Re: [v3] drm/amdgpu/mst: Stop ignoring error codes and deadlocking

["Limonciello, Mario" <mario.limonciello@xxxxxxx>]

On 11/18/2022 13:25, Lyude Paul wrote:
> It appears that amdgpu makes the mistake of completely ignoring the return
> values from the DP MST helpers, and instead just returns a simple
> true/false. In this case, it seems to have come back to bite us because as
> a result of simply returning false from
> compute_mst_dsc_configs_for_state(), amdgpu had no way of telling when a
> deadlock happened from these helpers. This could definitely result in some
> kernel splats.
>
> V2:
> * Address Wayne's comments (fix another bunch of spots where we weren't
>    passing down return codes)
> V3:
> * Fix uninitialized var in pre_compute_mst_dsc_configs_for_state()

FYI v2 was just merged recently, it's in the 6.2 pull request that was 
sent out and Alex planned to add it to 6.1-fixes next week too.

Can you send just the delta from v2->v3 as another patch so it can layer 
in cleanly?
> Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx>
> Fixes: 8c20a1ed9b4f ("drm/amd/display: MST DSC compute fair share")
> Reviewed-by: Wayne Lin <Wayne.Lin@xxxxxxx>
> Cc: Harry Wentland <harry.wentland@xxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx> # v5.6+
> ---
>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  18 +-
>   .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 235 ++++++++++--------
>   .../display/amdgpu_dm/amdgpu_dm_mst_types.h   |  12 +-
>   3 files changed, 147 insertions(+), 118 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 0db2a88cd4d7..852a2100c6b3 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -6462,7 +6462,7 @@ static int dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
>   	struct drm_connector_state *new_con_state;
>   	struct amdgpu_dm_connector *aconnector;
>   	struct dm_connector_state *dm_conn_state;
> -	int i, j;
> +	int i, j, ret;
>   	int vcpi, pbn_div, pbn, slot_num = 0;
>   
>   	for_each_new_connector_in_state(state, connector, new_con_state, i) {
> @@ -6509,8 +6509,11 @@ static int dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
>   			dm_conn_state->pbn = pbn;
>   			dm_conn_state->vcpi_slots = slot_num;
>   
> -			drm_dp_mst_atomic_enable_dsc(state, aconnector->port, dm_conn_state->pbn,
> -						     false);
> +			ret = drm_dp_mst_atomic_enable_dsc(state, aconnector->port,
> +							   dm_conn_state->pbn, false);
> +			if (ret < 0)
> +				return ret;
> +
>   			continue;
>   		}
>   
> @@ -9523,10 +9526,9 @@ static int amdgpu_dm_atomic_check(struct drm_device *dev,
>   
>   #if defined(CONFIG_DRM_AMD_DC_DCN)
>   	if (dc_resource_is_dsc_encoding_supported(dc)) {
> -		if (!pre_validate_dsc(state, &dm_state, vars)) {
> -			ret = -EINVAL;
> +		ret = pre_validate_dsc(state, &dm_state, vars);
> +		if (ret != 0)
>   			goto fail;
> -		}
>   	}
>   #endif
>   
> @@ -9621,9 +9623,9 @@ static int amdgpu_dm_atomic_check(struct drm_device *dev,
>   		}
>   
>   #if defined(CONFIG_DRM_AMD_DC_DCN)
> -		if (!compute_mst_dsc_configs_for_state(state, dm_state->context, vars)) {
> +		ret = compute_mst_dsc_configs_for_state(state, dm_state->context, vars);
> +		if (ret) {
>   			DRM_DEBUG_DRIVER("compute_mst_dsc_configs_for_state() failed\n");
> -			ret = -EINVAL;
>   			goto fail;
>   		}
>   
> 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 6ff96b4bdda5..2f72745660fb 100644
> --- 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
> @@ -703,13 +703,13 @@ static int bpp_x16_from_pbn(struct dsc_mst_fairness_params param, int pbn)
>   	return dsc_config.bits_per_pixel;
>   }
>   
> -static bool increase_dsc_bpp(struct drm_atomic_state *state,
> -			     struct drm_dp_mst_topology_state *mst_state,
> -			     struct dc_link *dc_link,
> -			     struct dsc_mst_fairness_params *params,
> -			     struct dsc_mst_fairness_vars *vars,
> -			     int count,
> -			     int k)
