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Subject[PATCH v5 4/7] gpu: ipu-v3: ipu-ic: Add support for Rec.709 encoding
Date
Add support for Rec.709 encoding and inverse encoding.

The determination of the CSC coefficients based on the input/output
colorspace parameters are moved to a new function calc_csc_coeffs().

Reported-by: Tim Harvey <tharvey@gateworks.com>
Signed-off-by: Steve Longerbeam <slongerbeam@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 | 120 ++++++++++++++++++++++++++++--------
1 file changed, 94 insertions(+), 26 deletions(-)

diff --git a/drivers/gpu/ipu-v3/ipu-ic.c b/drivers/gpu/ipu-v3/ipu-ic.c
index 02043f23f411..012ea2239e97 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:
*
@@ -237,28 +254,42 @@ static const struct ic_encode_coeff ic_encode_ycbcr2rgb_601 = {
.scale = 2,
};

-static int init_csc(struct ipu_ic *ic,
- const struct ipu_ic_colorspace *in,
- const struct ipu_ic_colorspace *out,
- int csc_index)
+/*
+ * 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)
{
- struct ipu_ic_priv *priv = ic->priv;
- const struct ic_encode_coeff *coeff;
- u32 __iomem *base;
- const u16 (*c)[3];
- const u16 *a;
- u32 param;
+ const struct ic_encode_coeff *encode_coeff;
+ bool inverse_encode;

if (in->colorspace != out->colorspace) {
dev_err(priv->ipu->dev, "Cannot convert colorspaces\n");
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 &&
@@ -275,26 +306,63 @@ static int init_csc(struct ipu_ic *ic,
return -ENOTSUPP;
}

+ if (in->cs == out->cs) {
+ *coeff_out = ic_encode_identity;
+
+ return 0;
+ }
+
+ inverse_encode = (in->cs == IPUV3_COLORSPACE_YUV);
+
+ 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;
+}
+
+static int init_csc(struct ipu_ic *ic,
+ const struct ipu_ic_colorspace *in,
+ const struct ipu_ic_colorspace *out,
+ int csc_index)
+{
+ struct ipu_ic_priv *priv = ic->priv;
+ struct ic_encode_coeff coeff;
+ u32 __iomem *base;
+ const u16 (*c)[3];
+ const u16 *a;
+ u32 param;
+ int ret;
+
+ ret = calc_csc_coeffs(priv, &coeff, in, out);
+ if (ret)
+ return ret;
+
base = (u32 __iomem *)
(priv->tpmem_base + ic->reg->tpmem_csc[csc_index]);

- if (in->cs == out->cs)
- coeff = &ic_encode_identity;
- else if (in->cs == IPUV3_COLORSPACE_YUV)
- coeff = &ic_encode_ycbcr2rgb_601;
- else
- coeff = &ic_encode_rgb2ycbcr_601;
-
/* Cast to unsigned */
- c = (const u16 (*)[3])coeff->coeff;
- a = (const u16 *)coeff->offset;
+ c = (const u16 (*)[3])coeff.coeff;
+ a = (const u16 *)coeff.offset;

param = ((a[0] & 0x1f) << 27) | ((c[0][0] & 0x1ff) << 18) |
((c[1][1] & 0x1ff) << 9) | (c[2][2] & 0x1ff);
writel(param, base++);

- param = ((a[0] & 0x1fe0) >> 5) | (coeff->scale << 8) |
- (coeff->sat << 10);
+ param = ((a[0] & 0x1fe0) >> 5) | (coeff.scale << 8) |
+ (coeff.sat << 10);
writel(param, base++);

param = ((a[1] & 0x1f) << 27) | ((c[0][1] & 0x1ff) << 18) |
--
2.17.1
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