NetBSD Wiki/ports/evbarm/ NetBSD/evbarm on Raspberry Pi

This page describes the NetBSD/evbarm port on Raspberry Pi hardware. All board variants earlier than the RPI4 are believed supported, and specific boards known to work are listed. We use e.g. "RPI2" to refer to "Raspberry Pi 2" to save precious bytes on this page.

Initial Raspberry Pi support was introduced in NetBSD 6.0. NetBSD 7.0 added complete support for the board, along with introducing support for the quad-core Raspberry Pi 2 board. Raspberry Pi 3 support was added for NetBSD 8. NetBSD 9 supports aarch64, meaning using the newer processors in 64-bit mode.

raspberrypi.jpg

  1. What works
    1. NetBSD 8
    2. NetBSD 9
    3. NetBSD current
    4. What needs documenting if it works
    5. What needs work
  2. CPU types
  3. Installation
    1. Using standard images
    2. SD card structure
    3. Building yourself
    4. Console approaches
    5. Installation via ebijun's image
    6. Boot Process
    7. Configuring 802.11
    8. Links
  4. Maintaining a system
    1. Booting single user
    2. vcgencmd
    3. Updating the kernel
    4. Updating dtb files
    5. Updating the firmware
    6. Booting
    7. Split-mode aarch32/aarch64
  5. X11 and GPU
    1. Video playback
    2. OpenGL ES
    3. Quake 3
    4. RetroArch / Libretro
  6. Developer notes
    1. Updating the firmware version in the NetBSD sources
    2. Testing with anita and qemu
  7. Misc notes
    1. Power supply needed (or: why there is a little rainbow square in the top-right corner?)
    2. Xenon death flash (Raspberry Pi 2 is camera-shy)

(Raspberry Pi image by Christopher Lee used under CC-By-2.0 license)

What works

NetBSD 8

NetBSD 9

NetBSD current

What needs documenting if it works

What needs work

CPU types

Note that one can run a build of earmv6hf on the 2 and 3. There will still be a kernel7, built to use the 2/3 hardware, but with the armv6 instruction set. In theory the code compiled for earmv7hf will be faster, but anecdotal experience is that it doesn't matter that much. Builds of NetBSD for earlier revisions of ARM are unsupported.

Installation

Using standard images

The simplest way is to download the appropriate SD card image from the NetBSD mirrors:

Decompress it and write it to the SD card:

$ gunzip armv7.img.gz
$ dd if=armv7.img of=/dev/rld0d conv=sync bs=1m progress=1

If you're not using NetBSD, your operating system's dd command's arguments may vary. On Windows, try Rawrite32.

The Raspberry Pi 4 requires the UEFI firmware. Write the UEFI firmware to the SD card, and then insert an USB drive with the standard NetBSD arm64.img written to it. The Pi will then boot from USB.

The Raspberry Pi 3 can also boot NetBSD from UEFI firmware, but the installation process is currently more complicated. However, there are some advantages, so you might want to try anyway.

SD card structure

The Raspberry Pi looks for firmware and kernel.img on the first FAT32 MBR partition of the uSD card. A separate kernel (kernel7.img) is used on RPI2 and RPI3. The NetBSD kernel will then find NetBSD MBR partition and within that the root disklabel partition, and use that FFS partition as the root filesystem.

A 2 GB card is the smallest workable size that the installation image will fit on. After the first boot, the system resizes the NetBSD root partition to fill the card. Note that swap is after /boot and before /, and not contained in the NetBSD fdisk partition. However, if you don't try to change the partition structure, this should not cause you any trouble.

Note that SD cards generally have limited write tolerance, so you may wish to disable atime updates via the noatime option, as is done by the default installation.

Building yourself

Getting sources and building a release with build.sh is not special for evbarm. However, the evbarm port has a very large number of CPU types, compared to i386 and amd64 which have one each. The standard approach is to use -m to define MACHINE and -a to define MACHINE_ARCH. build.sh supports aliases that can be passed as a MACHINE value, but denote both MACHINE and a MACHINE_ARCH. The third line uses an alias and is equal to the second, for RPI2/3. Note that the aliases start with "evb" while the MACHINE_ARCH values do not, and that aliases have "-el" or "-eb", while the MACHINE_ARCH values have no suffix or "eb".

Consider setting RELEASEMACHINEDIR if you wish to build multiple MACHINE_ARCH values for a MACHINE; see build.sh. Use something like "evbarm-earmv7hf", so that 1) earvm6 and earmv7 don't collide and 2) anita will recognize it as a type of evbarm.

Console approaches

The standard approach is to use a USB keyboard and an HDMI monitor for installation.

Serial Console

By default the rpi.img is set to use the HDMI output. If you wish to use a serial console, mount the FAT32 partition on another system and edit cmdline.txt and remove '"console=fb"'.