> +static int increase_dsc_bpp(struct drm_atomic_state *state,
> +			    struct drm_dp_mst_topology_state *mst_state,
> +			    struct dc_link *dc_link,
> +			    struct dsc_mst_fairness_params *params,
> +			    struct dsc_mst_fairness_vars *vars,
> +			    int count,
> +			    int k)
>   {
>   	int i;
>   	bool bpp_increased[MAX_PIPES];
> @@ -719,6 +719,7 @@ static bool increase_dsc_bpp(struct drm_atomic_state *state,
>   	int remaining_to_increase = 0;
>   	int link_timeslots_used;
>   	int fair_pbn_alloc;
> +	int ret = 0;
>   
>   	for (i = 0; i < count; i++) {
>   		if (vars[i + k].dsc_enabled) {
> @@ -757,52 +758,60 @@ static bool increase_dsc_bpp(struct drm_atomic_state *state,
>   
>   		if (initial_slack[next_index] > fair_pbn_alloc) {
>   			vars[next_index].pbn += fair_pbn_alloc;
> -			if (drm_dp_atomic_find_time_slots(state,
> -							  params[next_index].port->mgr,
> -							  params[next_index].port,
> -							  vars[next_index].pbn) < 0)
> -				return false;
> -			if (!drm_dp_mst_atomic_check(state)) {
> +			ret = drm_dp_atomic_find_time_slots(state,
> +							    params[next_index].port->mgr,
> +							    params[next_index].port,
> +							    vars[next_index].pbn);
> +			if (ret < 0)
> +				return ret;
> +
> +			ret = drm_dp_mst_atomic_check(state);
> +			if (ret == 0) {
>   				vars[next_index].bpp_x16 = bpp_x16_from_pbn(params[next_index], vars[next_index].pbn);
>   			} else {
>   				vars[next_index].pbn -= fair_pbn_alloc;
> -				if (drm_dp_atomic_find_time_slots(state,
> -								  params[next_index].port->mgr,
> -								  params[next_index].port,
> -								  vars[next_index].pbn) < 0)
> -					return false;
> +				ret = drm_dp_atomic_find_time_slots(state,
> +								    params[next_index].port->mgr,
> +								    params[next_index].port,
> +								    vars[next_index].pbn);
> +				if (ret < 0)
> +					return ret;
>   			}
>   		} else {
>   			vars[next_index].pbn += initial_slack[next_index];
> -			if (drm_dp_atomic_find_time_slots(state,
> -							  params[next_index].port->mgr,
> -							  params[next_index].port,
> -							  vars[next_index].pbn) < 0)
> -				return false;
> -			if (!drm_dp_mst_atomic_check(state)) {
> +			ret = drm_dp_atomic_find_time_slots(state,
> +							    params[next_index].port->mgr,
> +							    params[next_index].port,
> +							    vars[next_index].pbn);
> +			if (ret < 0)
> +				return ret;
> +
> +			ret = drm_dp_mst_atomic_check(state);
> +			if (ret == 0) {
>   				vars[next_index].bpp_x16 = params[next_index].bw_range.max_target_bpp_x16;
>   			} else {
>   				vars[next_index].pbn -= initial_slack[next_index];
> -				if (drm_dp_atomic_find_time_slots(state,
> -								  params[next_index].port->mgr,
> -								  params[next_index].port,
> -								  vars[next_index].pbn) < 0)
> -					return false;
> +				ret = drm_dp_atomic_find_time_slots(state,
> +								    params[next_index].port->mgr,
> +								    params[next_index].port,
> +								    vars[next_index].pbn);
> +				if (ret < 0)
> +					return ret;
>   			}
>   		}
>   
>   		bpp_increased[next_index] = true;
>   		remaining_to_increase--;
>   	}
> -	return true;
> +	return 0;
>   }
>   
> -static bool try_disable_dsc(struct drm_atomic_state *state,
> -			    struct dc_link *dc_link,
> -			    struct dsc_mst_fairness_params *params,
> -			    struct dsc_mst_fairness_vars *vars,
> -			    int count,
> -			    int k)
> +static int try_disable_dsc(struct drm_atomic_state *state,
> +			   struct dc_link *dc_link,
> +			   struct dsc_mst_fairness_params *params,
> +			   struct dsc_mst_fairness_vars *vars,
> +			   int count,
> +			   int k)
>   {
>   	int i;
>   	bool tried[MAX_PIPES];
> @@ -810,6 +819,7 @@ static bool try_disable_dsc(struct drm_atomic_state *state,
>   	int max_kbps_increase;
>   	int next_index;
>   	int remaining_to_try = 0;
> +	int ret;
>   
>   	for (i = 0; i < count; i++) {
