From: Florent Kermarrec <florent@enjoy-digital.fr>
Date: Tue, 31 Dec 2019 09:32:09 +0000 (+0100)
Subject: build/xilinx/vivado: update add_period_constraint behavior when clock is already... 
X-Git-Tag: 24jan2021_ls180~783
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=3022f02b3fb473618ff057d10133f10bf875f009;p=litex.git

build/xilinx/vivado: update add_period_constraint behavior when clock is already constrainted.
---

diff --git a/litex/build/xilinx/vivado.py b/litex/build/xilinx/vivado.py
index 01e1aca5..ef722d4d 100644
--- a/litex/build/xilinx/vivado.py
+++ b/litex/build/xilinx/vivado.py
@@ -311,9 +311,11 @@ class XilinxVivadoToolchain:
 
     def add_period_constraint(self, platform, clk, period):
         clk.attr.add("keep")
-        if clk in self.clocks:
-            raise ValueError("A period constraint already exists")
         period = math.floor(period*1e3)/1e3 # round to lowest picosecond
+        if clk in self.clocks:
+            if period != self.clocks[clk]:
+                raise ValueError("Clock already constrained to {:.2f}ns, new constraint to {:.2f}ns"
+                    .format(self.clocks[clk], period))
         self.clocks[clk] = period
 
     def add_false_path_constraint(self, platform, from_, to):