Disable kernel console debug messages for ttyS2

[Phil1988]

What happened?

I cant get my serial port ttyS2 to work as I want to.
I am using this OS:
Armbian-unofficial_24.2.0-trunk_Mkspi_bookworm_edge_6.6.7.img.xz

Its seems that even if all services being shut down/disabled/stopped, there is something using it.

How do I know?
My oscilloscope shows something.

TL;DR - nothing is actively running on the ttyS2

No process is using the ttyS2:

mks@mkspi:~/X3seriesLCD$ sudo lsof | grep ttyS*
systemd-l  694                      root    7r      REG               0,24      4096       5312 /sys/devices/virtual/tty/tty0/active
systemd-l  694                      root   17u      CHR                4,6       0t0         29 /dev/tty6
python     904                       mks   11uW     CHR               4,64       0t0        134 /dev/ttyS0
python     904                       mks   18uW     CHR              166,0       0t0        690 /dev/ttyACM0
python     904 1116 python           mks   11uW     CHR               4,64       0t0        134 /dev/ttyS0
python     904 1116 python           mks   18uW     CHR              166,0       0t0        690 /dev/ttyACM0
python     904 1587 python           mks   11uW     CHR               4,64       0t0        134 /dev/ttyS0
python     904 1587 python           mks   18uW     CHR              166,0       0t0        690 /dev/ttyACM0
python     904 1588 python           mks   11uW     CHR               4,64       0t0        134 /dev/ttyS0
python     904 1588 python           mks   18uW     CHR              166,0       0t0        690 /dev/ttyACM0
python     904 1617 python           mks   11uW     CHR               4,64       0t0        134 /dev/ttyS0
python     904 1617 python           mks   18uW     CHR              166,0       0t0        690 /dev/ttyACM0
python     904 1618 python           mks   11uW     CHR               4,64       0t0        134 /dev/ttyS0
python     904 1618 python           mks   18uW     CHR              166,0       0t0        690 /dev/ttyACM0
Xorg       952                      root   12u      CHR                4,2       0t0         25 /dev/tty2
Xorg       952 1229 InputThre       root   12u      CHR                4,2       0t0         25 /dev/tty2
agetty    1028                      root  cwd       DIR              179,2      4096          2 /
agetty    1028                      root  rtd       DIR              179,2      4096          2 /
agetty    1028                      root  txt       REG              179,2    134480      35604 /usr/sbin/agetty
agetty    1028                      root  mem       REG              179,2   3407104       9498 /usr/lib/locale/locale-archive
agetty    1028                      root  mem       REG              179,2    353616       3899 /usr/lib/locale/C.utf8/LC_CTYPE
agetty    1028                      root  mem       REG              179,2   1651472      31068 /usr/lib/aarch64-linux-gnu/libc.so.6
agetty    1028                      root  mem       REG              179,2    202912      30789 /usr/lib/aarch64-linux-gnu/ld-linux-aarch64.so.1
agetty    1028                      root  mem       REG              179,2     27028      59819 /usr/lib/aarch64-linux-gnu/gconv/gconv-modules.cache
agetty    1028                      root    0u      CHR                4,1       0t0         24 /dev/tty1
agetty    1028                      root    1u      CHR                4,1       0t0         24 /dev/tty1
agetty    1028                      root    2u      CHR                4,1       0t0         24 /dev/tty1
agetty    1028                      root    4r  a_inode               0,15         0       2074 inotify
sudo      5264                      root    8u      CHR                5,0       0t0         15 /dev/tty
sudo      5266                      root    8u      CHR                5,0       0t0         15 /dev/tty

no systemd-services running;

mks@mkspi:~/X3seriesLCD$ systemctl list-units | grep serial
  sys-devices-platform-ff110000.serial-tty-ttyS0.device                                                                  loaded active plugged   /sys/devices/platform/ff110000.serial/tty/ttyS0
  sys-devices-platform-ff120000.serial-tty-ttyS1.device                                                                  loaded active plugged   /sys/devices/platform/ff120000.serial/tty/ttyS1
  sys-devices-platform-ff130000.serial-tty-ttyS2.device                                                                  loaded active plugged   /sys/devices/platform/ff130000.serial/tty/ttyS2
  sys-devices-platform-serial8250-tty-ttyS3.device                                                                       loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS3
  sys-devices-platform-serial8250-tty-ttyS4.device                                                                       loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS4
  sys-devices-platform-serial8250-tty-ttyS5.device                                                                       loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS5
  sys-devices-platform-serial8250-tty-ttyS6.device                                                                       loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS6
  sys-devices-platform-serial8250-tty-ttyS7.device                                                                       loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS7
  system-serial\x2dgetty.slice                                                                                           loaded active active    Slice /system/serial-getty

