Public bug reported: 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! ** Affects: linux-raspi (Ubuntu) Importance: Undecided Status: New ** Description changed: 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`. + 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! -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux-raspi in Ubuntu. https://bugs.launchpad.net/bugs/2096796 Title: kernal compiled with different CONFIG_SERIAL_8250_NR_UARTS to Raspberry Pi OS Status in linux-raspi package in Ubuntu: New Bug description: 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! To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux-raspi/+bug/2096796/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
