The methods to fix setup violation include
HVT swap: HVT/NVT/LVT type cells have same size and pin position. In both leakage current and speed, LVT>NVT>HVT. So replace HVT with NVT or LVT will speed up the timing without disturb layout.
Increase driver size: Normally larger cell has higher speed. But some special cell may have larger cell slower than normal cell. Check the technology library timing table to find out these special cells. Increasing driver is very commonly used in setup fix.
Isolate fanouts: Check the fanouts of a violated cell, if more than two fanouts are not in critical path, insert a small buffer to drive these fanouts.
Insert buffers: If a violated cell has long distance to the load, add a proper size buffer in the wire.
Adjust cells position in layout: Adjust cells position to make the path align in the line from the start point to end point will definitely help timing, but the placement in layout may prevent such movement. Always use layout viewer to check if there any spare space to move the critical cell to a optimal location.
Clock skew: By delaying the clock to the end point can relax the timing of the path, but you have to make sure the downstream paths are not critical paths.
GofCall API fix_setup can do cell swapping and increasing driver size automatically.
GofECO timing ECO feature helps to do these fix methods in GUI mode.
The main method to fix hold violation is adding buffers or delay cells. The hold violation path may have its start point or end point in other setup violation paths. So care should be taken to add the buffers/delays in the right place.
E.G. if the hold violation end point is in other setup violation path, the buffers/delays should be inserted in the start point. Otherwise it will worsen the setup violation.
If the hold violation start point is in other setup violation path, the buffers/delays should be inserted in the end point side.
GofCall API fix_hold can insert buffers in the violated path to fix hold timing.
Use GofECO timing ECO to help fixing hold timing violation in GUI mode.