Permissions look good:

mks@mkspi:~/X3seriesLCD$ ls -l /dev/ttyS2
crw-rw---- 1 root dialout 4, 66 14. Jul 15:04 /dev/ttyS2

But the kernel messages seems to be configured to use ttyS2 as console:

mks@mkspi:~/X3seriesLCD$ dmesg | grep ttyS2
[    0.000000] Kernel command line: root=UUID=6e0fe519-a43a-40fe-a5c3-aa853b368360 rootwait rootfstype=ext4 splash=verbose console=ttyS2,1500000 console=tty1 consoleblank=0 loglevel=1 ubootpart=2ceabfd6-01 usb-storage.quirks=0x2537:0x1066:u,0x2537:0x1068:u   cgroup_enable=cpuset cgroup_memory=1 cgroup_enable=memory swapaccount=1
[    1.038417] ff130000.serial: ttyS2 at MMIO 0xff130000 (irq = 23, base_baud = 1500000) is a 16550A
[    1.038623] printk: console [ttyS2] enabled
[    7.471293] systemd[1]: Expecting device dev-ttyS2.device - /dev/ttyS2...
[    8.510699] systemd[1]: Found device dev-ttyS2.device - /dev/ttyS2.

How can I shut ther kernel down so its not using console=ttyS2,1500000?
I simply want to use this serial port for serial communication :)

Not related:
And it would be great of you can change the links from:
https://openqidi.com/books/build-entire-operating-system-and-klipper-from-scratch/page/freeqidi
to
https://github.com/Phil1988/FreeQIDI

See here:
https://github.com/redrathnure/armbian-mkspi/releases

and there
https://github.com/redrathnure/armbian-mkspi

How to reproduce?

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On which host OS are you observing this problem?

Other

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Code of Conduct

• I agree to follow this project's Code of Conduct

[redrathnure]

Most likely the /dev/ttyS2 is an UART2 port, which is connected to CH340C IC (USB Type C debug port). And most likely it's configured somehow via console/consoleargs boot arguments. UnfortunatelyI am not sure how to change it in Armbian. Perhaps something should be added into /boot/armbianEnv.txt files, and probably you should check official Armbian forum for instructions how to do this in right way.

BTW I found a file with following content:

if test "${console}" = "display" || test "${console}" = "both"; then setenv consoleargs "console=tty1"; fi
if test "${console}" = "serial" || test "${console}" = "both"; then setenv consoleargs "console=ttyS2,1500000 ${consoleargs}"; fi

Perhaps you may avoid second line condition explicitly declaring setenv console "display"...

[frap129]

@Phil1988 ttyS2 is UART 1. See my PR to this repo for the DTBO needed to enable it
EDIT: My bad ttyS1 is uart1. To get ttyS2 working, add console=none to /boot/armbianEnv.txt, and run

echo 'KERNEL=="ttyS2",MODE="0660"' > /etc/udev/rules.d/99-ttyS2.rules
systemctl mask [email protected]

to grant user permissions and prevent getty from taking over the port

[Phil1988]

@redrathnure
Thanks for your fast reply.
I was not successfull in working this out.

Im running the MKS OEM maiboard for Qidi named X-6 (similar to X-4).
It has serial pins connected to a "serial display".
The stock OS works and I quessed it was ttyS2 and tested.
There are high chances that acuallty ttyS1 is for this port and what I am measuring with the oscilloscope are not signals from the kernel messages but anything else on ttyS1.

The armbianEnv.txt cotains overlays=rk3328-i2c0 rk3328-uart1 which may be right.
I also tested overlays=mkspi-uart1 in the /boot/armbianEnv.txt that frap129 suggested here: #26
But it was not successfull.

@frap129
I only want to use the onboard serial pins.
In the meantime I believe that they are actually ttyS1, but neither with ‘rk3328-uart1’ nor with ‘overlays=mkspi-uart1’ does ttyS1 work.
At best I get this error:

raise SerialException("Could not configure port: {}".format(msg))
serial.serialutil.SerialException: Could not configure port: (5, 'Input/output error')

I can measure signals on the pins, even if nothing should actually access the serial ports.
I can not establish any serial connection with my script, but I know that the script does work properly as it was tested with an USB TTL adapter and on other hardware, where I exactly know the serial port and how to enable it :)

I hope you can help.

