Created attachment 168861 [details]
lspci -vvv -s 00_02.0
Screen LVDS1 turns black early at boot with kernel 3.14
The computer is a laptop and has been used with an external screen plugged (VGA) for several months.
After unplugging the VGA from the laptop I was getting a black screen at boot. Grub2 screen is ok but in the very early stage at boot just after showing the first few kernel lines the built-in screen turns black.
CTRL-ALT-F1 + CTRL-ALT--F7 does not help. Built-in screen stays black until a VGA is plugged.
With the VGA plugged (even when it's power is off) the boot is normal with all the boot messages visible on the built-in screen. This behaviour is reproducible:
VGA plugged: Screen is ok
VGA unplugged: Screen tuns black at boot
The problem seems to be fixed later in kernel v3.15
Created attachment 168871 [details]
dmesg without VGA plugged
Created attachment 168881 [details]
reverse git bisect
I did a reverse git bisect leading to 484b41dd70a9fbea894632d8926bbb93f05021c7
$ git branch --contains 484b41dd70a9fbea894632d8926bbb93f05021c7
$ git tag --contains 484b41dd70a9fbea894632d8926bbb93f05021c7
... until ...
Checked out v.3.15 for testing and was ok.
Created attachment 168891 [details]
Thanks for the reverse bisect, however the commit is too big to be backported to stable kernels. Please upgrade to v3.15 or later. Thanks for the report.