[Bug 80182] [IVB regression] screen not resuming on kernel 3.14.6 and above

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=80182

--- Comment #16 from Hans de Goede <jwrdegoede at fedoraproject.org> ---
(In reply to comment #14)
> (In reply to comment #8)
> > 3e873234bf01413486c9d7151dea202a7ffc6a43 is the first bad commit
> > commit 3e873234bf01413486c9d7151dea202a7ffc6a43
> > Author: Hans de Goede <hdegoede at redhat.com>
> > Date:   Mon May 5 11:38:08 2014 +0200
> > 
> >     ACPI / video: Add use_native_backlight quirks for more systems
> 
> CC: Hans and Aaron
> 
> Any thoughts before I close this as NOTOURBUG on i915 side?

What the commit to which this was bisected does, is change the used backlight
driver from acpi to the intel_backlight driver. So I'm not entirely sure it is
fair to say NOTOURBUG on i915 side.

Clearly something is not working right on the i915 side if the backlight does
not come up after suspend/resume when the acpi backlight code is not involved.
Things happened to work before since the acpi code path likely poked some
register which the i915 code forgets to poke ...

If you read: https://bugzilla.kernel.org/show_bug.cgi?id=51231 then you will
see that there are lots of problems with the Thinkpad T?30 / X230 series and
acpi-video, related to win8 support in the BIOS.

Also while the switch from acpi-video to intel as the backlight driver of
choice was done with a quirk in 3.14, but in 3.16 this behavior
(video.use_native_backlight) now is the default.

This also makes me wonder if there is anything special with Mariano's laptop,
or if this maybe is already fixed in 3.16, otherwise we should have a lot more
bug reports as the T430 is a quite popular model.

Mariano, any chance you could try with a 3.16 kernel ?

Also can you please try adding: "video.use_native_backlight=0" the the kernel
commandline with 3.14.6? That should fix things if your bisect has found the
right commit as the culprit.

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