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

[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(-)

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2.43.0