diff --git a/litex/build/altera/platform.py b/litex/build/altera/platform.py
index ca690dd77..59f1078ff 100644
--- a/litex/build/altera/platform.py
+++ b/litex/build/altera/platform.py
@@ -45,9 +45,6 @@ class AlteraPlatform(GenericPlatform):
         return self.toolchain.build(self, *args, **kwargs)
 
     def add_period_constraint(self, clk, period):
-        if clk is None: return
-        if hasattr(clk, "p"):
-            clk = clk.p
         self.toolchain.add_period_constraint(self, clk, period, keep=False)
 
     def add_false_path_constraint(self, from_, to):
diff --git a/litex/build/anlogic/anlogic.py b/litex/build/anlogic/anlogic.py
index bb239d2d2..838f0bf9c 100644
--- a/litex/build/anlogic/anlogic.py
+++ b/litex/build/anlogic/anlogic.py
@@ -204,12 +204,3 @@ class TangDinastyToolchain(GenericToolchain):
 
         (architecture, family, package) = devices[device]
         return (architecture, family, package)
-
-    def add_period_constraint(self, platform, clk, period):
-        clk.attr.add("keep")
-        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
diff --git a/litex/build/anlogic/platform.py b/litex/build/anlogic/platform.py
index 627882467..9979223df 100644
--- a/litex/build/anlogic/platform.py
+++ b/litex/build/anlogic/platform.py
@@ -36,5 +36,4 @@ class AnlogicPlatform(GenericPlatform):
         return self.toolchain.build(self, *args, **kwargs)
 
     def add_period_constraint(self, clk, period):
-        if clk is None: return
         self.toolchain.add_period_constraint(self, clk, period)
diff --git a/litex/build/efinix/platform.py b/litex/build/efinix/platform.py
index 14ec97d43..2ca80593a 100644
--- a/litex/build/efinix/platform.py
+++ b/litex/build/efinix/platform.py
@@ -63,9 +63,6 @@ class EfinixPlatform(GenericPlatform):
         return self.toolchain.build(self, *args, **kwargs)
 
     def add_period_constraint(self, clk, period):
-        if clk is None: return
-        if hasattr(clk, "p"):
-            clk = clk.p
         self.toolchain.add_period_constraint(self, clk, period)
 
     def add_false_path_constraint(self, from_, to):
diff --git a/litex/build/gowin/platform.py b/litex/build/gowin/platform.py
index b37e8d155..30c86bd6e 100644
--- a/litex/build/gowin/platform.py
+++ b/litex/build/gowin/platform.py
@@ -43,5 +43,4 @@ class GowinPlatform(GenericPlatform):
         return self.toolchain.build(self, *args, **kwargs)
 
     def add_period_constraint(self, clk, period):
-        if clk is None: return
         self.toolchain.add_period_constraint(self, clk, period)
diff --git a/litex/build/lattice/platform.py b/litex/build/lattice/platform.py
index 029ca578c..2aaa4e77b 100644
--- a/litex/build/lattice/platform.py
+++ b/litex/build/lattice/platform.py
@@ -48,9 +48,6 @@ class LatticePlatform(GenericPlatform):
         return self.toolchain.build(self, *args, **kwargs)
 
     def add_period_constraint(self, clk, period):
-        if clk is None: return
-        if hasattr(clk, "p"):
-            clk = clk.p
         self.toolchain.add_period_constraint(self, clk, period)
 
     def add_false_path_constraint(self, from_, to):
diff --git a/litex/build/microsemi/platform.py b/litex/build/microsemi/platform.py
index ace9bfe4a..a324a776b 100644
--- a/litex/build/microsemi/platform.py
+++ b/litex/build/microsemi/platform.py
@@ -34,10 +34,6 @@ class MicrosemiPlatform(GenericPlatform):
         return self.toolchain.build(self, *args, **kwargs)
 
     def add_period_constraint(self, clk, period):
-        if clk is None: return
-        clk.attr.add("keep")
-        if hasattr(clk, "p"):
-            clk = clk.p
         self.toolchain.add_period_constraint(self, clk, period)
 
     def add_false_path_constraint(self, from_, to):
diff --git a/litex/build/osfpga/platform.py b/litex/build/osfpga/platform.py
index b01516629..d3e822908 100644
--- a/litex/build/osfpga/platform.py
+++ b/litex/build/osfpga/platform.py
@@ -36,7 +36,6 @@ class OSFPGAPlatform(GenericPlatform):
         return self.toolchain.build(self, *args, **kwargs)
 
     def add_period_constraint(self, clk, period):
-        if clk is None: return
         self.toolchain.add_period_constraint(self, clk, period)
 
     def add_false_path_constraint(self, from_, to):
diff --git a/litex/build/xilinx/platform.py b/litex/build/xilinx/platform.py
index fd75dae1d..806516038 100644
--- a/litex/build/xilinx/platform.py
+++ b/litex/build/xilinx/platform.py
@@ -85,9 +85,6 @@ class XilinxPlatform(GenericPlatform):
         return self.toolchain.build(self, *args, **kwargs)
 
     def add_period_constraint(self, clk, period, keep=True):
-        if clk is None: return
-        if hasattr(clk, "p"):
-            clk = clk.p
         self.toolchain.add_period_constraint(self, clk, period, keep=keep)
 
     def add_false_path_constraint(self, from_, to):