Maarten and Ville noticed that we are enabling backlight via DP aux very
early in the modeset_init path via the intel_dp_aux_setup_backlight()
function, since commit e7156c83 ("drm/i915: Add Backlight Control using
DPCD for eDP connectors (v9)"). Looks like all we need to do during
_setup_backlight() is read the current brightness state instead of
modifying it.

v2: Rewrote commit message.

Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Yetunde Adebisi <yetundex.adebisi@intel.com>
Signed-off-by: NDhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Reviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Acked-by: NJani Nikula <jani.nikula@intel.com>
Tested-by: NPuthikorn Voravootivat <puthik@chromium.org>
Fixes: e7156c83 ("drm/i915: Add Backlight Control using DPCD for eDP connectors (v9)")
Link: http://patchwork.freedesktop.org/patch/msgid/1497384239-2965-1-git-send-email-dhinakaran.pandiyan@intel.comSigned-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
(cherry picked from commit f6262bda)
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1497895708-19422-1-git-send-email-dhinakaran.pandiyan@intel.com