drm/i915: Don't use split gamma when we don't have to

Using the split gamma mode when we don't have to has the annoying
requirement of loading a linear LUT to the unused half. Instead
let's make life simpler by switching to the 10bit gamma mode
and duplicating each entry.

This also allows us to load the software gamma LUT into the
hardware degamma LUT, thus removing some of the buggy
configurations we currently allow (YCbCr/limited range RGB
+ gamma LUT). We do still have other configurations that are
also buggy, but those will need more complicated fixes
or they just need to be rejected. Sadly GLK doesn't have
this flexibility anymore and the degamma and gamma LUTs
are very different so no help there.

v2: Apply a mask when checking gamma_mode on icl since it
    contains more bits than just the gamma mode
v3: Rebase due to EXT_GC_MAX/EXT2_GC_MAX changes
v4: s/advertize/advertise/ (Uma)
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190401200231.2333-3-ville.syrjala@linux.intel.comReviewed-by: Uma Shankar <uma.shankar@intel.com>

drivers/gpu/drm/i915/i915_reg.h

@@ -7214,6 +7214,7 @@ enum {
 #define GAMMA_MODE(pipe) _MMIO_PIPE(pipe, _GAMMA_MODE_A, _GAMMA_MODE_B)
 #define  PRE_CSC_GAMMA_ENABLE	(1 << 31)
 #define  POST_CSC_GAMMA_ENABLE	(1 << 30)
+#define  GAMMA_MODE_MODE_MASK	(3 << 0)
 #define  GAMMA_MODE_MODE_8BIT	(0 << 0)
 #define  GAMMA_MODE_MODE_10BIT	(1 << 0)
 #define  GAMMA_MODE_MODE_12BIT	(2 << 0)
@@ -10127,6 +10128,7 @@ enum skl_power_gate {
 #define   PAL_PREC_SPLIT_MODE		(1 << 31)
 #define   PAL_PREC_AUTO_INCREMENT	(1 << 15)
 #define   PAL_PREC_INDEX_VALUE_MASK	(0x3ff << 0)
+#define   PAL_PREC_INDEX_VALUE(x)	((x) << 0)
 #define _PAL_PREC_DATA_A	0x4A404
 #define _PAL_PREC_DATA_B	0x4AC04
 #define _PAL_PREC_DATA_C	0x4B404

drivers/gpu/drm/i915/intel_color.c

@@ -466,115 +466,83 @@ static void skl_color_commit(const struct intel_crtc_state *crtc_state)
 		ilk_load_csc_matrix(crtc_state);
 }
 
-static void bdw_load_degamma_lut(const struct intel_crtc_state *crtc_state)
+static void bdw_load_lut_10(struct intel_crtc *crtc,
+			    const struct drm_property_blob *blob,
+			    u32 prec_index, bool duplicate)
 {
-	struct intel_crtc *crtc = to_intel_crtc(crtc_state->base.crtc);
 	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
-	const struct drm_property_blob *degamma_lut = crtc_state->base.degamma_lut;
-	u32 i, lut_size = INTEL_INFO(dev_priv)->color.degamma_lut_size;
+	const struct drm_color_lut *lut = blob->data;
+	int i, lut_size = drm_color_lut_size(blob);
 	enum pipe pipe = crtc->pipe;
 
-	I915_WRITE(PREC_PAL_INDEX(pipe),
-		   PAL_PREC_SPLIT_MODE | PAL_PREC_AUTO_INCREMENT);
-
-	if (degamma_lut) {
-		const struct drm_color_lut *lut = degamma_lut->data;
+	I915_WRITE(PREC_PAL_INDEX(pipe), prec_index |
+		   PAL_PREC_AUTO_INCREMENT);
 
