Re: systemd doesn't see ttyPS0 devices from udev

[Michael Olbrich <m.olbrich@xxxxxxxxxxxxxx>]

Hi,

On Wed, Sep 23, 2020 at 04:58:57PM +0800, ZhouPeng wrote:
> I find that boot with the 'rescue' option, then exit 'rescue' mode, then
> I can login to the ttyPS0, as below

You're using a custom kernel, right? Please check the README in the systemd
source tree. Specifically the kernel config options.

>From what I remember, what you describe happens when CONFIG_FHANDLE is
disabled in the kernel.

Regards,
Michael


> bash-4.4# exit  // *here exit rescue mode*
> exit
> Reloading system manager configuration
> Starting default target
> [ 1708.910000] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
> [ 1712.080000] macb e000b000.ethernet eth0: link up (100/Full)
> [ 1712.080000] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
> ...
> Build date: 2019-08-22 21:56
> 
> 
> Kernel 4.18.0-14480-gc4490f2dabc1 on an riscv64 (ttyPS0)
> ...
> stage4 login: root
> Password: 
> [root@stage4 ~]#
> 
> 
> 
> 
> But how boot directly normally.
> Thanks all,
> At 2020-09-23 16:37:48, "ZhouPeng" <zhoupengwork01@xxxxxxx> wrote:
> >Thank you very much.  ' udevadm info -a /dev/ttyPS0' output:
> >
> >
> >bash-4.4# udevadm info -a /dev/ttyPS0
> >
> >Udevadm info starts with the device specified by the devpath and then
> >walks up the chain of parent devices. It prints for every device
> >found, all possible attributes in the udev rules key format.
> >A rule to match, can be composed by the attributes of the device
> >and the attributes from one single parent device.
> >
> >  looking at device '/devices/platform/soc/e0000000.serial/tty/ttyPS0':
> >    KERNEL=="ttyPS0"
> >    SUBSYSTEM=="tty"
> >    DRIVER==""
> >    ATTR{close_delay}=="50"
> >    ATTR{closing_wait}=="3000"
> >    ATTR{custom_divisor}=="0"
> >    ATTR{flags}=="0x10000000"
> >    ATTR{io_type}=="3"
> >    ATTR{iomem_base}=="0xE0000000"
> >    ATTR{iomem_reg_shift}=="0"
> >    ATTR{irq}=="2"
> >    ATTR{line}=="0"
> >    ATTR{port}=="0x0"
> >    ATTR{type}=="98"
> >    ATTR{uartclk}=="100000000"
> >    ATTR{xmit_fifo_size}=="64"
> >
> >  looking at parent device '/devices/platform/soc/e0000000.serial':
> >    KERNELS=="e0000000.serial"
> >    SUBSYSTEMS=="platform"
> >    DRIVERS=="xuartps"
> >    ATTRS{driver_override}=="(null)"
> >
> >  looking at parent device '/devices/platform/soc':
> >    KERNELS=="soc"
> >    SUBSYSTEMS=="platform"
> >    DRIVERS==""
> >    ATTRS{driver_override}=="(null)"
> >
> >  looking at parent device '/devices/platform':
> >    KERNELS=="platform"
> >    SUBSYSTEMS==""
> >    DRIVERS==""
> >bash-4.4# ls /dev/ttyPS0 -lh
> >crw-rw---- 1 root dialout 254, 0 Jan 28 16:05 /dev/ttyPS0
> >
> >
> >Thanks,
> >
> >On Wed, Sep 23, 2020, 15:34，"Mantas Mikulėnas" <grawity@xxxxxxxxx> wrote:
> >
> >
> >On Wed, Sep 23, 2020, 09:21 ZhouPeng <zhoupengwork01@xxxxxxx> wrote:
> >
> >
> >
> >Thank you  very much for you great suggestions.
> >
> >
> >
> >I chroot the rootfs and tried to the 3 methods in '/usr/lib/udev/rules.d'  respectively:
> >
> >
> >
> >try 1) add  a line of  ACTION!="remove", KERNEL=="ttyPS0", TAG+="systemd" below the line of  "ACTION=="remove", GOTO="systemd_end"" in file 99-systemd.rules
> >
> >try 2) add  a line of  ACTION!="remove", KERNEL=="ttyPS0",  NAME="ttyPS0", TAG+="systemd"  below the line of  "ACTION=="remove", GOTO="systemd_end"" in file 99-systemd.rules
> >
> >try 3) replace the line  "SUBSYSTEM=="tty", KERNEL=="tty[a-zA-Z]*|hvc*|xvc*|hvsi*|ttysclp*|sclp_line*|3270/tty[0-9]*", TAG+="systemd" with "SUBSYSTEM=="tty", KERNEL=="ttyPS[0-9]|tty[a-zA-Z]*|hvc*|xvc*|hvsi*|ttysclp*|sclp_line*|3270/tty[0-9]*", TAG+="systemd"",  in file 99-systemd.rules.
