drm/amd/display: Fix dynamic link encoder access.

[Why]
Assuming DIG link encoders are statically mapped to links can cause
system instability due to null pointer accesses.

[How]
- Add checks for non-null link encoder pointers before trying to access
them.
- When a hardware platform uses dynamic DIG assignment (i.e. resource
function 'link_encs_assign' defined) and a link supports flexible
mapping to DIGs, use the link_enc_cfg API to access the DIG assigned to
a link or stream.
Reviewed-by: Meenakshikumar Somasundaram <meenakshikumar.somasundaram@amd.com>
Acked-by: Mikita Lipski <mikita.lipski@amd.com>
Signed-off-by: Jimmy Kizito <Jimmy.Kizito@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/clk_mgr/dcn31/dcn31_clk_mgr.c

@@ -87,7 +87,7 @@ int dcn31_get_active_display_cnt_wa(
 		const struct dc_link *link = dc->links[i];
 
 		/* abusing the fact that the dig and phy are coupled to see if the phy is enabled */
-		if (link->link_enc->funcs->is_dig_enabled &&
+		if (link->link_enc && link->link_enc->funcs->is_dig_enabled &&
 				link->link_enc->funcs->is_dig_enabled(link->link_enc))
 			display_count++;
 	}

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

@@ -3457,6 +3457,10 @@ static enum dc_status deallocate_mst_payload(struct pipe_ctx *pipe_ctx)
 static void update_psp_stream_config(struct pipe_ctx *pipe_ctx, bool dpms_off)
 {
 	struct cp_psp *cp_psp = &pipe_ctx->stream->ctx->cp_psp;
+#if defined(CONFIG_DRM_AMD_DC_DCN)
+	struct link_encoder *link_enc = NULL;
+#endif
+
 	if (cp_psp && cp_psp->funcs.update_stream_config) {
 		struct cp_psp_stream_config config = {0};
 		enum dp_panel_mode panel_mode =
@@ -3468,8 +3472,21 @@ static void update_psp_stream_config(struct pipe_ctx *pipe_ctx, bool dpms_off)
 		config.dig_be = pipe_ctx->stream->link->link_enc_hw_inst;
 #if defined(CONFIG_DRM_AMD_DC_DCN)
 		config.stream_enc_idx = pipe_ctx->stream_res.stream_enc->id - ENGINE_ID_DIGA;
-		config.link_enc_idx = pipe_ctx->stream->link->link_enc->transmitter - TRANSMITTER_UNIPHY_A;
-		config.phy_idx = pipe_ctx->stream->link->link_enc->transmitter - TRANSMITTER_UNIPHY_A;
+		if (pipe_ctx->stream->link->ep_type == DISPLAY_ENDPOINT_PHY) {
+			link_enc = pipe_ctx->stream->link->link_enc;
+			config.phy_idx = link_enc->transmitter - TRANSMITTER_UNIPHY_A;
+		} else if (pipe_ctx->stream->link->dc->res_pool->funcs->link_encs_assign) {
+			/* Use link encoder assignment from current DC state - which may differ from the DC state to be
+			 * committed - when updating PSP config.
+			 */
+			link_enc = link_enc_cfg_get_link_enc_used_by_stream(
+					pipe_ctx->stream->link->dc->current_state,
+					pipe_ctx->stream);
+			config.phy_idx = 0; /* Clear phy_idx for non-physical display endpoints. */
+		}
+		ASSERT(link_enc);
+		if (link_enc)
+			config.link_enc_idx = link_enc->transmitter - TRANSMITTER_UNIPHY_A;
 		if (is_dp_128b_132b_signal(pipe_ctx)) {
 			config.stream_enc_idx = pipe_ctx->stream_res.hpo_dp_stream_enc->id - ENGINE_ID_HPO_DP_0;
 			config.link_enc_idx = pipe_ctx->stream->link->hpo_dp_link_enc->inst;
@@ -3576,6 +3593,7 @@ void core_link_enable_stream(
 	struct dc_stream_state *stream = pipe_ctx->stream;
 	struct dc_link *link = stream->sink->link;
 	enum dc_status status;
+	struct link_encoder *link_enc;
 #if defined(CONFIG_DRM_AMD_DC_DCN)
 	enum otg_out_mux_dest otg_out_dest = OUT_MUX_DIO;
 #endif
@@ -3585,15 +3603,22 @@ void core_link_enable_stream(
 			dc_is_virtual_signal(pipe_ctx->stream->signal))
 		return;
 
