[systemd-devel] systemd doesn't see ttyPS0 devices from udev

[ZhouPeng]

Hi all, 

When I use Fedora image as rootfs on Xilinx PYNQ-Z2, I encountered the issue  when use the /dev/ttyPS0.
I think the issue is because systemd and udev on fedora can didn't detect ttyPS0 properly. Do I need to install any other package or do some special configuration?

**systemd version the issue has been seen with**
udevadm --version
237
systemd-udev.riscv64                     237-1.0.riscv64.fc28


**Unexpected behaviour you saw**
We can see ttyPS0 boots ok in the kernel boot period:
[    0.180000] console [ttyPS0] enabledat MMIO 0xe0000000 (irq = 2, base_baud = 6250000) is a xuartps
[    0.180000] console [ttyPS0] enabled

But, when boot into systemd, it failed on dev ttyPS0:
[ TIME ] Timed out waiting for device dev-ttyPS0.device. // **here**
[DEPEND] Dependency failed for Serial Getty on ttyPS0. // **here**
[  OK  ] Started Rebuild Hardware Database.
         Starting Update is Completed...
         Starting udev Kernel Device Manager...
[  OK  ] Started Update is Completed.
[  OK  ] Started udev Kernel Device Manager.

I found there was a similar issue  https://github.com/systemd/systemd/issues/3446 which is on Ubuntu,  and @jeras reported it can be fixed by 'apt get install udev' on Ubuntu, But on Fedora 28 (Rawhide) and the latest version, I searched there is no udev package now, there is only 
systemd-udev package, and the systemd-udev is installed. So  I didn't find a way to fix this issue.

**Steps to reproduce the problem**
Boot the Fedora 28 (Rawhide) using Linux  kernel version 4.18 (or newer), with kernel bootargs as below
Kernel command line: console=ttyPS0,115200n8 root=/dev/mmcblk0p2 rootfstype=ext4 rw rootwait earlycon clk_ignore_unused

Appreciate for any reply. Thanks in advance.

Best,
--
Peng Zhou