>   		if (vars[i + k].dsc_enabled
> @@ -840,49 +850,52 @@ static bool try_disable_dsc(struct drm_atomic_state *state,
>   			break;
>   
>   		vars[next_index].pbn = kbps_to_peak_pbn(params[next_index].bw_range.stream_kbps);
> -		if (drm_dp_atomic_find_time_slots(state,
> -						  params[next_index].port->mgr,
> -						  params[next_index].port,
> -						  vars[next_index].pbn) < 0)
> -			return false;
> +		ret = drm_dp_atomic_find_time_slots(state,
> +						    params[next_index].port->mgr,
> +						    params[next_index].port,
> +						    vars[next_index].pbn);
> +		if (ret < 0)
> +			return ret;
>   
> -		if (!drm_dp_mst_atomic_check(state)) {
> +		ret = drm_dp_mst_atomic_check(state);
> +		if (ret == 0) {
>   			vars[next_index].dsc_enabled = false;
>   			vars[next_index].bpp_x16 = 0;
>   		} else {
>   			vars[next_index].pbn = kbps_to_peak_pbn(params[next_index].bw_range.max_kbps);
> -			if (drm_dp_atomic_find_time_slots(state,
> -							  params[next_index].port->mgr,
> -							  params[next_index].port,
> -							  vars[next_index].pbn) < 0)
> -				return false;
> +			ret = drm_dp_atomic_find_time_slots(state,
> +							    params[next_index].port->mgr,
> +							    params[next_index].port,
> +							    vars[next_index].pbn);
> +			if (ret < 0)
> +				return ret;
>   		}
>   
>   		tried[next_index] = true;
>   		remaining_to_try--;
>   	}
> -	return true;
> +	return 0;
>   }
>   
> -static bool compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
> -					     struct dc_state *dc_state,
> -					     struct dc_link *dc_link,
> -					     struct dsc_mst_fairness_vars *vars,
> -					     struct drm_dp_mst_topology_mgr *mgr,
> -					     int *link_vars_start_index)
> +static int compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
> +					    struct dc_state *dc_state,
> +					    struct dc_link *dc_link,
> +					    struct dsc_mst_fairness_vars *vars,
> +					    struct drm_dp_mst_topology_mgr *mgr,
> +					    int *link_vars_start_index)
>   {
>   	struct dc_stream_state *stream;
>   	struct dsc_mst_fairness_params params[MAX_PIPES];
>   	struct amdgpu_dm_connector *aconnector;
>   	struct drm_dp_mst_topology_state *mst_state = drm_atomic_get_mst_topology_state(state, mgr);
>   	int count = 0;
> -	int i, k;
> +	int i, k, ret;
>   	bool debugfs_overwrite = false;
>   
>   	memset(params, 0, sizeof(params));
>   
>   	if (IS_ERR(mst_state))
> -		return false;
> +		return PTR_ERR(mst_state);
>   
>   	mst_state->pbn_div = dm_mst_get_pbn_divider(dc_link);
>   #if defined(CONFIG_DRM_AMD_DC_DCN)
> @@ -933,7 +946,7 @@ static bool compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
>   
>   	if (count == 0) {
>   		ASSERT(0);
> -		return true;
> +		return 0;
>   	}
>   
>   	/* k is start index of vars for current phy link used by mst hub */
> @@ -947,13 +960,17 @@ static bool compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
>   		vars[i + k].pbn = kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
>   		vars[i + k].dsc_enabled = false;
>   		vars[i + k].bpp_x16 = 0;
> -		if (drm_dp_atomic_find_time_slots(state, params[i].port->mgr, params[i].port,
> -						  vars[i + k].pbn) < 0)
> -			return false;
> +		ret = drm_dp_atomic_find_time_slots(state, params[i].port->mgr, params[i].port,
> +						    vars[i + k].pbn);
> +		if (ret < 0)
> +			return ret;
>   	}
> -	if (!drm_dp_mst_atomic_check(state) && !debugfs_overwrite) {
> +	ret = drm_dp_mst_atomic_check(state);
> +	if (ret == 0 && !debugfs_overwrite) {
>   		set_dsc_configs_from_fairness_vars(params, vars, count, k);
> -		return true;
> +		return 0;
> +	} else if (ret != -ENOSPC) {
> +		return ret;
>   	}
>   
>   	/* Try max compression */
> @@ -962,31 +979,36 @@ static bool compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
>   			vars[i + k].pbn = kbps_to_peak_pbn(params[i].bw_range.min_kbps);
>   			vars[i + k].dsc_enabled = true;