-		for (i = 0; i < lut_size; i++)
-			I915_WRITE(PREC_PAL_DATA(pipe), ilk_lut_10(&lut[i]));
-	} else {
+	/*
+	 * We advertise the split gamma sizes. When not using split
+	 * gamma we just duplicate each entry.
+	 *
+	 * TODO: expose the full LUT to userspace
+	 */
+	if (duplicate) {
 		for (i = 0; i < lut_size; i++) {
-			u32 v = (i * ((1 << 10) - 1)) / (lut_size - 1);
-
-			I915_WRITE(PREC_PAL_DATA(pipe),
-				   (v << 20) | (v << 10) | v);
+			I915_WRITE(PREC_PAL_DATA(pipe), ilk_lut_10(&lut[i]));
+			I915_WRITE(PREC_PAL_DATA(pipe), ilk_lut_10(&lut[i]));
 		}
+	} else {
+		for (i = 0; i < lut_size; i++)
+			I915_WRITE(PREC_PAL_DATA(pipe), ilk_lut_10(&lut[i]));
 	}
+
+	/*
+	 * Reset the index, otherwise it prevents the legacy palette to be
+	 * written properly.
+	 */
+	I915_WRITE(PREC_PAL_INDEX(pipe), 0);
 }
 
-static void bdw_load_gamma_lut(const struct intel_crtc_state *crtc_state, u32 offset)
+static void bdw_load_lut_10_max(struct intel_crtc *crtc)
 {
-	struct intel_crtc *crtc = to_intel_crtc(crtc_state->base.crtc);
 	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
-	const struct drm_property_blob *gamma_lut = crtc_state->base.gamma_lut;
-	u32 i, lut_size = INTEL_INFO(dev_priv)->color.gamma_lut_size;
 	enum pipe pipe = crtc->pipe;
 
-	WARN_ON(offset & ~PAL_PREC_INDEX_VALUE_MASK);
-
-	I915_WRITE(PREC_PAL_INDEX(pipe),
-		   (offset ? PAL_PREC_SPLIT_MODE : 0) |
-		   PAL_PREC_AUTO_INCREMENT |
-		   offset);
-
-	if (gamma_lut) {
-		const struct drm_color_lut *lut = gamma_lut->data;
-
-		for (i = 0; i < lut_size; i++)
-			I915_WRITE(PREC_PAL_DATA(pipe), ilk_lut_10(&lut[i]));
-
-		/*
-		 * Program the max register to clamp values > 1.0.
-		 * ToDo: Extend the ABI to be able to program values
-		 * from 1.0 to 3.0
-		 */
-		I915_WRITE(PREC_PAL_EXT_GC_MAX(pipe, 0), (1 << 16));
-		I915_WRITE(PREC_PAL_EXT_GC_MAX(pipe, 1), (1 << 16));
-		I915_WRITE(PREC_PAL_EXT_GC_MAX(pipe, 2), (1 << 16));
-
-		/*
-		 * Program the gc max 2 register to clamp values > 1.0.
-		 * ToDo: Extend the ABI to be able to program values
-		 * from 3.0 to 7.0
-		 */
-		if (INTEL_GEN(dev_priv) >= 10 || IS_GEMINILAKE(dev_priv)) {
-			I915_WRITE(PREC_PAL_EXT2_GC_MAX(pipe, 0), (1 << 16));
-			I915_WRITE(PREC_PAL_EXT2_GC_MAX(pipe, 1), (1 << 16));
-			I915_WRITE(PREC_PAL_EXT2_GC_MAX(pipe, 2), (1 << 16));
-		}
-	} else {
-		for (i = 0; i < lut_size; i++) {
-			u32 v = (i * ((1 << 10) - 1)) / (lut_size - 1);
-
-			I915_WRITE(PREC_PAL_DATA(pipe),
-				   (v << 20) | (v << 10) | v);
-		}
-
-		I915_WRITE(PREC_PAL_EXT_GC_MAX(pipe, 0), (1 << 16));
-		I915_WRITE(PREC_PAL_EXT_GC_MAX(pipe, 1), (1 << 16));
-		I915_WRITE(PREC_PAL_EXT_GC_MAX(pipe, 2), (1 << 16));
-
-		/*
-		 * Program the gc max 2 register to clamp values > 1.0.
-		 * ToDo: Extend the ABI to be able to program values
-		 * from 3.0 to 7.0
-		 */
-		if (INTEL_GEN(dev_priv) >= 10 || IS_GEMINILAKE(dev_priv)) {
-			I915_WRITE(PREC_PAL_EXT2_GC_MAX(pipe, 0), (1 << 16));
-			I915_WRITE(PREC_PAL_EXT2_GC_MAX(pipe, 1), (1 << 16));
-			I915_WRITE(PREC_PAL_EXT2_GC_MAX(pipe, 2), (1 << 16));
-		}
-	}
+	/* Program the max register to clamp values > 1.0. */
+	I915_WRITE(PREC_PAL_EXT_GC_MAX(pipe, 0), 1 << 16);
+	I915_WRITE(PREC_PAL_EXT_GC_MAX(pipe, 1), 1 << 16);
+	I915_WRITE(PREC_PAL_EXT_GC_MAX(pipe, 2), 1 << 16);
 
