drm/amd/display: add protection in link encoder matching logic

[Why]
Link encoders are created based on its engine ID. The position of a link
encoder in an array could be null since it didn't be allocated.  Current
matching logic didn't consider this situation and could get null
encoder.

[How]
To add null encoder check to make the matching logic can go to next to
get a valid one.

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Martin Tsai <martin.tsai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

7 files changed, 36 insertions, 92 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 8a46b8430f1e..c0ab23274f96 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -8366,7 +8366,7 @@ void amdgpu_dm_connector_init_helper(struct amdgpu_display_manager *dm,
 		break;
 	case DRM_MODE_CONNECTOR_DisplayPort:
 		aconnector->base.polled = DRM_CONNECTOR_POLL_HPD;
-		link->link_enc = dp_get_link_enc(link);
+		link->link_enc = link_enc_cfg_get_link_enc(link);
 		ASSERT(link->link_enc);
 		if (link->link_enc)
 			aconnector->base.ycbcr_420_allowed =
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 64584a472f4a..147a03a1500b 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
@@ -4621,16 +4621,7 @@ bool dc_link_is_fec_supported(const struct dc_link *link)
 	 */
 	struct link_encoder *link_enc = NULL;
 
-	/* Links supporting dynamically assigned link encoder will be assigned next
-	 * available encoder if one not already assigned.
-	 */
-	if (link->is_dig_mapping_flexible &&
-			link->dc->res_pool->funcs->link_encs_assign) {
-		link_enc = link_enc_cfg_get_link_enc_used_by_link(link->ctx->dc, link);
-		if (link_enc == NULL)
-			link_enc = link_enc_cfg_get_next_avail_link_enc(link->ctx->dc);
-	} else
-		link_enc = link->link_enc;
+	link_enc = link_enc_cfg_get_link_enc(link);
 	ASSERT(link_enc);
 
 	return (dc_is_dp_signal(link->connector_signal) && link_enc &&
diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
index 68f9e099beae..a514f19d8f8b 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
@@ -261,14 +261,7 @@ static enum dc_dp_training_pattern decide_eq_training_pattern(struct dc_link *li
 	struct dpcd_caps *rx_caps = &link->dpcd_caps;
 	enum dc_dp_training_pattern pattern = DP_TRAINING_PATTERN_SEQUENCE_2;
 
-	/* Access link encoder capability based on whether it is statically
-	 * or dynamically assigned to a link.
-	 */
-	if (link->is_dig_mapping_flexible &&
-			link->dc->res_pool->funcs->link_encs_assign)
-		link_enc = link_enc_cfg_get_link_enc_used_by_link(link->ctx->dc, link);
-	else
-		link_enc = link->link_enc;
+	link_enc = link_enc_cfg_get_link_enc(link);
 	ASSERT(link_enc);
 	enc_caps = &link_enc->features;
 
@@ -2997,16 +2990,7 @@ bool dc_link_dp_get_max_link_enc_cap(const struct dc_link *link, struct dc_link_
 		return false;
 	}
 
-	/* Links supporting dynamically assigned link encoder will be assigned next
-	 * available encoder if one not already assigned.
-	 */
-	if (link->is_dig_mapping_flexible &&
-			link->dc->res_pool->funcs->link_encs_assign) {
-		link_enc = link_enc_cfg_get_link_enc_used_by_link(link->ctx->dc, link);
-		if (link_enc == NULL)
-			link_enc = link_enc_cfg_get_next_avail_link_enc(link->ctx->dc);
-	} else
-		link_enc = link->link_enc;
+	link_enc = link_enc_cfg_get_link_enc(link);
 	ASSERT(link_enc);
 
 	if (link_enc && link_enc->funcs->get_max_link_cap) {
@@ -3027,16 +3011,7 @@ struct dc_link_settings dp_get_max_link_cap(struct dc_link *link)
 	enum dc_link_rate lttpr_max_link_rate;
 	struct link_encoder *link_enc = NULL;
 
-	/* Links supporting dynamically assigned link encoder will be assigned next
-	 * available encoder if one not already assigned.
-	 */
-	if (link->is_dig_mapping_flexible &&
-			link->dc->res_pool->funcs->link_encs_assign) {
-		link_enc = link_enc_cfg_get_link_enc_used_by_link(link->ctx->dc, link);
-		if (link_enc == NULL)
-			link_enc = link_enc_cfg_get_next_avail_link_enc(link->ctx->dc);
-	} else
-		link_enc = link->link_enc;
+	link_enc = link_enc_cfg_get_link_enc(link);
 	ASSERT(link_enc);
 