[frap129]

I made mkspi-uart1 while working on images for the QIDI X-7 (Q1 Pro mainboard), which uses ttyS1 for the screen, so I would say it's likely that the X-6 uses the same. For reference, I am using a patched version of the nextion python library for interacting with the display.

Could you share more details on how your script connects, like baud rate? Also, have you checked that your user has permissions on /dev/ttyS1?

[Phil1988]

I do also think that the X-6 uses the same as the X-7.
My script connect like KlipperLCD on ttyS1/ttyS2 (testing both) with a baud rate of 115200.

Permissions look good for both:

mks@mkspi: ls -l /dev/ttyS*
crw-rw---- 1 root dialout 4, 64 17. Jul 22:59 /dev/ttyS0
crw-rw---- 1 root dialout 4, 65 17. Jul 19:17 /dev/ttyS1
crw-rw---- 1 root dialout 4, 66 17. Jul 19:17 /dev/ttyS2
crw-rw---- 1 root dialout 4, 67 17. Jul 19:17 /dev/ttyS3
crw-rw---- 1 root dialout 4, 68 17. Jul 19:17 /dev/ttyS4
crw-rw---- 1 root dialout 4, 69 17. Jul 19:17 /dev/ttyS5
crw-rw---- 1 root dialout 4, 70 17. Jul 19:17 /dev/ttyS6
crw-rw---- 1 root dialout 4, 71 17. Jul 19:17 /dev/ttyS7

nothing uses them:

mks@mkspi:~$ systemctl list-units | grep serial

 sys-devices-platform-ff110000.serial-tty-ttyS0.device                                                                  loaded active plugged   /sys/devices/platform/ff110000.serial/tty/ttyS0
  sys-devices-platform-ff130000.serial-tty-ttyS2.device                                                                  loaded active plugged   /sys/devices/platform/ff130000.serial/tty/ttyS2
  sys-devices-platform-serial8250-tty-ttyS1.device                                                                       loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS1
  sys-devices-platform-serial8250-tty-ttyS3.device                                                                       loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS3
  sys-devices-platform-serial8250-tty-ttyS4.device                                                                       loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS4
  sys-devices-platform-serial8250-tty-ttyS5.device                                                                       loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS5
  sys-devices-platform-serial8250-tty-ttyS6.device                                                                       loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS6
  sys-devices-platform-serial8250-tty-ttyS7.device                                                                       loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS7

mks@mkspi:~$ sudo lsof | grep ttyS*
[sudo] Passwort für mks:
systemd-l  715                      root    7r      REG               0,24      4096       5260 /sys/devices/virtual/tty/tty0/active
systemd-l  715                      root   17u      CHR                4,6       0t0         29 /dev/tty6
python     916                       mks   11uW     CHR               4,64       0t0        134 /dev/ttyS0
python     916                       mks   18uW     CHR              166,0       0t0        661 /dev/ttyACM0
python     916 1107 python           mks   11uW     CHR               4,64       0t0        134 /dev/ttyS0
python     916 1107 python           mks   18uW     CHR              166,0       0t0        661 /dev/ttyACM0
python     916 1613 python           mks   11uW     CHR               4,64       0t0        134 /dev/ttyS0
python     916 1613 python           mks   18uW     CHR              166,0       0t0        661 /dev/ttyACM0
python     916 1614 python           mks   11uW     CHR               4,64       0t0        134 /dev/ttyS0
python     916 1614 python           mks   18uW     CHR              166,0       0t0        661 /dev/ttyACM0
python     916 1642 python           mks   11uW     CHR               4,64       0t0        134 /dev/ttyS0
python     916 1642 python           mks   18uW     CHR              166,0       0t0        661 /dev/ttyACM0
python     916 1643 python           mks   11uW     CHR               4,64       0t0        134 /dev/ttyS0
python     916 1643 python           mks   18uW     CHR              166,0       0t0        661 /dev/ttyACM0
Xorg       959                      root   12u      CHR                4,2       0t0         25 /dev/tty2
Xorg       959 1234 InputThre       root   12u      CHR                4,2       0t0         25 /dev/tty2
agetty    1029                      root  cwd       DIR              179,2      4096          2 /
agetty    1029                      root  rtd       DIR              179,2      4096          2 /
agetty    1029                      root  txt       REG              179,2    134480      35604 /usr/sbin/agetty
agetty    1029                      root  mem       REG              179,2   3407104       9498 /usr/lib/locale/locale-archive
agetty    1029                      root  mem       REG              179,2    353616       3899 /usr/lib/locale/C.utf8/LC_CTYPE
agetty    1029                      root  mem       REG              179,2   1651472      31068 /usr/lib/aarch64-linux-gnu/libc.so.6
agetty    1029                      root  mem       REG              179,2    202912      30789 /usr/lib/aarch64-linux-gnu/ld-linux-aarch64.so.1
agetty    1029                      root  mem       REG              179,2     27028      59819 /usr/lib/aarch64-linux-gnu/gconv/gconv-modules.cache
agetty    1029                      root    0u      CHR                4,1       0t0         24 /dev/tty1
agetty    1029                      root    1u      CHR                4,1       0t0         24 /dev/tty1
agetty    1029                      root    2u      CHR                4,1       0t0         24 /dev/tty1
agetty    1029                      root    4r  a_inode               0,15         0       2074 inotify
sudo      2108                      root    8u      CHR                5,0       0t0         15 /dev/tty
sudo      2112                      root    8u      CHR                5,0       0t0         15 /dev/tty

