Uart1-3 not working on Duo64


I’m struggling to get the additional uarts working on a duo64. I’m running a compiled kernel from the buildroot (just with PPP support added) and have arch as my rootfs.

ttyS0 works and I have the console on that but when I try to use ttyS1 - 3 it doesn’t work, checking /proc/tty/driver/serial it loads all the uarts but they all have tx:0 rx:0. Using Kermit to access the uarts and with a loop back I get no echo and the it timeouts when closing.

I’ve checked the dts which has all the uarts enabled. Looking in dmesg there is a ‘dwb-apb-uart 4160000.serial:failed to request DMA’ as well as ‘dwb-apb-uart 4160000.serial: forbid DMA for kernel console’

Is it perhaps an issue with DMA on the uarts that aren’t the kernel console?

Thanks in advance.

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