[PATCH v6 4/7] gpu: ipu-v3: ipu-ic: Add support for Rec.709 encoding

[Steve Longerbeam]

Add support for Rec.709 encoding and inverse encoding.

Reported-by: Tim Harvey <tharvey at gateworks.com>
Signed-off-by: Steve Longerbeam <slongerbeam at gmail.com>
---
Changes in v5:
- moved API changes to a previous patch.
- moved CSC coeff calc to new function calc_csc_coeffs().
Changes in v4:
- fix compile error.
Chnges in v3:
- none.
Changes in v2:
- only return "Unsupported YCbCr encoding" error if inf != outf,
  since if inf == outf, the identity matrix can be used. Reported
  by Tim Harvey.
---
 drivers/gpu/ipu-v3/ipu-ic.c | 63 ++++++++++++++++++++++++++++++++-----
 1 file changed, 56 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/ipu-v3/ipu-ic.c b/drivers/gpu/ipu-v3/ipu-ic.c
index c4048c921801..1460901af9b5 100644
--- a/drivers/gpu/ipu-v3/ipu-ic.c
+++ b/drivers/gpu/ipu-v3/ipu-ic.c
@@ -214,6 +214,23 @@ static const struct ic_encode_coeff ic_encode_identity = {
 	.scale = 2,
 };
 
+/*
+ * REC.709 encoding from RGB full range to YUV full range:
+ *
+ * Y =  .2126 * R + .7152 * G + .0722 * B
+ * U = -.1146 * R - .3854 * G + .5000 * B + 128
+ * V =  .5000 * R - .4542 * G - .0458 * B + 128
+ */
+static const struct ic_encode_coeff ic_encode_rgb2ycbcr_709 = {
+	.coeff = {
+		{  54, 183,  19 },
+		{ 483, 413, 128 },
+		{ 128, 396, 500 },
+	},
+	.offset = { 0, 512, 512 },
+	.scale = 1,
+};
+
 /*
  * Inverse BT.601 encoding from YUV full range to RGB full range:
  *
@@ -237,11 +254,35 @@ static const struct ic_encode_coeff ic_encode_ycbcr2rgb_601 = {
 	.scale = 2,
 };
 
+/*
+ * Inverse REC.709 encoding from YUV full range to RGB full range:
+ *
+ * R = 1. * Y +      0 * (Cb - 128) + 1.5748 * (Cr - 128)
+ * G = 1. * Y -  .1873 * (Cb - 128) -  .4681 * (Cr - 128)
+ * B = 1. * Y + 1.8556 * (Cb - 128) +      0 * (Cr - 128)
+ *
+ * equivalently (factoring out the offsets):
+ *
+ * R = 1. * Y  +      0 * Cb + 1.5748 * Cr - 201.574
+ * G = 1. * Y  -  .1873 * Cb -  .4681 * Cr +  83.891
+ * B = 1. * Y  + 1.8556 * Cb +      0 * Cr - 237.517
+ */
+static const struct ic_encode_coeff ic_encode_ycbcr2rgb_709 = {
+	.coeff = {
+		{  128,   0, 202 },
+		{  128, 488, 452 },
+		{  128, 238,   0 },
+	},
+	.offset = { -403, 168, -475 },
+	.scale = 2,
+};
+
 static int calc_csc_coeffs(struct ipu_ic_priv *priv,
 			   struct ic_encode_coeff *coeff_out,
 			   const struct ipu_ic_colorspace *in,
 			   const struct ipu_ic_colorspace *out)
 {
+	const struct ic_encode_coeff *encode_coeff;
 	bool inverse_encode;
 
 	if (in->colorspace != out->colorspace) {
@@ -249,11 +290,6 @@ static int calc_csc_coeffs(struct ipu_ic_priv *priv,
 		return -ENOTSUPP;
 	}
 
-	if (out->enc != V4L2_YCBCR_ENC_601) {
-		dev_err(priv->ipu->dev, "Only BT.601 encoding supported\n");
-		return -ENOTSUPP;
-	}
-
 	if ((in->cs == IPUV3_COLORSPACE_YUV &&
 	     in->quant != V4L2_QUANTIZATION_FULL_RANGE) ||
 	    (out->cs == IPUV3_COLORSPACE_YUV &&
@@ -278,8 +314,21 @@ static int calc_csc_coeffs(struct ipu_ic_priv *priv,
 
 	inverse_encode = (in->cs == IPUV3_COLORSPACE_YUV);
 
-	*coeff_out = inverse_encode ?
-		ic_encode_ycbcr2rgb_601 : ic_encode_rgb2ycbcr_601;
+	switch (out->enc) {
+	case V4L2_YCBCR_ENC_601:
+		encode_coeff = inverse_encode ?
+			&ic_encode_ycbcr2rgb_601 : &ic_encode_rgb2ycbcr_601;
+		break;
+	case V4L2_YCBCR_ENC_709:
+		encode_coeff = inverse_encode ?
+			&ic_encode_ycbcr2rgb_709 : &ic_encode_rgb2ycbcr_709;
+		break;
+	default:
+		dev_err(priv->ipu->dev, "Unsupported YCbCr encoding\n");
+		return -ENOTSUPP;
+	}
+
+	*coeff_out = *encode_coeff;
 
 	return 0;
 }
-- 
2.17.1