ACK: [SRU][O:raspi][N:raspi][PATCH 0/1] Kernel compiled with different CONFIG_SERIAL_8250_NR_UARTS to Raspberry Pi OS (LP: #2096796)

[Agathe Porte]

2025-02-13 11:26 CET, Juerg Haefliger:
> BugLink: https://bugs.launchpad.net/bugs/2096796
> 
> 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!
> 
> Juerg Haefliger (1):
>   UBUNTU: [Config] raspi: Set SERIAL_8250_NR_UARTS=16
> 
>  debian.raspi/config/annotations | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Acked-by: Agathe Porte <agathe.porte at canonical.com>