drm/amd/display: Fix DSC not Enabled on Direct MST Sink

[WHY & HOW]
For the scenario when a dsc capable MST sink device is directly
connected, it needs to use max dsc compression as the link bw constraint.

Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Reviewed-by: Roman Li <roman.li@amd.com>
Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Fangzhi Zuo <jerry.zuo@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_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
index d3b13d362edacc676c8b70a8a10bfa028728f7f3..11da0eebee6c4b0afd34ee5b7a499e046c4be413 100644 (file)
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
@@ -1604,31 +1604,31 @@ enum dc_status dm_dp_mst_is_port_support_mode(
        unsigned int upper_link_bw_in_kbps = 0, down_link_bw_in_kbps = 0;
        unsigned int max_compressed_bw_in_kbps = 0;
        struct dc_dsc_bw_range bw_range = {0};
-       struct drm_dp_mst_topology_mgr *mst_mgr;
+       uint16_t full_pbn = aconnector->mst_output_port->full_pbn;
 
        /*
-        * check if the mode could be supported if DSC pass-through is supported
-        * AND check if there enough bandwidth available to support the mode
-        * with DSC enabled.
+        * Consider the case with the depth of the mst topology tree is equal or less than 2
+        * A. When dsc bitstream can be transmitted along the entire path
+        *    1. dsc is possible between source and branch/leaf device (common dsc params is possible), AND
+        *    2. dsc passthrough supported at MST branch, or
+        *    3. dsc decoding supported at leaf MST device
+        *    Use maximum dsc compression as bw constraint
+        * B. When dsc bitstream cannot be transmitted along the entire path
+        *    Use native bw as bw constraint
         */
        if (is_dsc_common_config_possible(stream, &bw_range) &&
-           aconnector->mst_output_port->passthrough_aux) {
-               mst_mgr = aconnector->mst_output_port->mgr;
-               mutex_lock(&mst_mgr->lock);
-
+          (aconnector->mst_output_port->passthrough_aux ||
+           aconnector->dsc_aux == &aconnector->mst_output_port->aux)) {
                cur_link_settings = stream->link->verified_link_cap;
 
                upper_link_bw_in_kbps = dc_link_bandwidth_kbps(aconnector->dc_link,
-                                                              &cur_link_settings
-                                                              );
-               down_link_bw_in_kbps = kbps_from_pbn(aconnector->mst_output_port->full_pbn);
+                                                              &cur_link_settings);
+               down_link_bw_in_kbps = kbps_from_pbn(full_pbn);
 
                /* pick the bottleneck */
                end_to_end_bw_in_kbps = min(upper_link_bw_in_kbps,
                                            down_link_bw_in_kbps);
 
-               mutex_unlock(&mst_mgr->lock);
-
                /*
                 * use the maximum dsc compression bandwidth as the required
                 * bandwidth for the mode
@@ -1643,8 +1643,7 @@ enum dc_status dm_dp_mst_is_port_support_mode(
                /* check if mode could be supported within full_pbn */
                bpp = convert_dc_color_depth_into_bpc(stream->timing.display_color_depth) * 3;
                pbn = drm_dp_calc_pbn_mode(stream->timing.pix_clk_100hz / 10, bpp, false);
-
-               if (pbn > aconnector->mst_output_port->full_pbn)
+               if (pbn > full_pbn)
                        return DC_FAIL_BANDWIDTH_VALIDATE;
        }