media: rkisp1: Allow setting all color space fields on ISP source pad

The ISP output color space is configured through the ISP source pad. At
the moment, only the quantization can be set. Extend it to the three
other color space fields:

- The ycbcr_enc field will be used to configure the RGB to YUV matrix
  (currently hardcoded to Rec. 601).

- The colorspace (which controls the color primaries) and xfer_func
  fields will not be used to configure the ISP, as the corresponding
  hardware blocks (the cross-talk RGB to RGB matrix and the tone mapping
  curve) are programmed directly by applications through ISP parameters.
  Nonetheless, those two fields should be set by applications to match
  the ISP configuration, in order to propagate the correct color space
  down the pipeline up to the capture video nodes.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Dafna Hirschfeld <dafna@fastmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/platform/rockchip/rkisp1/rkisp1-isp.c

@@ -487,6 +487,7 @@ static void rkisp1_isp_set_src_fmt(struct rkisp1_isp *isp,
 	struct v4l2_mbus_framefmt *sink_fmt;
 	struct v4l2_mbus_framefmt *src_fmt;
 	const struct v4l2_rect *src_crop;
+	bool set_csc;
 
 	sink_fmt = rkisp1_isp_get_pad_fmt(isp, sd_state,
 					  RKISP1_ISP_PAD_SINK_VIDEO, which);
@@ -523,20 +524,60 @@ static void rkisp1_isp_set_src_fmt(struct rkisp1_isp *isp,
 	src_fmt->height = src_crop->height;
 
 	/*
-	 * The CSC API is used to allow userspace to force full
-	 * quantization on YUV formats.
+	 * Copy the color space for the sink pad. When converting from Bayer to
+	 * YUV, default to a limited quantization range.
 	 */
-	if (format->flags & V4L2_MBUS_FRAMEFMT_SET_CSC &&
-	    format->quantization == V4L2_QUANTIZATION_FULL_RANGE &&
+	src_fmt->colorspace = sink_fmt->colorspace;
+	src_fmt->xfer_func = sink_fmt->xfer_func;
+	src_fmt->ycbcr_enc = sink_fmt->ycbcr_enc;
+
+	if (sink_info->pixel_enc == V4L2_PIXEL_ENC_BAYER &&
 	    src_info->pixel_enc == V4L2_PIXEL_ENC_YUV)
-		src_fmt->quantization = V4L2_QUANTIZATION_FULL_RANGE;
-	else if (src_info->pixel_enc == V4L2_PIXEL_ENC_YUV)
 		src_fmt->quantization = V4L2_QUANTIZATION_LIM_RANGE;
 	else
-		src_fmt->quantization = V4L2_QUANTIZATION_FULL_RANGE;
+		src_fmt->quantization = sink_fmt->quantization;
+
+	/*
+	 * Allow setting the source color space fields when the SET_CSC flag is
+	 * set and the source format is YUV. If the sink format is YUV, don't
+	 * set the color primaries, transfer function or YCbCr encoding as the
+	 * ISP is bypassed in that case and passes YUV data through without
+	 * modifications.
+	 *
+	 * The color primaries and transfer function are configured through the
+	 * cross-talk matrix and tone curve respectively. Settings for those
+	 * hardware blocks are conveyed through the ISP parameters buffer, as
+	 * they need to combine color space information with other image tuning
+	 * characteristics and can't thus be computed by the kernel based on the
+	 * color space. The source pad colorspace and xfer_func fields are thus
+	 * ignored by the driver, but can be set by userspace to propagate
+	 * accurate color space information down the pipeline.
+	 */
+	set_csc = format->flags & V4L2_MBUS_FRAMEFMT_SET_CSC;
+
+	if (set_csc && src_info->pixel_enc == V4L2_PIXEL_ENC_YUV) {
+		if (sink_info->pixel_enc == V4L2_PIXEL_ENC_BAYER) {
+			if (format->colorspace != V4L2_COLORSPACE_DEFAULT)
+				src_fmt->colorspace = format->colorspace;
+			if (format->xfer_func != V4L2_XFER_FUNC_DEFAULT)
+				src_fmt->xfer_func = format->xfer_func;
+			if (format->ycbcr_enc != V4L2_YCBCR_ENC_DEFAULT)
+				src_fmt->ycbcr_enc = format->ycbcr_enc;
+		}
+
+		if (format->quantization != V4L2_QUANTIZATION_DEFAULT)
+			src_fmt->quantization = format->quantization;
+	}
 
 	*format = *src_fmt;
 
+	/*
+	 * Restore the SET_CSC flag if it was set to indicate support for the
+	 * CSC setting API.
+	 */
+	if (set_csc)
+		format->flags |= V4L2_MBUS_FRAMEFMT_SET_CSC;
+
 	/* Store the source format info when setting the active format. */
 	if (which == V4L2_SUBDEV_FORMAT_ACTIVE)
 		isp->src_fmt = src_info;