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skgucek
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Joined: 10 Feb 2015
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PostPosted: Sun Mar 22, 2015 7:31 pm    Post subject: Strange graphics corruption when GRUB is loading Reply with quote

Hey people,

I have set up a nice Gentoo system on an ASUS N56VZ Ivy Bridge/Nvidia "Optimus" laptop. My simplified boot setup is EFI>GRUB2>Gentoo (no initramfs). I generated the GRUB config with "grub2-mkconfig -o /boot/grub/grub.cfg".

The only quirk that bothers me is that when GRUB loads (after the "Welcome to GRUB!" text) there for a second or so always appears a strange form of graphics corruption, a large square on the left with lots of strangely coloured lines and dots. Then it disappears and the GRUB boot selection menu loads up just fine. Otherwise the system and the dual-boot with Windows 8.1 on the same machine appear to function just fine, including both graphics chips.

I'm attaching some pictures so you can visualise what I'm describing ... http://pbrd.co/1B47S3A http://pbrd.co/1B48qqd (on the second one it is fading away to the GRUB selection screen).

"eix grub":
Code:
[I] sys-boot/grub
     Available versions: 
     (0)    0.97-r14
     (2)    2.00_p5107-r2^t 2.02_beta2-r3^t (~)2.02_beta2-r6^t (~)2.02_beta2-r7^t **9999-r1^t
       {custom-cflags debug device-mapper doc efiemu +fonts libzfs mount +multislot ncurses netboot nls sdl static test +themes truetype GRUB_PLATFORMS="coreboot efi-32 efi-64 emu ieee1275 loongson multiboot pc qemu qemu-mips xen yeeloong"}
     Installed versions:  2.02_beta2-r7(2)^t(16:25:38 11. 02. 2015)(fonts multislot nls sdl themes truetype -debug -device-mapper -doc -efiemu -libzfs -mount -static -test GRUB_PLATFORMS="efi-64 pc -coreboot -efi-32 -emu -ieee1275 -loongson -multiboot -qemu -qemu-mips -xen")
     Homepage:            http://www.gnu.org/software/grub/
     Description:         GNU GRUB boot loader

Do you need any more info/uploaded configuration files? I'm not really sure what to post, but I'll heed any request you might have. And, I know I'm using the ~ branch (for the whole system), but I can assure you, the same thing was happening in exactly the same manner even before I went "unstable".

Thanks for any help you can spare!
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Logicien
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Joined: 16 Sep 2005
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PostPosted: Sun Mar 22, 2015 9:32 pm    Post subject: Reply with quote

Hello,

did you configure /etc/default/grub (or /etc/conf.d/grub) before doing grub-mkconfig? This file can set the resolution of Grub2 menu with the GRUB_GFXMODE variable. The mine is

Code:
GRUB_GFXMODE=1024x768x32


You can retreive the available modes if you press the c key at the Grub menu to go to the command line and execute

Code:
videoinfo

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skgucek
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PostPosted: Mon Mar 23, 2015 3:00 am    Post subject: Reply with quote

Logicien wrote:
Hello,

did you configure /etc/default/grub (or /etc/conf.d/grub) before doing grub-mkconfig? This file can set the resolution of Grub2 menu with the GRUB_GFXMODE variable. The mine is

Code:
GRUB_GFXMODE=1024x768x32


You can retreive the available modes if you press the c key at the Grub menu to go to the command line and execute

Code:
videoinfo


Thank you for your suggestion!

I found out that this setting was foolishly set by me to 1920x1080x32, apparently without checking videoinfo first, as this resolution is not listed there (just 1024x768 and 800x600). So I set it to the default "auto" and ran grub2-mkconfig (twice), but the problem still persists and videoinfo still lists 1920x1080 as the "preferred resolution". Does this mean that the computer somehow suggests an unsupported resolution to GRUB or that the config is not updating properly? It did so earlier today when I updated to the 3.19.2 kernel.

EDIT: Just in case, I just re-ran:
Code:
grub2-install --target=x86_64-efi /dev/sdan
grub2-mkconfig -o /boot/grub/grub.cfg


And nothing changed. I also checked the generated grub.conf for "set gfxmode=auto" and manually changed the name of a menuentry so that I could confirm that GRUB is parsing the new config. Also, I tried with 1024x768 instead of auto and the result is the same.

Last thing I would like to add, this is not the first time I'm setting the gfxmode variable, I also went through a similar problem (unsupported resolutions) on another laptop and I learned my lesson. I'm really sure that when I was configuring GRUB (about a month ago) I did check videoinfo and 1080p was listed there along with many other resolutions (not just 1024x768 and 800x600 like now). Why would these suddenly disappear and this graphics problem start appearing?
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