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Diffstat (limited to 'doc/arch')
| -rw-r--r-- | doc/arch/arm64.rst | 59 | ||||
| -rw-r--r-- | doc/arch/index.rst | 1 |
2 files changed, 60 insertions, 0 deletions
diff --git a/doc/arch/arm64.rst b/doc/arch/arm64.rst new file mode 100644 index 00000000000..80498f6f6b8 --- /dev/null +++ b/doc/arch/arm64.rst @@ -0,0 +1,59 @@ +.. SPDX-License-Identifier: GPL-2.0+ + +ARM64 +===== + +Summary +------- +The initial arm64 U-Boot port was developed before hardware was available, +so the first supported platforms were the Foundation and Fast Model for ARMv8. +These days U-Boot runs on a variety of 64-bit capable ARM hardware, from +embedded development boards to servers. + +Notes +----- + +1. U-Boot can run at any exception level it is entered in, it is + recommened to enter it in EL3 if U-Boot takes some responsibilities of a + classical firmware (like initial hardware setup, CPU errata workarounds + or SMP bringup). U-Boot can be entered in EL2 when its main purpose is + that of a boot loader. It can drop to lower exception levels before + entering the OS. + +2. U-Boot for arm64 is compiled with AArch64-gcc. AArch64-gcc + use rela relocation format, a tool(tools/relocate-rela) by Scott Wood + is used to encode the initial addend of rela to u-boot.bin. After running, + the U-Boot will be relocated to destination again. + +3. Earlier Linux kernel versions required the FDT to be placed at a + 2 MB boundary and within the same 512 MB section as the kernel image, + resulting in fdt_high to be defined specially. + Since kernel version 4.2 Linux is more relaxed about the DT location, so it + can be placed anywhere in memory. + Please reference linux/Documentation/arm64/booting.txt for detail. + +4. Spin-table is used to wake up secondary processors. One location + (or per processor location) is defined to hold the kernel entry point + for secondary processors. It must be ensured that the location is + accessible and zero immediately after secondary processor + enter slave_cpu branch execution in start.S. The location address + is encoded in cpu node of DTS. Linux kernel store the entry point + of secondary processors to it and send event to wakeup secondary + processors. + Please reference linux/Documentation/arm64/booting.txt for detail. + +5. Generic board is supported. + +6. CONFIG_ARM64 instead of CONFIG_ARMV8 is used to distinguish aarch64 and + aarch32 specific codes. + + +Contributors +------------ + * Tom Rini <trini@ti.com> + * Scott Wood <scottwood@freescale.com> + * York Sun <yorksun@freescale.com> + * Simon Glass <sjg@chromium.org> + * Sharma Bhupesh <bhupesh.sharma@freescale.com> + * Rob Herring <robherring2@gmail.com> + * Sergey Temerkhanov <s.temerkhanov@gmail.com> diff --git a/doc/arch/index.rst b/doc/arch/index.rst index f24b4a3882c..360b5d92826 100644 --- a/doc/arch/index.rst +++ b/doc/arch/index.rst @@ -6,5 +6,6 @@ Architecture-specific doc .. toctree:: :maxdepth: 2 + arm64 mips x86 |