[PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and deadlocking

[PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and deadlocking

[Lyude Paul]

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.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Fixes: 8c20a1ed9b4f ("drm/amd/display: MST DSC compute fair share")
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: <stable@vger.kernel.org> # v5.6+
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  18 +--
 .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 107 ++++++++++--------
 .../display/amdgpu_dm/amdgpu_dm_mst_types.h   |  12 +-
 3 files changed, 73 insertions(+), 64 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 0db2a88cd4d7b..6f76b2c84cdb5 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 6ff96b4bdda5c..30bc2e5058b70 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
@@ -864,25 +864,25 @@ static bool try_disable_dsc(struct drm_atomic_state *state,
 	return true;
 }
 
-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 +933,7 @@ 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 */
@@ -949,11 +949,14 @@ static bool compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
 		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;
+			return -EINVAL;
 	}
-	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 == -EDEADLK) {
+		return ret;
 	}
 
 	/* Try max compression */
@@ -964,29 +967,30 @@ static bool compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
 			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;
+				return -EINVAL;
 		} 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;
+				return -EINVAL;
 		}
 	}
-	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;
+		return -ENOSPC;
 
 	if (!try_disable_dsc(state, dc_link, params, vars, count, k))
-		return false;
+		return -ENOSPC;
 
 	set_dsc_configs_from_fairness_vars(params, vars, count, k);
 
-	return true;
+	return 0;
 }
 
 static bool is_dsc_need_re_compute(
@@ -1087,15 +1091,16 @@ 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 +1123,19 @@ 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 +1150,22 @@ 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;
 
 	for (i = 0; i < dc_state->stream_count; i++)
 		computed_streams[i] = false;
@@ -1184,13 +1191,12 @@ 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)) {
-			mutex_unlock(&aconnector->mst_mgr.lock);
-			return false;
-		}
+		ret = compute_mst_dsc_configs_for_link(state, dc_state, stream->link, vars,
+						       &aconnector->mst_mgr,
+						       &link_vars_start_index);
 		mutex_unlock(&aconnector->mst_mgr.lock);
+		if (ret != 0)
+			return ret;
 
 		for (j = 0; j < dc_state->stream_count; j++) {
 			if (dc_state->streams[j]->link == stream->link)
@@ -1198,7 +1204,7 @@ static bool
 		}
 	}
 
-	return true;
+	return ret;
 }
 
 static int find_crtc_index_in_state_by_stream(struct drm_atomic_state *state,
@@ -1253,9 +1259,9 @@ 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 +1270,12 @@ 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 +1287,7 @@ 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 +1323,9 @@ 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 +1356,7 @@ 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 b92a7c5671aa2..97fd70df531bf 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,
-- 
2.37.3

RE: [PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and deadlocking

[Lin, Wayne]

[Public]

Thanks, Lyude!
Comments inline.

