drm/i915: Hook PSR functionality

PSR must be enabled after transcoder and port are running.
And it is only available for HSW.

v2: move enable/disable to intel_ddi
v3: The spec suggests PSR should be disabled even before backlight (by pzanoni)
v4: also disabling and enabling whenever panel is disabled/enabled.
v5: make it last patch to avoid breaking whenever bisecting. So calling for
    update and force exit came to this patch along with enable/disable calls.
v6: Remove unused and unecessary psr_enable/disable calls, as notice by Paulo.

CC: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
[danvet: Drop the psr exit code in the busy ioctl since I didn't merge
that part of the infrastructure yet - it needs more thought.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_ddi.c

@@ -1117,6 +1117,7 @@ static void intel_enable_ddi(struct intel_encoder *intel_encoder)
 			intel_dp_stop_link_train(intel_dp);
 
 		ironlake_edp_backlight_on(intel_dp);
+		intel_edp_psr_enable(intel_dp);
 	}
 
 	if (intel_crtc->eld_vld && type != INTEL_OUTPUT_EDP) {
@@ -1147,6 +1148,7 @@ static void intel_disable_ddi(struct intel_encoder *intel_encoder)
 	if (type == INTEL_OUTPUT_EDP) {
 		struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
 
+		intel_edp_psr_disable(intel_dp);
 		ironlake_edp_backlight_off(intel_dp);
 	}
 }

drivers/gpu/drm/i915/intel_display.c

@@ -2274,6 +2274,7 @@ intel_pipe_set_base(struct drm_crtc *crtc, int x, int y,
 	}
 
 	intel_update_fbc(dev);
+	intel_edp_psr_update(dev);
 	mutex_unlock(&dev->struct_mutex);
 
 	intel_crtc_update_sarea_pos(crtc, x, y);