Flow and PDK variables are too many and few of them are usually needed to be modified

[mo-hosni]

Description

Most of the flow and PDK variables in the documentation are not needed to be modified in the usual hardening process of macros. Some users might get lost searching for a variable to fix the usual timing/congestion/pv issues in PnR. So, I created a list of the most common variables to be modified by the users in the flow. Many macros were hardened successfully using these variables only.

Proposal

A short list of the most used variables (flow and PDK) and the issues those variables address would be very useful for OpenLane users. A starting point could be:

1- Required variables for the flow:

DESIGN_NAME
VERILOG_FILES
CLOCK_PERIOD
CLOCK_PORT

2- Variables that are usually needed:

DESIGN_IS_CORE
FP_CORE_UTIL
FP_ASPECT_RATIO
FP_PIN_ORDER_CFG
VERILOG_FILES_BLACKBOX
EXTRA_LEFS
EXTRA_LIBS
EXTRA_GDS_FILES
BASE_SDC_FILE
RCX_SDC_FILE
PL_TARGET_DENSITY
PL_RESIZER_HOLD_SLACK_MARGIN
GLB_RESIZER_HOLD_SLACK_MARGIN

3- Useful in many scenarios:

MAX_TRANSITION_CONSTRAINT
MAX_FANOUT_CONSTRAINT
CTS_MAX_CAP
PL_RESIZER_MAX_SLEW_MARGIN
PL_RESIZER_MAX_CAP_MARGIN
PL_RESIZER_SETUP_SLACK_MARGIN
GLB_RESIZER_MAX_SLEW_MARGIN
GLB_RESIZER_MAX_CAP_MARGIN
GLB_RESIZER_SETUP_SLACK_MARGIN
RUN_HEURISTIC_DIODE_INSERTION
GRT_REPAIR_ANTENNAS
VSRC_LOC_FILES
MAGIC_EXT_USE_GDS
FP_PDN_MACRO_HOOKS