> -----Original Message-----
> From: Lyude Paul <lyude@redhat.com>
> Sent: Saturday, November 5, 2022 7:59 AM
> To: amd-gfx@lists.freedesktop.org
> Cc: Wentland, Harry <Harry.Wentland@amd.com>; stable@vger.kernel.org;
> Li, Sun peng (Leo) <Sunpeng.Li@amd.com>; Siqueira, Rodrigo
> <Rodrigo.Siqueira@amd.com>; Deucher, Alexander
> <Alexander.Deucher@amd.com>; Koenig, Christian
> <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; David
> Airlie <airlied@gmail.com>; Daniel Vetter <daniel@ffwll.ch>; Kazlauskas,
> Nicholas <Nicholas.Kazlauskas@amd.com>; Pillai, Aurabindo
> <Aurabindo.Pillai@amd.com>; Li, Roman <Roman.Li@amd.com>; Zuo, Jerry
> <Jerry.Zuo@amd.com>; Wu, Hersen <hersenxs.wu@amd.com>; Lin, Wayne
> <Wayne.Lin@amd.com>; Thomas Zimmermann <tzimmermann@suse.de>;
> Mahfooz, Hamza <Hamza.Mahfooz@amd.com>; Hung, Alex
> <Alex.Hung@amd.com>; Francis, David <David.Francis@amd.com>; Mikita
> Lipski <mikita.lipski@amd.com>; Liu, Wenjing <Wenjing.Liu@amd.com>;
> open list:DRM DRIVERS <dri-devel@lists.freedesktop.org>; open list <linux-
> kernel@vger.kernel.org>
> Subject: [PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and
> deadlocking
> 
> 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.
> 
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Fixes: 8c20a1ed9b4f ("drm/amd/display: MST DSC compute fair share")
> Cc: Harry Wentland <harry.wentland@amd.com>
> Cc: <stable@vger.kernel.org> # v5.6+
> ---
>  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  18 +--
>  .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 107 ++++++++++------
> --
>  .../display/amdgpu_dm/amdgpu_dm_mst_types.h   |  12 +-
>  3 files changed, 73 insertions(+), 64 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 0db2a88cd4d7b..6f76b2c84cdb5 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 6ff96b4bdda5c..30bc2e5058b70 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
> @@ -864,25 +864,25 @@ static bool try_disable_dsc(struct
> drm_atomic_state *state,
>  	return true;
>  }
> 
> -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 +933,7 @@ 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 */ @@
> -949,11 +949,14 @@ static bool compute_mst_dsc_configs_for_link(struct
> drm_atomic_state *state,
>  		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;
> +			return -EINVAL;

Should we also return the error code get from drm_dp_atomic_find_time_slots() rather than 
assigning a new one here?

>  	}
> -	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 == -EDEADLK) {
> +		return ret;

I think we should return here whenever there is an error. Not just for EDEADLK case. 

>  	}
> 
>  	/* Try max compression */
> @@ -964,29 +967,30 @@ static bool
> compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
>  			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;
> +				return -EINVAL;

Same as above.

>  		} 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;
> +				return -EINVAL;

Same as above.

>  		}
>  	}
> -	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;
> +		return -ENOSPC;
> 
>  	if (!try_disable_dsc(state, dc_link, params, vars, count, k))
> -		return false;
> +		return -ENOSPC;
> 
>  	set_dsc_configs_from_fairness_vars(params, vars, count, k);
> 
> -	return true;
> +	return 0;
>  }
> 
>  static bool is_dsc_need_re_compute(
> @@ -1087,15 +1091,16 @@ 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 +1123,19 @@ 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 +1150,22 @@ 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;
> 
>  	for (i = 0; i < dc_state->stream_count; i++)
>  		computed_streams[i] = false;
> @@ -1184,13 +1191,12 @@ 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)) {
> -			mutex_unlock(&aconnector->mst_mgr.lock);
> -			return false;
> -		}
> +		ret = compute_mst_dsc_configs_for_link(state, dc_state,
> stream->link, vars,
> +						       &aconnector->mst_mgr,
> +						       &link_vars_start_index);
>  		mutex_unlock(&aconnector->mst_mgr.lock);
> +		if (ret != 0)
> +			return ret;
> 
>  		for (j = 0; j < dc_state->stream_count; j++) {
>  			if (dc_state->streams[j]->link == stream->link) @@ -
> 1198,7 +1204,7 @@ static bool
>  		}
>  	}
> 
> -	return true;
> +	return ret;
>  }
> 
>  static int find_crtc_index_in_state_by_stream(struct drm_atomic_state
> *state, @@ -1253,9 +1259,9 @@ 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 +1270,12 @@ 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 +1287,7 @@ 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 +1323,9 @@ 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 +1356,7 @@ 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 b92a7c5671aa2..97fd70df531bf 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,
> --
> 2.37.3
---
Regards,
Wayne Lin

Re: [PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and deadlocking

[Lyude Paul]