+	if (dc->res_pool->funcs->link_encs_assign && stream->link->ep_type != DISPLAY_ENDPOINT_PHY)
+		link_enc = stream->link_enc;
+	else
+		link_enc = stream->link->link_enc;
+	ASSERT(link_enc);
+
 #if defined(CONFIG_DRM_AMD_DC_DCN)
 	if (!dc_is_virtual_signal(pipe_ctx->stream->signal)
 			&& !is_dp_128b_132b_signal(pipe_ctx)) {
 #else
 	if (!dc_is_virtual_signal(pipe_ctx->stream->signal)) {
 #endif
-		stream->link->link_enc->funcs->setup(
-			stream->link->link_enc,
-			pipe_ctx->stream->signal);
+		if (link_enc)
+			link_enc->funcs->setup(
+				link_enc,
+				pipe_ctx->stream->signal);
 		pipe_ctx->stream_res.stream_enc->funcs->setup_stereo_sync(
 			pipe_ctx->stream_res.stream_enc,
 			pipe_ctx->stream_res.tg->inst,
@@ -3748,9 +3773,10 @@ void core_link_enable_stream(
 #else
 		if (!dc_is_virtual_signal(pipe_ctx->stream->signal))
 #endif
-			stream->link->link_enc->funcs->setup(
-				stream->link->link_enc,
-				pipe_ctx->stream->signal);
+			if (link_enc)
+				link_enc->funcs->setup(
+					link_enc,
+					pipe_ctx->stream->signal);
 
 		dc->hwss.enable_stream(pipe_ctx);
 

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

@@ -2624,13 +2624,27 @@ static enum dc_link_rate get_lttpr_max_link_rate(struct dc_link *link)
 
 bool dc_link_dp_get_max_link_enc_cap(const struct dc_link *link, struct dc_link_settings *max_link_enc_cap)
 {
+	struct link_encoder *link_enc = NULL;
+
 	if (!max_link_enc_cap) {
 		DC_LOG_ERROR("%s: Could not return max link encoder caps", __func__);
 		return false;
 	}
 
-	if (link->link_enc->funcs->get_max_link_cap) {
-		link->link_enc->funcs->get_max_link_cap(link->link_enc, max_link_enc_cap);
+	/* 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->dc->current_state, link);
+		if (link_enc == NULL)
+			link_enc = link_enc_cfg_get_next_avail_link_enc(link->dc, link->dc->current_state);
+	} else
+		link_enc = link->link_enc;
+	ASSERT(link_enc);
+
+	if (link_enc && link_enc->funcs->get_max_link_cap) {
+		link_enc->funcs->get_max_link_cap(link_enc, max_link_enc_cap);
 		return true;
 	}
 
@@ -2646,9 +2660,23 @@ static struct dc_link_settings get_max_link_cap(struct dc_link *link)
 #if defined(CONFIG_DRM_AMD_DC_DCN)
 	enum dc_link_rate lttpr_max_link_rate;
 #endif
+	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->dc->current_state, link);
+		if (link_enc == NULL)
+			link_enc = link_enc_cfg_get_next_avail_link_enc(link->dc, link->dc->current_state);
+	} else
+		link_enc = link->link_enc;
+	ASSERT(link_enc);
 
 	/* get max link encoder capability */
-	link->link_enc->funcs->get_max_link_cap(link->link_enc, &max_link_cap);
+	if (link_enc)
+		link_enc->funcs->get_max_link_cap(link_enc, &max_link_cap);
 #if defined(CONFIG_DRM_AMD_DC_DCN)
 	if (max_link_cap.link_rate >= LINK_RATE_UHBR10 &&
 			!link->hpo_dp_link_enc)
@@ -2867,7 +2895,7 @@ bool dp_verify_link_cap(
 	 * PHY will sometimes be in bad state on hotplugging display from certain USB-C dongle,
 	 * so add extra cycle of enabling and disabling the PHY before first link training.
 	 */
-	if (link->link_enc->features.flags.bits.DP_IS_USB_C &&
+	if (link->link_enc && link->link_enc->features.flags.bits.DP_IS_USB_C &&
 			link->dc->debug.usbc_combo_phy_reset_wa) {
 		dp_enable_link_phy(link, link->connector_signal, dp_cs_id, cur);
 		dp_disable_link_phy(link, link->connector_signal);

