drm/sun4i: Move the BT.601 CSC coefficients to the frontend

Both the backend and the frontend need the BT.601 CSC coefficients for
YUV to RGB conversion. Since the backend has a dependency on the
frontend (and not the other way round), move the coefficients there
so that both can access them without having to duplicate them.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190118145133.21281-7-paul.kocialkowski@bootlin.com

1 files changed, 23 insertions, 0 deletions

diff --git a/drivers/gpu/drm/sun4i/sun4i_frontend.c b/drivers/gpu/drm/sun4i/sun4i_frontend.c
index 7c7a5ea0cf58..045013efdc57 100644
--- a/drivers/gpu/drm/sun4i/sun4i_frontend.c
+++ b/drivers/gpu/drm/sun4i/sun4i_frontend.c
@@ -48,6 +48,29 @@ static const u32 sun4i_frontend_horz_coef[64] = {
 	0x03ff0000, 0x0000fd41, 0x01ff0000, 0x0000fe42,
 };
 
+/*
+ * These coefficients are taken from the A33 BSP from Allwinner.
+ *
+ * The first three values of each row are coded as 13-bit signed fixed-point
+ * numbers, with 10 bits for the fractional part. The fourth value is a
+ * constant coded as a 14-bit signed fixed-point number with 4 bits for the
+ * fractional part.
+ *
+ * The values in table order give the following colorspace translation:
+ * G = 1.164 * Y - 0.391 * U - 0.813 * V + 135
+ * R = 1.164 * Y + 1.596 * V - 222
+ * B = 1.164 * Y + 2.018 * U + 276
+ *
+ * This seems to be a conversion from Y[16:235] UV[16:240] to RGB[0:255],
+ * following the BT601 spec.
+ */
+const u32 sunxi_bt601_yuv2rgb_coef[12] = {
+	0x000004a7, 0x00001e6f, 0x00001cbf, 0x00000877,
+	0x000004a7, 0x00000000, 0x00000662, 0x00003211,
+	0x000004a7, 0x00000812, 0x00000000, 0x00002eb1,
+};
+EXPORT_SYMBOL(sunxi_bt601_yuv2rgb_coef);
+
 static void sun4i_frontend_scaler_init(struct sun4i_frontend *frontend)
 {
 	int i;