drm/i915: Rework legacy LUT handling

Currently crtc_state_is_legacy_gamma() has a very specific set
of conditions, not all of which are actually necessary. Also
when we detect those conditions check_luts() just skips all
the checks. That will no longer work for glk soon when we'll
start to use the hw degamma LUT in place of the hw gamma LUT
for YCbCr output. So let's rework the logic to only really consider
whether the user provided gamma_lut is one that matches the hw
legacy LUT capabilities or not.

We'll need to reject C8+degamma on ivb+ since the presence of
degamma_lut would either mean we have to really use the LUT
for degamma as opposed to C8 palette, or we have to enable
split gamma mode which also can't work as the C8 palette.

Otherwise this will now cause the legacy LUT to go through the
regular lut checks as well. As a side effect we also start to
allow the use of the legacy LUT with CTM, but that is perfectly
fine as far a the hardware is concerned.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221114153732.11773-17-ville.syrjala@linux.intel.comReviewed-by: Uma Shankar <uma.shankar@intel.com>

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

@@ -154,15 +154,7 @@ static const u16 ilk_csc_postoff_rgb_to_ycbcr[3] = {
 
 static bool lut_is_legacy(const struct drm_property_blob *lut)
 {
-	return drm_color_lut_size(lut) == LEGACY_LUT_LENGTH;
-}
-
-static bool crtc_state_is_legacy_gamma(const struct intel_crtc_state *crtc_state)
-{
-	return !crtc_state->hw.degamma_lut &&
-		!crtc_state->hw.ctm &&
-		crtc_state->hw.gamma_lut &&
-		lut_is_legacy(crtc_state->hw.gamma_lut);
+	return lut && drm_color_lut_size(lut) == LEGACY_LUT_LENGTH;
 }
 
 /*
@@ -1317,6 +1309,42 @@ intel_color_add_affected_planes(struct intel_crtc_state *new_crtc_state)
 	return 0;
 }
 
+static u32 intel_gamma_lut_tests(const struct intel_crtc_state *crtc_state)
+{
+	struct drm_i915_private *i915 = to_i915(crtc_state->uapi.crtc->dev);
+	const struct drm_property_blob *gamma_lut = crtc_state->hw.gamma_lut;
+
+	if (lut_is_legacy(gamma_lut))
+		return 0;
+
+	return INTEL_INFO(i915)->display.color.gamma_lut_tests;
+}
+
+static u32 intel_degamma_lut_tests(const struct intel_crtc_state *crtc_state)
+{
+	struct drm_i915_private *i915 = to_i915(crtc_state->uapi.crtc->dev);
+
+	return INTEL_INFO(i915)->display.color.degamma_lut_tests;
+}
+
+static int intel_gamma_lut_size(const struct intel_crtc_state *crtc_state)
+{
+	struct drm_i915_private *i915 = to_i915(crtc_state->uapi.crtc->dev);
+	const struct drm_property_blob *gamma_lut = crtc_state->hw.gamma_lut;
+
+	if (lut_is_legacy(gamma_lut))
+		return LEGACY_LUT_LENGTH;
+
+	return INTEL_INFO(i915)->display.color.gamma_lut_size;
+}
+
+static u32 intel_degamma_lut_size(const struct intel_crtc_state *crtc_state)
+{
+	struct drm_i915_private *i915 = to_i915(crtc_state->uapi.crtc->dev);
+
+	return INTEL_INFO(i915)->display.color.degamma_lut_size;
+}
+
 static int check_lut_size(const struct drm_property_blob *lut, int expected)
 {
 	int len;
@@ -1342,21 +1370,17 @@ static int check_luts(const struct intel_crtc_state *crtc_state)
 	int gamma_length, degamma_length;
 	u32 gamma_tests, degamma_tests;
 
-	/* Always allow legacy gamma LUT with no further checking. */
-	if (crtc_state_is_legacy_gamma(crtc_state))
-		return 0;
-
 	/* C8 relies on its palette being stored in the legacy LUT */
-	if (crtc_state->c8_planes) {
+	if (crtc_state->c8_planes && !lut_is_legacy(crtc_state->hw.gamma_lut)) {
 		drm_dbg_kms(&i915->drm,
 			    "C8 pixelformat requires the legacy LUT\n");
 		return -EINVAL;
 	}
 
