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Raspberry Pi 4 Platform

Summary

This is a port of 64-bit Tiano Core UEFI firmware for the Raspberry Pi 4B platform.

This is intended to be useful 64-bit TF-A + UEFI implementation for the Raspberry Pi variants based on the BCM2711 SoC, which should be good enough for most kind of UEFI development, as well running consumer Operating Systems.

Raspberry Pi is a trademark of the Raspberry Pi Foundation.

Hardware Supported

The RPi4 target supports Pi revisions based on the BCM2711 SoC:

  • Raspberry Pi 4B

Please see the RPi3 target for the BCM2837-based variants, such as the Raspberry Pi 3B.

Status

This firmware is still in development stage, meaning that it comes with the following major limitations:

  • xHCI USB may only work in pre-OS phase due to nonstandard DMA constraints. For 4 GB models running Linux, limiting the RAM to 3 GB should help. The 3 GB limitation is currently enabled by default in the user settings.
  • Device Tree boot of OSes such as Linux may not work at all. For this reason, the provision of a Device Tree is disabled by default in the user settings, in order to enforce ACPI boot.
  • Serial I/O from the OS may not work due to CPU throttling affecting the miniUART baudrate. This can be worked around by using the PL011 UART through the device tree overlays.

Building

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

Booting the firmware

  1. Format a uSD card as FAT16 or 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
  • bcm2711-rpi-4-b.dtb
  • fixup4.dat
  • start4.elf
  • overlays/miniuart-bt.dbto or overlays/disable-bt.dtbo (Optional)
  1. Create a config.txt with the following content: 
    arm_64bit=1
enable_uart=1
enable_gic=1
armstub=RPI_EFI.fd
disable_commandline_tags=2
device_tree_address=0x3e0000
device_tree_end=0x400000
    Additionally, if you want to use PL011 instead of the miniUART, you can add the lines: 
    dtoverlay=miniuart-bt
    Note: doing so requires miniuart-bt.dbto to have been copied into an overlays/ directory on the uSD card. Alternatively, you may use disable-bt instead of miniuart-bt if you don't require Bluetooth.
  2. Insert the uSD card and power up the Pi.

Notes

ARM Trusted Firmware (TF-A)

The TF-A binary was compiled from the latest TF-A release. No aleration to the official source has been applied.

For more details on the TF-A compilation, see the relevant Readme in the TrustedFirmware/ directory from edk2-non-osi.

Device Tree

By default, UEFI will use the device tree loaded by the VideoCore firmware. This depends on the model/variant, and relies on the presence on specific files on your boot media. E.g.:

  • bcm2711-rpi-4-b.dtb (for Pi 4B)

You can override the DTB and provide a custom one. 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=0x3e0000
device_tree_end=0x400000
device_tree=your_fdt_file.dtb

Note: the address range must be [0x3e0000:0x400000]. dtoverlay and dtparam parameters are also supported.

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:

  • GPU-passed hardware configuration.
  • Additional boot options passed via cmdline.txt.

Limitations

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 within an Operating System 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.

USB

This UEFI supports both the USB3 xHCI ports (front ports), and the Pi 3-style DesignWare USB2 controller via the Type-C port (host only).

The following only apply to the Type-C port:

  • USB1 BBB mass storage devices untested (USB2 and USB3 devices are fine).
  • Some USB1 CBI (e.g. UFI floppy) mass storage devices may not work.

ACPI

OS support for ACPI description of Pi-specific devices is still in development. Not all functionality may be available.

Missing Functionality

  • Network booting via onboard NIC.
  • SPCR hardcodes type to PL011, and thus will not expose correct (miniUART) UART if DT overlays to switch UART are used on Pi 4B.

Configuration Settings

The Raspberry Pi UEFI configuration settings can be viewed and changed using both the UI configuration menu (under Device Manager -> Raspberry Pi Configuration), as well as the UEFI Shell. To configure using the UEFI Shell, use setvar command to read/write the UEFI variables with GUID = CD7CC258-31DB-22E6-9F22-63B0B8EED6B5.

