Screen does not turn on after a long time off

[yak_sk]

There might be several causes for this so I will try to describe the situation in as much detail as possible. I've got a
T440s with gentoo linux and 3.14.2-gentoo kernel.

I am running the kernel with the parameters append="quiet init=/usr/lib/systemd/systemd acpi_backlight=vendor", because
otherwise I cannot properly set dosplay brightness using the function buttons and KDE4.

In the KDE screensaver management I turned off all sleep and hibernate feautures. Basically what I want to achieve is have the
screen turn off (dpms) instead of the screen saver after several minutes. It turns back on when I move the mouse or tap the
keyboard. However, if I leave it for several hours (e.g. overnight) the screen won't come back on. I know everything else works - I am able
to operate the computer blind or plug in an external monitor, but the LCD does not turn on until I reboot the machine. (tried xset dpms force on, didn't help)

I suspect this might have something to do with some unsupported features, but I'm completely lost here.
At boot I get this error:

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[    2.084187] thinkpad_acpi: ThinkPad ACPI Extras v0.25
[    2.084188] thinkpad_acpi: http://ibm-acpi.sf.net/
[    2.084189] thinkpad_acpi: ThinkPad BIOS GJET67WW (2.17 ), EC unknown
[    2.084190] thinkpad_acpi: Lenovo ThinkPad T440s, model 20AQ006BMC
[    2.084822] thinkpad_acpi: Unsupported brightness interface, please contact ibm-acpi-devel@lists.sourceforge.net
[    2.084886] thinkpad_acpi: radio switch found; radios are enabled

But apart from this issue, I have none.

[ilakast]

I have no experience with gentoo, only debian, but take a look in the

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/var/log/

folder for logs

For example if I do

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less /var/log/syslog | grep GPU

I get

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Jun 14 19:11:44 t61 kernel: [28264.000032] [drm] GPU crash dump saved to /sys/class/drm/card0/error
Jun 14 19:11:44 t61 kernel: [28264.000035] [drm] GPU hangs can indicate a bug anywhere in the entire gfx stack, including userspace.
Jun 14 21:57:14 t61 kernel: [ 9809.000079] [drm] GPU crash dump saved to /sys/class/drm/card0/error
Jun 14 21:57:14 t61 kernel: [ 9809.000081] [drm] GPU hangs can indicate a bug anywhere in the entire gfx stack, including userspace.

(Yes, I do get some crashes now and then which I'm trying to troubleshoot too). Hope that helps