Arm Development Platform Build Options
======================================

Arm Platform Build Options
--------------------------

-  ``ARM_BL31_IN_DRAM``: Boolean option to select loading of BL31 in TZC secured
   DRAM. By default, BL31 is in the secure SRAM. Set this flag to 1 to load
   BL31 in TZC secured DRAM. If TSP is present, then setting this option also
   sets the TSP location to DRAM and ignores the ``ARM_TSP_RAM_LOCATION`` build
   flag.

-  ``ARM_CONFIG_CNTACR``: boolean option to unlock access to the ``CNTBase<N>``
   frame registers by setting the ``CNTCTLBase.CNTACR<N>`` register bits. The
   frame number ``<N>`` is defined by ``PLAT_ARM_NSTIMER_FRAME_ID``, which
   should match the frame used by the Non-Secure image (normally the Linux
   kernel). Default is true (access to the frame is allowed).

-  ``ARM_FW_CONFIG_LOAD_ENABLE``: Boolean option to enable the loading of
   FW_CONFIG device trees from the Firmware Image Package (FIP). When enabled,
   BL2 calls the platform specific function `arm_bl2_el3_plat_config_load`.
   This function is responsible for loading, parsing, and validating the
   FW_CONFIG device trees from the FIP. The option depends on RESET_TO_BL2.

-  ``ARM_DISABLE_TRUSTED_WDOG``: boolean option to disable the Trusted Watchdog.
   By default, Arm platforms use a watchdog to trigger a system reset in case
   an error is encountered during the boot process (for example, when an image
   could not be loaded or authenticated). The watchdog is enabled in the early
   platform setup hook at BL1 and disabled in the BL1 prepare exit hook. The
   Trusted Watchdog may be disabled at build time for testing or development
   purposes.

-  ``ARM_LINUX_KERNEL_AS_BL33``: The Linux kernel expects registers x0-x3 to
   have specific values at boot. This boolean option allows the Trusted Firmware
   to have a Linux kernel image as BL33 by preparing the registers to these
   values before jumping to BL33. This option defaults to 0 (disabled). For
   AArch64 ``RESET_TO_BL31`` and for AArch32 ``RESET_TO_SP_MIN`` must be 1 when
   using it. If this option is set to 1, ``ARM_PRELOADED_DTB_BASE`` must be set
   to the location of a device tree blob (DTB) already loaded in memory. The
   Linux Image address must be specified using the ``PRELOADED_BL33_BASE``
   option.

-  ``ARM_PLAT_MT``: This flag determines whether the Arm platform layer has to
   cater for the multi-threading ``MT`` bit when accessing MPIDR. When this flag
   is set, the functions which deal with MPIDR assume that the ``MT`` bit in
   MPIDR is set and access the bit-fields in MPIDR accordingly. Default value of
   this flag is 0. Note that this option is not used on FVP platforms.

-  ``ARM_RECOM_STATE_ID_ENC``: The PSCI1.0 specification recommends an encoding
   for the construction of composite state-ID in the power-state parameter.
   The existing PSCI clients currently do not support this encoding of
   State-ID yet. Hence this flag is used to configure whether to use the
   recommended State-ID encoding or not. The default value of this flag is 0,
   in which case the platform is configured to expect NULL in the State-ID
   field of power-state parameter.

-  ``ARM_ROTPK_LOCATION``: used when ``TRUSTED_BOARD_BOOT=1``. It specifies the
   location of the ROTPK returned by the function ``plat_get_rotpk_info()``
   for Arm platforms. Depending on the selected option, the proper private key
   must be specified using the ``ROT_KEY`` option when building the Trusted
   Firmware. This private key will be used by the certificate generation tool
   to sign the BL2 and Trusted Key certificates. Available options for
   ``ARM_ROTPK_LOCATION`` are:

   -  ``regs`` : return the ROTPK hash stored in the Trusted root-key storage
      registers.
   -  ``devel_rsa`` : return a development public key hash embedded in the BL1
      and BL2 binaries. This hash corresponds to the development private key
      ``plat/arm/board/common/rotpk/arm_rotprivk_rsa.pem``.
      The hashing algorithm is selected by ``HASH_ALG``; sha256 is used if
      ``HASH_ALG`` is not specified. A different RSA key can be specified by setting
      ``ROT_KEY``, there are 3k and 4k RSA keys in ``plat/arm/board/common/rotpk/``.
   -  ``devel_ecdsa`` : return a development public key hash embedded in the BL1
      and BL2 binaries. This hash corresponds to the development private key
      ``plat/arm/board/common/rotpk/arm_rotprivk_ecdsa.pem`` unless a different key
      is specified with ``ROT_KEY``, such as the 384 bit key in the same directory.
      he hashing algorithm is selected by ``HASH_ALG``; sha256 is used if ``HASH_ALG``
      is not specified.
   -  ``devel_full_dev_rsa_key`` : return a development public key embedded in
      the BL1 and BL2 binaries. This key corresponds to the RSA private
      key ``plat/arm/board/common/rotpk/arm_rotprivk.pem`` by default, but can
      be changed by setting ``ROT_KEY``, there are 3k and 4k RSA keys in
      ``plat/arm/board/common/rotpk/``.
   - ``devel_full_dev_ecdsa_key`` : return a development public key embedded in
      the BL1 and BL2 binaries. This key corresponds to the EC private key
      ``plat/arm/board/common/rotpk/arm_rotprivk_ecdsa.pem``, unless a different
      ECDSA key is specified by ``ROT_KEY``, such as the 384 bit key in the same directory.

-  ``ARM_TSP_RAM_LOCATION``: location of the TSP binary. Options:

   -  ``tsram`` : Trusted SRAM (default option when TBB is not enabled)
   -  ``tdram`` : Trusted DRAM (if available)
   -  ``dram`` : Secure region in DRAM (default option when TBB is enabled,
      configured by the TrustZone controller)

-  ``ARM_XLAT_TABLES_LIB_V1``: boolean option to compile TF-A with version 1
   of the translation tables library instead of version 2. It is set to 0 by
   default, which selects version 2.

-  ``ARM_GPT_SUPPORT``: Enable GPT parser to get the entry address and length of
   the various partitions present in the GPT image. This support is available
   only for the BL2 component, and it is disabled by default.
   The following diagram shows the view of the FIP partition inside the GPT
   image:

   |FIP in a GPT image|

For a better understanding of these options, the Arm development platform memory
map is explained in the :ref:`Firmware Design`.

.. _build_options_arm_css_platform:

Arm CSS Platform-Specific Build Options
---------------------------------------

-  ``CSS_DETECT_PRE_1_7_0_SCP``: Boolean flag to detect SCP version
   incompatibility. Version 1.7.0 of the SCP firmware made a non-backwards
   compatible change to the MTL protocol, used for AP/SCP communication.
   TF-A no longer supports earlier SCP versions. If this option is set to 1
   then TF-A will detect if an earlier version is in use. Default is 1.

-  ``CSS_LOAD_SCP_IMAGES``: Boolean flag, which when set, adds SCP_BL2 and
   SCP_BL2U to the FIP and FWU_FIP respectively, and enables them to be loaded
   during boot. Default is 1.

-  ``CSS_USE_SCMI_SDS_DRIVER``: Boolean flag which selects SCMI/SDS drivers
   instead of SCPI/BOM driver for communicating with the SCP during power
   management operations and for SCP RAM Firmware transfer. If this option
   is set to 1, then SCMI/SDS drivers will be used. Default is 0.

- ``CSS_SYSTEM_GRACEFUL_RESET``: Build option to enable graceful powerdown of
   CPU core on reset. This build option can be used on CSS platforms that
   require all the CPUs to execute the CPU specific power down sequence to
   complete a warm reboot sequence in which only the CPUs are power cycled.

Arm FVP Build Options
---------------------

- ``FVP_TRUSTED_SRAM_SIZE``: Size (in kilobytes) of the Trusted SRAM region to
  utilize when building for the FVP platform. This option defaults to 256.

Arm Juno Build Options
----------------------

-  ``JUNO_AARCH32_EL3_RUNTIME``: This build flag enables you to execute EL3
   runtime software in AArch32 mode, which is required to run AArch32 on Juno.
   By default this flag is set to '0'. Enabling this flag builds BL1 and BL2 in
   AArch64 and facilitates the loading of ``SP_MIN`` and BL33 as AArch32 executable
   images.

Arm Neoverse RD Platform Build Options
--------------------------------------

 - ``NRD_CHIP_COUNT``: Configures the number of chips on a Neoverse RD platform
   which supports multi-chip operation. If ``NRD_CHIP_COUNT`` is set to any
   valid value greater than 1, the platform code performs required configuration
   to support multi-chip operation.

- ``NRD_PLATFORM_VARIANT``: Selects the variant of a Neoverse RD platform. A
  particular Neoverse RD platform may have multiple variants which may differ in
  core count, cluster count or other peripherals. This build option is used to
  select the appropriate platform variant for the build. The range of valid
  values is platform specific.

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

.. |FIP in a GPT image| image:: ../../resources/diagrams/FIP_in_a_GPT_image.png

*Copyright (c) 2019-2024, Arm Limited. All rights reserved.*