>   			vars[i + k].bpp_x16 = params[i].bw_range.min_target_bpp_x16;
> -			if (drm_dp_atomic_find_time_slots(state, params[i].port->mgr,
> -							  params[i].port, vars[i + k].pbn) < 0)
> -				return false;
> +			ret = drm_dp_atomic_find_time_slots(state, params[i].port->mgr,
> +							    params[i].port, vars[i + k].pbn);
> +			if (ret < 0)
> +				return ret;
>   		} else {
>   			vars[i + k].pbn = kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
>   			vars[i + k].dsc_enabled = false;
>   			vars[i + k].bpp_x16 = 0;
> -			if (drm_dp_atomic_find_time_slots(state, params[i].port->mgr,
> -							  params[i].port, vars[i + k].pbn) < 0)
> -				return false;
> +			ret = drm_dp_atomic_find_time_slots(state, params[i].port->mgr,
> +							    params[i].port, vars[i + k].pbn);
> +			if (ret < 0)
> +				return ret;
>   		}
>   	}
> -	if (drm_dp_mst_atomic_check(state))
> -		return false;
> +	ret = drm_dp_mst_atomic_check(state);
> +	if (ret != 0)
> +		return ret;
>   
>   	/* Optimize degree of compression */
> -	if (!increase_dsc_bpp(state, mst_state, dc_link, params, vars, count, k))
> -		return false;
> +	ret = increase_dsc_bpp(state, mst_state, dc_link, params, vars, count, k);
> +	if (ret < 0)
> +		return ret;
>   
> -	if (!try_disable_dsc(state, dc_link, params, vars, count, k))
> -		return false;
> +	ret = try_disable_dsc(state, dc_link, params, vars, count, k);
> +	if (ret < 0)
> +		return ret;
>   
>   	set_dsc_configs_from_fairness_vars(params, vars, count, k);
>   
> -	return true;
> +	return 0;
>   }
>   
>   static bool is_dsc_need_re_compute(
> @@ -1087,15 +1109,16 @@ static bool is_dsc_need_re_compute(
>   	return is_dsc_need_re_compute;
>   }
>   
> -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> -				       struct dc_state *dc_state,
> -				       struct dsc_mst_fairness_vars *vars)
> +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> +				      struct dc_state *dc_state,
> +				      struct dsc_mst_fairness_vars *vars)
>   {
>   	int i, j;
>   	struct dc_stream_state *stream;
>   	bool computed_streams[MAX_PIPES];
>   	struct amdgpu_dm_connector *aconnector;
>   	int link_vars_start_index = 0;
> +	int ret = 0;
>   
>   	for (i = 0; i < dc_state->stream_count; i++)
>   		computed_streams[i] = false;
> @@ -1118,17 +1141,19 @@ bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
>   			continue;
>   
>   		if (dcn20_remove_stream_from_ctx(stream->ctx->dc, dc_state, stream) != DC_OK)
> -			return false;
> +			return -EINVAL;
>   
>   		if (!is_dsc_need_re_compute(state, dc_state, stream->link))
>   			continue;
>   
>   		mutex_lock(&aconnector->mst_mgr.lock);
> -		if (!compute_mst_dsc_configs_for_link(state, dc_state, stream->link, vars,
> -						      &aconnector->mst_mgr,
> -						      &link_vars_start_index)) {
> +
> +		ret = compute_mst_dsc_configs_for_link(state, dc_state, stream->link, vars,
> +						       &aconnector->mst_mgr,
> +						       &link_vars_start_index);
> +		if (ret != 0) {
>   			mutex_unlock(&aconnector->mst_mgr.lock);
> -			return false;
> +			return ret;
>   		}
>   		mutex_unlock(&aconnector->mst_mgr.lock);
>   
> @@ -1143,22 +1168,22 @@ bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
>   
>   		if (stream->timing.flags.DSC == 1)
>   			if (dc_stream_add_dsc_to_resource(stream->ctx->dc, dc_state, stream) != DC_OK)
> -				return false;
> +				return -EINVAL;
>   	}
>   
> -	return true;
> +	return ret;
>   }
>   
> -static bool
> -	pre_compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> -					      struct dc_state *dc_state,
> -					      struct dsc_mst_fairness_vars *vars)
> +static int pre_compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> +						 struct dc_state *dc_state,
> +						 struct dsc_mst_fairness_vars *vars)
>   {
>   	int i, j;
>   	struct dc_stream_state *stream;
>   	bool computed_streams[MAX_PIPES];
>   	struct amdgpu_dm_connector *aconnector;
>   	int link_vars_start_index = 0;
