dim screen after kernel upgrade
#1
So it appears there's a problem when upgrading from older kernels to something around 5.5 or later.  The symptom is that when you boot the new kernel, the screen is very dim, possibly appearing completely black.
The problem seems to be that with the older kernels, screen brightness was on a 8-bit 0-to-255 scale, and the newer kernels use a 12-bit 0-to-4095 scale.  So the reasonably bright "224" (for example) brightness that you had with the old kernel becomes a rather dim "224" with the new kernel.

It seems that this issue occurs with a few different distributions' kernel packages.  I'm not sure if any distributions have any fixes (maybe a transition script) built into their kernel packages.

My current thinking is that the best approach (for individual users) is to verify that your Fn-F1 and Fn-F2 are working for adjusting your screen brightness before upgrading the kernel.  Then when you boot your new kernel and you can't read the screen you can use them to turn up the backlight.  I neglected to do this.

A hackish approach could be to poke at the files in /sys/class/backlight/edp-backlight/ (you could do this via SSH if you can't adjust brightness via the keyboard/trackpad/screen)
  Reply
#2
I noticed while booting the new kernel that it starts out at a reasonable brightness, but at some point, around a second in, it switches to the lower brightness level.  My wild guess is that the kernel starts out with a compiled-in reasonable default, and then at some point in the bootup, it reads a config file from the filesystem and changes the brightness based on that.  (The downside to solid state storage is that this all scrolls by too fast for me to read what is printed when it changes the brightness).

I'm also wondering if this change affects intel-based laptops as well, or if it is limited to Arm64 laptops.  Or just the pinebook pro?
  Reply
#3
i have replied a few times to this issue over the last few weeks. see danielt's thread. i solved this by:

login to a tty
brightnessctl s 100%
done
  Reply
#4
"brightnessctl" is not installed on either of the installs on my PBP.  Guess it's not part of the default install.

However, it's easy enough to find as the package is called "brightnessctl" (at least in Debian).
  Reply
#5
yes i use brightness-udev, brightnessctl and light on mainline kernel with good results.
  Reply


Possibly Related Threads…
Thread Author Replies Views Last Post
  Compile of Anbox fails because kernel function kallsyms_lookup_name() is unexported Tsvi Bar-David 6 233 06-30-2020, 06:41 AM
Last Post: tophneal
  ayufan Ubuntu Mate 0.9.14 black screen boot on new Pinebook Pro EricL 3 346 06-22-2020, 09:45 PM
Last Post: trinapicot
  eMMC frequently not found by Linux kernel (especially on low battery) v-man 7 408 06-21-2020, 04:30 PM
Last Post: Arwen
  A true mainline Linux Kernel for the Pinebook Pro tsys 148 25,007 06-16-2020, 03:13 PM
Last Post: xmixahlx
  How does one get working deep/S3 sleep with Ubuntu Focal/5.7 mainline kernel? Syonyk 6 345 06-14-2020, 10:36 PM
Last Post: Syonyk
  mainline kernel hardware acceleration xmixahlx 33 5,485 06-11-2020, 10:41 AM
Last Post: xmixahlx
  No EDID data for built in screen, PHY missing? bus-error 0 96 06-07-2020, 12:23 PM
Last Post: bus-error
  apt upgrade GloriousCoffee 0 100 05-16-2020, 12:23 PM
Last Post: GloriousCoffee
  iommu page fault causes blank screen under Manjaro 20.04? Damon 3 186 04-18-2020, 05:10 PM
Last Post: Damon
  Adjusting screen resolution lead to a black screen Linux-Rob 15 1,022 03-23-2020, 08:50 AM
Last Post: tophneal

Forum Jump:


Users browsing this thread: 1 Guest(s)