tree 5dfaf5544a7343b43547b65062eb135e3ebb23dd
parent 437b15b8017e0d946453c10794b0c5d4591cf180
author Jani Nikula <jani.nikula@intel.com> 1441374914 +0300
committer Daniel Vetter <daniel.vetter@ffwll.ch> 1441643341 +0200

drm/i915: initialize backlight max from VBT

Normally we determine the backlight PWM modulation frequency (which we
also use as backlight max value) from the backlight registers at module
load time, expecting the registers have been initialized by the BIOS. If
this is not the case, we fail.

The VBT contains the backlight modulation frequency in Hz. Add platform
specific functions to convert the frequency in Hz to backlight PWM
modulation frequency, and use them to initialize the backlight when the
registers are not initialized by the BIOS.

v2: Fix SPT and VLV. Thanks to Clint for the VLV code.

Cc: Clint Taylor <clinton.a.taylor@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Clint Taylor <Clinton.A.Taylor@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>