Enabling ssh for installation without any console

If you want to enable ssh with the standard image, so that you can log in over the net without either a serial or HDMI console, you can edit the configuration of a uSD card before booting. On another computer, mount the ffs partition, place /root/.ssh/authorized_keys, uncomment PermitRootLogin in /etc/ssh/sshd_config, and comment out the rc_configure=NO in /etc/rc.conf. Besides having to find the IP address (e.g. from DHCP server logs), you will have to wait for the partition resizing and reboot.

Installation with sshramdisk image

build.sh (and hence the FTP site) also creates an image 'rpi_inst.img.gz' specifically for installation without HDMI or a serial console, when built for earmv6hf. Note that this image is much smaller and that you will need to fetch the sets over the network. To use this method, write that image to a uSD card as above, and then:

The rpi_inst.img.gz image will only work for systems that use earmv6hf kernels (so not RPI2/3). See this port-arm message for details.

Installation via ebijun's image

As an alternative to the standard installation images, Jun Ebihara provides an install image for Raspberry Pi that includes packages. It is based on NetBSD-current and is built for earmv6hf, and thus will work on Raspberry Pi 1, 2 and 3. This image is typically updated every few weeks.

Boot Process

https://www.raspberrypi.org/documentation/configuration/config-txt/boot.md

DTBs

Note that generally, a single dtb is loaded. On NetBSD 9, the dtb file for the system is loaded by the bootloader (in flash).

The RPI bootloader looks for a magic string in a trailer after the kernel to determine if it should use DTB support (the new normal) or something called ATAG (apparently the old way). See upstream commit introducing DTB trailer for more information.

Kernel format variants

In netbsd-8, only the ELF and bin variants of RPI2 are built. The bin version is used.

In netbsd-9 releasedir/binary/kernels, the following 4 versions of GENERIC are produced. (This might be the same in current.)

netbsd-GENERIC.gz

This is regular ELF and not used on RPI.

netbsd-GENERIC.bin.gz

It is unclear why this file exists on 9. It seems to be like img, but without the trailer for DTB; this makes sense for 8.

netbsd-GENERIC.img.gz

On NetBSD >=9, the kernel with the .img suffix has the trailer to cause the bootloader to load DTB files.

netbsd-GENERIC.ub.gz

This is for u-boot and not used on RPI.

Configuring 802.11

After installation, the Ethernet will function as on any other NetBSD system; simply enable dhcpcd or configure a static address. USB WiFi devices will also function as on any other NetBSD system; in addition to dhcpcd or static, configure and enable wpa_supplicant.

Note that the built-in WiFi in the RPI3 is not yet supported. USB WiFi interfaces (that work on NetBSD in general) should all work. In particular, the following are known to work:

Links

The following pages have been published by NetBSD community members. (Note that some of them are old.)

Maintaining a system

Booting single user

\todo Describe how to boot single user via the serial console and via the fb console.

vcgencmd

The program vcgencmd, referenced in the boot section, can be found in pkgsrc/misc/raspberrypi-userland.

Updating the kernel

\todo Explain if updating firmware is necessary when e.g. moving from 8 to 9, or 9 to current.

Updating dtb files

NetBSD 8

On NetBSD 8, dtb files are not used.

NetBSD 9

Build a release. gunzip the armv7.img, vnconfig it, and mount the MSDOS partition (e) e.g. on /mnt. Copy the dtb files from /mnt/foo.dtb to /boot, and from /mnt/dtb/foo.dtb to /boot/dtb.

It seems that some systems, including RPI, require dtb files in /boot, and some expect them in /boot/dtb.

NetBSD current

When updating, ensure that /boot is mounted and that you unpack the dtb set.

Updating the firmware

It is highly likely that running NetBSD from a given branch X with firmware from a branch Y < X will not go well. It is unclear if firmware from a branch Y > X will work. It is standard practice to use firmware from the right branch.

A section below describes the process of updating NetBSD's copy of the firmware from upstream, with testing, by NetBSD developers. This section is about updating a system's firmware from the firmware in a version of NetBSD.

(Updating the firmware is harder than it should be.) Build a release. gunzip the armv7.img, vnconfig it, and mount the MSDOS partition (e) e.g. on /mnt. Copy files from that to /boot that have changes, carefully.

Relevant files include bootcode.bin, start.elf and start_cd.elf.

Compare cmdline.txt, but beware that just overwriting it will lose customizations like using the serial console instead of the framebuffer.

\todo Explain where the firmware is in the source tree, and note that it is not in the installed system image (such as /usr/mdec). Explain how to update a system (presumably /boot) from either an installed system's new firmware files, or the source tree. Explain any particular cautions.

\todo Explain if using updated firmware from one branch (e.g. netbsd-current) on a system using a different branch (e.g. netbsd-8) is safe. Explain if pullups are done to release branches with new firmware.

