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

[Andrei Borzenkov]

On Tue, Sep 22, 2020 at 1:35 PM ZhouPeng <zhoupengwork01 at 163.com> wrote:
>
> 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**

systemd only monitors for devices with "sysemd" tag. Tags are assigned
by udev rules. You should add rule to assign tag to ttyPS0. I have no
idea what it is, but something like

ACTION!="remove", KERNEL=="ttyPS0", TAG+="systemd"

should do it. Whether this should go upstream depends on how common
this device is.

> [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
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