and user mks is part of the "dialout" group:

mks@mkspi:~$ groups mks
mks : mks tty disk dialout sudo audio video plugdev games users systemd-journal input netdev

PS: I would appreciate if you could accept my DM in discord - maybe we solve it there better (tomorrow) and I will post the findings here

[Phil1988]

We could figure out and solve the problem.
The measured signal has nothing to do with ttyS2, so the initial report is not right.

Instead ttyS1 is the one that is sending something on the onboard serial pins.
We could solve it by changing the dtb overlays.
Basicaly this solves it:
#26

I leave this open for you @redrathnure to see it.
Feel free to close this as you read it because this problem is not linked to the kernel console output.

[redrathnure]

Sorry, I was bit busy and lost the meaning of this thread:)
@Phil1988 m @frap129, questions:

1. Do we need the Add DTBO to allow enabling UART1 #26 PR with "QIDI X-7 (Q1 Pro mainboard)," remark?
2. Do we need to add Disable kernel console debug messages for ttyS2 #31 (comment) info to readme?
3. Have you guys managed to make it working on "Qidi named X-6 (similar to X-4)" board?

[Phil1988]

Hey @redrathnure

1. Yes please include it. It will make the onboard serial (ttyS1) usable for the boards: X-4, X-6 and X-7
2. I think we don't need it. It's a very rare case and my initial intention was to make the serial working. I was unsure of the kernel messages interfere with the serial and thought that the onboard might be ttyS2. In short: leave it out (my opinion).
3. Yes! It's working on X-4 and X-6 bopards with the dtbo of @frap129 . It would be great somehow the "mkspi-uart1" could be selected in the armbian-config hardware section (to add overlays=mkspi-uart1 to the /boot/armbianEnv.txt.) This would make it work easier for ever X-4 to X-7 user.

[frap129]

1. Do we need the [Add DTBO to allow enabling UART1 #26](https://github.com/redrathnure/armbian-mkspi/pull/26) PR with "QIDI X-7 (Q1 Pro mainboard)," remark?

I don't think the remark about the specific board is needed. UART1 is a valid port on all MKS PI based boards, per the schematic in makerbase-mks/MKS-PI, not just the ones QIDI uses

2. Do we need to add [Disable kernel console debug messages for ttyS2 #31 (comment)](https://github.com/redrathnure/armbian-mkspi/issues/31#issuecomment-2233345983) info to readme?

I think thats a good idea, it would be useful for any needing ttyS2

3. Have you guys managed to make it working on "Qidi named X-6 (similar to X-4)"  board?

Yes!

[Phil1988]

I think I misread the question of @redrathnure.
frap129 is right. Its not a specific remark. I just wanted to let you know that the DTBO PR is a good think and should be added in my opinion.

[redrathnure]

Done. Please see https://github.com/redrathnure/armbian-mkspi?tab=readme-ov-file#disable-debug-console-uart2--or-freeup-uart1-interface and https://github.com/redrathnure/armbian-mkspi/releases/tag/mkspi%2F0.3.5-24.2.0-trunk for more details.