rpi3: add RPI3_RUNTIME_UART build option
Some OSes (e.g. Ubuntu 18.04 LTS on Raspberry Pi 3) may disable the
runtime UART in a manner that prevents the system from rebooting if
ATF tries to send runtime messages there.
Also, we don't want the firmware to share the UART with normal
world, as this can be a DoS attack vector into the secure world.
This patch fixes these 2 issues by introducing new build option
RPI3_RUNTIME_UART, that disables the runtime UART by default.
Fixes ARM-software/tf-issues#647
Signed-off-by: Pete Batard <pete@akeo.ie>
diff --git a/docs/plat/rpi3.rst b/docs/plat/rpi3.rst
index db47564..ea8171f 100644
--- a/docs/plat/rpi3.rst
+++ b/docs/plat/rpi3.rst
@@ -231,6 +231,10 @@
``RPI3_DIRECT_LINUX_BOOT=1``. This option allows to specify the location of a
DTB in memory.
+- ``RPI3_RUNTIME_UART``: Indicates whether the UART should be used at runtime
+ or disabled. ``-1`` (default) disables the runtime UART. Any other value
+ enables the default UART (currently UART1) for runtime messages.
+
- ``BL32``: This port can load and run OP-TEE. The OP-TEE image is optional.
Please use the code from `here <https://github.com/OP-TEE/optee_os>`__.
Build the Trusted Firmware with option ``BL32=tee-header_v2.bin