 	/*
-	 * Reset the index, otherwise it prevents the legacy palette to be
-	 * written properly.
+	 * Program the gc max 2 register to clamp values > 1.0.
+	 * ToDo: Extend the ABI to be able to program values
+	 * from 3.0 to 7.0
 	 */
-	I915_WRITE(PREC_PAL_INDEX(pipe), 0);
+	if (INTEL_GEN(dev_priv) >= 10 || IS_GEMINILAKE(dev_priv)) {
+		I915_WRITE(PREC_PAL_EXT2_GC_MAX(pipe, 0), 1 << 16);
+		I915_WRITE(PREC_PAL_EXT2_GC_MAX(pipe, 1), 1 << 16);
+		I915_WRITE(PREC_PAL_EXT2_GC_MAX(pipe, 2), 1 << 16);
+	}
 }
 
-/* Loads the palette/gamma unit for the CRTC on Broadwell+. */
-static void broadwell_load_luts(const struct intel_crtc_state *crtc_state)
+static void bdw_load_luts(const struct intel_crtc_state *crtc_state)
 {
 	struct intel_crtc *crtc = to_intel_crtc(crtc_state->base.crtc);
-	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
+	const struct drm_property_blob *gamma_lut = crtc_state->base.gamma_lut;
+	const struct drm_property_blob *degamma_lut = crtc_state->base.degamma_lut;
 
-	if (crtc_state_is_legacy_gamma(crtc_state)) {
+	if (crtc_state->gamma_mode == GAMMA_MODE_MODE_8BIT) {
 		i9xx_load_luts(crtc_state);
+	} else if (crtc_state->gamma_mode == GAMMA_MODE_MODE_SPLIT) {
+		bdw_load_lut_10(crtc, degamma_lut, PAL_PREC_SPLIT_MODE |
+				PAL_PREC_INDEX_VALUE(0), false);
+		bdw_load_lut_10_max(crtc);
+		bdw_load_lut_10(crtc, gamma_lut, PAL_PREC_SPLIT_MODE |
+				PAL_PREC_INDEX_VALUE(512),  false);
 	} else {
-		bdw_load_degamma_lut(crtc_state);
-		bdw_load_gamma_lut(crtc_state,
-				   INTEL_INFO(dev_priv)->color.degamma_lut_size);
+		const struct drm_property_blob *blob = gamma_lut ?: degamma_lut;
+
+		bdw_load_lut_10(crtc, blob,
+				PAL_PREC_INDEX_VALUE(0), true);
+		bdw_load_lut_10_max(crtc);
 	}
 }
 
@@ -646,6 +614,9 @@ static void glk_load_degamma_lut_linear(const struct intel_crtc_state *crtc_stat
 
 static void glk_load_luts(const struct intel_crtc_state *crtc_state)
 {
+	const struct drm_property_blob *gamma_lut = crtc_state->base.gamma_lut;
+	struct intel_crtc *crtc = to_intel_crtc(crtc_state->base.crtc);
+
 	/*
 	 * On GLK+ both pipe CSC and degamma LUT are controlled
 	 * by csc_enable. Hence for the cases where the CSC is
@@ -659,22 +630,29 @@ static void glk_load_luts(const struct intel_crtc_state *crtc_state)
 	else
 		glk_load_degamma_lut_linear(crtc_state);
 
