The Wiert Corner – irregular stream of stuff

Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

  • My badges

  • Twitter Updates

  • My Flickr Stream

  • Pages

  • All categories

  • Enter your email address to subscribe to this blog and receive notifications of new posts by email.

    Join 1,512 other followers

OpenSuSE Tumbleweed on RaspberryPi 3: adding ” modprobe.blacklist=vc4″ to the kernel commandline was a lot tougher than I hoped for.

Posted by jpluimers on 2019/01/08

I run most of my Raspberry Pi systems headless, so I was a bit surprised that OpenSuSE tumbleweed on a Raspberry Pi 3B didn’t show anything on my HDMI monitor after I installed KDE after it switches away from text-mode boot output.

[WayBackHCL:Raspberry Pi3 – openSUSE suggests to

I see HDMI output in U-Boot, but not in Linux

The upstream Linux graphics driver for the Raspberry Pi has problems with a few monitors. The same applies to the 7″ LCD displays. In those cases, please fall back to the efi frame buffer console by passing the following into the kernel command line:

 modprobe.blacklist=vc4

However, it does not explain how to modify that “the kernel command line”.

Searching for obvious ways via “Raspberry Tumbleweed Kernel Command Line” got me to for instance

which all suggest editing /boot/cmdline.txt, however that file does not exist:

# ls -al /boot
total 34624
drwxr-xr-x  6 root root     4096 Jul 23 21:05 .
drwxr-xr-x 24 root root     4096 Jul 16 02:02 ..
-rw-r--r--  1 root root       65 Jul 16 12:42 .Image-4.4.76-7-default.hmac
-rw-r--r--  1 root root        0 Jul 16 16:56 0x75b762d5
lrwxrwxrwx  1 root root       22 Jul 16 16:34 Image -> Image-4.4.76-7-default
-rw-r--r--  1 root root 14878208 Jul 16 12:20 Image-4.4.76-7-default
-rw-r--r--  1 root root  3217519 Jul 16 12:20 System.map-4.4.76-7-default
lrwxrwxrwx  1 root root        1 Jul 16 02:00 boot -> .
-rw-r--r--  1 root root     1725 May 24 20:11 boot.readme
-rw-r--r--  1 root root     2405 Jul 16 16:56 boot.scr
-rw-r--r--  1 root root     2333 Jul 16 16:56 boot.script
-rw-r--r--  1 root root   152522 Jul 16 08:39 config-4.4.76-7-default
lrwxrwxrwx  1 root root       12 Jul 23 16:13 dtb -> dtb-4.11.6-1
drwxr-xr-x  3 root root     4096 Jul 23 16:13 dtb-4.11.6-1
drwxr-xr-x  5 root root    16384 Jan  1  1970 efi
drwxr-xr-x  7 root root     4096 Jul 24 18:27 grub2
lrwxrwxrwx  1 root root       23 Jul 16 16:34 initrd -> initrd-4.4.76-7-default
-rw-------  1 root root  8080932 Jul 23 21:05 initrd-4.4.76-7-default
-rw-r--r--  1 root root   288571 Jul 16 12:42 symvers-4.4.76-7-default.gz
-rw-r--r--  1 root root      377 Jul 16 12:42 sysctl.conf-4.4.76-7-default
-rw-r--r--  1 root root  1484762 Jul 16 16:56 unicode.pf2
drwxr-xr-x  2 root root     4096 Jul 24 09:05 vc
-rw-r--r--  1 root root  7282031 Jul 15 07:00 vmlinux-4.4.76-7-default.gz

There are other config.txt files:

# find / | grep config.txt
/boot/efi/config.txt
/boot/vc/config.txt

However, these seems to be unclear which of the two is actually used and what options can be set at all: [WayBackRaspberry Pi • View topic – aarch64 on Pi3.

So the quest continues, as a lot of settings can be applied in these files:

Setting “modprobe.blacklist=vc4”

I’ve temporarily given up on the /boot/config.txt editing, but continued searching for “modprobe.blacklist=vc4”, which lead to a few interesting results:

All of those suggest adding modprobe.blacklist=vc4 to the grub configuration. The second post actually has the most elaborate steps for this, which I’ve paraphrased into:

  1. As root, edit /etc/default/grub (make a backup first)
  2. Search for the variable GRUB_CMDLINE_LINUX
  3. Add the modprobe.blacklist=vc4to the end of the variable initialisation (ensure there is a space before it and you keep the terminating double-quote)
  4. Re-generate the grub configuration file used at boot time (make a backup first): grub2-mkconfig > /boot/grub2/grub.cfg

This solved my problem: no text output on HDMI.

Note that in order to get graphical output, you need to install any of the non-JeOS images. Installing just kde+kdm and dependencies isn’t enough to get the X server going.

–jeroen

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

 
%d bloggers like this: