Arch Linux

Reded

Member

From: Manchester, England

Registered: 2012-02-21

Posts: 242

Backlight turned off completely on boot, requires screen rotate?

Hi everyone, 

I've been running Arch on a GPD Win device for quite a while now - the experience is spotty to say the least, but with quite a lot of hard work being done on the kernel and a lot of those patches being upstreamed, I thought I'd try booting into the stock Arch Linux kernel (I've been using the linux-jwrdegoede-git from the AUR, and prior to its AUR inclusion my own custom PKGBUILD for this). 

When I booted up, I actually thought the device wasn't booting at all, however upon looking at it extra-close I saw that the screen was displaying SDDM as normal, but the backlight was switched off completely. I shined a torch at the screen, typed my login details and got into Plasma. I fumbled for the brightness applet and poked around on the slider, but nothing happened. 

I pretty much gave up trying all sorts of weird tweaks to try and make this work, but then I accidentally held the device sideways - Plasma auto-rotated, and the screen suddenly lit up! I rotated it the right way again, and all the brightness sliders worked perfectly. Annoyingly this doesn't seem to stick upon reboot, and I have to keep rotating the screen. 

So, as the brightness settings seem to work after this rotation re-jig, I assume the stock kernel supports this device's backlight (which is a good start), but I can't seem to shake off the requirement for the rotation dance. 

My /boot/loader/entries/archstock.conf looks like this:

title Arch Linux
linux vmlinuz-linux-jwrdegoede
initrd /intel-ucode.img
initrd /initramfs-linux-jwrdegoede.img
options scsi_mod.use_blk_mq=y dm_mod.use_blk_mq=y i915.nuclear_pageflip=1 i915.semaphores=1 intel_idle.max_cstate=1 i915.enable_rc6=0 i915.fastboot=1 acpi_backlight=native video=efifb fbcon=rotate:1 dmi_product_name=GPD-WINI55 cryptdevice=/dev/encryptedrootdisk:cryptroot:allow-discards cryptkey=/device-for-keyfilexfs:/keyfile root=/dev/mapper/cryptroot rw quiet loglevel=3 vga=current udev.log-priority=3 splash
# dmi_product_name=GPD-WINI55

Quite a lengthy one, but it seems to work with the linux-jwrdegoede kernel fine. I have tried changing acpi_backlight= to all four options (native, video, vendor, none), as well as deleting it completely. I have tried i915.invert_brightness=1, and quiet video.only_lcd=0 (found on this thread: https://bbs.archlinux.org/viewtopic.php?id=236473)

I also went through all of the options in this Ubuntu wiki article: https://wiki.ubuntu.com/Kernel/Debuggin … Techniques It's a bit outdated by the look of things but thought it'd be worth trying. 

I feel like this is going to be yet another case of something dumb and small that I've overlooked without even thinking, but I could do with a prod in the right direction!

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"Some humans would do anything to see if it was possible to do it. If you put a large switch in some cave somewhere, with a sign on it saying "End-of-the-World Switch. PLEASE DO NOT TOUCH", the paint wouldn't even have time to dry."

loqs

Member

Registered: 2014-03-06

Posts: 19,113

Re: Backlight turned off completely on boot, requires screen rotate?

Please post the dmesg from both kernels.  Have you tried  the arch kernel package with the config from linux-jwrdegoede or the linux-jwrdegoede kernel with the config from arch kernel package?
You could also try linux-mainline from AUR to see if it is related to commits only in linux-jwrdegoede that are not in linux mainline 4.17-rc5.

Last edited by loqs (2018-05-19 17:13:51)

Reded

Member

From: Manchester, England

Registered: 2012-02-21

Posts: 242

Re: Backlight turned off completely on boot, requires screen rotate?

It's completely possible that the jwrdegoede kernel still has a couple of patches in there that the stock Arch kernel doesn't, but surely this wouldn't explain why I get the specific behaviour of 'it only works once you spin the screen around'?

I've not tried rebuilding the stock Arch kernel. I did originally build the jwrdegoede kernel using its supplied config but recently took to using modprobed-db to cut back compile times. Both kernels use identical bootloader configs, aside from the obvious name and .img files supplied. 

I wasn't sure which part of the dmesg's you'd like so I just dumped the lot. 

jwrdegoede kernel and  stock kernel pastebinned here! 

Thanks for responding/helping!

---

"Some humans would do anything to see if it was possible to do it. If you put a large switch in some cave somewhere, with a sign on it saying "End-of-the-World Switch. PLEASE DO NOT TOUCH", the paint wouldn't even have time to dry."

loqs

Member

Registered: 2014-03-06

Posts: 19,113

Re: Backlight turned off completely on boot, requires screen rotate?

Immediate difference I noticed was

[   12.149701] [drm] Using 80862288:00 pwm-device for backlight control

Which seems to be caused by https://github.com/jwrdegoede/linux-sun … e936b333a8
Not sure if this is related https://github.com/jwrdegoede/linux-sun … ceed933626

Reded

Member

From: Manchester, England

Registered: 2012-02-21

Posts: 242

Re: Backlight turned off completely on boot, requires screen rotate?

Those are fairly old patches though judging by the dates, and I've generally been building my jwrdegoede kernel from git (Unless you mean that these patches *fix* the issue, and haven't made their way into the Arch kernel yet!)

For now I don't mind going back to the jwrdegoede, but would be nice to keep to stock as much as I can eventually!

---

"Some humans would do anything to see if it was possible to do it. If you put a large switch in some cave somewhere, with a sign on it saying "End-of-the-World Switch. PLEASE DO NOT TOUCH", the paint wouldn't even have time to dry."

loqs

Member

Registered: 2014-03-06

Posts: 19,113

Re: Backlight turned off completely on boot, requires screen rotate?

Those patches are not in the arch linux package which is based on linux-stable tree from kernel.org or the mainline (Linus's) tree from kernel.org.