linux-kernel - blank screen on boot with i915/DRM_FBDEV

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Date:	Sat, 26 Mar 2016 12:21:23 +0100
From:	Florian Zumbiehl <florz@...rz.de>
To:	intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	Daniel Vetter <daniel.vetter@...el.com>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	David Airlie <airlied@...ux.ie>
Subject: blank screen on boot with i915/DRM_FBDEV_EMULATION

Hi,

I just compiled a new kernel version 4.4.5, replacing a previous 4.1.9 for
my thinkpad x40, which replaced CONFIG_DRM_I915_FBDEV with
CONFIG_DRM_FBDEV_EMULATION--now, when the i915 and fbcon modules get loaded
during boot, the screen goes blank (with backlight still on), which didn't
happen with the old kernel.

The funny thing is that starting an X server makes text reappear on the
console!? (And the X server also works just fine, as far as I can tell so
far ...)

i915 is loaded with modeset=1 (I remember I had some problem without it
with some earlier kernels, I don't really remember the details anymore
...).

Any hints what to try? Any further information that could be useful?

Regards, Florian