drm/i915: Enable VBT based BL control for DP

Currently, BXT_PP is hardcoded with value '0'.
It practically disabled eDP backlight on MRB (BXT) platform.

This patch will tell which BXT_PP registers (there are two set of
PP_CONTROL in the spec) to be used as defined in VBT (Video Bios Timing
table) and this will enabled eDP backlight controller on MRB (BXT)
platform.

v2:
 - Remove unnecessary information in commit message.
 - Assign vbt.backlight.controller to a backlight_controller variable and
   return the variable value.
v3:
 - Rebased to latest code base.
 - updated commit title.

Signed-off-by: Mustamin B Mustaffa <mustamin.b.mustaffa@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180227030734.37901-1-mustamin.b.mustaffa@intel.com
(cherry picked from commit 73c0fcac97bf7f4a6a61b825b205d1cf127cfca7)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

1 files changed, 3 insertions, 7 deletions

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 35c5299feab6..a29868cd30c7 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -620,19 +620,15 @@ static int
 bxt_power_sequencer_idx(struct intel_dp *intel_dp)
 {
         struct drm_i915_private *dev_priv = to_i915(intel_dp_to_dev(intel_dp));
+        int backlight_controller = dev_priv->vbt.backlight.controller;
 
         lockdep_assert_held(&dev_priv->pps_mutex);
 
         /* We should never land here with regular DP ports */
         WARN_ON(!intel_dp_is_edp(intel_dp));
 
-        /*
-         * TODO: BXT has 2 PPS instances. The correct port->PPS instance
-         * mapping needs to be retrieved from VBT, for now just hard-code to
-         * use instance #0 always.
-         */
         if (!intel_dp->pps_reset)
-                return 0;
+                return backlight_controller;
 
         intel_dp->pps_reset = false;
 
@@ -642,7 +638,7 @@ bxt_power_sequencer_idx(struct intel_dp *intel_dp)
          */
         intel_dp_init_panel_power_sequencer_registers(intel_dp, false);
 
-        return 0;
+        return backlight_controller;
 }
 
 typedef bool (*vlv_pipe_check)(struct drm_i915_private *dev_priv,