Booting

The device boots by finding a file "bootcode.bin". The primary location is a FAT32 partition on the uSD card, and an additional location is on a USB drive. See the upstream documentation on booting and read all the subpages.

The standard approach is to use a uSD card, with a fdisk partition table containing a FAT32 partition marked active, and a NetBSD partition. The NetBSD partition will then contain a disklabel, pointing to an FFS partition (a), a swap partition (b) and the FAT32 boot partition mounted as /boot (e). The file /boot/cmdline.txt has a line to set the root partition.

One wrinkle in the standard approach is that the disk layout is "boot swap /", but the NetBSD fdisk partition starts at the location of /, so the swap partition is not within the NetBSD fdisk partition. The / partition can hold a disklabel, while swap cannot. It is normal to have swap after / (and thus within the fdisk partition), but the arrangement used permits growing / on first boot, for the typical case where a larger uSD is used, compared to the minimum image size.

An alternate approach is to have the boot FAT32 partition as above, but to have the entire system including root on an external disk. This is configured by changing root=ld0a to root=sd0a or root=dk0 (depending on disklabel/GPT). Besides greater space, part of the point is to avoid writing to the uSD card.

A third approach, workable on the Pi 3 only, is to configure USB host booting (already enabled on the 3+; see the upstream documentation) and have the boot partition also on the external device. In this case the external device must have an MBR because the hardware's first-stage boot does not have GPT support. In theory the procedure to program USB host boot mode will function on a NetBSD system because the programming is done by bootcode.bin. \todo Confirm that putting program_usb_boot_mode=1 in config.txt and booting works to program the OTP bit. Confirm that one can then boot NetBSD from external USB.

There is no well-defined USB enumeration order, so the preferred approach if one has multiple USB mass storage devices is to use named wedges in both fstab and cmdline.txt.

Split-mode aarch32/aarch64

\todo Verify this, and add any necessary cautions about boot code.

The aarch64 kernel can run aarch32 binaries, so one can boot an aarch64 kernel on a system with an aarch32 userland.

X11 and GPU

Video acceleration currently only works with 32-bit (ARMv7 and ARMv6) kernels due to the Broadcom code not being 64-bit clean.

Since applications require specialized support for the GPU, only a few applications are normally accelerated. NetBSD/aarch64 normally uses llvmpipe to provide fast parallel CPU-driven support for OpenGL, so should be faster when running normal applications.

The situation should be improved, ideally by writing a DRM/KMS driver.

Video playback

Accelerated video playback is supported with the OMXPlayer application and through GStreamer with the omx plugin.

OpenGL ES

Accelerated OpenGL ES is supported. The GL ES client libraries are included with the misc/raspberrypi-userland package.

Quake 3

A Raspberry Pi optimized build of ioquake3 is available in the games/ioquake3-raspberrypi package. To use it, the following additional resources are required:

Place the pak0.pk3 file in the /usr/pkg/lib/ioquake3/baseq3 directory.

RetroArch / Libretro

Using emulators/retroarch it is possible to run many emulators at full speed the Raspberry Pi. Emulator cores for various gaming consoles are available in the emulators/libretro-* packages. To begin using retroarch:

Developer notes

These notes are for people working on improvements to RPI support in NetBSD.

Updating the firmware version in the NetBSD sources

(Note that trying new firmware may result in a non-bootable system, so be prepared to recover the bootable media with another system.)

Upstream firmware releases are on GitHub. Copy all files except kernel*.img into /boot and reboot.

New firmware should pass all of the following tests before being committed to NetBSD.

Tests should be run on all of rpi[0123].

Testing with anita and qemu

See the anita section in the evbarm page.

It is not currently known how to emulate a RPI in qemu, and therefore anita does not yet have support for this. \todo Add a command-line example to run qemu emulating some RPI model.

Misc notes

Miscellaneous notes about Raspberry PI.

Power supply needed (or: why there is a little rainbow square in the top-right corner?)

Raspberry Pi devices are powered by 5V micro USB and a 2.5A (2500mA) power supply is recommended. For more information please read:

https://www.raspberrypi.org/documentation/faqs/#pi-power

Power glitches can also manifest in other ways, e.g. with an USB disk plugged:

sd0(umass0:0:0:0): generic HBA error
sd0: cache synchronization failed

Using a recommended power supply avoid such issues.

Xenon death flash (Raspberry Pi 2 is camera-shy)

When using laser pointers or xenon flashes in cameras (or other flashes of high-intensity long-wave light) against a Raspberry Pi 2 the Pi can power itself off. For more information please read:

https://www.raspberrypi.org/blog/xenon-death-flash-a-free-physics-lesson/

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Last edited early Saturday morning, February 27th, 2021
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