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

@@ -139,7 +139,7 @@ static struct dc_stream_state *get_stream_using_link_enc(
 	for (i = 0; i < state->stream_count; i++) {
 		struct link_enc_assignment assignment = state->res_ctx.link_enc_assignments[i];
 
-		if (assignment.valid && (assignment.eng_id == eng_id)) {
+		if ((assignment.valid == true) && (assignment.eng_id == eng_id)) {
 			stream_idx = i;
 			break;
 		}
@@ -254,7 +254,7 @@ struct dc_link *link_enc_cfg_get_link_using_link_enc(
 	for (i = 0; i < state->stream_count; i++) {
 		struct link_enc_assignment assignment = state->res_ctx.link_enc_assignments[i];
 
-		if (assignment.valid && (assignment.eng_id == eng_id)) {
+		if ((assignment.valid == true) && (assignment.eng_id == eng_id)) {
 			stream_idx = i;
 			break;
 		}
@@ -274,7 +274,6 @@ struct link_encoder *link_enc_cfg_get_link_enc_used_by_link(
 {
 	struct link_encoder *link_enc = NULL;
 	struct display_endpoint_id ep_id;
-	int stream_idx = -1;
 	int i;
 
 	ep_id = (struct display_endpoint_id) {
@@ -283,20 +282,15 @@ struct link_encoder *link_enc_cfg_get_link_enc_used_by_link(
 
 	for (i = 0; i < state->stream_count; i++) {
 		struct link_enc_assignment assignment = state->res_ctx.link_enc_assignments[i];
-
-		if (assignment.valid &&
+		if (assignment.valid == true &&
 				assignment.ep_id.link_id.id == ep_id.link_id.id &&
 				assignment.ep_id.link_id.enum_id == ep_id.link_id.enum_id &&
 				assignment.ep_id.link_id.type == ep_id.link_id.type &&
 				assignment.ep_id.ep_type == ep_id.ep_type) {
-			stream_idx = i;
-			break;
+			link_enc = link->dc->res_pool->link_encoders[assignment.eng_id - ENGINE_ID_DIGA];
 		}
 	}
 
-	if (stream_idx != -1)
-		link_enc = state->streams[stream_idx]->link_enc;
-
 	return link_enc;
 }
 
@@ -313,3 +307,14 @@ struct link_encoder *link_enc_cfg_get_next_avail_link_enc(
 
 	return link_enc;
 }
+
+struct link_encoder *link_enc_cfg_get_link_enc_used_by_stream(
+		struct dc_state *state,
+		const struct dc_stream_state *stream)
+{
+	struct link_encoder *link_enc;
+
+	link_enc = link_enc_cfg_get_link_enc_used_by_link(state, stream->link);
+
+	return link_enc;
+}

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

@@ -452,9 +452,10 @@ void dp_retrain_link_dp_test(struct dc_link *link,
 			if ((&pipes[i])->stream_res.audio && !link->dc->debug.az_endpoint_mute_only)
 				(&pipes[i])->stream_res.audio->funcs->az_disable((&pipes[i])->stream_res.audio);
 
-			link->link_enc->funcs->disable_output(
-					link->link_enc,
-					SIGNAL_TYPE_DISPLAY_PORT);
+			if (link->link_enc)
+				link->link_enc->funcs->disable_output(
+						link->link_enc,
+						SIGNAL_TYPE_DISPLAY_PORT);
 
 			/* Clear current link setting. */
 			memset(&link->cur_link_settings, 0,

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

@@ -2970,7 +2970,8 @@ enum dc_status dc_validate_stream(struct dc *dc, struct dc_stream_state *stream)
 		res = DC_FAIL_CONTROLLER_VALIDATE;
 
 	if (res == DC_OK) {
-		if (!link->link_enc->funcs->validate_output_with_stream(
+		if (link->ep_type == DISPLAY_ENDPOINT_PHY &&
+				!link->link_enc->funcs->validate_output_with_stream(
 						link->link_enc, stream))
 			res = DC_FAIL_ENC_VALIDATE;
 	}

drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c

@@ -46,6 +46,7 @@
 #include "transform.h"
 #include "stream_encoder.h"
 #include "link_encoder.h"
+#include "link_enc_cfg.h"
 #include "link_hwss.h"
 #include "dc_link_dp.h"
 #if defined(CONFIG_DRM_AMD_DC_DCN)
@@ -1192,6 +1193,7 @@ void dce110_disable_stream(struct pipe_ctx *pipe_ctx)
 	struct dc_stream_state *stream = pipe_ctx->stream;
 	struct dc_link *link = stream->link;
 	struct dc *dc = pipe_ctx->stream->ctx->dc;
+	struct link_encoder *link_enc = NULL;
 
 	if (dc_is_hdmi_tmds_signal(pipe_ctx->stream->signal)) {
 		pipe_ctx->stream_res.stream_enc->funcs->stop_hdmi_info_packets(
@@ -1213,6 +1215,13 @@ void dce110_disable_stream(struct pipe_ctx *pipe_ctx)
 
 	dc->hwss.disable_audio_stream(pipe_ctx);
 
+	/* Link encoder may have been dynamically assigned to non-physical display endpoint. */
+	if (link->ep_type == DISPLAY_ENDPOINT_PHY)
+		link_enc = link->link_enc;
+	else if (dc->res_pool->funcs->link_encs_assign)
+		link_enc = link_enc_cfg_get_link_enc_used_by_link(link->dc->current_state, link);
+	ASSERT(link_enc);
+
 #if defined(CONFIG_DRM_AMD_DC_DCN)
 	if (is_dp_128b_132b_signal(pipe_ctx)) {
 		pipe_ctx->stream_res.hpo_dp_stream_enc->funcs->disable(
@@ -1220,13 +1229,15 @@ void dce110_disable_stream(struct pipe_ctx *pipe_ctx)
 		setup_dp_hpo_stream(pipe_ctx, false);
 	/* TODO - DP2.0 HW: unmap stream from link encoder here */
 	} else {
-		link->link_enc->funcs->connect_dig_be_to_fe(
-				link->link_enc,
+		if (link_enc)
+			link_enc->funcs->connect_dig_be_to_fe(
+				link_enc,
 				pipe_ctx->stream_res.stream_enc->id,
 				false);
 	}
 #else
-	link->link_enc->funcs->connect_dig_be_to_fe(
+	if (link_enc)
+		link_enc->funcs->connect_dig_be_to_fe(
 			link->link_enc,
 			pipe_ctx->stream_res.stream_enc->id,
 			false);
@@ -1666,8 +1677,9 @@ static void power_down_encoders(struct dc *dc)
 		if (signal != SIGNAL_TYPE_EDP)
 			signal = SIGNAL_TYPE_NONE;
 
-		dc->links[i]->link_enc->funcs->disable_output(
-				dc->links[i]->link_enc, signal);
+		if (dc->links[i]->ep_type == DISPLAY_ENDPOINT_PHY)
+			dc->links[i]->link_enc->funcs->disable_output(
+					dc->links[i]->link_enc, signal);
 
 		dc->links[i]->link_status.link_active = false;
 		memset(&dc->links[i]->cur_link_settings, 0,

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_resource.c

@@ -1296,7 +1296,7 @@ struct stream_encoder *dcn10_find_first_free_match_stream_enc_for_link(
 			 * in daisy chain use case
 			 */
 			j = i;
-			if (pool->stream_enc[i]->id ==
+			if (link->ep_type == DISPLAY_ENDPOINT_PHY && pool->stream_enc[i]->id ==
 					link->link_enc->preferred_engine)
 				return pool->stream_enc[i];
 		}

drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c

@@ -2381,6 +2381,13 @@ void dcn20_enable_stream(struct pipe_ctx *pipe_ctx)
 	uint32_t active_total_with_borders;
 	uint32_t early_control = 0;
 	struct timing_generator *tg = pipe_ctx->stream_res.tg;
+	struct link_encoder *link_enc;
+
+	if (link->is_dig_mapping_flexible &&
+			link->dc->res_pool->funcs->link_encs_assign)
+		link_enc = pipe_ctx->stream->link_enc;
+	else
+		link_enc = link->link_enc;
 
 	/* For MST, there are multiply stream go to only one link.
 	 * connect DIG back_end to front_end while enable_stream and
@@ -2397,9 +2404,9 @@ void dcn20_enable_stream(struct pipe_ctx *pipe_ctx)
 				link->hpo_dp_link_enc->inst);
 	}
 