On Wed, 2022-11-09 at 09:48 +0000, Lin, Wayne wrote:
> [Public]
> 
> Thanks, Lyude!
> Comments inline.
> 
> > -----Original Message-----
> > From: Lyude Paul <lyude@redhat.com>
> > Sent: Saturday, November 5, 2022 7:59 AM
> > To: amd-gfx@lists.freedesktop.org
> > Cc: Wentland, Harry <Harry.Wentland@amd.com>; stable@vger.kernel.org;
> > Li, Sun peng (Leo) <Sunpeng.Li@amd.com>; Siqueira, Rodrigo
> > <Rodrigo.Siqueira@amd.com>; Deucher, Alexander
> > <Alexander.Deucher@amd.com>; Koenig, Christian
> > <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; David
> > Airlie <airlied@gmail.com>; Daniel Vetter <daniel@ffwll.ch>; Kazlauskas,
> > Nicholas <Nicholas.Kazlauskas@amd.com>; Pillai, Aurabindo
> > <Aurabindo.Pillai@amd.com>; Li, Roman <Roman.Li@amd.com>; Zuo, Jerry
> > <Jerry.Zuo@amd.com>; Wu, Hersen <hersenxs.wu@amd.com>; Lin, Wayne
> > <Wayne.Lin@amd.com>; Thomas Zimmermann <tzimmermann@suse.de>;
> > Mahfooz, Hamza <Hamza.Mahfooz@amd.com>; Hung, Alex
> > <Alex.Hung@amd.com>; Francis, David <David.Francis@amd.com>; Mikita
> > Lipski <mikita.lipski@amd.com>; Liu, Wenjing <Wenjing.Liu@amd.com>;
> > open list:DRM DRIVERS <dri-devel@lists.freedesktop.org>; open list <linux-
> > kernel@vger.kernel.org>
> > Subject: [PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and
> > deadlocking
> > 
> > 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.
> > 
> > Signed-off-by: Lyude Paul <lyude@redhat.com>
> > Fixes: 8c20a1ed9b4f ("drm/amd/display: MST DSC compute fair share")
> > Cc: Harry Wentland <harry.wentland@amd.com>
> > Cc: <stable@vger.kernel.org> # v5.6+
> > ---
> >  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  18 +--
> >  .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 107 ++++++++++------
> > --
> >  .../display/amdgpu_dm/amdgpu_dm_mst_types.h   |  12 +-
> >  3 files changed, 73 insertions(+), 64 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 0db2a88cd4d7b..6f76b2c84cdb5 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 6ff96b4bdda5c..30bc2e5058b70 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
> > @@ -864,25 +864,25 @@ static bool try_disable_dsc(struct
> > drm_atomic_state *state,
> >  	return true;
> >  }
> > 
> > -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 +933,7 @@ 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 */ @@
> > -949,11 +949,14 @@ static bool compute_mst_dsc_configs_for_link(struct
> > drm_atomic_state *state,
> >  		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;
> > +			return -EINVAL;
> 
> Should we also return the error code get from drm_dp_atomic_find_time_slots() rather than 
> assigning a new one here?

Yes we should, nice catch!

> 
> >  	}
> > -	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 == -EDEADLK) {
> > +		return ret;
> 
> I think we should return here whenever there is an error. Not just for EDEADLK case. 

