drm/amd/display: add a check for display depth validity

[why]
HDMI 2.0 fails to validate 4K@60 timing with 10 bpc
[how]
Adding a helper function that would verify if the display depth
assigned would pass a bandwidth validation.
Drop the display depth by one level till calculated pixel clk
is lower than maximum TMDS clk.

Bugzilla: https://bugs.freedesktop.org/106959

Tested-by: Mike Lothian <mike@fireburn.co.uk>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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 f97dfc1..770c6b2 100644 (file)
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -2175,6 +2175,46 @@ 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)
+{
+       int normalized_clk;
+       if (timing_out->display_color_depth <= COLOR_DEPTH_888)
+               return;
+       do {
+               normalized_clk = timing_out->pix_clk_khz;
+               /* 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) {
+               case COLOR_DEPTH_101010:
+                       normalized_clk = (normalized_clk * 30) / 24;
+                       break;
+               case COLOR_DEPTH_121212:
+                       normalized_clk = (normalized_clk * 36) / 24;
+                       break;
+               case COLOR_DEPTH_161616:
+                       normalized_clk = (normalized_clk * 48) / 24;
+                       break;
+               default:
+                       return;
+               }
+               if (normalized_clk <= info->max_tmds_clock)
+                       return;
+               reduce_mode_colour_depth(timing_out);
+
+       } while (timing_out->display_color_depth > COLOR_DEPTH_888);
+
+}
 /*****************************************************************************/
 
 static void
@@ -2231,6 +2271,8 @@ fill_stream_properties_from_drm_display_mode(struct dc_stream_state *stream,
 
        stream->out_transfer_func->type = TF_TYPE_PREDEFINED;
        stream->out_transfer_func->tf = TRANSFER_FUNCTION_SRGB;
+       if (stream->sink->sink_signal == SIGNAL_TYPE_HDMI_TYPE_A)
+               adjust_colour_depth_from_display_info(timing_out, info);
 }
 
 static void fill_audio_info(struct audio_info *audio_info,