drm/omap: cleanup color space conversion

The setup code for color space conversion is a bit messy. This patch
cleans it up.

For some reason the TRM uses values in YCrCb order, which is also used
in the current driver, whereas everywhere else it's YCbCr (which also
matches YUV order). This patch changes the tables to use the common
order to avoid confusion.

The tables are split into separate lines, and comments added for
clarity.

WB color conversion registers are similar but different than non-WB, but
the same function was used to write both. It worked fine because the
coef table was adjusted accordingly, but that was rather confusing. This
patch adds a separate function to write the WB values so that the coef
table can be written in an understandable way.

Recalculation also showed that 'bcb' value in yuv-to-rgb conversion had
been rounded wrongly, and it should be 516 instead of 517.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

drivers/gpu/drm/omapdrm/dss/dispc.c

@@ -352,11 +352,6 @@ static const struct {
 	},
 };
 
-struct color_conv_coef {
-	int ry, rcr, rcb, gy, gcr, gcb, by, bcr, bcb;
-	int full_range;
-};
-
 static unsigned long dispc_fclk_rate(struct dispc_device *dispc);
 static unsigned long dispc_core_clk_rate(struct dispc_device *dispc);
 static unsigned long dispc_mgr_lclk_rate(struct dispc_device *dispc,
@@ -868,10 +863,19 @@ static void dispc_ovl_set_scale_coef(struct dispc_device *dispc,
 	}
 }
 
+struct csc_coef_yuv2rgb {
+	int ry, rcb, rcr, gy, gcb, gcr, by, bcb, bcr;
+	bool full_range;
+};
+
+struct csc_coef_rgb2yuv {
+	int yr, yg, yb, cbr, cbg, cbb, crr, crg, crb;
+	bool full_range;
+};
 
 static void dispc_ovl_write_color_conv_coef(struct dispc_device *dispc,
 					    enum omap_plane_id plane,
-					    const struct color_conv_coef *ct)
+					    const struct csc_coef_yuv2rgb *ct)
 {
 #define CVAL(x, y) (FLD_VAL(x, 26, 16) | FLD_VAL(y, 10, 0))
 
@@ -886,25 +890,50 @@ static void dispc_ovl_write_color_conv_coef(struct dispc_device *dispc,
 #undef CVAL
 }
 
+static void dispc_wb_write_color_conv_coef(struct dispc_device *dispc,
+					   const struct csc_coef_rgb2yuv *ct)
+{
+	const enum omap_plane_id plane = OMAP_DSS_WB;
+
+#define CVAL(x, y) (FLD_VAL(x, 26, 16) | FLD_VAL(y, 10, 0))
+
+	dispc_write_reg(dispc, DISPC_OVL_CONV_COEF(plane, 0), CVAL(ct->yg,  ct->yr));
+	dispc_write_reg(dispc, DISPC_OVL_CONV_COEF(plane, 1), CVAL(ct->crr, ct->yb));
+	dispc_write_reg(dispc, DISPC_OVL_CONV_COEF(plane, 2), CVAL(ct->crb, ct->crg));
+	dispc_write_reg(dispc, DISPC_OVL_CONV_COEF(plane, 3), CVAL(ct->cbg, ct->cbr));
+	dispc_write_reg(dispc, DISPC_OVL_CONV_COEF(plane, 4), CVAL(0, ct->cbb));
+
+	REG_FLD_MOD(dispc, DISPC_OVL_ATTRIBUTES(plane), ct->full_range, 11, 11);
+
+#undef CVAL
+}
+
 static void dispc_setup_color_conv_coef(struct dispc_device *dispc)
 {
 	int i;
 	int num_ovl = dispc_get_num_ovls(dispc);
-	const struct color_conv_coef ctbl_bt601_5_ovl = {
-		/* YUV -> RGB */
-		298, 409, 0, 298, -208, -100, 298, 0, 517, 0,
+
+	/* YUV -> RGB, ITU-R BT.601, limited range */
+	const struct csc_coef_yuv2rgb coefs_yuv2rgb_bt601_lim = {
+		298,    0,  409,	/* ry, rcb, rcr */
+		298, -100, -208,	/* gy, gcb, gcr */
+		298,  516,    0,	/* by, bcb, bcr */
+		false,			/* limited range */
 	};
-	const struct color_conv_coef ctbl_bt601_5_wb = {
-		/* RGB -> YUV */
-		66, 129, 25, 112, -94, -18, -38, -74, 112, 0,
+
+	/* RGB -> YUV, ITU-R BT.601, limited range */
+	const struct csc_coef_rgb2yuv coefs_rgb2yuv_bt601_lim = {
+		 66, 129,  25,		/* yr,   yg,  yb */
+		-38, -74, 112,		/* cbr, cbg, cbb */
+		112, -94, -18,		/* crr, crg, crb */
+		false,			/* limited range */
 	};
 
 	for (i = 1; i < num_ovl; i++)
-		dispc_ovl_write_color_conv_coef(dispc, i, &ctbl_bt601_5_ovl);
+		dispc_ovl_write_color_conv_coef(dispc, i, &coefs_yuv2rgb_bt601_lim);
 
 	if (dispc->feat->has_writeback)
-		dispc_ovl_write_color_conv_coef(dispc, OMAP_DSS_WB,
-						&ctbl_bt601_5_wb);
+		dispc_wb_write_color_conv_coef(dispc, &coefs_rgb2yuv_bt601_lim);
 }
 
 static void dispc_ovl_set_ba0(struct dispc_device *dispc,