drm/i915: Polish CHV CGM CSC loading

Only load the CGM CSC based on the cgm_mode bit like we
do with the gamma/degamma LUTs. And make the function
naming and arguments consistent as well.

TODO: the code to convert the coefficients look totally
bogus. IIRC CHV uses two's complement format but the code
certainly doesn't generate that, so probably negative
coefficients are totally busted.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200303173313.28117-2-ville.syrjala@linux.intel.comReviewed-by: Swati Sharma <swati2.sharma@intel.com>

drivers/gpu/drm/i915/display/intel_color.c

@@ -348,32 +348,29 @@ static void icl_load_csc_matrix(const struct intel_crtc_state *crtc_state)
 		       crtc_state->csc_mode);
 }
 
-/*
- * Set up the pipe CSC unit on CherryView.
- */
-static void cherryview_load_csc_matrix(const struct intel_crtc_state *crtc_state)
+static void chv_load_cgm_csc(struct intel_crtc *crtc,
+			     const struct drm_property_blob *blob)
 {
-	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
 	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
+	const struct drm_color_ctm *ctm = blob->data;
 	enum pipe pipe = crtc->pipe;
-
-	if (crtc_state->hw.ctm) {
-		const struct drm_color_ctm *ctm = crtc_state->hw.ctm->data;
-		u16 coeffs[9] = {};
+	u16 coeffs[9];
 	int i;
 
 	for (i = 0; i < ARRAY_SIZE(coeffs); i++) {
-			u64 abs_coeff =
-				((1ULL << 63) - 1) & ctm->matrix[i];
+		u64 abs_coeff = ((1ULL << 63) - 1) & ctm->matrix[i];
 
 		/* Round coefficient. */
 		abs_coeff += 1 << (32 - 13);
 		/* Clamp to hardware limits. */
 		abs_coeff = clamp_val(abs_coeff, 0, CTM_COEFF_8_0 - 1);
 
+		coeffs[i] = 0;
+
 		/* Write coefficients in S3.12 format. */
 		if (ctm->matrix[i] & (1ULL << 63))
-				coeffs[i] = 1 << 15;
+			coeffs[i] |= 1 << 15;
+
 		coeffs[i] |= ((abs_coeff >> 32) & 7) << 12;
 		coeffs[i] |= (abs_coeff >> 20) & 0xfff;
 	}
@@ -386,10 +383,8 @@ static void cherryview_load_csc_matrix(const struct intel_crtc_state *crtc_state
 		       coeffs[5] << 16 | coeffs[4]);
 	intel_de_write(dev_priv, CGM_PIPE_CSC_COEFF67(pipe),
 		       coeffs[7] << 16 | coeffs[6]);
-		intel_de_write(dev_priv, CGM_PIPE_CSC_COEFF8(pipe), coeffs[8]);
-	}
-
-	intel_de_write(dev_priv, CGM_PIPE_MODE(pipe), crtc_state->cgm_mode);
+	intel_de_write(dev_priv, CGM_PIPE_CSC_COEFF8(pipe),
+		       coeffs[8]);
 }
 
 static u32 i9xx_lut_8(const struct drm_color_lut *color)
@@ -1020,10 +1015,13 @@ static void chv_load_cgm_gamma(struct intel_crtc *crtc,
 static void chv_load_luts(const struct intel_crtc_state *crtc_state)
 {
 	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
-	const struct drm_property_blob *gamma_lut = crtc_state->hw.gamma_lut;
+	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
 	const struct drm_property_blob *degamma_lut = crtc_state->hw.degamma_lut;
+	const struct drm_property_blob *gamma_lut = crtc_state->hw.gamma_lut;
+	const struct drm_property_blob *ctm = crtc_state->hw.ctm;
 
-	cherryview_load_csc_matrix(crtc_state);
+	if (crtc_state->cgm_mode & CGM_PIPE_MODE_CSC)
+		chv_load_cgm_csc(crtc, ctm);
 
 	if (crtc_state->cgm_mode & CGM_PIPE_MODE_DEGAMMA)
 		chv_load_cgm_degamma(crtc, degamma_lut);
@@ -1032,6 +1030,9 @@ static void chv_load_luts(const struct intel_crtc_state *crtc_state)
 		chv_load_cgm_gamma(crtc, gamma_lut);
 	else
 		i965_load_luts(crtc_state);
+
+	intel_de_write(dev_priv, CGM_PIPE_MODE(crtc->pipe),
+		       crtc_state->cgm_mode);
 }
 
 void intel_color_load_luts(const struct intel_crtc_state *crtc_state)