 	/* get max link encoder capability */
@@ -6175,14 +6150,7 @@ enum dc_status dp_set_fec_ready(struct dc_link *link, const struct link_resource
 	enum dc_status status = DC_OK;
 	uint8_t fec_config = 0;
 
-	/* Access link encoder based on whether it is statically
-	 * or dynamically assigned to a link.
-	 */
-	if (link->is_dig_mapping_flexible &&
-			link->dc->res_pool->funcs->link_encs_assign)
-		link_enc = link_enc_cfg_get_link_enc_used_by_link(link->ctx->dc, link);
-	else
-		link_enc = link->link_enc;
+	link_enc = link_enc_cfg_get_link_enc(link);
 	ASSERT(link_enc);
 
 	if (!dc_link_should_enable_fec(link))
@@ -6222,14 +6190,7 @@ void dp_set_fec_enable(struct dc_link *link, bool enable)
 {
 	struct link_encoder *link_enc = NULL;
 
-	/* Access link encoder based on whether it is statically
-	 * or dynamically assigned to a link.
-	 */
-	if (link->is_dig_mapping_flexible &&
-			link->dc->res_pool->funcs->link_encs_assign)
-		link_enc = link_enc_cfg_get_link_enc_used_by_link(link->ctx->dc, link);
-	else
-		link_enc = link->link_enc;
+	link_enc = link_enc_cfg_get_link_enc(link);
 	ASSERT(link_enc);
 
 	if (!dc_link_should_enable_fec(link))
@@ -6255,23 +6216,6 @@ void dp_set_fec_enable(struct dc_link *link, bool enable)
 	}
 }
 
-struct link_encoder *dp_get_link_enc(struct dc_link *link)
-{
-	struct link_encoder *link_enc;
-
-	link_enc = link->link_enc;
-	if (link->is_dig_mapping_flexible &&
-	    link->dc->res_pool->funcs->link_encs_assign) {
-		link_enc = link_enc_cfg_get_link_enc_used_by_link(link->ctx->dc,
-								  link);
-		if (!link->link_enc)
-			link_enc = link_enc_cfg_get_next_avail_link_enc(
-				link->ctx->dc);
-	}
-
-	return link_enc;
-}
-
 void dpcd_set_source_specific_data(struct dc_link *link)
 {
 	if (!link->dc->vendor_signature.is_valid) {
diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_enc_cfg.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_enc_cfg.c
index a55944da8d53..a380611b1e42 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_enc_cfg.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_enc_cfg.c
@@ -486,7 +486,8 @@ struct link_encoder *link_enc_cfg_get_next_avail_link_enc(struct dc *dc)
 	}
 
 	for (i = 0; i < dc->res_pool->res_cap->num_dig_link_enc; i++) {
-		if (encs_assigned[i] == ENGINE_ID_UNKNOWN) {
+		if (encs_assigned[i] == ENGINE_ID_UNKNOWN &&
+				dc->res_pool->link_encoders[i] != NULL) {
 			link_enc = dc->res_pool->link_encoders[i];
 			break;
 		}
@@ -506,6 +507,26 @@ struct link_encoder *link_enc_cfg_get_link_enc_used_by_stream(
 	return link_enc;
 }
 
+struct link_encoder *link_enc_cfg_get_link_enc(
+		const struct dc_link *link)
+{
+	struct link_encoder *link_enc = NULL;
+
+	/* Links supporting dynamically assigned link encoder will be assigned next
+	 * available encoder if one not already assigned.
+	 */
+	if (link->is_dig_mapping_flexible &&
+	    link->dc->res_pool->funcs->link_encs_assign) {
+		link_enc = link_enc_cfg_get_link_enc_used_by_link(link->ctx->dc, link);
+		if (link_enc == NULL)
+			link_enc = link_enc_cfg_get_next_avail_link_enc(
+				link->ctx->dc);
+	} else
+		link_enc = link->link_enc;
+
+	return link_enc;
+}
+
 bool link_enc_cfg_is_link_enc_avail(struct dc *dc, enum engine_id eng_id, struct dc_link *link)
 {
 	bool is_avail = true;
diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_hwss.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_hwss.c
index c5146263f93c..5e9054fdb339 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_hwss.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_hwss.c
@@ -86,11 +86,7 @@ void dp_enable_link_phy(
 			link->dc->res_pool->dp_clock_source;
 	unsigned int i;
 
