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SubjectRe: [PATCH v2] drm/amd/display: Reduce HDMI pixel encoding if max clock is exceeded
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On 2019-12-02 4:47 p.m., Thomas Anderson wrote:
> For high-res (8K) or HFR (4K120) displays, using uncompressed pixel
> formats like YCbCr444 would exceed the bandwidth of HDMI 2.0, so the
> "interesting" modes would be disabled, leaving only low-res or low
> framerate modes.
>
> This change lowers the pixel encoding to 4:2:2 or 4:2:0 if the max TMDS
> clock is exceeded. Verified that 8K30 and 4K120 are now available and
> working with a Samsung Q900R over an HDMI 2.0b link from a Radeon 5700.
>
> Signed-off-by: Thomas Anderson <thomasanderson@google.com>

Apologies for the late response.

Thanks for getting high-res modes working on HDMI.

This change is
Reviewed-by: Harry Wentland <harry.wentland@amd.com>

Harry

> ---
> .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 45 ++++++++++---------
> 1 file changed, 23 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 7aac9568d3be..803e59d97411 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -3356,27 +3356,21 @@ get_output_color_space(const struct dc_crtc_timing *dc_crtc_timing)
> return color_space;
> }
>
> -static void reduce_mode_colour_depth(struct dc_crtc_timing *timing_out)
> -{
> - if (timing_out->display_color_depth <= COLOR_DEPTH_888)
> - return;
> -
> - timing_out->display_color_depth--;
> -}
> -
> -static void adjust_colour_depth_from_display_info(struct dc_crtc_timing *timing_out,
> - const struct drm_display_info *info)
> +static bool adjust_colour_depth_from_display_info(
> + struct dc_crtc_timing *timing_out,
> + const struct drm_display_info *info)
> {
> + enum dc_color_depth depth = timing_out->display_color_depth;
> int normalized_clk;
> - if (timing_out->display_color_depth <= COLOR_DEPTH_888)
> - return;
> do {
> normalized_clk = timing_out->pix_clk_100hz / 10;
> /* YCbCr 4:2:0 requires additional adjustment of 1/2 */
> if (timing_out->pixel_encoding == PIXEL_ENCODING_YCBCR420)
> normalized_clk /= 2;
> /* Adjusting pix clock following on HDMI spec based on colour depth */
> - switch (timing_out->display_color_depth) {
> + switch (depth) {
> + case COLOR_DEPTH_888:
> + break;
> case COLOR_DEPTH_101010:
> normalized_clk = (normalized_clk * 30) / 24;
> break;
> @@ -3387,14 +3381,15 @@ static void adjust_colour_depth_from_display_info(struct dc_crtc_timing *timing_
> normalized_clk = (normalized_clk * 48) / 24;
> break;
> default:
> - return;
> + /* The above depths are the only ones valid for HDMI. */
> + return false;
> }
> - if (normalized_clk <= info->max_tmds_clock)
> - return;
> - reduce_mode_colour_depth(timing_out);
> -
> - } while (timing_out->display_color_depth > COLOR_DEPTH_888);
> -
> + if (normalized_clk <= info->max_tmds_clock) {
> + timing_out->display_color_depth = depth;
> + return true;
> + }
> + } while (--depth > COLOR_DEPTH_666);
> + return false;
> }
>
> static void fill_stream_properties_from_drm_display_mode(
> @@ -3474,8 +3469,14 @@ static void fill_stream_properties_from_drm_display_mode(
>
> stream->out_transfer_func->type = TF_TYPE_PREDEFINED;
> stream->out_transfer_func->tf = TRANSFER_FUNCTION_SRGB;
> - if (stream->signal == SIGNAL_TYPE_HDMI_TYPE_A)
> - adjust_colour_depth_from_display_info(timing_out, info);
> + if (stream->signal == SIGNAL_TYPE_HDMI_TYPE_A) {
> + if (!adjust_colour_depth_from_display_info(timing_out, info) &&
> + drm_mode_is_420_also(info, mode_in) &&
> + timing_out->pixel_encoding != PIXEL_ENCODING_YCBCR420) {
> + timing_out->pixel_encoding = PIXEL_ENCODING_YCBCR420;
> + adjust_colour_depth_from_display_info(timing_out, info);
> + }
> + }
> }
>
> static void fill_audio_info(struct audio_info *audio_info,
>

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