###############################
Details for the platform folder
###############################

*********************
Interfacing with TF-M
*********************

platform/ext/target/tfm_peripherals_def.h
=========================================
This file should enumerate the hardware peripherals that are available for TF-M
on the platform. The name of the peripheral used by a service is set in its
manifest file. The platform have to provide a macro for each of the provided
peripherals, that is substituted to a pointer to type
``struct platform_data_t``. The memory that the pointer points
to is allocated by the platform code. The pointer gets stored in the partitions
database in SPM, and it is provided to the SPM HAL functions.

Peripherals currently used by the services in TF-M
--------------------------------------------------
- ``TFM_PERIPHERAL_UART1``-  UART1

.. Note::

    If a platform doesn't support a peripheral, that is used by a service, then
    the service cannot be used on the given platform. Using a peripheral in
    TF-M that is not supported by the platform results in compile error.

platform/include/tfm_spm_hal.h
==============================
This file contains the declarations of functions that a platform implementation
has to provide for TF-M's SPM. For details see the comments in the file.

platform/include/tfm_platform_system.h
======================================
This file contains the declarations of functions that a platform implementation
has to provide for TF-M's Platform Service. For details see
``docs/user_guides/services/tfm_platform_integration_guide.rst``

**************
System Startup
**************

Before calling ``main()``, platform startup code should initialise all system
clocks, perform runtime initialisation and other steps such as setting the
vector table. Configuration of the following features is optional as TF-M
architecture code will check and initialise them:

  - The Security Extension.
  - The Floating-point Extension.

*****************************
Debug authentication settings
*****************************

A platform may provide the option to configure debug authentication. TF-M core
calls the HAL function ``enum tfm_hal_status_t tfm_hal_platform_init(void)``
in which debug authentication is configured based on the following defines:

  - `DAUTH_NONE`: Debugging the system is not enabled.
  - `DAUTH_NS_ONLY`: Invasive and non invasive debugging of non-secure code is
    enabled.
  - `DAUTH_FULL`: Invasive and non-invasive debugging of non-secure and secure
    code is enabled.
  - `DAUTH_CHIP_DEFAULT`: The debug authentication options are used that are set
    by the chip vendor.

The desired debug authentication configuration can be selected by setting one of
the options above to the cmake command with the
`-DDEBUG_AUTHENTICATION="<define>"` option. The default value of
`DEBUG_AUTHENTICATION` is `DAUTH_CHIP_DEFAULT`.

.. Note::
   ``enum tfm_hal_status_t tfm_hal_platform_init(void)`` is called during the
   TF-M core initialisation phase, before initialising secure partition. This
   means that BL2 runs with the chip default setting.

***********
Sub-folders
***********

include
=======
This folder contains the interfaces that TF-M expects every target to provide.
The code in this folder is created as a part of the TF-M project therefore it
adheres to the BSD 3.0 license.

ext
===
This folder contains code that has been imported from other projects so it may
have licenses other than the BSD 3.0 used by the TF-M project.

Please see the :doc:`platform_ext_folder` for details.

--------------

*Copyright (c) 2017-2022, Arm Limited. All rights reserved.*