Step 3: Understanding the Report - 2021.2 English

Vivado Design Suite Tutorial: Design Analysis and Closure Techniques
Document ID
UG938
Release Date
2021-11-17
Version
2021.2 English

This step explains the different sections of the generated QoR Suggestions report. On the left of the report window, you can navigate to the different sections of the report; on the right, more information is provided.

  1. The report is broken down into two main sections; the QoR Assessment and the Suggestion Report. All items below the Suggestion Report are also related to suggestions. Click RQA Summary under the QoR Assessment section of the report. This shows the QoR Assessment Score and the Flow Guidance.

    The QoR Assessment score is 3. This means that there is some chance of meeting timing, but it is unlikely. The flow guidance recommends seeing if QoR suggestions can improve the design.
    Note: The report_qor_assessment command runs using the latest data available to it. For example, clock skew is only accurate after logic is placed so less emphasis is given to the clock skew score at the pre-place stage in the implementation flow.
  2. Click on the Assessment Details section of the report.

    The detailed table shows the categories that have passed the assessment and individual failed metrics. The score is an aggregate of the failed metrics.

    The metrics failing are timing based, and all the others are passing. Items marked as OK can be ignored, but items marked REVIEW should be compared against the threshold to see how severe the failure is.
    Note: For paths failing net and LUT budgeting, refer to the QoR suggestion RQS_XDC-1-1 for more details on the timing paths.
  3. In the Suggestion Report, select GENERATED. This brings up the report section shown in the following figure.

    The GENERATED section provides a list of all the suggestions that have been generated at this stage of the current run. Each suggestion has a description that details the reason for the suggestion. For each suggestion, the following information is also provided.

    Table 1. RQS Summary Column Description
    Item Description Comment
    GENERATED_AT This shows what stage of the design the suggestion was generated at. Typical values are place_design or route_design. As you progress through the design stages, the decisions that the tool makes are based on the information available at the time. Information accuracy increases after placement and again after routing.
    APPLICABLE_FOR This stage must be rerun for the suggestion to take effect. Most suggestions are executed at either synth_design or place_design.
    AUTOMATIC Indicates if the suggestion is executed automatically or if manual intervention is required. Automatic suggestions either recommend a switch to the tool or a property to be added to a cell or net.
    INCREMENTAL FRIENDLY Indicates if the suggestion is optimized for the incremental flow. Non-incremental friendly suggestions must be already present in the reference checkpoint. If you want to add non-incremental friendly suggestions, an updated reference checkpoint must be used.
    SCOPE Indicates the target synthesis run level. GLOBALSCOPE is top level. Otherwise, a sub-module is targeted.. Allows a single RQS file to be used on top-level and sub-module out of context (OOC) synthesis runs. Only applicable to synthesis suggestions.

    Under the other sections of the report there are usually details about the individual suggestions that have been generated.

  4. Click the RQS_XDC_1_1 hyperlink. This takes you to the details section for this suggestion.

    The suggestion description says that the timing constraint is too tight for the given path(s).

    The path has a large negative slack which would stand out in a timing report. Timing paths use net delays that are optimal. This gives the tools the correct order to place and route them. Close analysis shows this is a 600 MHz path with high logic levels. This path needs to be fixed.

  5. Click the back arrow button ( ) to go back to the GENERATED view.
  6. In the GENERATED view, click the RQS_TIMING-33_2-1 row. You can see this is an AUTOMATIC suggestion that is applicable for synth_design (see the APPLICABLE_FOR column). This indicates that you must rerun the synth_design command to make use of this suggestion.

    When you select the row in the RQS Summary view, the suggestion object is selected and the properties can be seen in the QoR Suggestion Properties window. If you examine the command property, you can confirm that it generates a retiming forward property for synth_design.



  7. In the GENERATED view, click the RQS_TIMING-33_2-1 ID to go to the details table for that suggestion. Careful examination of the Endpoint column confirms that this is the same path that was mentioned for RQS_XDC-1-1.

  8. In the GENERATED view, you can see the remaining suggestions. The RQS_CLOCK-9 suggestion is applicable for place_design. The other RQS_TIMING-33/44 suggestions are similar to the existing one. This is shown in the following figure:

  9. The RQS_TIMING-27-1 suggestion uses BLOCK_SYNTH properties at synthesis and applies to the entire module. You can determine the target cell by looking at the properties of the object as described in step 4. Uncheck the box for RQS_TIMING-27-1. This suggestion applies to the entire module and overlaps with the other suggestions. For clarity, it will not be applied.
  10. With the remaining boxes checked, click Add Suggestions to Project. When the Export Suggestion dialog box opens, change the file name to rqs_report.rqs and select Copy sources to project as shown in the following figure.

  11. Examine the Sources window. The RQS file has been added to the utils_1 fileset. This ensures that the file is captured using the get_files command and recognized in the next step when you add the file to a run.