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NixOS on ARM/Raspberry Pi 3: Difference between revisions

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Split off the Raspberry Pi 3 information in its own spin-off page
 
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First follow the [[NixOS_on_ARM#Installation|generic installation steps]] to get the installer image and install using the [[NixOS_on_ARM#NixOS_installation_.26_configuration|installation and configuration steps]].
First follow the [[NixOS_on_ARM#Installation|generic installation steps]] to get the installer image and install using the [[NixOS_on_ARM#NixOS_installation_.26_configuration|installation and configuration steps]].
{{warning|1=To avoid running out of memory and ''failing'' to build, it is advised to create a swap file (see e.g. [https://wiki.archlinux.org/title/swap#Swap_file_creation]) ''before'' executing <code>nixos-rebuild</code> for the first time.}}


=== Raspberry Pi 3B and 3B+ ===
=== Raspberry Pi 3B and 3B+ ===
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Both the AArch64 and ARMv7 images boot out-of-the-box. Using the 64-bit AArch64 image is highly recommended, as the availability of binaries is much better and allows the use of the 64-bit instruction set.
Both the AArch64 and ARMv7 images boot out-of-the-box. Using the 64-bit AArch64 image is highly recommended, as the availability of binaries is much better and allows the use of the 64-bit instruction set.


For the UART console, edit <code>/extlinux/extlinux.conf</code> on the boot partition of the SD card to set <code>console=ttyS1,115200n8</code> in the kernel boot parameters, and use the following GPIO Pins with an USB-TTL connector:  
For the UART console, edit <code>/extlinux/extlinux.conf</code> on the main partition of the SD card to set <code>console=ttyS1,115200n8</code> in the kernel boot parameters, making sure to replace the existing <code>console=ttyS0,115200n8</code> parameter. Use the following GPIO Pins with an USB-TTL connector:  
<syntaxhighlight>
<syntaxhighlight>
GND        - 3rd in top row, black cable
GND        - 3rd in top row, black cable
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GPIO 15 RXD - 5th in top row, green cable
GPIO 15 RXD - 5th in top row, green cable
</syntaxhighlight>
</syntaxhighlight>
Use <code>nix-shell -p screen --run "screen /dev/ttyUSB0 115200"</code> to connect to the console.  
Use <code>nix-shell -p screen --run "screen /dev/ttyUSB0 115200"</code> (or <code>nix run nixpkgs#screen -- /dev/ttyUSB0 115200</code> if you're using nix flakes) to connect to the console.  
{{note|The mainline kernel (tested with nixos kernel 4.18.7) [https://github.com/raspberrypi/linux/wiki/Upstreaming#downstream-drivers does not include support for cpu frequency scaling] on the Raspberry Pi. To get higher clock speed, set [https://www.raspberrypi.org/documentation/configuration/config-txt/overclocking.md <code><nowiki>force_turbo=1</nowiki></code>] in <code>/boot/config.txt</code> }}
{{note|The mainline kernel (tested with nixos kernel 4.18.7) [https://github.com/raspberrypi/linux/wiki/Upstreaming#downstream-drivers does not include support for cpu frequency scaling] on the Raspberry Pi. To get higher clock speed, set [https://www.raspberrypi.org/documentation/configuration/config-txt/overclocking.md <code><nowiki>force_turbo=1</nowiki></code>] in <code>/boot/config.txt</code> with {{nixos:option|boot.loader.raspberryPi.firmwareConfig}}}}


<syntaxhighlight lang=nix>
<syntaxhighlight lang=nix>
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== Tools ==
== Tools ==


The raspberry tools are available in the <code>raspberrypi-tools</code> package and include commands like <code>vcgencmd</code> to measure temperature and CPU frequency.
The raspberry tools are available in the <code>libraspberrypi</code> package and include commands like <code>vcgencmd</code> to measure temperature and CPU frequency.


== Audio ==
== Audio ==
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If the Raspberry Pi downstream kernel is used the serial interface is named <code>serial0</code> instead.
If the Raspberry Pi downstream kernel is used the serial interface is named <code>serial0</code> instead.
=== Early boot ===
Raspberry Pi 3's UART rate is tied to the GPU core frequency, set by default to 400MHz on Raspberry Pi 3 and later. This results in garbled serial output in bootloaders. Setting <code>core_freq=250</code> in <code>config.txt</code> solves this issue (as per [https://forums.raspberrypi.com/viewtopic.php?p=942203#p942203 thread on the Raspberry Pi forum]).
It can be done declaratively as such:
{{file|/etc/nixos/configuration.nix|nix|<nowiki>
{ config, pkgs, lib, ... }:
{
  boot.loader.raspberryPi = {
    enable = true;
    version = 3;
    firmwareConfig = ''
      core_freq=250
    '';
  };
}
</nowiki>}}
Note that this [https://github.com/RealVNC/raspi-documentation/blob/fc6b4711f91791db7acd19ae743fcfddc9c89546/configuration/config-txt/overclocking.md#overclocking-options may have a negative impact on performance]:
<blockquote>Frequency of the GPU processor core in MHz. It has an impact on CPU performance because it drives the L2 cache and memory bus.</blockquote>


== Bluetooth ==
== Bluetooth ==
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Using the 3.3v serial port via the pin headers (exact location depends on hardware version) will get u-boot output and, when configured, a Linux kernel console.
Using the 3.3v serial port via the pin headers (exact location depends on hardware version) will get u-boot output and, when configured, a Linux kernel console.
=== Updating U-Boot ===
[https://github.com/NixOS/nixpkgs/issues/82455#issuecomment-959797355 These steps can be followed to update the platform firmware.]


