USB Issue on Raspberry Pi 4 Running Fedora - Complex Solution

Sep 21, 2020 Updated: Oct 7, 2020 7 minutes to read

In the previous post we looked at a very simple solution to fix the USB ports on Raspberry Pi 4B 4GB/8GB RAM models running Fedora, which involves a trade-off between the USB ports' functionality and the amount of RAM available to the operating system. This post will give you another solution that takes more steps but no longer limits available memory to 3 GiB.

As said in the previous post, no action is required for the 2GB model. The symptoms of this issue are available there as well.

Overview

You probably are already feeling this solution is not so simple just by finding that an overview section like this is needed for it. To summarize, this solution involves using the bootloader and firmware of openSUSE - another GNU/Linux distribution - on Fedora. So, you will need to

obtain those files from openSUSE,
copy them to the SD card on which you have installed Fedora, then
modify openSUSE’s boot configuration file for Fedora.

I will go over many details on how each step should be performed. From the length and content of this post, you might think the procedure is complicated, but it really boils down to only these objectives.

Obtain Files from openSUSE

Download openSUSE’s Image

For the mere purpose of extracting some critical boot and firmware files, I would recommend downloading the openSUSE Leap JeOS image. Leap is openSUSE’s regular release channel, so it is supposed to be more stable. JeOS stands for Just enough Operating System, which is a minimal distribution without a desktop environment, helping to reduce download size and disk usage.

As of this post was initially composed, the newest version of the openSUSE Leap JeOS image for Raspberry Pi 4 was Leap 15.2. You may also get the latest image from this page on the openSUSE Wiki.

Extract the Image

The downloaded file is a .xz file, a compressed image. Before doing anything with the image, you need to decompress the .xz file.

If the xz program is available to you, you may decompress the file with the following command:

$ xz -dv openSUSE-Leap-15.2-ARM-JeOS-raspberrypi4.aarch64-2020.07.08-Build1.35.raw.xz

Depending on the version of the image you download and where you download it to, you might need to change the file name in this command and all subsequent commands in the later steps.

In this command, the -d flag tells xz to decompress. The -v flag is optional, as it does nothing more than enabling progress reporting.

When the command completes, the decompressed image replaces the original .xz file in the same directory, with the .xz suffix removed.

Mount the Image

After the image is decompressed, it can be mounted so you are able to copy out the files in it. The image consists of multiple partitions; the main focus is on the first of them, which is the EFI partition and contains the files you will need. Therefore, you just need to mount the first partition of the image.

You may use whatever tool available on your operating system for mounting, as long as you can achieve the goal of this step, which is to ensure you can copy the files in that partition from the openSUSE image to the SD card containing your Fedora installation.

The following instructions are for mounting the image’s first partition on a GNU/Linux system with the mount program.

Get the offset of the EFI partition in the image. This information is available indirectly from fdisk.

$ fdisk -l openSUSE-Leap-15.2-ARM-JeOS-raspberrypi4.aarch64-2020.07.08-Build1.35.raw
Disk openSUSE-Leap-15.2-ARM-JeOS-raspberrypi4.aarch64-2020.07.08-Build1.35.raw: 2.2 GiB, 2353004544 bytes, 4595712 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x52b80fee

Device                                                                     Boot   Start     End Sectors  Size Id Type
openSUSE-Leap-15.2-ARM-JeOS-raspberrypi4.aarch64-2020.07.08-Build1.35.raw1         2048  133119  131072   64M  c W95
openSUSE-Leap-15.2-ARM-JeOS-raspberrypi4.aarch64-2020.07.08-Build1.35.raw2       133120 1157119 1024000  500M 82 Linu
openSUSE-Leap-15.2-ARM-JeOS-raspberrypi4.aarch64-2020.07.08-Build1.35.raw3      1157120 4595678 3438559  1.7G 83 Linu

The above output shows that the size of one sector is 512 bytes, and the first partition starts at sector 2048. Sectors are numbered from 0, so being sector 2048 means there are exactly 2048 sectors before it. Thus, the number of bytes from the image’s start to the partition’s beginning in that image is 512 * 2048 = 1,048,576 bytes, and that is the value of offset, which you will need later.