> >
> >
> >
> >At least the 1st one *should* have worked, though NAME= seems wrong in the 2nd one...
> >
> >
> >
> >
> >
> >
> >
> >At the same time, I replace the line of "KERNEL=="tty[A-Z]*[0-9]|ttymxc[0-9]*|pppox[0-9]*|ircomm[0-9]*|noz[0-9]*|rfcomm[0-9]*", GROUP="dialout"" with "KERNEL=="ttyPS[0-9]|tty[A-Z]*[0-9]|ttymxc[0-9]*|pppox[0-9]*|ircomm[0-9]*|noz[0-9]*|rfcomm[0-9]*", GROUP="dialout"".
> >
> >
> >
> >This line is irrelevant, since TAG+="systemd" is the important part – groups and modes shouldn't be the problem.
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >But they didn't take any effect.
> >
> >
> >
> >Then at the same time, I do
> >
> >cp /usr/lib/systemd/system/serial-getty@.service /etc/systemd/system/serial-getty@ttyPS0.service
> >
> >Edit /etc/systemd/system/serial-getty\@ttyPS0.service:  replace  "ExecStart=-/sbin/agetty --keep-baud 115200,38400,9600 %I $TERM" with "ExecStart=-/sbin/agetty --keep-baud 115200 %I $TERM"
> >
> >ln -s /etc/systemd/system/serial-getty@ttyPS0.service /etc/systemd/system/getty.target.wants/
> >
> >
> >
> >But there was still no effect. There is still boot failure logs like:
> >
> >[ *] (3 of 3) a start job is running for dev-ttyPS0.device (41s / 1min 30s)// **here**
> >
> >...
> >
> > [ TIME ] Timed out waiting for device dev-ttyPS0.device. // **here**
> >
> >...
> >
> >
> >
> >Yeah, the baudrate won't change anything if systemd doesn't even see the device in the first place. It doesn't even get to the point of launching agetty.
> >
> >
> >
> >
> >
> >
> >
> >By the way, Do I need to add some configuration to tiger executing something like 'mknod /dev/ttyPS0 c 248 0'  for systemd or udev pls? If needed, where is the proper place to add this action pls?
> >
> >
> >
> >No. The kernel automatically creates device nodes (as long as /dev has a "devtmpfs" mounted); udev only applies modes/symlinks. The problem here is that udev doesn't properly inform systemd about the new device.
> >
> >
> >
> >
> >
> >
> >
> >>What does "udevadm info -a /dev/ttyPS0" output?
> >
> >I can not get a console from ttyPS0, so I can not run  "udevadm info -a /dev/ttyPS0" in the target(xilinx pynq) board.
> >
> >
> >
> >Try booting with the 'rescue' option, this should directly create a root login prompt on the kernel console.
> >
> >
> >
> >
> >
> >Alternatively, try creating a simple .service that runs this command, then you'll find its output in the journal or in the boot console (depending on what StandardOutput= you set).
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >Thanks all,
> >
> >At 2020-09-22 20:34:15, "Andrei Borzenkov" <arvidjaar@xxxxxxxxx> wrote:
> >
> >>On Tue, Sep 22, 2020 at 2:53 PM Mantas Mikulėnas <grawity@xxxxxxxxx> wrote:
> >
> >>>
> >
> >>> On Tue, Sep 22, 2020 at 1:46 PM Andrei Borzenkov <arvidjaar@xxxxxxxxx> wrote:
> >
> >>>>
> >
> >>>> On Tue, Sep 22, 2020 at 1:35 PM ZhouPeng <zhoupengwork01@xxxxxxx> 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"Mantas
> >
> >>>>
> >
> >>>> should do it. Whether this should go upstream depends on how common
> >
> >>>> this device is.
> >
> >>>
> >
> >>>
> >
> >>> Well yes, but that should have been already covered by the existing upstream rules:
> >
> >>>
> >
> >>> 99-systemd.rules:12:SUBSYSTEM=="tty", KERNEL=="tty[a-zA-Z]*|hvc*|xvc*|hvsi*|ttysclp*|sclp_line*|3270/tty[0-9]*", TAG+="systemd"
> >
> >>>
> >
> >>
> >
> >>Are you sure ttyPS0 has the "tty" subsystem?
> >
> >

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