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 59445c83f023..c0297201acb6 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
@@ -84,11 +84,13 @@ static ssize_t dm_dp_aux_transfer(struct drm_dp_aux *aux,
 	enum i2caux_transaction_action action;
 	enum aux_transaction_type type;
 
+	DRM_DEBUG_KMS("msg=%p, aux=%p\n", msg, aux);
 	if (WARN_ON(msg->size > 16))
 		return -E2BIG;
 
 	switch (msg->request & ~DP_AUX_I2C_MOT) {
 	case DP_AUX_NATIVE_READ:
+		DRM_DEBUG_KMS("%s\n", "DP_AUX_NATIVE_READ");
 		type = AUX_TRANSACTION_TYPE_DP;
 		action = I2CAUX_TRANSACTION_ACTION_DP_READ;
 
@@ -101,6 +103,7 @@ static ssize_t dm_dp_aux_transfer(struct drm_dp_aux *aux,
 					      action);
 		break;
 	case DP_AUX_NATIVE_WRITE:
+		DRM_DEBUG_KMS("%s\n", "DP_AUX_NATIVE_WRITE");
 		type = AUX_TRANSACTION_TYPE_DP;
 		action = I2CAUX_TRANSACTION_ACTION_DP_WRITE;
 
@@ -114,6 +117,7 @@ static ssize_t dm_dp_aux_transfer(struct drm_dp_aux *aux,
 		result = msg->size;
 		break;
 	case DP_AUX_I2C_READ:
+		DRM_DEBUG_KMS("%s\n", "DP_AUX_I2C_READ");
 		type = AUX_TRANSACTION_TYPE_I2C;
 		if (msg->request & DP_AUX_I2C_MOT)
 			action = I2CAUX_TRANSACTION_ACTION_I2C_READ_MOT;
@@ -129,6 +133,7 @@ static ssize_t dm_dp_aux_transfer(struct drm_dp_aux *aux,
 					      action);
 		break;
 	case DP_AUX_I2C_WRITE:
+		DRM_DEBUG_KMS("%s\n", "DP_AUX_I2C_WRITE");
 		type = AUX_TRANSACTION_TYPE_I2C;
 		if (msg->request & DP_AUX_I2C_MOT)
 			action = I2CAUX_TRANSACTION_ACTION_I2C_WRITE_MOT;
@@ -142,9 +147,11 @@ static ssize_t dm_dp_aux_transfer(struct drm_dp_aux *aux,
 				     msg->size,
 				     type,
 				     action);
+		DRM_DEBUG_KMS("%s\n", "BACK FROM DP_AUX_I2C_WRITE");
 		result = msg->size;
 		break;
 	default:
+		DRM_DEBUG_KMS("%s\n", "-EINVAL");
 		return -EINVAL;
 	}
 
diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_ddc.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_ddc.c
index 8def0d9fa0ff..f241f8c554e2 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_ddc.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_ddc.c
@@ -647,10 +647,26 @@ int dc_link_aux_transfer(struct ddc_service *ddc,
 	int res = -1;
 	uint32_t status;
 
+	DRM_DEBUG_KMS("%s: ddc=%p, reply=%p, buffer=%p\n",
+		"DC_LINK_AUX_TRANSFER", ddc, reply, buffer);
+	DRM_DEBUG_KMS("ddc->ddc_pin=%p\n", ddc->ddc_pin);
+	DRM_DEBUG_KMS("ddc->ddc_pin->pin_data=%p\n", ddc->ddc_pin->pin_data);
+	DRM_DEBUG_KMS("ddc->ddc_pin->pin_data->en=%d\n", ddc->ddc_pin->pin_data->en);
 	memset(&aux_req, 0, sizeof(aux_req));
 	memset(&aux_rep, 0, sizeof(aux_rep));
 
+	DRM_DEBUG_KMS("ddc->ctx=%p", ddc->ctx);
+	DRM_DEBUG_KMS("ddc->ctx->dc=%p", ddc->ctx->dc);
+	DRM_DEBUG_KMS("ddc->ctx->dc->res_pool=%p", ddc->ctx->dc->res_pool);
+	DRM_DEBUG_KMS("ddc->ctx->dc->res_pool->engines=%p", ddc->ctx->dc->res_pool->engines);
+	DRM_DEBUG_KMS("ddc->ctx->dc->res_pool->engines[ddc_pin->pin_data->en]=%p",
+		ddc->ctx->dc->res_pool->engines[ddc_pin->pin_data->en]);
 	aux_engine = ddc->ctx->dc->res_pool->engines[ddc_pin->pin_data->en];
+	DRM_DEBUG_KMS("aux_engine=%p\n", aux_engine);
+	if (!aux_engine) {
+		DRM_DEBUG_KMS("%s\n", "Cowardly refusing to call through null pointer");
+		return -1;
+	}
 	aux_engine->funcs->acquire(aux_engine, ddc_pin);
 
 	aux_req.type = type;
@@ -668,10 +684,13 @@ int dc_link_aux_transfer(struct ddc_service *ddc,
 	case AUX_CHANNEL_OPERATION_SUCCEEDED:
 		res = returned_bytes;
 
-		if (res <= size && res >= 0)
+		if (res <= size && res >= 0) {
+			if (!buffer)
+				DRM_DEBUG_KMS("%s\n", "calling READ_CHANNEL_REPLY w/null buffer");
 			res = aux_engine->funcs->read_channel_reply(aux_engine, size,
 								buffer, reply,
 								&status);
+		}
 
 		break;
 	case AUX_CHANNEL_OPERATION_FAILED_HPD_DISCON: