[Bug 2101104] Re: Raspberry Pi 5 serial console device changes with EEPROM upgrade

[Dave Jones]

Technically this is an issue for the pi-gadget snap, but I'll leave it
here and target it for the 26.04 milestone to remind me to deal with
this.

** Changed in: rpi-eeprom (Ubuntu)
    Milestone: None => ubuntu-26.04

** Changed in: rpi-eeprom (Ubuntu)
       Status: New => Triaged

** Changed in: rpi-eeprom (Ubuntu)
   Importance: Undecided => Medium

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Title:
  Raspberry Pi 5 serial console device changes with EEPROM upgrade

Status in linux-raspi package in Ubuntu:
  Invalid
Status in rpi-eeprom package in Ubuntu:
  Triaged

Bug description:
  Sorry if I'm reporting this against the wrong package.

  The default `/boot/firmware/config.txt` file in `noble` server
  contains the directive `enable_uart=1` in a section for `[all]`
  Raspberry Pi versions. The documentation at
  https://www.raspberrypi.com/documentation/computers/config_txt.html#enable_uart
  says:

  `enable_uart=1` (in conjunction with `console=serial0,115200` in
  `cmdline.txt`) requests that the kernel creates a serial console,
  accessible using GPIOs 14 and 15 (pins 8 and 10 on the 40-pin header).
  Editing `cmdline.txt` to remove the line `quiet` enables boot messages
  from the kernel to also appear there.

  This makes sense for Ubuntu Server on the Raspberry Pi 4, but the
  Raspberry Pi 5 has a dedicated UART connector for the console that's
  not on the GPIO header. Up until now it appears that `enable_uart=1`
  actually did nothing on the Raspberry Pi 5, but as of EEPROM version
  2025-02-12 this directive *does* move the console from the dedicated
  UART and `/dev/ttyAMA10` to the GPIO pins and `/dev/ttyAMA0`.

  So a problem arises if one is already using `/dev/ttyAMA0` on the GPIO
  pins for some reason and then upgrades the EEPROM. To work around this
  problem one can comment out `enable_uart=1` or add `enable_uart=0` to
  the bottom of `config.txt`.

  Ubuntu should consider moving `enable_uart=1` out of `[all]` so that
  it doesn't apply to the `[pi5]`. It probably should be applied to more
  than just the `[pi4]`, though.

  See also: https://github.com/raspberrypi/rpi-eeprom/issues/673

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