drm/amd/display: Add fallback path for YCBCR422

[Why]
DP validation may fail with multiple displays and higher color depths.
The sink may support others though.

[How]
When DP bandwidth validation fails, progressively fallback through:
- YUV422 8bpc (bandwidth efficient)
- YUV422 6bpc (reduced color depth)
- YUV420 (last resort)

This resolves cases where displays would show no image due to insufficient
DP link bandwidth for the requested RGB mode.

Suggested-by: Mauri Carvalho <mcarvalho3@lenovo.com>
Reviewed-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Mario Limonciello <Mario.Limonciello@amd.com>
Signed-off-by: Ray Wu <ray.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@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 cb22cad279be2f8ddcfb9abaf9166c342134496b..7495122358bdb64799346e5339fc0f945c2b1d7b 100644 (file)
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -6407,7 +6407,8 @@ static void fill_stream_properties_from_drm_display_mode(
                        && aconnector->force_yuv420_output)
                timing_out->pixel_encoding = PIXEL_ENCODING_YCBCR420;
        else if ((connector->display_info.color_formats & DRM_COLOR_FORMAT_YCBCR422)
-                       && stream->signal == SIGNAL_TYPE_HDMI_TYPE_A)
+                       && aconnector
+                       && aconnector->force_yuv422_output)
                timing_out->pixel_encoding = PIXEL_ENCODING_YCBCR422;
        else if ((connector->display_info.color_formats & DRM_COLOR_FORMAT_YCBCR444)
                        && stream->signal == SIGNAL_TYPE_HDMI_TYPE_A)
@@ -7669,6 +7670,7 @@ create_validate_stream_for_sink(struct drm_connector *connector,
                bpc_limit = 8;
 
        do {
+               drm_dbg_kms(connector->dev, "Trying with %d bpc\n", requested_bpc);
                stream = create_stream_for_sink(connector, drm_mode,
                                                dm_state, old_stream,
                                                requested_bpc);
@@ -7704,16 +7706,41 @@ create_validate_stream_for_sink(struct drm_connector *connector,
 
        } while (stream == NULL && requested_bpc >= bpc_limit);
 
-       if ((dc_result == DC_FAIL_ENC_VALIDATE ||
-            dc_result == DC_EXCEED_DONGLE_CAP) &&
-            !aconnector->force_yuv420_output) {
-               DRM_DEBUG_KMS("%s:%d Retry forcing yuv420 encoding\n",
-                                    __func__, __LINE__);
-
-               aconnector->force_yuv420_output = true;
+       switch (dc_result) {
+       /*
+        * If we failed to validate DP bandwidth stream with the requested RGB color depth,
+        * we try to fallback and configure in order:
+        * YUV422 (8bpc, 6bpc)
+        * YUV420 (8bpc, 6bpc)
+        */
+       case DC_FAIL_ENC_VALIDATE:
+       case DC_EXCEED_DONGLE_CAP:
+       case DC_NO_DP_LINK_BANDWIDTH:
+               /* recursively entered twice and already tried both YUV422 and YUV420 */
+               if (aconnector->force_yuv422_output && aconnector->force_yuv420_output)
+                       break;
+               /* first failure; try YUV422 */
+               if (!aconnector->force_yuv422_output) {
+                       drm_dbg_kms(connector->dev, "%s:%d Validation failed with %d, retrying w/ YUV422\n",
+                                   __func__, __LINE__, dc_result);
+                       aconnector->force_yuv422_output = true;
+               /* recursively entered and YUV422 failed, try YUV420 */
+               } else if (!aconnector->force_yuv420_output) {
+                       drm_dbg_kms(connector->dev, "%s:%d Validation failed with %d, retrying w/ YUV420\n",
+                                   __func__, __LINE__, dc_result);
+                       aconnector->force_yuv420_output = true;
+               }
                stream = create_validate_stream_for_sink(connector, drm_mode,
-                                               dm_state, old_stream);
+                                                        dm_state, old_stream);
+               aconnector->force_yuv422_output = false;
                aconnector->force_yuv420_output = false;
+               break;
+       case DC_OK:
+               break;
+       default:
+               drm_dbg_kms(connector->dev, "%s:%d Unhandled validation failure %d\n",
+                           __func__, __LINE__, dc_result);
+               break;
        }
 
        return stream;

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
index ce74125c713e9a8223b6032dc9735c3fbbe58a11..2967cd28efe4e2f9657ea2907586d82532f34b74 100644 (file)
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
@@ -794,6 +794,7 @@ struct amdgpu_dm_connector {
 
        bool fake_enable;
        bool force_yuv420_output;
+       bool force_yuv422_output;
        struct dsc_preferred_settings dsc_settings;
        union dp_downstream_port_present mst_downstream_port_present;
        /* Cached display modes */