drm/amd/display: Enable aux transfer path via dmub for dp tunneling

[Why]
Aux transfer retries path does not support dp tunneling.

[How]
Based on ddc pin check, aux will be issued in legacy path or DMUB.
Signed-off-by: Meenakshikumar Somasundaram <meenakshikumar.somasundaram@amd.com>
Reviewed-by: Eric Yang <eric.yang@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dce/dce_aux.c

@@ -735,7 +735,15 @@ bool dce_aux_transfer_with_retries(struct ddc_service *ddc,
 					(unsigned int) payload->mot);
 		if (payload->write)
 			dce_aux_log_payload("  write", payload->data, payload->length, 16);
-		ret = dce_aux_transfer_raw(ddc, payload, &operation_result);
+
+		/* Check whether aux to be processed via dmub or dcn directly */
+		if (ddc->ctx->dc->debug.enable_dmub_aux_for_legacy_ddc
+			|| ddc->ddc_pin == NULL) {
+			ret = dce_aux_transfer_dmub_raw(ddc, payload, &operation_result);
+		} else {
+			ret = dce_aux_transfer_raw(ddc, payload, &operation_result);
+		}
+
 		DC_TRACE_LEVEL_MESSAGE(DAL_TRACE_LEVEL_INFORMATION,
 					LOG_FLAG_I2cAux_DceAux,
 					"dce_aux_transfer_with_retries: link_index=%u: END: retry %d of %d: address=0x%04x length=%u write=%d mot=%d: ret=%d operation_result=%d payload->reply=%u",