diff --git a/docs/design/reset-design.rst b/docs/design/reset-design.rst index 7b10c956c..666ee4f0d 100644 --- a/docs/design/reset-design.rst +++ b/docs/design/reset-design.rst @@ -141,19 +141,26 @@ CPU executes a modified BL31 initialization, as described below. Platform initialization ~~~~~~~~~~~~~~~~~~~~~~~ -In this configuration, when the CPU resets to BL31 there are no parameters that -can be passed in registers by previous boot stages. Instead, the platform code -in BL31 needs to know, or be able to determine, the location of the BL32 (if -required) and BL33 images and provide this information in response to the +In this configuration, when the CPU resets to BL31 there should be no parameters +that can be passed in registers by previous boot stages. Instead, the platform +code in BL31 needs to know, or be able to determine, the location of the BL32 +(if required) and BL33 images and provide this information in response to the ``bl31_plat_get_next_image_ep_info()`` function. +.. note:: + Some platforms that configure ``RESET_TO_BL31`` might still be able to + receive parameters in registers depending on their actual boot sequence. On + those occasions, and in addition to ``RESET_TO_BL31``, these platforms should + set ``RESET_TO_BL31_WITH_PARAMS`` to avoid the input registers from being + zeroed before entering BL31. + Additionally, platform software is responsible for carrying out any security initialisation, for example programming a TrustZone address space controller. This might be done by the Trusted Boot Firmware or by platform code in BL31. -------------- -*Copyright (c) 2015-2019, Arm Limited and Contributors. All rights reserved.* +*Copyright (c) 2015-2022, Arm Limited and Contributors. All rights reserved.* .. |Default reset code flow| image:: ../resources/diagrams/default_reset_code.png .. |Reset code flow with programmable reset address| image:: ../resources/diagrams/reset_code_no_boot_type_check.png diff --git a/docs/getting_started/build-options.rst b/docs/getting_started/build-options.rst index 4dbf5cb9f..46d57406b 100644 --- a/docs/getting_started/build-options.rst +++ b/docs/getting_started/build-options.rst @@ -709,6 +709,11 @@ Common build options entrypoint) or 1 (CPU reset to BL31 entrypoint). The default value is 0. +- ``RESET_TO_BL31_WITH_PARAMS``: If ``RESET_TO_BL31`` has been enabled, setting + this additional option guarantees that the input registers are not cleared + therefore allowing parameters to be passed to the BL31 entrypoint. + The default value is 0. + - ``RESET_TO_SP_MIN``: SP_MIN is the minimal AArch32 Secure Payload provided in TF-A. This flag configures SP_MIN entrypoint as the CPU reset vector instead of the BL1 entrypoint. It can take the value 0 (CPU reset to BL1