0ee80f35a2
Sometimes when changing UART clock from TBG to XTAL, UART HW enters into some broken state. It does not transit characters from TX FIFO anymore and TX FIFO stays always empty. TX FIFO reset does not recover UART HW from this broken state. Experiments show that external reset can fix UART HW from this broken state. TF-A fatal error handler calls console_a3700_core_init() function to initialize UART HW. This handler may be called anytime during CPU runtime, also when kernel is running. U-Boot or Linux kernel may change UART clock to TBG to achieve higher baudrates. During initialization, console_a3700_core_init() resets UART configuration to default settings, which means that it also changes UART clock from TBG to XTAL. Do an external reset of UART via North Bridge Peripheral reset register to prevent this UART hangup. Signed-off-by: Pali Rohár <pali@kernel.org> Change-Id: I8990bce24d1a6fd8ccc47a2cd0a5ff932fcfcf14 |
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readme.rst
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.