STM32 generic RCC binding

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.. dtcompatible:: st,stm32-rcc
.. _dtbinding_st_stm32_rcc:

st,stm32-rcc
############

Vendor: :ref:`STMicroelectronics <dt_vendor_st>`

Description
***********



.. code-block:: none

   STM32 Reset and Clock controller node.
   This node is in charge of system clock ('SYSCLK') source selection and controlling
   clocks for AHB (Advanced High Performance) and APB (Advanced Peripheral) bus domains.

   Configuring STM32 Reset and Clock controller node:

   System clock source should be selected amongst the clock nodes available in "clocks"
   node (typically 'clk_hse, clk_hsi', 'pll', ...).
   Core clock frequency should also be defined, using "clock-frequency" property.
   Note:
           Core clock frequency  = SYSCLK / AHB prescaler
   Last, peripheral bus clocks (typically PCLK1, PCLK2) should be configured using matching
   prescaler properties.
   Here is an example of correctly configured rcc node:
   &rcc {
            clocks = <&pll>;  /* Select 80MHz pll as SYSCLK source */
            ahb-prescaler = <2>;
            clock-frequency = <DT_FREQ_M(40)>; /* = SYSCLK / AHB prescaler */
            apb1-presacler = <1>;
            apb2-presacler = <1>;
   }

   Specifying a gated clock:

   To specify a gated clock, a peripheral should define a "clocks" property encoded
   in the following way:
   ... {
            ...
            clocks = <&rcc STM32_CLOCK_BUS_APB2 0x00000020>;
            ...
   }
   After the phandle referring to rcc node, the first index specifies the registers of
   the bus controlling the peripheral and the second index specifies the bit used to
   control the peripheral clock in that bus register.
   The gated clock is required when accessing to the peripheral controller is needed
   (generally for configuring the device). If dual clock domain is not used, it is
   also used for peripheral operation.

   Specifying a domain clock source:

   Specifying a domain source clock could be done by adding a clock specifier to the
   clock property:
   ... {
            ...
            clocks = <&rcc STM32_CLOCK_BUS_APB2 0x00000020>,
                         <&rcc STM32_SRC_HSI I2C1_SEL(2)>;
            ...
   }
   In this example, I2C1 device is assigned HSI as domain clock source.
   Domain clock is independent from the bus/gated clock and allows access to the device's
   register while the gated clock is off. As it doesn't feed the peripheral's controller, it
   allows peripheral operation, but can't be used for peripheral configuration.
   It is peripheral driver's responsibility to query and use clock source information in
   accordance with clock_control API specifications.

   Since the peripheral subsystem rate is dictated by the clock used for peripheral
   operation, same clock should be used in calls to `clock_control_get_rate()`

   Note 1: No additional specifier means gating clock is also the clock source (ie
           'PCLK/PCLK1/PCLK2' depending on the device). There is no need to add a second
           cell to explicitly set it.
   Note 2: Default peripheral clock configuration (ie the one provided in *.dsti files)
           should be the one matching SoC reset state. Confere reference manual to check
           what is the reset value of the clock source for each peripheral.

Properties
**********

.. tabs::

   .. group-tab:: Node specific properties

      Properties not inherited from the base binding file.

      .. list-table::
         :widths: 1 1 4
         :header-rows: 1

         * - Name
           - Type
           - Details

         * - ``#clock-cells``
           - ``int``
           - .. code-block:: none

                Number of items to expect in a Clock specifier


             This property is **required**.

             Constant value: ``2``

         * - ``clock-frequency``
           - ``int``
           - .. code-block:: none

                default frequency in Hz for clock output



             This property is **required**.

         * - ``ahb-prescaler``
           - ``int``
           - .. code-block:: none

                AHB prescaler. Defines actual core clock frequency (HCLK)
                based on system frequency input.
                The HCLK clocks CPU, AHB, memories and DMA.



             This property is **required**.

             Legal values: ``1``, ``2``, ``4``, ``8``, ``16``, ``64``, ``128``, ``256``, ``512``

         * - ``apb1-prescaler``
           - ``int``
           - This property is **required**.

             Legal values: ``1``, ``2``, ``4``, ``8``, ``16``

         * - ``apb2-prescaler``
           - ``int``
           - This property is **required**.