The syntax to read a setting is:

setvar <NAME> -guid CD7CC258-31DB-22E6-9F22-63B0B8EED6B5

The syntax to write a setting is:

setvar <NAME> -guid CD7CC258-31DB-22E6-9F22-63B0B8EED6B5 -bs -rt -nv =<VALUE>

For string-type settings (e.g. Asset Tag), the syntax to write is:

setvar <NAME> -guid CD7CC258-31DB-22E6-9F22-63B0B8EED6B5 -bs -rt -nv =L"<VALUE>" =0x0000
UEFI Setting NAME VALUE
CPU Configuration
CPU Clock CpuClock Low = 0x00000000
Default = 0x00000001 (default)
Max = 0x00000002
Custom = 0x00000003
CPU Clock Rate (MHz) CustomCpuClock Hex numeric value, 4-bytes
(e.g. 0x000005DC for 1500 MHz)
Display Configuration
Virtual 640x480 DisplayEnableScaledVModes Checked = Bit 1 set (i.e. <DisplayEnableScaledVModes> | 0x02)
Virtual 800x600 DisplayEnableScaledVModes Checked = Bit 0 set (i.e. <DisplayEnableScaledVModes> | 0x01)
Virtual 1024x768 DisplayEnableScaledVModes Checked = Bit 2 set (i.e. <DisplayEnableScaledVModes> | 0x04)
Virtual 720p DisplayEnableScaledVModes Checked = Bit 3 set (i.e. <DisplayEnableScaledVModes> | 0x08)
Virtual 1080p DisplayEnableScaledVModes Checked = Bit 4 set (i.e. <DisplayEnableScaledVModes> | 0x10)
Native resolution DisplayEnableScaledVModes Checked = Bit 5 set (i.e. <DisplayEnableScaledVModes> | 0x20) (default)
Screenshot support DisplayEnableSShot Control-Alt-F12 = 0x00000001 (default)
Not Enabled = 0x00000000
Advanced Configuration
Limit RAM to 3 GB RamLimitTo3GB Disable = 0x00000000
Enabled= 0x00000001 (default)
System Table Selection SystemTableMode ACPI = 0x00000000 (default)
ACPI + Devicetree = 0x00000001
Devicetree = 0x00000002
Asset Tag AssetTag String, 32 characters or less (e.g. L"ABCD123")
(default L"")
SD/MMC Configuration
uSD/eMMC Routing SdIsArasan Arasan SDHC = 0x00000001
eMMC2 SDHCI = 0x00000000 (default)
Multi-Block Support MmcDisableMulti Multi-block transfers = 0x00000000 (default)
Single block transfers = 0x00000001
uSD Max Bus Width MmcForce1Bit 4-bit Mode = 0x00000000 (default)
1-bit Mode = 0x00000001
uSD Force Default Speed MmcForceDefaultSpeed Allow High Speed = 0x00000000 (default)
Force Default Speed = 0x00000001
SD Default Speed (MHz) MmcSdDefaultSpeedMHz Hex numeric value, 4-bytes (e.g. 0x00000019 for 25 MHz)
(default 25)
SD High Speed (MHz) MmcSdHighSpeedMHz Hex numeric value, 4-bytes (e.g. 0x00000032 for 50 MHz)
(default 50)
Debugging Configuration
JTAG Routing DebugEnableJTAG Enable JTAG via GPIO = 0x00000001
Disable JTAG= 0x00000000 (default)

Examples:

  • To read the 'System Table Selection' setting :
setvar SystemTableMode -guid CD7CC258-31DB-22E6-9F22-63B0B8EED6B5
  • To change the 'System Table Selection' setting to 'Devicetree' :
setvar SystemTableMode -guid CD7CC258-31DB-22E6-9F22-63B0B8EED6B5 -bs -rt -nv =0x00000002
  • To read the 'Limit RAM to 3 GB' setting:
setvar RamLimitTo3GB -guid CD7CC258-31DB-22E6-9F22-63B0B8EED6B5
  • To change the 'Limit RAM to 3 GB' setting to 'Disabled':
setvar RamLimitTo3GB -guid CD7CC258-31DB-22E6-9F22-63B0B8EED6B5 -bs -rt -nv =0x00000000
  • To change the Asset Tag to the string "ASSET-TAG-123" :
setvar AssetTag -guid CD7CC258-31DB-22E6-9F22-63B0B8EED6B5 -bs -rt -nv =L"ASSET-TAG-123" =0x0000