oNO. Even if setup and hold timing checks pass, significant Design Rule Violations (DRVs) either on data or clock needs to be fixed.
Reliability: Slow transitions (max_transition violation) make sequential elements susceptible to noise, glitches, and potential metastability
Timing Accuracy: buffers/inverters are characterized based on expected input transitions and output loads. Violating max_transition or max_capacitance means the library timing models used for setup/hold analysis are inaccurate, invalidating the “clean” timing result. The actual delays might be worse.
Power: Slow transitions increase short-circuit power consumption in the clock buffers and the receiving flip-flops.
Jitter: Poor signal integrity on the clock net can increase clock jitter
Identifying Clock DRVs:
STA Reports: Run STA reports specifically targeting DRVs on the clock tree.
report_constraint -all_violators (or similar) will list max_cap, max_tran violations. Filter for clock nets/pins.
Fixing Clock DRVs: These are fixed using techniques similar to fixing DRVs on signal nets, but applied specifically to the clock tree, often during post-route optimization or ECOs:
Buffer Insertion: Insert additional clock buffers/inverters to break long nets (fixes max_cap, max_tran) or to isolate high capacitance sinks.
Cell Sizing (Upsizing): Increase the drive strength of the clock buffer driving the violating net segment. A stronger driver provides faster transitions and can handle higher capacitance.
Cell Sizing (Downsizing): If a buffer is oversized for its load, downsizing it can reduce the load on the previous stage, potentially fixing a violation there.
VT Swapping (Lower Vt): Swapping to lower Vt clock buffers can provide faster transitions (fixing max_tran) but increases leakage.
Net Topology/Routing Changes: Minor re-routing (e.g., layer change, shortening path) might slightly reduce capacitance or resistance, helping fix violations (less common as a primary fix).
Load Splitting/Cloning: If a single buffer drives too many sinks causing max_fanout or max_cap issues, clone the buffer and split the sinks between the clones.