sgtm


> 
> >  	}
> > 
> >  	/* Try max compression */
> > @@ -964,29 +967,30 @@ static bool
> > compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
> >  			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;
> > +				return -EINVAL;
> 
> Same as above.
> 
> >  		} 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;
> > +				return -EINVAL;
> 
> Same as above.
> 
> >  		}
> >  	}
> > -	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;
> > +		return -ENOSPC;
> > 
> >  	if (!try_disable_dsc(state, dc_link, params, vars, count, k))
> > -		return false;
> > +		return -ENOSPC;
> > 
> >  	set_dsc_configs_from_fairness_vars(params, vars, count, k);
> > 
> > -	return true;
> > +	return 0;
> >  }
> > 
> >  static bool is_dsc_need_re_compute(
> > @@ -1087,15 +1091,16 @@ 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 +1123,19 @@ 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 +1150,22 @@ 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;
> > 
> >  	for (i = 0; i < dc_state->stream_count; i++)
> >  		computed_streams[i] = false;
> > @@ -1184,13 +1191,12 @@ 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)) {
> > -			mutex_unlock(&aconnector->mst_mgr.lock);
> > -			return false;
> > -		}
> > +		ret = compute_mst_dsc_configs_for_link(state, dc_state,
> > stream->link, vars,
> > +						       &aconnector->mst_mgr,
> > +						       &link_vars_start_index);
> >  		mutex_unlock(&aconnector->mst_mgr.lock);
> > +		if (ret != 0)
> > +			return ret;
> > 
> >  		for (j = 0; j < dc_state->stream_count; j++) {
> >  			if (dc_state->streams[j]->link == stream->link) @@ -
> > 1198,7 +1204,7 @@ static bool
> >  		}
> >  	}
> > 
> > -	return true;
> > +	return ret;
> >  }
> > 
> >  static int find_crtc_index_in_state_by_stream(struct drm_atomic_state
> > *state, @@ -1253,9 +1259,9 @@ 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 +1270,12 @@ 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 +1287,7 @@ 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 +1323,9 @@ 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 +1356,7 @@ 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 b92a7c5671aa2..97fd70df531bf 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,
> > --
> > 2.37.3
> ---
> Regards,
> Wayne Lin
> 

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat

Re: [PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and deadlocking

[Lyude Paul]

On Wed, 2022-11-09 at 09:48 +0000, Lin, Wayne wrote:
> >   	}
> > -	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 == -EDEADLK) {
> > +		return ret;
> 
> I think we should return here whenever there is an error. Not just for
> EDEADLK case. 

Are we sure about this one? I think we may actually want to make this so it
returns on ret != -ENOSPC, since we want the function to continue if there's
no space in the atomic state available so it can try recomputing things with
compression enabled. On ret == 0 it should return early without doing
compression, and on ret == -ENOSPC it should just continue the function from
there

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat

RE: [PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and deadlocking

[Lin, Wayne]

[Public]



> -----Original Message-----
> From: Lyude Paul <lyude@redhat.com>
> Sent: Tuesday, November 15, 2022 5:55 AM
> To: Lin, Wayne <Wayne.Lin@amd.com>; amd-gfx@lists.freedesktop.org
> Cc: Wentland, Harry <Harry.Wentland@amd.com>; stable@vger.kernel.org;
> Li, Sun peng (Leo) <Sunpeng.Li@amd.com>; Siqueira, Rodrigo
> <Rodrigo.Siqueira@amd.com>; Deucher, Alexander
> <Alexander.Deucher@amd.com>; Koenig, Christian
> <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; David
> Airlie <airlied@gmail.com>; Daniel Vetter <daniel@ffwll.ch>; Kazlauskas,
> Nicholas <Nicholas.Kazlauskas@amd.com>; Pillai, Aurabindo
> <Aurabindo.Pillai@amd.com>; Li, Roman <Roman.Li@amd.com>; Zuo, Jerry
> <Jerry.Zuo@amd.com>; Wu, Hersen <hersenxs.wu@amd.com>; Thomas
> Zimmermann <tzimmermann@suse.de>; Mahfooz, Hamza
> <Hamza.Mahfooz@amd.com>; Hung, Alex <Alex.Hung@amd.com>; Francis,
> David <David.Francis@amd.com>; Mikita Lipski <mikita.lipski@amd.com>; Liu,
> Wenjing <Wenjing.Liu@amd.com>; open list:DRM DRIVERS <dri-
> devel@lists.freedesktop.org>; open list <linux-kernel@vger.kernel.org>
> Subject: Re: [PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and
> deadlocking
> 
> On Wed, 2022-11-09 at 09:48 +0000, Lin, Wayne wrote:
> > >   	}
> > > -	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 == -EDEADLK) {
> > > +		return ret;
> >
> > I think we should return here whenever there is an error. Not just for
> > EDEADLK case.
> 
> Are we sure about this one? I think we may actually want to make this so it
> returns on ret != -ENOSPC, since we want the function to continue if there's
> no space in the atomic state available so it can try recomputing things with
> compression enabled. On ret == 0 it should return early without doing
> compression, and on ret == -ENOSPC it should just continue the function
> from there
> 
Oh, right.. Thanks for saving me from causing disaster : )

