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pbatard and leiflindholm Platforms/RPi3: Add multiple embedded Device Tree selection
The Raspberry Pi 3 platform currently has 2 different models, each with a
different Device Tree. Rather than embedding a single one, and requiring
users to manually provide the other, this patch ensures that we now embed
both and and serve the relevant one at runtime.

This patch also adds support for the Raspberry Pi 4 in FdtDxe.

Signed-off-by: Pete Batard <pete@akeo.ie>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
Latest commit 7da906b Aug 16, 2019

Readme.md

Raspberry Pi Platform

Summary

This is a port of 64-bit Tiano Core UEFI firmware for the Raspberry Pi 3/3B+ platforms, based on Ard Bisheuvel's 64-bit and Microsoft's 32-bit implementations, as maintained by Andrei Warkentin.

This is meant as a generally useful 64-bit ATF + UEFI implementation for the Raspberry Pi 3/3B+ which should be good enough for most kind of UEFI development, as well as for running consummer Operating Systems in such as Linux or Windows.

Raspberry Pi is a trademark of the Raspberry Pi Foundation.

Status

This firmware, that has been validated to compile against the current edk2/edk2-platforms, should be able to boot Linux (Debian, Ubuntu, SUSE), NetBSD, FreeBSD as well as Windows 10 ARM64 (full GUI version).

It also provides support for ATF (Arm Trusted Platform).

HDMI and the mini-UART serial port can be used for output devices, with mirrored output. USB keyboards and the mini-UART serial port can be used as input.

The default for the firmware is to first attempt boot from SD then USB. The UEFI Shell can also be accessed by pressing F1. To change the boot order you can edit the preferences in the Boot Maintenance Manager menu.

For additional information about the tested systems and how to set them up, please see Systems.md.

Building

Build instructions from the top level edk2-platforms Readme.md apply.

Booting the firmware

  1. Format a uSD card as FAT32
  2. Copy the generated RPI_EFI.fd firmware onto the partition
  3. Download and copy the following files from https://github.com/raspberrypi/firmware/tree/master/boot
  • bootcode.bin
  • fixup.dat
  • start.elf
  1. Create a config.txt with the following content:
arm_control=0x200
enable_uart=1
armstub=RPI_EFI.fd
disable_commandline_tags=1
  1. Insert the uSD card and power up the Pi.

Note that if you have a model 3+ or a model 3 where you enabled USB boot through OTP (see here) you may also be able to boot from a FAT32 USB driver rather than uSD.

Notes

ARM Trusted Firmware (ATF)

The ATF binaries being used were compiled from the latest ATF source. No aleration to the official source have been applied.

For more details on the ATF compilation, see the Readme in the TrustedFirmware/ directory.

Custom Device Tree

The default Device Tree included in the firmware is the one for a Raspberry Pi 3 Model B (not B+). If you want to use a different Device Tree, to boot a Pi 3 Model B+ for instance (for which a DTB is also provided under DeviceTree/), you should copy the relevant .dtb into the root of the SD or USB, and then edit your config.txt so that it looks like:

(...)
disable_commandline_tags=2
device_tree_address=0x10000
device_tree_end=0x20000
device_tree=bcm2710-rpi-3-b-plus.dtb

Note: the address range must be [0x10000:0x20000]. dtoverlay and dtparam parameters are also supported when providing a Device Tree`.

Custom bootargs

This firmware will honor the command line passed by the GPU via cmdline.txt.

Note, that the ultimate contents of /chosen/bootargs are a combination of several pieces:

  • Original /chosen/bootargs if using the internal DTB. Seems to be completely discarded by GPU when booting with a custom device tree.
  • GPU-passed hardware configuration. This one is always present.
  • Additional boot options passed via cmdline.txt.

Limitations

HDMI

The UEFI HDMI video support relies on the VC (that's the GPU) firmware to correctly detect and configure the attached screen. Some screens are slow, and this detection may not occur fast enough. Finally, you may wish to be able to boot your Pi headless, yet be able to attach a display to it later for debugging.

To accommodate these issues, the following extra lines are recommended for your config.txt:

  • hdmi_force_hotplug=1 to allow plugging in video after system is booted.
  • hdmi_group=1 and hdmi_mode=4 to force a specific mode, both to accommodate late-plugged screens or buggy/slow screens. See official documentation to make sense of these parameters (example above sets up 720p 60Hz).

NVRAM

The Raspberry Pi has no NVRAM.

NVRAM is emulated, with the non-volatile store backed by the UEFI image itself. This means that any changes made in UEFI proper are persisted, but changes made from a High Level Operating System (HLOS) aren't.

RTC

The Rasberry Pi has no RTC.

An RtcEpochSeconds NVRAM variable is used to store the boot time. This should allow you to set whatever date/time you want using the Shell date and time commands. While in UEFI or HLOS, the time will tick forward. RtcEpochSeconds is not updated on reboots.

uSD

UEFI supports both the Arasan SDHCI and the Broadcom SDHost controllers to access the uSD slot. You can use either. The other controller gets routed to the SDIO card. The choice made will impact ACPI OSes booted (e.g. Windows 10). Arasan, being an SDIO controller, is usually used with the WiFi adapter where available. SDHost cannot be used with SDIO. In UEFI setup screen:

  • go to Device Manager
  • go to Raspberry Pi Configuration
  • go to Chipset
  • configure Boot uSD Routing

Known issues:

  • Arasan HS/4bit support is missing.
  • No 8 bit mode support for (e)MMC (irrelevant for the Pi 3).
  • Hacky (e)MMC support (no HS).
  • No card removal/replacement detection, tons of timeouts and slow down during boot without an uSD card present.

USB

  • USB1 BBB mass storage devices untested (USB2 and USB3 devices are fine).
  • USB1 CBI mass storage devices don't work (e.g. HP FD-05PUB floppy).

ACPI

Both Arasan and SDHost SD controllers are exposed.

Note that the ACPI tables were derived or copied from the MS-IoT one. This means that they are not truly ACPI compliant, especially when it comes to their descriptors, and therefore not suitable for Linux environments. If you want to use a Linux HLOS, you are encouraged to install a kernel that relies on Device Tree rather than ACPI.

Missing Functionality

  • Network booting via onboard NIC.
  • Ability to switch UART use to PL011.
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