drm/amd/display: move get_link_hwss to dc_resource

[why]
Isolate the way to obtain link_hwss from the actual implemenation of
link_hwss. So the caller can call link_hwss without knowing the
implementation detail of link_hwss.

Tested-by: Daniel Wheeler <[e-mail]>
Reviewed-by: Jun Lei <[e-mail]>
Acked-by: Stylon Wang <[e-mail]>
Signed-off-by: Wenjing Liu <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/core/dc_link_hwss.c

···
 static void virtual_reset_stream_encoder(struct pipe_ctx *pipe_ctx);
 
 /************************* below goes to dio_link_hwss ************************/
-static bool can_use_dio_link_hwss(const struct dc_link *link,
-		const struct link_resource *link_res)
-{
-	return link->link_enc != NULL;
-}
-
 static void set_dio_throttled_vcp_size(struct pipe_ctx *pipe_ctx,
 		struct fixed31_32 throttled_vcp_size)
 {
···
 	},
 };
 
-/*********************** below goes to hpo_dp_link_hwss ***********************/
-static bool can_use_dp_hpo_link_hwss(const struct dc_link *link,
+bool can_use_dio_link_hwss(const struct dc_link *link,
 		const struct link_resource *link_res)
 {
-	return link_res->hpo_dp_link_enc != NULL;
+	return link->link_enc != NULL;
 }
 
-static void set_dp_hpo_throttled_vcp_size(struct pipe_ctx *pipe_ctx,
+const struct link_hwss *get_dio_link_hwss(void)
+{
+	return &dio_link_hwss;
+}
+
+/*********************** below goes to hpo_dp_link_hwss ***********************/
+static void set_hpo_dp_throttled_vcp_size(struct pipe_ctx *pipe_ctx,
 		struct fixed31_32 throttled_vcp_size)
 {
 	struct hpo_dp_stream_encoder *hpo_dp_stream_encoder =
···
 			throttled_vcp_size);
 }
 
-static void set_dp_hpo_hblank_min_symbol_width(struct pipe_ctx *pipe_ctx,
+static void set_hpo_dp_hblank_min_symbol_width(struct pipe_ctx *pipe_ctx,
 		const struct dc_link_settings *link_settings,
 		struct fixed31_32 throttled_vcp_size)
 {
···
 	.setup_stream_encoder = setup_hpo_dp_stream_encoder,
 	.reset_stream_encoder = reset_hpo_dp_stream_encoder,
 	.ext = {
-		.set_throttled_vcp_size = set_dp_hpo_throttled_vcp_size,
-		.set_hblank_min_symbol_width = set_dp_hpo_hblank_min_symbol_width,
+		.set_throttled_vcp_size = set_hpo_dp_throttled_vcp_size,
+		.set_hblank_min_symbol_width = set_hpo_dp_hblank_min_symbol_width,
 		.enable_dp_link_output = enable_hpo_dp_link_output,
 		.disable_dp_link_output = disable_hpo_dp_link_output,
 		.set_dp_link_test_pattern  = set_hpo_dp_link_test_pattern,
 		.set_dp_lane_settings = set_hpo_dp_lane_settings,
 	},
 };
-/*********************** below goes to dpia_link_hwss *************************/
-static bool can_use_dpia_link_hwss(const struct dc_link *link,
+
+bool can_use_hpo_dp_link_hwss(const struct dc_link *link,
 		const struct link_resource *link_res)
 {
-	return link->is_dig_mapping_flexible &&
-			link->dc->res_pool->funcs->link_encs_assign;
+	return link_res->hpo_dp_link_enc != NULL;
 }
 
+const struct link_hwss *get_hpo_dp_link_hwss(void)
+{
+	return &hpo_dp_link_hwss;
+}
+
+/*********************** below goes to dpia_link_hwss *************************/
 static const struct link_hwss dpia_link_hwss = {
 	.setup_stream_encoder = setup_dio_stream_encoder,
 	.reset_stream_encoder = reset_dio_stream_encoder,
···
 	},
 };
 
