rpi4: Add stdout-path to device tree ...

Some device tree users like to find a pointer to the standard serial
console in the device tree, in the "stdout-path" property of the /chosen
node.

Add the location of the Mini UART in that property, so that DT users are
happy, for instance Linux' earlycon detection.

Change-Id: I178e55016e5640de5ab0bc6e061944bd3583ea96
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

rpi4: Add GIC maintenance interrupt to GIC DT node ...

For being able to use the virtualisation support the GIC offers, we need
to know the interrupt number of the maintenance interrupt. This
information is missing from the official RPi4 device tree.

Use libfdt to add the "interrupts" property to the GIC node, which
allows hypervisors like KVM or Xen to be able to use the GIC's help on
virtualising interrupts.

Change-Id: Iab84f0885a5bf29fb84ca8f385e8a39d27700c75
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

rpi4: Cleanup memory regions, move pens to first page ...

Now that we have the SMP pens in the first page of DRAM, we can get rid
of all the fancy RPi3 memory regions that our RPi4 port does not really
need. This avoids using up memory all over the place, restricting ATF
to just run in the first 512KB of DRAM.

Remove the now unused regions. This also moves the SMP pens into our
first memory page (holding the firmware magic), where the original
firmware put them, but where there is also enough space for them.

Since the pens will require code execution privileges, we amend the
memory attributes used for that page to include write and execution
rights.

Change-Id: I131633abeb4a4d7b9057e737b9b0d163b73e47c6
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

rpi4: Reserve resident BL31 region from non-secure world ...

The GPU firmware loads the armstub8.bin (BL31) image at address 0, the
beginning of DRAM. As this holds the resident PSCI code and the SMP
pens, the non-secure world should better know about this, to avoid
accessing memory owned by TF-A. This is particularly criticial as the
Raspberry Pi 4 does not feature a secure memory controller, so
overwriting code is a very real danger.

Use the newly introduced function to add a node into reserved-memory
node, where non-secure world can check for regions to be excluded from
its mappings.

Reserve the first 512KB of memory for now. We can refine this later if
need be.

Change-Id: I00e55e70c5c02615320d79ff35bc32b805d30770
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

rpi4: Amend DTB to advertise PSCI ...

The device tree provided by the official Raspberry Pi firmware uses
spin tables for SMP bringup.

One of the benefit of having TF-A is that it provides PSCI services, so
let's rewrite the DTB to advertise PSCI instead of spin tables.
This uses the (newly exported) routine from the QEMU platform port.

Change-Id: Ifddcb14041ca253a333f8c2d5e97a42db152470c
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

rpi4: Determine BL33 entry point at runtime ...

Now that we have the armstub magic value in place, the GPU firmware will
write the kernel load address (and DTB address) into our special page,
so we can always easily access the actual location without hardcoding
any addresses into the BL31 image.

Make the compile-time defined PRELOADED_BL33_BASE macro optional, and
read the BL33 entry point from the magic location, if the macro was not
defined. We do the same for the DTB address.

This also splits the currently "common" definition of
plat_get_ns_image_entrypoint() to be separate between RPi3 and RPi4.

Change-Id: I6f26c0adc6fce2df47786b271c490928b4529abb
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

rpi4: Accommodate "armstub8.bin" header at the beginning of BL31 image ...

The Raspberry Pi GPU firmware checks for a magic value at offset 240
(0xf0) of the armstub8.bin image it loads. If that value matches,
it writes the kernel load address and the DTB address into subsequent
memory locations.
We can use these addresses to avoid hardcoding these values into the BL31
image, to make it more flexible and a drop-in replacement for the
official armstub8.bin.

Reserving just 16 bytes at offset 240 of the final image file is not easily
possible, though, as this location is in the middle of the generic BL31
entry point code.
However we can prepend an extra section before the actual BL31 image, to
contain the magic and addresses. This needs to be 4KB, because the
actual BL31 entry point needs to be page aligned.

Use the platform linker script hook that the generic code provides, to
add an almost empty 4KB code block before the entry point code. The very
first word contains a branch instruction to jump over this page, into
the actual entry code.
This also gives us plenty of room for the SMP pens later.

Change-Id: I38caa5e7195fa39cbef8600933a03d86f09263d6
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

Add basic support for Raspberry Pi 4 ...

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>