-	if (!is_dp_128b_132b_signal(pipe_ctx))
-		link->link_enc->funcs->connect_dig_be_to_fe(
-			link->link_enc, pipe_ctx->stream_res.stream_enc->id, true);
+	if (!is_dp_128b_132b_signal(pipe_ctx) && link_enc)
+		link_enc->funcs->connect_dig_be_to_fe(
+			link_enc, pipe_ctx->stream_res.stream_enc->id, true);
 
 	if (dc_is_dp_signal(pipe_ctx->stream->signal))
 		dp_source_sequence_trace(link, DPCD_SOURCE_SEQ_AFTER_CONNECT_DIG_FE_BE);

drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c

@@ -87,6 +87,7 @@
 #include "dce/dce_aux.h"
 #include "dce/dce_i2c.h"
 #include "vm_helper.h"
+#include "link_enc_cfg.h"
 
 #include "amdgpu_socbb.h"
 
@@ -1596,12 +1597,29 @@ static void get_pixel_clock_parameters(
 	const struct dc_stream_state *stream = pipe_ctx->stream;
 	struct pipe_ctx *odm_pipe;
 	int opp_cnt = 1;
+	struct dc_link *link = stream->link;
+	struct link_encoder *link_enc = NULL;
 
 	for (odm_pipe = pipe_ctx->next_odm_pipe; odm_pipe; odm_pipe = odm_pipe->next_odm_pipe)
 		opp_cnt++;
 
 	pixel_clk_params->requested_pix_clk_100hz = stream->timing.pix_clk_100hz;
-	pixel_clk_params->encoder_object_id = stream->link->link_enc->id;
+
+	/* 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_stream(stream->link->dc->current_state, stream);
+		if (link_enc == NULL)
+			link_enc = link_enc_cfg_get_next_avail_link_enc(stream->link->dc,
+				stream->link->dc->current_state);
+	} else
+		link_enc = stream->link->link_enc;
+	ASSERT(link_enc);
+
+	if (link_enc)
+		pixel_clk_params->encoder_object_id = link_enc->id;
 	pixel_clk_params->signal_type = pipe_ctx->stream->signal;
 	pixel_clk_params->controller_id = pipe_ctx->stream_res.tg->inst + 1;
 	/* TODO: un-hardcode*/

drivers/gpu/drm/amd/display/dc/dcn31/dcn31_hwseq.c

@@ -157,6 +157,9 @@ void dcn31_init_hw(struct dc *dc)
 		 */
 		struct dc_link *link = dc->links[i];
 
+		if (link->ep_type != DISPLAY_ENDPOINT_PHY)
+			continue;
+
 		link->link_enc->funcs->hw_init(link->link_enc);
 
 		/* Check for enabled DIG to identify enabled display */
@@ -184,7 +187,8 @@ void dcn31_init_hw(struct dc *dc)
 						     &dpcd_power_state, sizeof(dpcd_power_state));
 			if (status == DC_OK && dpcd_power_state == DP_POWER_STATE_D0) {
 				/* blank dp stream before power off receiver*/
-				if (dc->links[i]->link_enc->funcs->get_dig_frontend) {
+				if (dc->links[i]->ep_type == DISPLAY_ENDPOINT_PHY &&
+						dc->links[i]->link_enc->funcs->get_dig_frontend) {
 					unsigned int fe;
 
 					fe = dc->links[i]->link_enc->funcs->get_dig_frontend(
@@ -248,7 +252,8 @@ void dcn31_init_hw(struct dc *dc)
 			for (i = 0; i < dc->link_count; i++) {
 				struct dc_link *link = dc->links[i];
 
-				if (link->link_enc->funcs->is_dig_enabled &&
+				if (link->ep_type == DISPLAY_ENDPOINT_PHY &&
+						link->link_enc->funcs->is_dig_enabled &&
 						link->link_enc->funcs->is_dig_enabled(link->link_enc) &&
 						dc->hwss.power_down) {
 					dc->hwss.power_down(dc);

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

@@ -88,4 +88,9 @@ struct link_encoder *link_enc_cfg_get_next_avail_link_enc(
 	const struct dc *dc,
 	const struct dc_state *state);
 
+/* Return DIG link encoder used by stream. NULL if unused. */
+struct link_encoder *link_enc_cfg_get_link_enc_used_by_stream(
+		struct dc_state *state,
+		const struct dc_stream_state *stream);
+
 #endif /* DC_INC_LINK_ENC_CFG_H_ */