-	degamma_length = INTEL_INFO(i915)->display.color.degamma_lut_size;
-	gamma_length = INTEL_INFO(i915)->display.color.gamma_lut_size;
-	degamma_tests = INTEL_INFO(i915)->display.color.degamma_lut_tests;
-	gamma_tests = INTEL_INFO(i915)->display.color.gamma_lut_tests;
+	degamma_length = intel_degamma_lut_size(crtc_state);
+	gamma_length = intel_gamma_lut_size(crtc_state);
+	degamma_tests = intel_degamma_lut_tests(crtc_state);
+	gamma_tests = intel_gamma_lut_tests(crtc_state);
 
 	if (check_lut_size(degamma_lut, degamma_length) ||
 	    check_lut_size(gamma_lut, gamma_length))
@@ -1372,7 +1396,7 @@ static int check_luts(const struct intel_crtc_state *crtc_state)
 static u32 i9xx_gamma_mode(struct intel_crtc_state *crtc_state)
 {
 	if (!crtc_state->gamma_enable ||
-	    crtc_state_is_legacy_gamma(crtc_state))
+	    lut_is_legacy(crtc_state->hw.gamma_lut))
 		return GAMMA_MODE_MODE_8BIT;
 	else
 		return GAMMA_MODE_MODE_10BIT; /* i965+ only */
@@ -1441,14 +1465,12 @@ static u32 chv_cgm_mode(const struct intel_crtc_state *crtc_state)
 {
 	u32 cgm_mode = 0;
 
-	if (crtc_state_is_legacy_gamma(crtc_state))
-		return 0;
-
 	if (crtc_state->hw.degamma_lut)
 		cgm_mode |= CGM_PIPE_MODE_DEGAMMA;
 	if (crtc_state->hw.ctm)
 		cgm_mode |= CGM_PIPE_MODE_CSC;
-	if (crtc_state->hw.gamma_lut)
+	if (crtc_state->hw.gamma_lut &&
+	    !lut_is_legacy(crtc_state->hw.gamma_lut))
 		cgm_mode |= CGM_PIPE_MODE_GAMMA;
 
 	return cgm_mode;
@@ -1475,7 +1497,7 @@ static int chv_color_check(struct intel_crtc_state *crtc_state)
 	 * Otherwise we bypass it and use the CGM gamma instead.
 	 */
 	crtc_state->gamma_enable =
-		crtc_state_is_legacy_gamma(crtc_state) &&
+		lut_is_legacy(crtc_state->hw.gamma_lut) &&
 		!crtc_state->c8_planes;
 
 	crtc_state->gamma_mode = GAMMA_MODE_MODE_8BIT;
@@ -1510,7 +1532,7 @@ static bool ilk_csc_enable(const struct intel_crtc_state *crtc_state)
 static u32 ilk_gamma_mode(const struct intel_crtc_state *crtc_state)
 {
 	if (!crtc_state->gamma_enable ||
-	    crtc_state_is_legacy_gamma(crtc_state))
+	    lut_is_legacy(crtc_state->hw.gamma_lut))
 		return GAMMA_MODE_MODE_8BIT;
 	else
 		return GAMMA_MODE_MODE_10BIT;
@@ -1656,6 +1678,12 @@ static int ivb_color_check(struct intel_crtc_state *crtc_state)
 	if (ret)
 		return ret;
 
+	if (crtc_state->c8_planes && crtc_state->hw.degamma_lut) {
+		drm_dbg_kms(&i915->drm,
+			    "C8 pixelformat and degamma together are not possible\n");
+		return -EINVAL;
+	}
+
 	if (crtc_state->output_format != INTEL_OUTPUT_FORMAT_RGB &&
 	    crtc_state->hw.ctm) {
 		drm_dbg_kms(&i915->drm,
@@ -1694,7 +1722,7 @@ static int ivb_color_check(struct intel_crtc_state *crtc_state)
 static u32 glk_gamma_mode(const struct intel_crtc_state *crtc_state)
 {
 	if (!crtc_state->gamma_enable ||
-	    crtc_state_is_legacy_gamma(crtc_state))
+	    lut_is_legacy(crtc_state->hw.gamma_lut))
 		return GAMMA_MODE_MODE_8BIT;
 	else
 		return GAMMA_MODE_MODE_10BIT;
@@ -1779,7 +1807,7 @@ static u32 icl_gamma_mode(const struct intel_crtc_state *crtc_state)
 		gamma_mode |= POST_CSC_GAMMA_ENABLE;
 
 	if (!crtc_state->hw.gamma_lut ||
-	    crtc_state_is_legacy_gamma(crtc_state))
+	    lut_is_legacy(crtc_state->hw.gamma_lut))
 		gamma_mode |= GAMMA_MODE_MODE_8BIT;
 	/*
 	 * Enable 10bit gamma for D13