drm/i915: prepare scaler for YCBCR420 modeset

To get a YCBCR420 output from intel platforms, we need one
scaler to scale down YCBCR444 samples to YCBCR420 samples.

This patch:
- Does scaler allocation for HDMI ycbcr420 outputs.
- Programs PIPE_MISC register for ycbcr420 output.

V2: rebase
V3: rebase
V4: rebase
V5: addressed review comments from Ander:
    - No need to check both scaler_user && hdmi_output.
      Check for scaler_user is enough.
V6: rebase
V7: Do not create a new scaler user, use existing pipe scaler user.
V8: rebase
V9: Addressed review comments from Ville:
    - Remove leftover comment for HDMI scaler user.
    - Remove unnecessary blank line.
    - Make scaler alocation failure a DEBUG log instead of ERROR.
    Added r-b from Ville
V10: Update commit message as per latest code (Imre)
     Added r-b from Imre

Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Ander Conselvan De Oliveira <conselvan2@gmail.com>
Cc: Imre Deak <imre.deak@intel.com>

Reviewed-by: Ville Syrjala <ville.syrjala@linux.intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1500650709-14447-3-git-send-email-shashank.sharma@intel.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -4487,6 +4487,9 @@ skl_update_scaler(struct intel_crtc_state *crtc_state, bool force_detach,
 	 */
 	need_scaling = src_w != dst_w || src_h != dst_h;
 
+	if (crtc_state->ycbcr420 && scaler_user == SKL_CRTC_INDEX)
+		need_scaling = true;
+
 	/*
 	 * Scaling/fitting not supported in IF-ID mode in GEN9+
 	 * TODO: Interlace fetch mode doesn't support YUV420 planar formats.

drivers/gpu/drm/i915/intel_hdmi.c

@@ -1354,6 +1354,8 @@ intel_hdmi_ycbcr420_config(struct drm_connector *connector,
 			   struct intel_crtc_state *config,
 			   int *clock_12bpc, int *clock_8bpc)
 {
+	struct intel_crtc *intel_crtc = to_intel_crtc(config->base.crtc);
+
 	if (!connector->ycbcr_420_allowed) {
 		DRM_ERROR("Platform doesn't support YCBCR420 output\n");
 		return false;
@@ -1364,6 +1366,16 @@ intel_hdmi_ycbcr420_config(struct drm_connector *connector,
 	*clock_12bpc /= 2;
 	*clock_8bpc /= 2;
 	config->ycbcr420 = true;
+
+	/* YCBCR 420 output conversion needs a scaler */
+	if (skl_update_scaler_crtc(config)) {
+		DRM_DEBUG_KMS("Scaler allocation for output failed\n");
+		return false;
+	}
+
+	intel_pch_panel_fitting(intel_crtc, config,
+				DRM_MODE_SCALE_FULLSCREEN);
+
 	return true;
 }
 

drivers/gpu/drm/i915/intel_panel.c

@@ -110,7 +110,8 @@ intel_pch_panel_fitting(struct intel_crtc *intel_crtc,
 
 	/* Native modes don't need fitting */
 	if (adjusted_mode->crtc_hdisplay == pipe_config->pipe_src_w &&
-	    adjusted_mode->crtc_vdisplay == pipe_config->pipe_src_h)
+	    adjusted_mode->crtc_vdisplay == pipe_config->pipe_src_h &&
+	    !pipe_config->ycbcr420)
 		goto done;
 
 	switch (fitting_mode) {