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arm-bsp/docs: Update fvp-baser-aemv8r64 docs

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Document U-Boot addition, add new architecture section and update the
change log.

Issue-Id: SCM-3871
Signed-off-by: Peter Hoyes <Peter.Hoyes@arm.com>
Change-Id: Ie0e1ff35ade634f2b523c14bb058c9d775802632
Signed-off-by: Jon Mason <jon.mason@arm.com>
This commit is contained in:
Peter Hoyes
2022-02-17 16:09:59 +00:00
committed by Jon Mason
parent 0519fdf444
commit 692ca08b1d
1 changed files with 63 additions and 2 deletions
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meta-arm-bsp/documentation/fvp-baser-aemv8r64.md
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@@ -28,12 +28,65 @@ where either a standard or Real-Time Linux kernel (PREEMPT\_RT) can be built
and run:
- boot-wrapper-aarch64: provides PSCI support
- Linux kernel: linux-yocto-5.14
- Linux kernel with PREEMPT\_RT support: linux-yocto-rt-5.14
- U-Boot: v2022.01 - provides UEFI services
- Linux kernel: linux-yocto-5.15
- Linux kernel with PREEMPT\_RT support: linux-yocto-rt-5.15
Note that the Real-Time Linux kernel (PREEMPT\_RT) does not use the real-time
architectural extensions of the Armv8-R feature set.
High-Level Architecture
-----------------------
The diagram below shows the current boot flow:
+---------------------------------------------------------------+
| Linux kernel |
+---------------------------------------------------------------+
/|\ /|\
| |
| UEFI services |
| PSCI services |
\|/ |
+----------------+ | S-EL1
----| U-Boot |------------------------------|-----------
+----------------+ | S-EL2
/|\ |
| |
| |
| |
+--------------------------------------------------\|/----------+
| +----------------+ +----------------+ |
| boot-wrapper-aarch64 | Device tree | | PSCI handler | |
| +----------------+ +----------------+ |
+---------------------------------------------------------------+
The firmware binary (generated as `linux-system.axf`) includes
boot-wrapper-aarch64, the flattened device tree and U-Boot. U-Boot is configured
to automatically detect a virtio block device and boot the UEFI payload at the
path `/efi/boot/bootaa64.efi`. Using the standard build, the first partition
contains a Grub image at this path, which boots the Linux kernel at `/Image` on
the same partition. The second partition of the image contains the Linux root
file system.
There is no EL3 or non-secure world in the Armv8-R AArch64 architecture, so the
reset vector starts boot-wrapper-aarch64 at S-EL2. Boot-wrapper-aarch64 is
compiled with the `--enable-keep-el` flag, which causes it to boot U-Boot at
S-EL2 too. U-Boot is compiled with the `CONFIG_ARMV8_SWITCH_TO_EL1` flag, which
causes it to switch to S-EL1 before booting Linux.
The bundled device tree is passed to U-Boot via register x0. U-Boot passes the
same device tree to Linux via the UEFI system table.
Power state management is provided by PSCI services in boot-wrapper-aarch64.
Linux accesses the PSCI handler via HVC calls to S-EL2. U-Boot has been patched
to prevent it from overriding the exception vector at S-EL2. The PSCI handler
memory region is added to a `/memreserve/` node in the device tree.
Please note that the final firmware architecture for the fvp-baser-aemv8r64 is
not yet stabilized. The patches in this layer are provided for development and
evaluation purposes only, and should not be used in production firmware.
Quick start: Howto Build and Run
--------------------------------
@@ -167,6 +220,14 @@ Known Issues and Limitations
Change Log
----------
- Added U-Boot v2022.01 for UEFI support.
- Updated Linux kernel version from 5.14 to 5.15 for both standard and
Real-Time (PREEMPT\_RT) builds.
- Updated boot-wrapper-aarch64 revision and added support for booting U-Boot.
- Included boot-wrapper-aarch64 PSCI services in /memreserve/ region.
- Fixed the counter frequency initialization in boot-wrapper-aarch64.
- Configured the FVP to use the default RAM size of 4 Gb
- Fixed PL011 and SP805 register sizes in the device tree.
- Added virtio_net User Networking mode by default and removed instructions
about tap networking setup.
- Updated Linux kernel version from 5.10 to 5.14 for both standard and