> --
> Cheers,
>  Lyude Paul (she/her)
>  Software Engineer at Red Hat
--
Regards,
Wayne

[PATCH 2/2] drm/display/dp_mst: Fix drm_dp_mst_add_affected_dsc_crtcs() return code

[Lyude Paul]

Looks like that we're accidentally dropping a pretty important return code
here. For some reason, we just return -EINVAL if we fail to get the MST
topology state. This is wrong: error codes are important and should never
be squashed without being handled, which here seems to have the potential
to cause a deadlock.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Fixes: 8ec046716ca8 ("drm/dp_mst: Add helper to trigger modeset on affected DSC MST CRTCs")
Cc: <stable@vger.kernel.org> # v5.6+
---
 drivers/gpu/drm/display/drm_dp_mst_topology.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
index ecd22c038c8c0..51a46689cda70 100644
--- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
@@ -5186,7 +5186,7 @@ int drm_dp_mst_add_affected_dsc_crtcs(struct drm_atomic_state *state, struct drm
 	mst_state = drm_atomic_get_mst_topology_state(state, mgr);
 
 	if (IS_ERR(mst_state))
-		return -EINVAL;
+		return PTR_ERR(mst_state);
 
 	list_for_each_entry(pos, &mst_state->payloads, next) {
 
-- 
2.37.3

RE: [PATCH 2/2] drm/display/dp_mst: Fix drm_dp_mst_add_affected_dsc_crtcs() return code

[Lin, Wayne]

[AMD Official Use Only - General]

Hi Lyude,

It LGTM. Feel free to add 
Reviewed-by: Wayne Lin <Wayne.Lin@amd.com>

> -----Original Message-----
> From: Lyude Paul <lyude@redhat.com>
> Sent: Saturday, November 5, 2022 7:59 AM
> To: amd-gfx@lists.freedesktop.org
> Cc: stable@vger.kernel.org; David Airlie <airlied@gmail.com>; Daniel Vetter
> <daniel@ffwll.ch>; Jani Nikula <jani.nikula@intel.com>; Thomas
> Zimmermann <tzimmermann@suse.de>; Lin, Wayne
> <Wayne.Lin@amd.com>; Imre Deak <imre.deak@intel.com>; Mikita Lipski
> <mikita.lipski@amd.com>; Deucher, Alexander
> <Alexander.Deucher@amd.com>; open list:DRM DRIVERS <dri-
> devel@lists.freedesktop.org>; open list <linux-kernel@vger.kernel.org>
> Subject: [PATCH 2/2] drm/display/dp_mst: Fix
> drm_dp_mst_add_affected_dsc_crtcs() return code
> 
> Looks like that we're accidentally dropping a pretty important return code
> here. For some reason, we just return -EINVAL if we fail to get the MST
> topology state. This is wrong: error codes are important and should never be
> squashed without being handled, which here seems to have the potential to
> cause a deadlock.
> 
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Fixes: 8ec046716ca8 ("drm/dp_mst: Add helper to trigger modeset on
> affected DSC MST CRTCs")
> Cc: <stable@vger.kernel.org> # v5.6+
> ---
>  drivers/gpu/drm/display/drm_dp_mst_topology.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> index ecd22c038c8c0..51a46689cda70 100644
> --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> @@ -5186,7 +5186,7 @@ int drm_dp_mst_add_affected_dsc_crtcs(struct
> drm_atomic_state *state, struct drm
>  	mst_state = drm_atomic_get_mst_topology_state(state, mgr);
> 
>  	if (IS_ERR(mst_state))
> -		return -EINVAL;
> +		return PTR_ERR(mst_state);
> 
>  	list_for_each_entry(pos, &mst_state->payloads, next) {
> 
> --
> 2.37.3