-	/* Link should always be assigned encoder when en-/disabling. */
-	if (link->is_dig_mapping_flexible && dc->res_pool->funcs->link_encs_assign)
-		link_enc = link_enc_cfg_get_link_enc_used_by_link(dc, link);
-	else
-		link_enc = link->link_enc;
+	link_enc = link_enc_cfg_get_link_enc(link);
 	ASSERT(link_enc);
 
 	if (link->connector_signal == SIGNAL_TYPE_EDP) {
@@ -228,11 +224,7 @@ void dp_disable_link_phy(struct dc_link *link, const struct link_resource *link_
 	struct hpo_dp_link_encoder *hpo_link_enc = link_res->hpo_dp_link_enc;
 	struct link_encoder *link_enc;
 
-	/* Link should always be assigned encoder when en-/disabling. */
-	if (link->is_dig_mapping_flexible && dc->res_pool->funcs->link_encs_assign)
-		link_enc = link_enc_cfg_get_link_enc_used_by_link(dc, link);
-	else
-		link_enc = link->link_enc;
+	link_enc = link_enc_cfg_get_link_enc(link);
 	ASSERT(link_enc);
 
 	if (!link->wa_flags.dp_keep_receiver_powered)
@@ -360,14 +352,8 @@ void dp_set_hw_test_pattern(
 	struct link_encoder *encoder;
 	enum dp_link_encoding link_encoding_format = dp_get_link_encoding_format(&link->cur_link_settings);
 
-	/* Access link encoder based on whether it is statically
-	 * or dynamically assigned to a link.
-	 */
-	if (link->is_dig_mapping_flexible &&
-			link->dc->res_pool->funcs->link_encs_assign)
-		encoder = link_enc_cfg_get_link_enc_used_by_link(link->ctx->dc, link);
-	else
-		encoder = link->link_enc;
+	encoder = link_enc_cfg_get_link_enc(link);
+	ASSERT(encoder);
 
 	pattern_param.dp_phy_pattern = test_pattern;
 	pattern_param.custom_pattern = custom_pattern;
diff --git a/drivers/gpu/drm/amd/display/dc/inc/dc_link_dp.h b/drivers/gpu/drm/amd/display/dc/inc/dc_link_dp.h
index b18c8198f66d..b7c5c42d67ed 100644
--- a/drivers/gpu/drm/amd/display/dc/inc/dc_link_dp.h
+++ b/drivers/gpu/drm/amd/display/dc/inc/dc_link_dp.h
@@ -171,7 +171,6 @@ uint8_t dc_dp_initialize_scrambling_data_symbols(
 
 enum dc_status dp_set_fec_ready(struct dc_link *link, const struct link_resource *link_res, bool ready);
 void dp_set_fec_enable(struct dc_link *link, bool enable);
-struct link_encoder *dp_get_link_enc(struct dc_link *link);
 bool dp_set_dsc_enable(struct pipe_ctx *pipe_ctx, bool enable);
 bool dp_set_dsc_pps_sdp(struct pipe_ctx *pipe_ctx, bool enable, bool immediate_update);
 void dp_set_dsc_on_stream(struct pipe_ctx *pipe_ctx, bool enable);
diff --git a/drivers/gpu/drm/amd/display/dc/inc/link_enc_cfg.h b/drivers/gpu/drm/amd/display/dc/inc/link_enc_cfg.h
index a4e43b4826e0..c2f08514a1d9 100644
--- a/drivers/gpu/drm/amd/display/dc/inc/link_enc_cfg.h
+++ b/drivers/gpu/drm/amd/display/dc/inc/link_enc_cfg.h
@@ -96,6 +96,9 @@ struct link_encoder *link_enc_cfg_get_link_enc_used_by_stream(
 		struct dc *dc,
 		const struct dc_stream_state *stream);
 
+/* Return DIG link encoder. NULL if unused. */
+struct link_encoder *link_enc_cfg_get_link_enc(const struct dc_link *link);
+
 /* Return true if encoder available to use. */
 bool link_enc_cfg_is_link_enc_avail(struct dc *dc, enum engine_id eng_id, struct dc_link *link);