Unable to access UART2and UART4

[JasonLaunchbury]

Ubuntu 23.10 6.5.0-1008-raspi

I've summarized the problem here, and asked for help:

https://askubuntu.com/questions/1496927/raspberry-pi-5-uart2-and-uart4-problem

This question hasn't elicited a response. I'm assuming this is a problem with 6.5.0 kernel on Pi 5 hardware.

ProblemType: Bug
DistroRelease: Ubuntu 23.10
Package: linux-image-6.5.0-1008-raspi 6.5.0-1008.11
ProcVersionSignature: Ubuntu 6.5.0-1008.11-raspi 6.5.3
Uname: Linux 6.5.0-1008-raspi aarch64
ApportVersion: 2.27.0-0ubuntu5
Architecture: arm64
CasperMD5CheckResult: unknown
CloudArchitecture: aarch64
CloudID: nocloud
CloudName: unknown
CloudPlatform: nocloud
CloudSubPlatform: config-disk (/dev/mmcblk0p1)
Date: Tue Dec 19 09:54:18 2023
ProcEnviron:
 LANG=C.UTF-8
 PATH=(custom, no user)
 SHELL=/bin/bash
 TERM=xterm
 XDG_RUNTIME_DIR=<set>
SourcePackage: linux-raspi
UpgradeStatus: No upgrade log present (probably fresh install)

[JasonLaunchbury (jmonnz)]

I think this is related to what is explained here: https://forums.raspberrypi.com/viewtopic.php?t=361397#p2171244

"However, the pinmuxing isn't working as it should, so although the /dev/ttyAMA* devices are appearing, the UART functions are not enabled on the correct pins. I think this is another problem with the Ubuntu kernel - 6.5.0-1008-raspi in my case."

[Juerg Haefliger (juergh)]

From the post you linked:

I have the following in config.txt

enable_uart=1
dtoverlay=uart0-pi5
dtoverlay=uart2-pi5
dtoverlay=uart4-pi5

Interestingly when I boot with that I don't see any additional /dev/AMA* devices present. I need to do:

sudo dtoverlay uart0-pi5
sudo dtoverlay uart2-pi5
sudo dtoverlay uart4-pi5

To see /dev/ttyAMA0, /dev/ttyAMA2 and /dev/ttyAMA4

[Juerg Haefliger (juergh)]

That should not happen, i.e., you shouldn't have to manually load the DT overlays. I'm seeing something strange on my systems as well. Looking into it.

[Juerg Haefliger (juergh)]

Oh this is funny. Can you try the following and reboot and check if the DT overlays are automatically loaded and ttyAMA* behave as expected?

sudo mv /boot/firmware/overlays /boot/firmware/overlays.foo
sudo mv /boot/firmware/overlays.foo /boot/firmware/overlays

[Juerg Haefliger (juergh)]

The booloader does not want to read files from the original overlays directory for some reason.

[JasonLaunchbury (jmonnz)]

Apologies, I'm away on holiday and dont have access to the Pi currently. I'll take a look on Monday and get back to you. Thanks.

[Juerg Haefliger (juergh)]

Confirmed, it's a bootloader issue: https://github.com/raspberrypi/rpi-eeprom/issues/514

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux-firmware-raspi - 11-0ubuntu1

---------------
linux-firmware-raspi (11-0ubuntu1) noble; urgency=medium

  * New upstream boot firmware (LP: #2056588)
    - Add [pi5] to config.txt on 2711 and earlier platforms
    - Add support for the HAT map
    - video_decode: Add support for 32bpp RGB conversion
    - Fix non-standard console UARTs
    - Improve UART console selection
    - Set WiFi MAC address if all zeroes
    - Use os_prefix when looking for stubs
    - Don't overwrite kernel path, check before loading stub
    - Move non-kernels back to 512KB (u-boot fix)
    - Add HAT+ support
    - Add Compute Module 5 model info string
    - Handle SFN-only entries in FAT correctly (LP: #2046841)
  * New upstream wifi firmware, 1:20230625-2+rpt2
    - Use a generic CYW43455 firmware
    - Add Pi 5-specific links to the 43455 firmware
  * New upstream bluetooth firmware, 1.2-9+rpt2
    - Import 43456 firmware: Fix BLE advertising on new phones
    - More model-specific firmware links
  * Use dh_links to create symlinks

 -- Dave Jones <email address hidden> Fri, 08 Mar 2024 17:03:45 +0000