drm/amd/display: Add work around for tunneled MST.

[Why]
Certain USB4 docks do not seem to be able to handle disabling
DSC once it has been enabled on an MST stream. This can result
in blank displays.

[How]
As a work around, always enable DSC on docks exhibiting this issue. The
flag to indicate the use of DSC for MST streams on a USB4 dock is set
during detection of the dock and only cleared when the USB4 dock is
disconnected.

Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Jimmy Kizito <Jimmy.Kizito@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/dc/core/dc_link.c b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
index dad7a4f..9639d7a 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
@@ -758,6 +758,18 @@ static bool detect_dp(struct dc_link *link,
                        dal_ddc_service_set_transaction_type(link->ddc,
                                                             sink_caps->transaction_type);
 
+#if defined(CONFIG_DRM_AMD_DC_DCN)
+                       /* Apply work around for tunneled MST on certain USB4 docks. Always use DSC if dock
+                        * reports DSC support.
+                        */
+                       if (link->ep_type == DISPLAY_ENDPOINT_USB4_DPIA &&
+                                       link->type == dc_connection_mst_branch &&
+                                       link->dpcd_caps.branch_dev_id == DP_BRANCH_DEVICE_ID_90CC24 &&
+                                       link->dpcd_caps.dsc_caps.dsc_basic_caps.fields.dsc_support.DSC_SUPPORT &&
+                                       !link->dc->debug.dpia_debug.bits.disable_mst_dsc_work_around)
+                               link->wa_flags.dpia_mst_dsc_always_on = true;
+#endif
+
 #if defined(CONFIG_DRM_AMD_DC_HDCP)
                        /* In case of fallback to SST when topology discovery below fails
                         * HDCP caps will be querried again later by the upper layer (caller
@@ -1203,6 +1215,10 @@ static bool dc_link_detect_helper(struct dc_link *link,
                        LINK_INFO("link=%d, mst branch is now Disconnected\n",
                                  link->link_index);
 
+                       /* Disable work around which keeps DSC on for tunneled MST on certain USB4 docks. */
+                       if (link->ep_type == DISPLAY_ENDPOINT_USB4_DPIA)
+                               link->wa_flags.dpia_mst_dsc_always_on = false;
+
                        dm_helpers_dp_mst_stop_top_mgr(link->ctx, link);
 
                        link->mst_stream_alloc_table.stream_count = 0;

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_resource.c b/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
index a2cf35a..0da692c 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
@@ -2258,16 +2258,6 @@ enum dc_status dc_validate_global_state(
 
        if (!new_ctx)
                return DC_ERROR_UNEXPECTED;
-#if defined(CONFIG_DRM_AMD_DC_DCN)
-
-       /*
-        * Update link encoder to stream assignment.
-        * TODO: Split out reason allocation from validation.
-        */
-       if (dc->res_pool->funcs->link_encs_assign && fast_validate == false)
-               dc->res_pool->funcs->link_encs_assign(
-                       dc, new_ctx, new_ctx->streams, new_ctx->stream_count);
-#endif
 
        if (dc->res_pool->funcs->validate_global) {
                result = dc->res_pool->funcs->validate_global(dc, new_ctx);
@@ -2319,6 +2309,16 @@ enum dc_status dc_validate_global_state(
                if (!dc->res_pool->funcs->validate_bandwidth(dc, new_ctx, fast_validate))
                        result = DC_FAIL_BANDWIDTH_VALIDATE;
 
+#if defined(CONFIG_DRM_AMD_DC_DCN)
+       /*
+        * Only update link encoder to stream assignment after bandwidth validation passed.
+        * TODO: Split out assignment and validation.
+        */
+       if (result == DC_OK && dc->res_pool->funcs->link_encs_assign && fast_validate == false)
+               dc->res_pool->funcs->link_encs_assign(
+                       dc, new_ctx, new_ctx->streams, new_ctx->stream_count);
+#endif
+
        return result;
 }
 

diff --git a/drivers/gpu/drm/amd/display/dc/dc.h b/drivers/gpu/drm/amd/display/dc/dc.h
index 0e27c0b..caa338a 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/dc.h
+++ b/drivers/gpu/drm/amd/display/dc/dc.h
@@ -511,7 +511,8 @@ union dpia_debug_options {
                uint32_t disable_dpia:1;
                uint32_t force_non_lttpr:1;
                uint32_t extend_aux_rd_interval:1;
-               uint32_t reserved:29;
+               uint32_t disable_mst_dsc_work_around:1;
+               uint32_t reserved:28;
        } bits;
        uint32_t raw;
 };

diff --git a/drivers/gpu/drm/amd/display/dc/dc_link.h b/drivers/gpu/drm/amd/display/dc/dc_link.h
index d5887d9..9eb4cf0 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/dc_link.h
+++ b/drivers/gpu/drm/amd/display/dc/dc_link.h
@@ -192,6 +192,8 @@ struct dc_link {
                bool dp_skip_DID2;
                bool dp_skip_reset_segment;
                bool dp_mot_reset_segment;
+               /* Some USB4 docks do not handle turning off MST DSC once it has been enabled. */
+               bool dpia_mst_dsc_always_on;
        } wa_flags;
        struct link_mst_stream_allocation_table mst_stream_alloc_table;