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The Raspberry Pi 4 is a single board computer with four Cortex-A72
cores. From a TF-A perspective it is quite similar to the Raspberry Pi
3, although it comes with more memory (up to 4GB) and has a GIC.

This initial port though differs quite a lot from the existing rpi3
platform port, mainly due to taking a much simpler and more robust
approach to loading the non-secure payload:
The GPU firmware of the SoC, which is responsible for initial platform
setup (including DRAM initialisation), already loads the kernel, device
tree and the "armstub" into DRAM. We take advantage of this, by placing
just a BL31 component into the armstub8.bin component, which will be
executed first, in AArch64 EL3.
The non-secure payload can be a kernel or a boot loader (U-Boot or
EDK-2), disguised as the "kernel" image and loaded by the GPU firmware.

So this is just a BL31-only port, which directly drops into EL2
and executes whatever has been loaded as the "kernel" image, handing
over the DTB address in x0.

Change-Id: I636f4d1f661821566ad9e341d69ba36f6bbfb546
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

To initialise the arch timer configuration and some clock prescaler, we
need to do two MMIO access *once*, early during boot.

As tempting as it may sound, plat_reset_handler() is not the right place
to do this, as it will be called on every CPU coming up, both for
secondary cores as well as during warmboots. So this access will be done
multiple times, and even during a rich OS' runtime. Whether doing so anyway
is actually harmful is hard to say, but we should definitely avoid this if
possible.

Move the initialisation of these registers to C code in
bl1_early_platform_setup(), where it will still be executed early enough
(before enabling the console), but only once during the whole boot
process.

Change-Id: I081c41a5476d424411411488ff8f633e87d3bcc5
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

With the incoming support for the Raspberry Pi 4 boards, one directory
to serve both versions will not end up well.

Create an additional layer by inserting a "rpi" directory betweeen /plat
and rpi3, so that we can more easily share or separate files between the
two later.

Change-Id: I75adbb054fe7902f34db0fd5e579a55612dd8a5f
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

FIQs shouldn't be used at all as long as the interrupt routing doesn't
support them properly.

Change-Id: Ib1db7b523a62de2035d41197bc791048337cf791
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Switch to the new console APIs enabled by setting MULTI_CONSOLE_API=1.

The crash console doesn't use this API, it uses internally the core
functions of the 16550 console.

`bl31_plat_runtime_setup` is no longer needed. When this platform port
was introduced, that function used to disable the console. It was needed
to override that behaviour. The new behaviour is to switch to the
runtime console. The console is registered for all scopes (boot, crash
and runtime) in `rpi3_console_init` so it is not needed to override the
default behaviour anymore.

Update documentation.

Change-Id: If2ee8f91044216183b7ef142e5c05ad6220ae92f
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

This port can be compiled to boot an AArch64 or AArch32 payload with the
build option `RPI3_BL33_AARCH32`.

Note: This is not a secure port of the Trusted Firmware. This port is
only meant to be a reference implementation to experiment with an
inexpensive board in real hardware.

Change-Id: Ide58114299289bf765ef1366199eb05c46f81903
Co-authored-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>