Create a directory to be used as the partition’s mount point, like /mnt/tmp for example. /mnt is typically not writable by a normal user, so if you decide to use this path as the mount point, you need to run this command with superuser privilege (often by prepending sudo to it).
```
# mkdir /mnt/tmp
```
Mount the image, and specify the offset you calculated before. Note that the mount program usually needs to be run with superuser privilege.
```
# mount -o loop,offset=1048576 openSUSE-Leap-15.2-ARM-JeOS-raspberrypi4.aarch64-2020.07.08-Build1.35.raw /mnt/tmp/
```

The files in the EFI partition are now available at the mount point, so you are ready to copy them to elsewhere and have achieved the goal of mounting.

$ cd /mnt/tmp
$ ls
bcm2708-rpi-b.dtb       bcm2710-rpi-3-b-plus.dtb  LICENCE.broadcom
bcm2708-rpi-b-plus.dtb  bcm2710-rpi-cm3.dtb       overlays
bcm2708-rpi-cm.dtb      bcm2711-rpi-4-b.dtb       start4.elf
bcm2708-rpi-zero.dtb    bootcode.bin              start.elf
bcm2708-rpi-zero-w.dtb  config.txt                startup.nsh
bcm2709-rpi-2-b.dtb     EFI                       u-boot.bin
bcm2710-rpi-2-b.dtb     fixup4.dat                ubootconfig.txt
bcm2710-rpi-3-b.dtb     fixup.dat

Copy the Files to Fedora SD Card

This step is very straightforward; just copy every file and directory in openSUSE’s EFI partition to your Fedora SD card’s EFI partition. If you want to use a command for this task, run the following one under the SD card’s EFI partition:

$ cp -rv /mnt/tmp/* .

The -r flag let cp descend into child directories and copy their contents as well, and the -v flag is again an optional one merely for progress reporting.

As of Fedora 32 and Linux kernel 5.8, there is one file in openSUSE’s EFI partition that should not be used on Fedora, which is the U-Boot image u-boot.bin. When openSUSE’s U-Boot image is being used, Fedora fails to boot. You can keep using Fedora’s image rpi4-u-boot.bin instead, by first deleting openSUSE’s u-boot.bin and then renaming rpi4-u-boot.bin to u-boot.bin.

The file deletion and renaming operations can be done together with a single command, if you are willing to use it:

$ mv {rpi4-,}u-boot.bin

Extra Step for Fedora 33

When the U-Boot image shipped with Fedora 33 is used together with openSUSE’s boot files, the boot process will get stuck until you connect the Raspberry Pi to a monitor. This can be easily fixed by creating a file called extraconfig.txt under the SD card’s EFI partition and inserting the following line into the file:

hdmi_force_hotplug=1

This may be done by running the following command under the SD card’s EFI partition:

$ echo 'hdmi_force_hotplug=1' > extraconfig.txt

Modify Boot Configuration File

The bootloader you have ported from openSUSE to Fedora will attempt to read files from an invalid location and fail to boot unless it is reconfigured for Fedora. You need to tell the bootloader the correct path to Fedora’s boot files.

Replace everything in file EFI/BOOT/grub.cfg under your SD card’s EFI partition with the following lines:

set prefix=($root)/EFI/fedora
normal

Save the file and safely eject the SD card. Insert it into your Raspberry Pi, power it on, and the USB ports should be working after the system boots. Enjoy using your USB peripherals on Raspberry Pi running Fedora!

Clean Up

If everything works well, you can start cleaning up the trace you have left on your computer. Should you have used mount to mount the openSUSE’s image, unmount it and remove the mount point with the following commands.

# umount /mnt/tmp
# rmdir /mnt/tmp

Known Issues

When Fedora 32 runs on the 8GB model, regardless of whether this solution has been applied, the amount of RAM available to the operating system is limited to 4 GiB. This is caused by Fedora 32’s outdated U-Boot image. Fedora 33 fixes this particular problem by shipping a newer U-Boot image.

References

This post is basically just a detailed explanation of the issue’s solution described in this page written by Robert Gadsdon on rglinuxtech.com. Any credit for the abstract idea behind this solution should go to that author; what I have done here is merely writing step-by-step instructions on how to apply it.