This bug was fixed in the package linux-raspi - 6.8.0-1024.28
---------------
linux-raspi (6.8.0-1024.28) noble; urgency=medium
* noble/linux-raspi: 6.8.0-1024.28 -proposed tracker (LP: #2107068)
* Remove obsolete build flags in derivative kernels (LP: #2077306)
- [Packaging] raspi: Remove obsolete do_source_package build flag
* Packaging resync (LP: #1786013)
- [Packaging] debian.raspi/dkms-versions -- update from kernel-versions
(main/s2025.03.17)
* mmc0 error on boot with eMMC CM5 (LP: #2089555)
- DTS: bcm2712: emmc2 clock frequency is 200MHz
- DTS: bcm2712: defer SDIO1 CQE selection to the board dtb
- dts: bcm2712: cm5: Disable HS400
- dts: bcm2712: cm5: There is no card detect signal
- dts: bcm2712: cm5: Add antenna controls
- dts: bcm2712: cm5: Force the ANT pins to GPIOs
- dts: bcm2712: cm5: fix typo and declare HS400es support
* GPIO sysfs disabled in raspi kernel (LP: #2099685)
- [Config] raspi: Set GPIO_SYSFS=y
* Kernel compiled with different CONFIG_SERIAL_8250_NR_UARTS to Raspberry Pi
OS (LP: #2096796)
- [Config] raspi: Set SERIAL_8250_NR_UARTS=16
-- Juerg Haefliger <[email protected]> Thu, 17 Apr 2025
13:09:26 +0200
** Changed in: linux-raspi (Ubuntu Noble)
Status: Fix Committed => Fix Released
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https://bugs.launchpad.net/bugs/2096796
Title:
Kernel compiled with different CONFIG_SERIAL_8250_NR_UARTS to
Raspberry Pi OS
Status in linux-raspi package in Ubuntu:
Fix Released
Status in linux-raspi source package in Noble:
Fix Released
Status in linux-raspi source package in Oracular:
Fix Released
Bug description:
[Impact]
Raspberry Pi OS is configured with CONFIG_SERIAL_8250_NR_UARTS=5 which
is different to the Ubuntu 24.04 LTS for Raspberry PI
(CONFIG_SERIAL_8250_NR_UARTS=1).
The Broadcom BCM7271 UART uses that one 8250 Serial UART meaning none
are left for user configuration and use. I came across this whilst
using an RS485 PCIE board that has 4 UART ports. None were about to
initialise, and the driver gave the error `Couldn't register serial
... error -28`. To resolve this I reconfigured and compiled the kernel
with `CONFIG_SERIAL_8250_NR_UARTS=32`
Raspberry Pi OS decided on 5, but I would be interested to know why it
shouldn't be higher. We looked at PCIE boards that can have up to 8
UART ports which would require at least CONFIG_SERIAL_8250_NR_UARTS=9
I am using `Ubuntu 24.04.1 LTS` with `linux-raspi 6.8.0-1017.19`
Before reporting here I also made a post here
https://discourse.ubuntu.com/t/limited-8250-serial-ports-on-
ubuntu-24-04-raspberry-pi/54064
I not familiar with the process of resolving bugs but I would be
interested in contributing!
Thank you!
[Test Case]
With relevant HW, check that the UARTs are available.
[Where Problems Could Occur]
Enables more UARTs, so anything UART related could break.
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