-	if (crtc_state_is_legacy_gamma(crtc_state))
+	if (crtc_state->gamma_mode == GAMMA_MODE_MODE_8BIT) {
 		i9xx_load_luts(crtc_state);
-	else
-		bdw_load_gamma_lut(crtc_state, 0);
+	} else {
+		bdw_load_lut_10(crtc, gamma_lut, PAL_PREC_INDEX_VALUE(0), false);
+		bdw_load_lut_10_max(crtc);
+	}
 }
 
 static void icl_load_luts(const struct intel_crtc_state *crtc_state)
 {
+	const struct drm_property_blob *gamma_lut = crtc_state->base.gamma_lut;
+	struct intel_crtc *crtc = to_intel_crtc(crtc_state->base.crtc);
+
 	if (crtc_state->base.degamma_lut)
 		glk_load_degamma_lut(crtc_state);
 
-	if (crtc_state_is_legacy_gamma(crtc_state))
+	if ((crtc_state->gamma_mode & GAMMA_MODE_MODE_MASK) ==
+	    GAMMA_MODE_MODE_8BIT) {
 		i9xx_load_luts(crtc_state);
-	else
-		/* ToDo: Add support for multi segment gamma LUT */
-		bdw_load_gamma_lut(crtc_state, 0);
+	} else {
+		bdw_load_lut_10(crtc, gamma_lut, PAL_PREC_INDEX_VALUE(0), false);
+		bdw_load_lut_10_max(crtc);
+	}
 }
 
 static void cherryview_load_luts(const struct intel_crtc_state *crtc_state)
@@ -959,8 +937,25 @@ static u32 bdw_gamma_mode(const struct intel_crtc_state *crtc_state)
 	if (!crtc_state->gamma_enable ||
 	    crtc_state_is_legacy_gamma(crtc_state))
 		return GAMMA_MODE_MODE_8BIT;
-	else
+	else if (crtc_state->base.gamma_lut &&
+		 crtc_state->base.degamma_lut)
 		return GAMMA_MODE_MODE_SPLIT;
+	else
+		return GAMMA_MODE_MODE_10BIT;
+}
+
+static u32 bdw_csc_mode(const struct intel_crtc_state *crtc_state)
+{
+	/*
+	 * CSC comes after the LUT in degamma, RGB->YCbCr,
+	 * and RGB full->limited range mode.
+	 */
+	if (crtc_state->base.degamma_lut ||
+	    crtc_state->output_format != INTEL_OUTPUT_FORMAT_RGB ||
+	    crtc_state->limited_color_range)
+		return 0;
+
+	return CSC_POSITION_BEFORE_GAMMA;
 }
 
 static int bdw_color_check(struct intel_crtc_state *crtc_state)
@@ -982,7 +977,7 @@ static int bdw_color_check(struct intel_crtc_state *crtc_state)
 
 	crtc_state->gamma_mode = bdw_gamma_mode(crtc_state);
 
-	crtc_state->csc_mode = 0;
+	crtc_state->csc_mode = bdw_csc_mode(crtc_state);
 
 	ret = intel_color_add_affected_planes(crtc_state);
 	if (ret)
@@ -1116,7 +1111,7 @@ void intel_color_init(struct intel_crtc *crtc)
 		else if (IS_CANNONLAKE(dev_priv) || IS_GEMINILAKE(dev_priv))
 			dev_priv->display.load_luts = glk_load_luts;
 		else if (INTEL_GEN(dev_priv) >= 9 || IS_BROADWELL(dev_priv))
-			dev_priv->display.load_luts = broadwell_load_luts;
+			dev_priv->display.load_luts = bdw_load_luts;
 		else
 			dev_priv->display.load_luts = i9xx_load_luts;
 	}