makefile: cleanup

Signed-off-by: Øyvind Harboe <[email protected]>

Author: oharboe

docs/user/FlowVariables.md

@@ -182,7 +182,7 @@ configuration file.
 | <a name="SYNTH_HIERARCHICAL"></a>SYNTH_HIERARCHICAL| Enable to Synthesis hierarchically, otherwise considered flat synthesis.| 0| |
 | <a name="SYNTH_KEEP_MODULES"></a>SYNTH_KEEP_MODULES| Mark modules to keep from getting removed in flattening.| | |
 | <a name="SYNTH_MEMORY_MAX_BITS"></a>SYNTH_MEMORY_MAX_BITS| Maximum number of bits for memory synthesis.| 4096| |
-| <a name="SYNTH_MINIMUM_KEEP_SIZE"></a>SYNTH_MINIMUM_KEEP_SIZE| For hierarchical synthesis, we keep modules of larger area than given by this variable and flatten smaller modules. The area unit used is the size of a basic nand2 gate from the platform's standard cell library. The default value is platform specific.| | |
+| <a name="SYNTH_MINIMUM_KEEP_SIZE"></a>SYNTH_MINIMUM_KEEP_SIZE| For hierarchical synthesis, we keep modules of larger area than given by this variable and flatten smaller modules. The area unit used is the size of a basic nand2 gate from the platform's standard cell library. The default value is platform specific.| 0| |
 | <a name="SYNTH_NETLIST_FILES"></a>SYNTH_NETLIST_FILES| Skips synthesis and uses the supplied netlist files. If the netlist files contains duplicate modules, which can happen when using hierarchical synthesis on indvidual netlist files and combining here, subsequent modules are silently ignored and only the first module is used.| | |
 | <a name="SYNTH_WRAPPED_OPERATORS"></a>SYNTH_WRAPPED_OPERATORS| Synthesize multiple architectural options for each arithmetic operator in the design. These options are available for switching among in later stages of the flow.| | |
 | <a name="TAPCELL_TCL"></a>TAPCELL_TCL| Path to Endcap and Welltie cells file.| | |

flow/Makefile

@@ -159,9 +159,6 @@ include $(PLATFORM_DIR)/config.mk
 # is no way to escape space in defaults.py and get "foreach" to work.
 $(foreach line,$(shell $(SCRIPTS_DIR)/defaults.py),$(eval export $(subst __SPACE__, ,$(line))))
 
-# If the design, nor $(PLATFORM_DIR)/config.mk provided a default, provide one here
-export SYNTH_MINIMUM_KEEP_SIZE ?= 0
-
 # Not normally adjusted by user
 export SYNTH_OPERATIONS_ARGS ?= -extra-map $(FLOW_HOME)/platforms/common/lcu_kogge_stone.v
 export SYNTH_FULL_ARGS ?= $(SYNTH_ARGS) $(SYNTH_OPERATIONS_ARGS)

flow/scripts/variables.yaml

@@ -240,6 +240,7 @@ SYNTH_MINIMUM_KEEP_SIZE:
     platform's standard cell library. The default value is platform specific.
   stages:
     - synth
+  default: 0
 SYNTH_WRAPPED_OPERATORS:
   description: >
     Synthesize multiple architectural options for each arithmetic operator in the