scan_controller/sta: Add custom constraining

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>

openlane/scan_controller/base.sdc

diff --git a/openlane/scan_controller/base.sdc b/openlane/scan_controller/base.sdc
new file mode 100644
index 0000000..2204c60
--- /dev/null
+++ b/openlane/scan_controller/base.sdc
@@ -0,0 +1,58 @@
+# Create main clock
+create_clock [get_ports $::env(CLOCK_PORT)]  -name $::env(CLOCK_PORT)  -period $::env(CLOCK_PERIOD)
+
+# Create our generated clock
+create_generated_clock -edges {3 5 7} -source $::env(CLOCK_PORT) -name clk_scan_out [get_ports scan_clk_out]
+set_multicycle_path -start -hold -from [get_clocks $::env(CLOCK_PORT)] -to [get_clocks clk_scan_out] 1
+
+# Create feedback clock
+create_clock [get_ports scan_clk_in] -name clk_scan_in -period [expr {$::env(CLOCK_PERIOD) * 2}]
+
+# CDC
+set_min_delay 0.25                              -from [get_clocks clk_scan_in] -to [get_clocks $::env(CLOCK_PORT)]
+set_max_delay [expr {$::env(CLOCK_PERIOD) / 2}] -from [get_clocks clk_scan_in] -to [get_clocks $::env(CLOCK_PORT)]
+
+# IO delays
+
+	# Scan chain input  0.5 ns setup time, 0.5 ns hold time
+set_input_delay  -min  0.5 -clock [get_clocks clk_scan_in]  [get_ports {scan_data_in}]
+set_input_delay  -max  0.5 -clock [get_clocks clk_scan_in]  [get_ports {scan_data_in}]
+
+	# Scan chain output 1.5 ns setup time, 1.5 ns hold time
+set_output_delay -min -1.5 -clock [get_clocks clk_scan_out] [get_ports {scan_data_out}]
+set_output_delay -max  1.5 -clock [get_clocks clk_scan_out] [get_ports {scan_data_out}]
+
+	# Limit the max output delay on other outputs
+set_output_delay -max  1.5 -clock [get_clocks $::env(CLOCK_PORT)] [get_ports {scan_select scan_latch_en}]
+
+	# All the other IOs we consider asynchronous so ... no point in constraining
+set_false_path -from [get_ports {active_select inputs set_clk_div la_* driver_sel}]
+
+
+# Misc
+set_max_fanout $::env(SYNTH_MAX_FANOUT) [current_design]
+
+if { ![info exists ::env(SYNTH_CLK_DRIVING_CELL)] } {
+    set ::env(SYNTH_CLK_DRIVING_CELL) $::env(SYNTH_DRIVING_CELL)
+}
+
+if { ![info exists ::env(SYNTH_CLK_DRIVING_CELL_PIN)] } {
+    set ::env(SYNTH_CLK_DRIVING_CELL_PIN) $::env(SYNTH_DRIVING_CELL_PIN)
+}
+
+set_driving_cell -lib_cell $::env(SYNTH_DRIVING_CELL) -pin $::env(SYNTH_DRIVING_CELL_PIN) [get_ports {}]
+set_driving_cell -lib_cell $::env(SYNTH_CLK_DRIVING_CELL) -pin $::env(SYNTH_CLK_DRIVING_CELL_PIN) [get_ports {}]
+
+set cap_load [expr $::env(SYNTH_CAP_LOAD) / 1000.0]
+puts "\[INFO\]: Setting load to: $cap_load"
+set_load  $cap_load [all_outputs]
+
+puts "\[INFO\]: Setting clock uncertainity to: $::env(SYNTH_CLOCK_UNCERTAINITY)"
+set_clock_uncertainty $::env(SYNTH_CLOCK_UNCERTAINITY) [get_clocks "$::env(CLOCK_PORT) clk_scan_in clk_scan_out"]
+
+puts "\[INFO\]: Setting clock transition to: $::env(SYNTH_CLOCK_TRANSITION)"
+set_clock_transition $::env(SYNTH_CLOCK_TRANSITION) [get_clocks "$::env(CLOCK_PORT) clk_scan_in clk_scan_out"]
+
+puts "\[INFO\]: Setting timing derate to: [expr {$::env(SYNTH_TIMING_DERATE) * 10}] %"
+set_timing_derate -early [expr {1-$::env(SYNTH_TIMING_DERATE)}]
+set_timing_derate -late [expr {1+$::env(SYNTH_TIMING_DERATE)}]

openlane/scan_controller/config.tcl

diff --git a/openlane/scan_controller/config.tcl b/openlane/scan_controller/config.tcl
index b51552f..c52bd12 100644
--- a/openlane/scan_controller/config.tcl
+++ b/openlane/scan_controller/config.tcl
@@ -31,6 +31,11 @@
 set ::env(CLOCK_PERIOD) "10"
 set ::env(CLOCK_PORT) "clk"
 
+set ::env(BASE_SDC_FILE) $::env(DESIGN_DIR)/base.sdc
+
+set ::env(SYNTH_CLOCK_UNCERTAINITY) 0.20
+set ::env(SYNTH_CLOCK_TRANSITION)   0.15
+
 # macro needs to work inside Caravel, so can't be core and can't use metal 5
 set ::env(DESIGN_IS_CORE) 0
 set ::env(RT_MAX_LAYER) {met4}