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

Thank you for the patch.

On Sat, Feb 29, 2020 at 05:30:43PM +0100, Jernej Skrabec wrote:
> CEA 861 standard request that RGB quantization range is "limited" for

s/request/requests/

> CEA modes. Support that by adding CSC matrix which downscales values.

Interesting, that's related to what I asked in the review of 2/4 :-)

> This allows to 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>
> ---
> drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 36 +++++++++++++++++++++--
> 1 file changed, 34 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index 3d6021119942..101c90156fa0 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_limited[3][4] = {

Could you name this to make it explicit that we're converting from RGB
to RGB ? Maybe csc_coeff_rgb_full_to_rgb_limited ?

> + { 0x1B7C, 0x0000, 0x0000, 0x0020 },
> + { 0x0000, 0x1B7C, 0x0000, 0x0020 },
> + { 0x0000, 0x0000, 0x1B7C, 0x0020 }

Lowercase hex constants please.

> +};
> +
> 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 {
> @@ -960,6 +967,13 @@ static int is_color_space_conversion(struct dw_hdmi *hdmi)
> hdmi_bus_fmt_is_rgb(hdmi->hdmi_data.enc_out_bus_format);
> }
>
> +static int is_rgb_downscale_needed(struct dw_hdmi *hdmi)
> +{
> + return 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)
> {
> if (!hdmi_bus_fmt_is_yuv422(hdmi->hdmi_data.enc_out_bus_format))
> @@ -1006,6 +1020,8 @@ static void dw_hdmi_update_csc_coeffs(struct dw_hdmi *hdmi)
> csc_coeff = &csc_coeff_rgb_in_eitu709;
> csc_scale = 0;
> }
> + } else if (is_rgb_downscale_needed(hdmi)) {
> + csc_coeff = &csc_coeff_rgb_limited;
> }
>
> /* The CSC registers are sequential, alternating MSB then LSB */
> @@ -1615,6 +1631,18 @@ 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))
> @@ -1990,13 +2018,13 @@ static void dw_hdmi_enable_video_path(struct dw_hdmi *hdmi)
> hdmi_writeb(hdmi, hdmi->mc_clkdis, HDMI_MC_CLKDIS);
>
> /* Enable csc path */
> - if (is_color_space_conversion(hdmi)) {
> + if (is_color_space_conversion(hdmi) || is_rgb_downscale_needed(hdmi)) {

I would fold this change in is_color_space_conversion(), and modify
dw_hdmi_update_csc_coeffs() accordingly with something like

if (!hdmi_bus_fmt_is_rgb(hdmi->hdmi_data.enc_in_bus_format) &&
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) &&
!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_in_eitu601;
else
csc_coeff = &csc_coeff_rgb_in_eitu709;
csc_scale = 0;
} else if (is_rgb_downscale_needed(hdmi)) {
csc_coeff = &csc_coeff_rgb_limited;
}

> hdmi->mc_clkdis &= ~HDMI_MC_CLKDIS_CSCCLK_DISABLE;
> hdmi_writeb(hdmi, hdmi->mc_clkdis, HDMI_MC_CLKDIS);
> }
>
> /* Enable color space conversion if needed */
> - if (is_color_space_conversion(hdmi))
> + if (is_color_space_conversion(hdmi) || is_rgb_downscale_needed(hdmi))
> hdmi_writeb(hdmi, HDMI_MC_FLOWCTRL_FEED_THROUGH_OFF_CSC_IN_PATH,
> HDMI_MC_FLOWCTRL);
> else
> @@ -2100,6 +2128,10 @@ 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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