diff --git a/docs/plat/arm/arm_fpga/index.rst b/docs/plat/arm/arm_fpga/index.rst new file mode 100644 index 0000000..5427c1d --- /dev/null +++ b/docs/plat/arm/arm_fpga/index.rst @@ -0,0 +1,97 @@ +Arm FPGA Platform +================= + +This platform supports FPGA images used internally in Arm Ltd., for +testing and bringup of new cores. With that focus, peripheral support is +minimal: there is no mass storage or display output, for instance. Also +this port ignores any power management features of the platform. +Some interconnect setup is done internally by the platform, so the TF-A code +just needs to setup UART and GIC. + +The FPGA platform requires to pass on a DTB for the non-secure payload +(mostly Linux), so we let TF-A use information from the DTB for dynamic +configuration: the UART and GIC base addresses are read from there. + +As a result this port is a fairly generic BL31-only port, which can serve +as a template for a minimal new (and possibly DT-based) platform port. + +The aim of this port is to support as many FPGA images as possible with +a single build. Image specific data must be described in the DTB or should +be auto-detected at runtime. + +As the number and topology layout of the CPU cores differs significantly +across the various images, this is detected at runtime by BL31. +The /cpus node in the DT will be added and filled accordingly, as long as +it does not exist already. + +Platform-specific build options +------------------------------- + +- ``SUPPORT_UNKNOWN_MPID`` : Boolean option to allow unknown MPIDR registers. + Normally TF-A panics if it encounters a MPID value not matched to its + internal list, but for new or experimental cores this creates a lot of + churn. With this option, the code will fall back to some basic CPU support + code (only architectural system registers, and no errata). + Default value of this flag is 1. + +- ``PRELOADED_BL33_BASE`` : Physical address of the BL33 non-secure payload. + It must have been loaded into DRAM already, typically this is done by + the script that also loads BL31 and the DTB. + It defaults to 0x80080000, which is the traditional load address for an + arm64 Linux kernel. + +- ``FPGA_PRELOADED_DTB_BASE`` : Physical address of the flattened device + tree blob (DTB). This DT will be used by TF-A for dynamic configuration, + so it must describe at least the UART and a GICv3 interrupt controller. + The DT gets amended by the code, to potentially add a command line and + fill the CPU topology nodes. It will also be passed on to BL33, by + putting its address into the x0 register before jumping to the entry + point (following the Linux kernel boot protocol). + It defaults to 0x80070000, which is 64KB before the BL33 load address. + +- ``FPGA_PRELOADED_CMD_LINE`` : Physical address of the command line to + put into the devicetree blob. Due to the lack of a proper bootloader, + a command line can be put somewhere into memory, so that BL31 will + detect it and copy it into the DTB passed on to BL33. + To avoid random garbage, there needs to be a "CMD:" signature before the + actual command line. + Defaults to 0x1000, which is normally in the "ROM" space of the typical + FPGA image (which can be written by the FPGA payload uploader, but is + read-only to the CPU). The FPGA payload tool should be given a text file + containing the desired command line, prefixed by the "CMD:" signature. + +Building the TF-A image +----------------------- + + .. code:: shell + + make PLAT=arm_fgpa DEBUG=1 + + This will use the default load addresses as described above. When those + addresses need to differ for a certain setup, they can be passed on the + make command line: + + .. code:: shell + + make PLAT=arm_fgpa DEBUG=1 PRELOADED_BL33_BASE=0x80200000 FPGA_PRELOADED_DTB_BASE=0x80180000 bl31 + +Running the TF-A image +---------------------- + +After building TF-A, the actual TF-A code will be located in ``bl31.bin`` in +the build directory. +Additionally there is a ``bl31.axf`` ELF file, which contains BL31, as well +as some simple ROM trampoline code (required by the Arm FPGA boot flow) and +a generic DTB to support most of the FPGA images. This can be simply handed +over to the FPGA payload uploader, which will take care of loading the +components at their respective load addresses. In addition to this file +you need at least a BL33 payload (typically a Linux kernel image), optionally +a Linux initrd image file and possibly a command line: + + .. code:: shell + + fpga-run ... -m bl31.axf -l auto -m Image -l 0x80080000 -m initrd.gz -l 0x84000000 -m cmdline.txt -l 0x1000 + +-------------- + +*Copyright (c) 2020, Arm Limited. All rights reserved.* diff --git a/docs/plat/arm/index.rst b/docs/plat/arm/index.rst index 1afe475..9c2fcb1 100644 --- a/docs/plat/arm/index.rst +++ b/docs/plat/arm/index.rst @@ -9,6 +9,7 @@ fvp/index fvp-ve/index tc0/index + arm_fpga/index arm-build-options This chapter holds documentation related to Arm's development platforms,