drm/i915: Check VBIOS value for determining LVDS dual channel mode, too
authorTakashi Iwai <tiwai@suse.de>
Tue, 20 Mar 2012 12:07:05 +0000 (13:07 +0100)
committerDaniel Vetter <daniel.vetter@ffwll.ch>
Thu, 22 Mar 2012 22:23:45 +0000 (23:23 +0100)
commitb03543857fd75876b96e10d4320b775e95041bb7
tree3866fde96f20c80b2632ec2227ce618a7d7b0d57
parent1a8c55d37268d8b7ab7797e6d378caa697dbd029
drm/i915: Check VBIOS value for determining LVDS dual channel mode, too

Currently i915 driver checks [PCH_]LVDS register bits to decide
whether to set up the dual-link or the single-link mode.  This relies
implicitly on that BIOS initializes the register properly at boot.
However, BIOS doesn't initialize it always.  When the machine is
booted with the closed lid, BIOS skips the LVDS reg initialization.
This ends up in blank output on a machine with a dual-link LVDS when
you open the lid after the boot.

This patch adds a workaround for that problem by checking the initial
LVDS register value in VBT.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=37742
Tested-By: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
drivers/gpu/drm/i915/i915_drv.h
drivers/gpu/drm/i915/intel_bios.c
drivers/gpu/drm/i915/intel_display.c