== Troubleshooting ==
== Troubleshooting ==
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===WiFi / WLAN===
===WiFi / WLAN===
For a possible solution to 802.11 wireless connectivity issues, see: https://github.com/NixOS/nixpkgs/issues/82462#issuecomment-604634627
For a possible solution to 802.11 wireless connectivity issues, see: https://github.com/NixOS/nixpkgs/issues/82462#issuecomment-604634627
In case <code>wlan0</code> is missing, try overlaying an older <code>firmwareLinuxNonfree</code> confirmed to be working:
{{file|/etc/nixos/configuration.nix|nix|<nowiki>
{ config, pkgs, lib, ... }:
{
  nixpkgs.overlays = [
    (self: super: {
      firmwareLinuxNonfree = super.firmwareLinuxNonfree.overrideAttrs (old: {
        version = "2020-12-18";
        src = pkgs.fetchgit {
          url =
            "https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git";
          rev = "b79d2396bc630bfd9b4058459d3e82d7c3428599";
          sha256 = "1rb5b3fzxk5bi6kfqp76q1qszivi0v1kdz1cwj2llp5sd9ns03b5";
        };
        outputHash = "1p7vn2hfwca6w69jhw5zq70w44ji8mdnibm1z959aalax6ndy146";
      });
    })
  ];
}
</nowiki>}}


===HDMI===
===HDMI===
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=== Raspberry Pi 3B+ HDMI output issues ===
=== Raspberry Pi 3B+ HDMI output issues ===
{{outdated|Since late 2019 the situation '''must''' have changed. Please test and update this section.}}


As of 2019/08/19, the u-boot build and kernel build can disagree about the name of the dtb file for the Raspberry Pi 3B+. This happens because the upstream filename has changed, and the built u-boot has hardcoded expectations for the filename to load.
As of 2019/08/19, the u-boot build and kernel build can disagree about the name of the dtb file for the Raspberry Pi 3B+. This happens because the upstream filename has changed, and the built u-boot has hardcoded expectations for the filename to load.
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See {{issue|66960}}.
See {{issue|66960}}.


=== HDMI output issue with kernel 5.4 (NixOS 20.03 or NixOS unstable) ===
=== HDMI output issue with kernel ~6.1 (NixOS 23.05 or NixOS unstable) ===


(Unverified for 5.5 or 5.6)
When using HDMI and hardware acceleration (e.g. Kodi), an application may fail to start and/or crash with a dmesg like:


Some users have reported that the 5.4 kernel "hung at Starting kernel..." {{issue|82455}}. In all cases where it was possible to investigate, it was found that the device did boot, but that the HDMI out didn't function as expected.
<pre>
[232195.380745] [drm:vc4_bo_create [vc4]] *ERROR* Failed to allocate from CMA:
[232195.380751] [drm]                        kernel:    432kb BOs (1)
[232195.380755] [drm]                          dumb:  69064kb BOs (14)


It looks like it may be a setup-dependent issue, as a 20.03 image with 5.4 was verified as working.
[306160.152488] cma: cma_alloc: alloc failed, req-size: 142 pages, ret: -16
[306160.152498] [vc_sm_cma_ioctl_alloc]: dma_alloc_coherent alloc of 581632 bytes failed
[306160.152501] [vc_sm_cma_ioctl_alloc]: something failed - cleanup. ret -12
[317686.623989] [drm:vc4_bo_create [vc4]] *ERROR* Failed to allocate from CMA:
[317686.623998] [drm]                          dumb:  74752kb BOs (16)
</pre>


If your setup is having the issue, first report on {{issue|82455}} with the Raspberry Pi model (important to note whether it is a plus or non-plus) and the kind of display used with the HDMI out, including whether it is using adapters or not.
A workaround is to increase the pre-allocated CMA space (which, as of writing, defaults to 65M):


Then, you can work around the issue by configuring your system to use the 4.19 kernel (previous LTS) using one of the following tricks.
{{file|/etc/nixos/configuration.nix|nix|<nowiki>
 
{ config, pkgs, lib, ... }:
# Use the serial console to configure the system, and <code>nixos-rebuild boot</code> it.
# Use a 19.09 image, specify the kernel in its configuration and upgrade to 20.03
# Boot the image, poweroff blindly using a keyboard, edit on another computer <code>/home/nixos/.ssh/authorized_keys</code> from the SD to add your key file, chmod as 600, unmount, boot the Raspberry Pi and find it on your network by some means.
 
<syntaxHighlight>
{
{
   boot.kernelPackages = pkgs.linuxPackages_4_19;
   boot.kernelParams = ["cma=320M"];
}
}
</syntaxHighlight>
</nowiki>}}
 
===Additional Troubleshooting===
 
Additional troubleshooting information may be found [https://elinux.org/R-Pi_Troubleshooting at elinux.org].


<hr />
For more information see a post in raspberry pi forum<ref>https://forums.raspberrypi.com/viewtopic.php?t=285068</ref> and thios github issue<ref>https://github.com/raspberrypi/linux/issues/3861</ref>.
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