the I3C controller. If the device driver is written to
	only work with I\ :sup:`2`\ C controllers, define the node under
	the I\ :sup:`2`\ C virtual controller as described below.
	Otherwise, the ``reg`` property, similar to I3C devices,
	has 3 elements:

	* The first one is the static address of the device. This must be
	a valid address as I\ :sup:`2`\ C devices do not support
	dynamic address assignment.

	* Second element is always zero.

	* This is used by various helper macros to determine whether
	the device tree entry corresponds to a I\ :sup:`2`\ C device.

	* Third element is the LVR (Legacy Virtual Register):

	* bit[31:8] are unused.

	* bit[7:5] are the I\ :sup:`2`\ C device index:

	* Index ``0``

	* I3C device has a 50 ns spike filter where it is not
	affected by high frequency on SCL.

	* Index ``1``

	* I\ :sup:`2`\ C device does not have a 50 ns spike filter but
	can work with high frequency on SCL.

	* Index ``2``

	* I3C device does not have a 50 ns spike filter and
	cannot work with high frequency on SCL.

	* bit[4] is the I\ :sup:`2`\ C mode indicator:

	* ``0`` is FM+ mode.

	* ``1`` is FM mode.

	Similar to I3C devices, the unit-address must match the ``reg``
	property fully where each element is treated as 32-bit integer,
	combining to form a 96-bit integer.

	Device Drivers for I3C Devices
	==============================

	All of the transfer functions of I3C controller API require
	the use of device descriptors, :c:struct:`i3c_device_desc`.
	This struct contains runtime information about a I3C device,
	such as, its dynamic address, BCR, DCR, MRL and MWL. Therefore,
	the device driver of a I3C device should grab a pointer to
	this device descriptor from the controller using
	:c:func:`i3c_device_find`. This function takes an ID parameter
	of type :c:struct:`i3c_device_id` for matching. The returned
	pointer can then be used in subsequent API calls to
	the controller.

	I\ :sup:`2`\ C Devices under I3C Bus
	====================================

	Since I3C is backward compatible with I\ :sup:`2`\ C, the I3C controller
	API can accommodate I2C API calls without modifications if the controller
	device driver implements the I2C API. This has the advantage of using
	existing I2C devices without any modifications to their device drivers.
	However, since the I3C controller API works on device descriptors,
	any calls to I2C API will need to look up the corresponding device
	descriptor from the I2C device address. This adds a bit of processing
	cost to any I2C API calls.

	On the other hand, a device driver can be extended to utilize native
	I2C device support via the I3C controller API. During device
	initialization, :c:func:`i3c_i2c_device_find` needs to be called to
	retrieve the pointer to the device descriptor. This pointer can be used
	in subsequent API calls.

	Note that, with either methods mentioned above, the devicetree node of
	the I2C device must be declared according to I3C standard:

	The I\ :sup:`2`\ C virtual controller device driver provides a way to
	interface I\ :sup:`2`\ C devices on the I3C bus where the associated
	device drivers can be used as-is without modifications. This requires
	adding an intermediate node in the device tree:

	.. code-block:: devicetree

	i3c0: i3c@10000 {
	<... I3C controller related properties ...>
	<... Nodes of I3C devices, if any ...>

	i2c-dev0: i2c-dev0@420000000000000050 {
	compatible = "vendor-i2c-dev";

	reg = < 0x42 0x0 0x50 >;

	status = "okay";
	};
	};

	Configuration Options
	*********************

	Related configuration options:

	* :kconfig:option:`CONFIG_I3C`
	* :kconfig:option:`CONFIG_I3C_USE_GROUP_ADDR`
	* :kconfig:option:`CONFIG_I3C_USE_IBI`
	* :kconfig:option:`CONFIG_I3C_IBI_MAX_PAYLOAD_SIZE`
	* :kconfig:option:`CONFIG_I3C_CONTROLLER_INIT_PRIORITY`

	API Reference
	*************

	.. doxygengroup:: i3c_interface
	.. doxygengroup:: i3c_ccc
	.. doxygengroup:: i3c_addresses
	.. doxygengroup:: i3c_target_device

	.. _I3C Specification: https://www.mipi.org/specifications/i3c-sensor-specification