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SubjectRe: [PATCH v2 3/4] drm/bridge: dw-hdmi: Add support for RGB limited range
Hi Jernej,

Thank you for the patch.

On Thu, Mar 05, 2020 at 12:25:11AM +0100, Jernej Skrabec wrote:
> CEA 861 standard requestis that RGB quantization range is "limited" for
> CEA modes. Support that by adding CSC matrix which downscales values.
>
> This allows proper color reproduction on TV and PC monitor at the same
> time. In future, override property can be added, like "Broadcast RGB"
> in i915 driver.
>
> Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> ---
> drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 63 +++++++++++++++++------
> 1 file changed, 46 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index de2c7ec887c8..c8a02e5b5e1b 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -92,6 +92,12 @@ static const u16 csc_coeff_rgb_in_eitu709[3][4] = {
> { 0x6756, 0x78ab, 0x2000, 0x0200 }
> };
>
> +static const u16 csc_coeff_rgb_full_to_rgb_limited[3][4] = {
> + { 0x1b7c, 0x0000, 0x0000, 0x0020 },
> + { 0x0000, 0x1b7c, 0x0000, 0x0020 },
> + { 0x0000, 0x0000, 0x1b7c, 0x0020 }
> +};
> +
> struct hdmi_vmode {
> bool mdataenablepolarity;
>
> @@ -109,6 +115,7 @@ struct hdmi_data_info {
> unsigned int pix_repet_factor;
> unsigned int hdcp_enable;
> struct hdmi_vmode video_mode;
> + bool rgb_limited_range;
> };
>
> struct dw_hdmi_i2c {
> @@ -956,7 +963,11 @@ static void hdmi_video_sample(struct dw_hdmi *hdmi)
>
> static int is_color_space_conversion(struct dw_hdmi *hdmi)
> {
> - return hdmi->hdmi_data.enc_in_bus_format != hdmi->hdmi_data.enc_out_bus_format;
> + return (hdmi->hdmi_data.enc_in_bus_format !=
> + hdmi->hdmi_data.enc_out_bus_format) ||
> + (hdmi_bus_fmt_is_rgb(hdmi->hdmi_data.enc_in_bus_format) &&
> + hdmi_bus_fmt_is_rgb(hdmi->hdmi_data.enc_out_bus_format) &&
> + hdmi->hdmi_data.rgb_limited_range);
> }
>
> static int is_color_space_decimation(struct dw_hdmi *hdmi)
> @@ -986,25 +997,27 @@ static int is_color_space_interpolation(struct dw_hdmi *hdmi)
> static void dw_hdmi_update_csc_coeffs(struct dw_hdmi *hdmi)
> {
> const u16 (*csc_coeff)[3][4] = &csc_coeff_default;
> + bool is_input_rgb, is_output_rgb;
> unsigned i;
> u32 csc_scale = 1;
>
> - if (is_color_space_conversion(hdmi)) {
> - if (hdmi_bus_fmt_is_rgb(hdmi->hdmi_data.enc_out_bus_format)) {
> - if (hdmi->hdmi_data.enc_out_encoding ==
> - V4L2_YCBCR_ENC_601)
> - csc_coeff = &csc_coeff_rgb_out_eitu601;
> - else
> - csc_coeff = &csc_coeff_rgb_out_eitu709;
> - } else if (hdmi_bus_fmt_is_rgb(
> - hdmi->hdmi_data.enc_in_bus_format)) {
> - if (hdmi->hdmi_data.enc_out_encoding ==
> - V4L2_YCBCR_ENC_601)
> - csc_coeff = &csc_coeff_rgb_in_eitu601;
> - else
> - csc_coeff = &csc_coeff_rgb_in_eitu709;
> - csc_scale = 0;
> - }
> + is_input_rgb = hdmi_bus_fmt_is_rgb(hdmi->hdmi_data.enc_in_bus_format);
> + is_output_rgb = hdmi_bus_fmt_is_rgb(hdmi->hdmi_data.enc_out_bus_format);
> +
> + if (!is_input_rgb && is_output_rgb) {
> + if (hdmi->hdmi_data.enc_out_encoding == V4L2_YCBCR_ENC_601)
> + csc_coeff = &csc_coeff_rgb_out_eitu601;
> + else
> + csc_coeff = &csc_coeff_rgb_out_eitu709;
> + } else if (is_input_rgb && !is_output_rgb) {
> + if (hdmi->hdmi_data.enc_out_encoding == V4L2_YCBCR_ENC_601)
> + csc_coeff = &csc_coeff_rgb_in_eitu601;
> + else
> + csc_coeff = &csc_coeff_rgb_in_eitu709;
> + csc_scale = 0;
> + } else if (is_input_rgb && is_output_rgb &&
> + hdmi->hdmi_data.rgb_limited_range) {
> + csc_coeff = &csc_coeff_rgb_full_to_rgb_limited;
> }
>
> /* The CSC registers are sequential, alternating MSB then LSB */
> @@ -1614,6 +1627,18 @@ static void hdmi_config_AVI(struct dw_hdmi *hdmi, struct drm_display_mode *mode)
> drm_hdmi_avi_infoframe_from_display_mode(&frame,
> &hdmi->connector, mode);
>
> + if (hdmi_bus_fmt_is_rgb(hdmi->hdmi_data.enc_out_bus_format)) {
> + drm_hdmi_avi_infoframe_quant_range(&frame, &hdmi->connector,
> + mode,
> + hdmi->hdmi_data.rgb_limited_range ?
> + HDMI_QUANTIZATION_RANGE_LIMITED :
> + HDMI_QUANTIZATION_RANGE_FULL);
> + } else {
> + frame.quantization_range = HDMI_QUANTIZATION_RANGE_DEFAULT;
> + frame.ycc_quantization_range =
> + HDMI_YCC_QUANTIZATION_RANGE_LIMITED;
> + }
> +
> if (hdmi_bus_fmt_is_yuv444(hdmi->hdmi_data.enc_out_bus_format))
> frame.colorspace = HDMI_COLORSPACE_YUV444;
> else if (hdmi_bus_fmt_is_yuv422(hdmi->hdmi_data.enc_out_bus_format))
> @@ -2099,6 +2124,10 @@ static int dw_hdmi_setup(struct dw_hdmi *hdmi, struct drm_display_mode *mode)
> /* TOFIX: Default to RGB888 output format */
> hdmi->hdmi_data.enc_out_bus_format = MEDIA_BUS_FMT_RGB888_1X24;
>
> + hdmi->hdmi_data.rgb_limited_range = hdmi->sink_is_hdmi &&
> + drm_default_rgb_quant_range(mode) ==
> + HDMI_QUANTIZATION_RANGE_LIMITED;
> +
> hdmi->hdmi_data.pix_repet_factor = 0;
> hdmi->hdmi_data.hdcp_enable = 0;
> hdmi->hdmi_data.video_mode.mdataenablepolarity = true;

--
Regards,

Laurent Pinchart

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