             Legal values: ``1``, ``2``, ``4``, ``8``, ``16``

         * - ``undershoot-prevention``
           - ``boolean``
           - .. code-block:: none

                On some parts, it could be required to set up highest core frequencies
                (>80MHz) in two steps in order to prevent undershoot.
                This is done by applying an intermediate AHB prescaler before switching
                System Clock source to PLL. Once done, prescaler is set back to expected
                value.





   .. group-tab:: Deprecated node specific properties

      Deprecated properties not inherited from the base binding file.

      (None)

   .. group-tab:: Base properties

      Properties inherited from the base binding file, which defines
      common properties that may be set on many nodes. Not all of these
      may apply to the "st,stm32-rcc" compatible.

      .. list-table::
         :widths: 1 1 4
         :header-rows: 1

         * - Name
           - Type
           - Details

         * - ``wakeup-source``
           - ``boolean``
           - .. code-block:: none

                Property to identify that a device can be used as wake up source.

                When this property is provided a specific flag is set into the
                device that tells the system that the device is capable of
                wake up the system.

                Wake up capable devices are disabled (interruptions will not wake up
                the system) by default but they can be enabled at runtime if necessary.



         * - ``power-domain``
           - ``phandle``
           - .. code-block:: none


                Power domain the device belongs to.

                The device will be notified when the power domain it belongs to is either
                suspended or resumed.



         * - ``zephyr,pm-device-runtime-auto``
           - ``boolean``
           - .. code-block:: none

                Automatically configure the device for runtime power management after the
                init function runs.



         * - ``zephyr,disabling-power-states``
           - ``phandles``
           - .. code-block:: none

                List of power states that will disable this device power.



         * - ``status``
           - ``string``
           - .. code-block:: none

                indicates the operational status of a device


             Legal values: ``'ok'``, ``'okay'``, ``'disabled'``, ``'reserved'``, ``'fail'``, ``'fail-sss'``

             See :ref:`dt-important-props` for more information.

         * - ``compatible``
           - ``string-array``
           - .. code-block:: none

                compatible strings


             This property is **required**.

             See :ref:`dt-important-props` for more information.

         * - ``reg``
           - ``array``
           - .. code-block:: none

                register space


             This property is **required**.

             See :ref:`dt-important-props` for more information.

         * - ``reg-names``
           - ``string-array``
           - .. code-block:: none

                name of each register space


         * - ``interrupts``
           - ``array``
           - .. code-block:: none

                interrupts for device


             See :ref:`dt-important-props` for more information.

         * - ``interrupts-extended``
           - ``compound``
           - .. code-block:: none

                extended interrupt specifier for device


         * - ``interrupt-names``
           - ``string-array``
           - .. code-block:: none

                name of each interrupt


         * - ``interrupt-parent``
           - ``phandle``
           - .. code-block:: none

                phandle to interrupt controller node


         * - ``label``
           - ``string``
           - .. code-block:: none

                Human readable string describing the device (used as device_get_binding() argument)



             See :ref:`dt-important-props` for more information.

             This property is **deprecated**.

         * - ``clocks``
           - ``phandle-array``
           - .. code-block:: none

                Clock gate information


         * - ``clock-names``
           - ``string-array``
           - .. code-block:: none

                name of each clock


         * - ``#address-cells``
           - ``int``
           - .. code-block:: none

                number of address cells in reg property


         * - ``#size-cells``
           - ``int``
           - .. code-block:: none

                number of size cells in reg property


         * - ``dmas``
           - ``phandle-array``
           - .. code-block:: none

                DMA channels specifiers


         * - ``dma-names``
           - ``string-array``
           - .. code-block:: none

                Provided names of DMA channel specifiers


         * - ``io-channels``
           - ``phandle-array``
           - .. code-block:: none

                IO channels specifiers


         * - ``io-channel-names``
           - ``string-array``
           - .. code-block:: none

                Provided names of IO channel specifiers


         * - ``mboxes``
           - ``phandle-array``
           - .. code-block:: none

                mailbox / IPM channels specifiers


         * - ``mbox-names``
           - ``string-array``
           - .. code-block:: none

                Provided names of mailbox / IPM channel specifiers


         * - ``zephyr,deferred-init``
           - ``boolean``
           - .. code-block:: none

                Do not initialize device automatically on boot. Device should be manually
                initialized using device_init().






Specifier cell names
********************

- clock cells: bus, bits