-/*********************** below goes to link_hwss ******************************/
+bool can_use_dpia_link_hwss(const struct dc_link *link,
+		const struct link_resource *link_res)
+{
+	return link->is_dig_mapping_flexible &&
+			link->dc->res_pool->funcs->link_encs_assign;
+}
+
+const struct link_hwss *get_dpia_link_hwss(void)
+{
+	return &dpia_link_hwss;
+}
+/*********************** below goes to virtual_link_hwss ******************************/
 static void virtual_setup_stream_encoder(struct pipe_ctx *pipe_ctx)
 {
 }

drivers/gpu/drm/amd/display/dc/core/dc_resource.c

···
 #endif
 	return phy_idx;
 }
+
+const struct link_hwss *get_link_hwss(const struct dc_link *link,
+		const struct link_resource *link_res)
+{
+	/* Link_hwss is only accessible by getter function instead of accessing
+	 * by pointers in dc with the intent to protect against breaking polymorphism.
+	 */
+	if (can_use_hpo_dp_link_hwss(link, link_res))
+		/* TODO: some assumes that if decided link settings is 128b/132b
+		 * channel coding format hpo_dp_link_enc should be used.
+		 * Others believe that if hpo_dp_link_enc is available in link
+		 * resource then hpo_dp_link_enc must be used. This bound between
+		 * hpo_dp_link_enc != NULL and decided link settings is loosely coupled
+		 * with a premise that both hpo_dp_link_enc pointer and decided link
+		 * settings are determined based on single policy function like
+		 * "decide_link_settings" from upper layer. This "convention"
+		 * cannot be maintained and enforced at current level.
+		 * Therefore a refactor is due so we can enforce a strong bound
+		 * between those two parameters at this level.
+		 *
+		 * To put it simple, we want to make enforcement at low level so that
+		 * we will not return link hwss if caller plans to do 8b/10b
+		 * with an hpo encoder. Or we can return a very dummy one that doesn't
+		 * do work for all functions
+		 */
+		return get_hpo_dp_link_hwss();
+	else if (can_use_dpia_link_hwss(link, link_res))
+		return get_dpia_link_hwss();
+	else if (can_use_dio_link_hwss(link, link_res))
+		return get_dio_link_hwss();
+	else
+		return get_virtual_link_hwss();
+}

drivers/gpu/drm/amd/display/dc/inc/link_hwss.h

···
 	void (*reset_stream_encoder)(struct pipe_ctx *pipe_ctx);
 };
 
-const struct link_hwss *get_link_hwss(const struct dc_link *link, const struct link_resource *link_res);
+
+/*********************** below goes to virtual_link_hwss **********************/
+const struct link_hwss *get_virtual_link_hwss(void);
+/*********************** below goes to dpia_link_hwss *************************/
+bool can_use_dpia_link_hwss(const struct dc_link *link,
+		const struct link_resource *link_res);
+const struct link_hwss *get_dpia_link_hwss(void);
+/*********************** below goes to hpo_dp_link_hwss ***********************/
+bool can_use_hpo_dp_link_hwss(const struct dc_link *link,
+		const struct link_resource *link_res);
+const struct link_hwss *get_hpo_dp_link_hwss(void);
+/************************* below goes to dio_link_hwss ************************/
+bool can_use_dio_link_hwss(const struct dc_link *link,
+		const struct link_resource *link_res);
+const struct link_hwss *get_dio_link_hwss(void);
 
 #endif /* __DC_LINK_HWSS_H__ */
+

drivers/gpu/drm/amd/display/dc/inc/resource.h

···
 	uint8_t disabled_master_pipe_idx);
 uint8_t resource_transmitter_to_phy_idx(const struct dc *dc, enum transmitter transmitter);
 
+const struct link_hwss *get_link_hwss(const struct dc_link *link,
+		const struct link_resource *link_res);
+
 #endif /* DRIVERS_GPU_DRM_AMD_DC_DEV_DC_INC_RESOURCE_H_ */