Fix CDC issue: Synchronize i_hsb_stat[0] in bootp module

[umairsiddiqui-digitek]

Hi,

I noticed a Clock Domain Crossing (CDC) issue where the signal i_hsb_stat in the bootp.sv module is being used without proper synchronization.

Details:

Currently, only bit-0 (i_hsb_stat[0]) is connected in bootp.sv (Line 330).
 

holoscan-sensor-bridge/fpga/nv_hsb_ip/top/HOLOLINK_top.sv

Line 330 in fc2a6cf

assign hsb_stat = {7'h0, ptp_en_sync_rx};

This net is driven by the output signal o_ptp_en_sync_rx from the ptp_top block, as seen in ptp_top.sv (Line 58).
 

holoscan-sensor-bridge/fpga/nv_hsb_ip/ptp/ptp_top.sv

Line 58 in fc2a6cf

output o_ptp_en_sync_rx, //Enable Sync RX

Problem:
The i_hsb_stat[0] signal is generated in the ptp_top domain clocked by i_ptp_clk. However, the bootp block operates on i_hif_clk. Using this signal directly without synchronization can lead to metastability.

Solution:
This PR adds the necessary synchronization logic to safely cross i_hsb_stat[0] over to the i_hif_clk domain before it is consumed by the bootp block.

Regards,

Summary by CodeRabbit

• Bug Fixes
  • Improved BOOTP vendor data reliability by using a clock-synchronized status signal, reducing the risk of inconsistent or unstable data being exposed across clock domains.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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📥 Commits

Reviewing files that changed from the base of the PR and between fc2a6cf and 3de79b7.

📒 Files selected for processing (1)

• fpga/nv_hsb_ip/bootp/bootp.sv

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Walkthrough

The BOOTP module in bootp.sv now synchronizes the i_hsb_stat input into the i_clk clock domain using a new data_sync instance, producing i_hsb_stat_sync. The bootp_vend_data field is updated to use this synchronized signal instead of the raw i_hsb_stat.

Changes

BOOTP clock-domain sync

Layer / File(s)	Summary
Add status synchronizer and update usage fpga/nv_hsb_ip/bootp/bootp.sv	Instantiates a data_sync block to synchronize i_hsb_stat into i_clk (i_hsb_stat_sync) with reset handling, and updates bootp_vend_data to use i_hsb_stat_sync instead of i_hsb_stat.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Related Issues

None found.

Related PRs

None found.

Suggested labels: fpga, hardware

Suggested reviewers: None identified.

Poem: 🐰 A signal once raced through the clock's domain, / Now synced and steady, no more strain. / Through data_sync it hops in line, / bootp_vend_data reads it fine. / A tiny fix, a rabbit's cheer! 🎉

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly states the CDC fix and the BOOTP module synchronization change.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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