Black screen regression introduced in: efi: Refactor efi_memmap_init_early() into arch-neutral code

Black screen regression introduced in: efi: Refactor efi_memmap_init_early() into arch-neutral code

[Niklas Hambüchen]

Hello Matt,

I have just gone through a brutal week of kernel bisections, and found that the following refactoring breaks display output on my device:

    commit 9479c7cebfb568f8b8b424be7f1cac120e9eea95
    Author: Matt Fleming <matt@codeblueprint.co.uk>
    Date:   Fri Feb 26 21:22:05 2016 +0000

        efi: Refactor efi_memmap_init_early() into arch-neutral code

The problem is that the screen stays black and there is no modeset flash.

After my bisection showed up this commit, a quick Google for the message turned up:
    https://bugzilla.kernel.org/show_bug.cgi?id=197895
via
    https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1730069
which confirms that there's other hardware beyond my Chromebook Samsung 500C that suffers from this regression.
Both machines are x86_64.

Do you know what might be going wrong here?

I have no experience with EFI related kernel code but have the device around and can test patches, if that helps.

Best,
Niklas

PS:
I've also taken the liberty to CC the people that were on CC in the patch in case that helps with their work.

Re: Black screen regression introduced in: efi: Refactor efi_memmap_init_early() into arch-neutral code

[Niklas Hambüchen]

For posterity, a patch was posted that solves my problem:

https://bugzilla.kernel.org/show_bug.cgi?id=203463#c8