Today i decided to pacman -Syu my udoo quad.
Afterwards /dev/ttymxc3 which is normally used to communicate with the internal arduino chip is not seen anymore.
dmesg also only lists mxc1:
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][ 0.000000] Kernel command line: console=ttymxc1,115200 root=PARTUUID=1a2074b4-01 rw rootwait video=
[ 0.000032] clocksource: mxc_timer1: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 637086815595 ns
[ 1.326888] clocksource: Switched to clocksource mxc_timer1
[ 1.770051] 21e8000.serial: ttymxc1 at MMIO 0x21e8000 (irq = 62, base_baud = 5000000) is a IMX
[ 2.644136] console [ttymxc1] enabled
[ 2.812692] ehci-mxc: Freescale On-Chip EHCI Host driver
[/code]
I tried rolling back the kernel to 4.7 which worked fine.
my assumption now is that something after kernel 4.7 broke the ttymxc3 serial detection