> +	int ret = 0;
>   
>   	for (i = 0; i < dc_state->stream_count; i++)
>   		computed_streams[i] = false;
> @@ -1184,11 +1209,12 @@ static bool
>   			continue;
>   
>   		mutex_lock(&aconnector->mst_mgr.lock);
> -		if (!compute_mst_dsc_configs_for_link(state, dc_state, stream->link, vars,
> -						      &aconnector->mst_mgr,
> -						      &link_vars_start_index)) {
> +		ret = compute_mst_dsc_configs_for_link(state, dc_state, stream->link, vars,
> +						       &aconnector->mst_mgr,
> +						       &link_vars_start_index);
> +		if (ret != 0) {
>   			mutex_unlock(&aconnector->mst_mgr.lock);
> -			return false;
> +			return ret;
>   		}
>   		mutex_unlock(&aconnector->mst_mgr.lock);
>   
> @@ -1198,7 +1224,7 @@ static bool
>   		}
>   	}
>   
> -	return true;
> +	return ret;
>   }
>   
>   static int find_crtc_index_in_state_by_stream(struct drm_atomic_state *state,
> @@ -1253,9 +1279,9 @@ static bool is_dsc_precompute_needed(struct drm_atomic_state *state)
>   	return ret;
>   }
>   
> -bool pre_validate_dsc(struct drm_atomic_state *state,
> -		      struct dm_atomic_state **dm_state_ptr,
> -		      struct dsc_mst_fairness_vars *vars)
> +int pre_validate_dsc(struct drm_atomic_state *state,
> +		     struct dm_atomic_state **dm_state_ptr,
> +		     struct dsc_mst_fairness_vars *vars)
>   {
>   	int i;
>   	struct dm_atomic_state *dm_state;
> @@ -1264,11 +1290,12 @@ bool pre_validate_dsc(struct drm_atomic_state *state,
>   
>   	if (!is_dsc_precompute_needed(state)) {
>   		DRM_INFO_ONCE("DSC precompute is not needed.\n");
> -		return true;
> +		return 0;
>   	}
> -	if (dm_atomic_get_state(state, dm_state_ptr)) {
> +	ret = dm_atomic_get_state(state, dm_state_ptr);
> +	if (ret != 0) {
>   		DRM_INFO_ONCE("dm_atomic_get_state() failed\n");
> -		return false;
> +		return ret;
>   	}
>   	dm_state = *dm_state_ptr;
>   
> @@ -1280,7 +1307,7 @@ bool pre_validate_dsc(struct drm_atomic_state *state,
>   
>   	local_dc_state = kmemdup(dm_state->context, sizeof(struct dc_state), GFP_KERNEL);
>   	if (!local_dc_state)
> -		return false;
> +		return -ENOMEM;
>   
>   	for (i = 0; i < local_dc_state->stream_count; i++) {
>   		struct dc_stream_state *stream = dm_state->context->streams[i];
> @@ -1316,9 +1343,9 @@ bool pre_validate_dsc(struct drm_atomic_state *state,
>   	if (ret != 0)
>   		goto clean_exit;
>   
> -	if (!pre_compute_mst_dsc_configs_for_state(state, local_dc_state, vars)) {
> +	ret = pre_compute_mst_dsc_configs_for_state(state, local_dc_state, vars);
> +	if (ret != 0) {
>   		DRM_INFO_ONCE("pre_compute_mst_dsc_configs_for_state() failed\n");
> -		ret = -EINVAL;
>   		goto clean_exit;
>   	}
>   
> @@ -1349,7 +1376,7 @@ bool pre_validate_dsc(struct drm_atomic_state *state,
>   
>   	kfree(local_dc_state);
>   
> -	return (ret == 0);
> +	return ret;
>   }
>   
>   static unsigned int kbps_from_pbn(unsigned int pbn)
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> index b92a7c5671aa..97fd70df531b 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> @@ -53,15 +53,15 @@ struct dsc_mst_fairness_vars {
>   	struct amdgpu_dm_connector *aconnector;
>   };
>   
> -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> -				       struct dc_state *dc_state,
> -				       struct dsc_mst_fairness_vars *vars);
> +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> +				      struct dc_state *dc_state,
> +				      struct dsc_mst_fairness_vars *vars);
>   
>   bool needs_dsc_aux_workaround(struct dc_link *link);
>   
> -bool pre_validate_dsc(struct drm_atomic_state *state,
> -		      struct dm_atomic_state **dm_state_ptr,
> -		      struct dsc_mst_fairness_vars *vars);
> +int pre_validate_dsc(struct drm_atomic_state *state,
> +		     struct dm_atomic_state **dm_state_ptr,
> +		     struct dsc_mst_fairness_vars *vars);
>   
>   enum dc_status dm_dp_mst_is_port_support_mode(
>   	struct amdgpu_dm_connector *aconnector,