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This adds a basic PSCI implementation allow secondary CPUs to be released from an initial state and continue through to the warm boot entrypoint. Each secondary CPU is kept in a holding pen, whereby it polls the value representing its hold state, by reading this from an array that acts as a table for all the PEs. The hold states are initially set to 0 for all cores to indicate that the executing core should continue polling. To prevent the secondary CPUs from interfering with the platform's initialization, they are only updated by the primary CPU once the cold boot sequence has completed and fpga_pwr_domain_on(mpidr) is called. The polling target CPU will then read 1 (which indicates that it should branch to the warm reset entrypoint) and then jump to that address rather than continue polling. In addition to the initial polling behaviour of the secondary CPUs before their warm boot reset sequence, they are also placed in a low-power wfe() state at the end of each poll; accordingly, the PSCI fpga_pwr_domain_on(mpidr) function also signals an event to all cores (after updating the target CPU's hold entry) to wake them from this state, allowing any secondary CPUs that are still polling to check their hold state again. This method is in accordance with both the PSCI and Linux kernel recommendations, as the lessened overhead reduces the energy consumption associated with the busy-loop. The table of hold entries is implemented by a global array as shared SRAM (which is used by other platforms in similar implementations) is not available on the FPGA images. Signed-off-by: Oliver Swede <oli.swede@arm.com> Change-Id: I65cfd1892f8be1dfcb285f0e1e94e7a9870cdf5a |
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Trusted Firmware-A ================== Trusted Firmware-A (TF-A) is a reference implementation of secure world software for `Arm A-Profile architectures`_ (Armv8-A and Armv7-A), including an Exception Level 3 (EL3) `Secure Monitor`_. It provides a suitable starting point for productization of secure world boot and runtime firmware, in either the AArch32 or AArch64 execution states. TF-A implements Arm interface standards, including: - `Power State Coordination Interface (PSCI)`_ - `Trusted Board Boot Requirements CLIENT (TBBR-CLIENT)`_ - `SMC Calling Convention`_ - `System Control and Management Interface (SCMI)`_ - `Software Delegated Exception Interface (SDEI)`_ The code is designed to be portable and reusable across hardware platforms and software models that are based on the Armv8-A and Armv7-A architectures. In collaboration with interested parties, we will continue to enhance TF-A with reference implementations of Arm standards to benefit developers working with Armv7-A and Armv8-A TrustZone technology. Users are encouraged to do their own security validation, including penetration testing, on any secure world code derived from TF-A. More Info and Documentation --------------------------- To find out more about Trusted Firmware-A, please `view the full documentation`_ that is available through `trustedfirmware.org`_. -------------- *Copyright (c) 2013-2019, Arm Limited and Contributors. All rights reserved.* .. _Armv7-A and Armv8-A: https://developer.arm.com/products/architecture/a-profile .. _Secure Monitor: http://www.arm.com/products/processors/technologies/trustzone/tee-smc.php .. _Power State Coordination Interface (PSCI): PSCI_ .. _PSCI: http://infocenter.arm.com/help/topic/com.arm.doc.den0022d/Power_State_Coordination_Interface_PDD_v1_1_DEN0022D.pdf .. _Trusted Board Boot Requirements CLIENT (TBBR-CLIENT): https://developer.arm.com/docs/den0006/latest/trusted-board-boot-requirements-client-tbbr-client-armv8-a .. _SMC Calling Convention: http://infocenter.arm.com/help/topic/com.arm.doc.den0028b/ARM_DEN0028B_SMC_Calling_Convention.pdf .. _System Control and Management Interface (SCMI): SCMI_ .. _SCMI: http://infocenter.arm.com/help/topic/com.arm.doc.den0056a/DEN0056A_System_Control_and_Management_Interface.pdf .. _Software Delegated Exception Interface (SDEI): SDEI_ .. _SDEI: http://infocenter.arm.com/help/topic/com.arm.doc.den0054a/ARM_DEN0054A_Software_Delegated_Exception_Interface.pdf .. _Arm A-Profile architectures: https://developer.arm.com/architectures/cpu-architecture/a-profile .. _view the full documentation: https://www.trustedfirmware.org/docs/tf-a .. _trustedfirmware.org: http://www.trustedfirmware.org