build.{dsl,plat,res}: allow dir="oe".

Although a dir="oe" pin is generally equivalent to dir="io" pin with
the i* signal(s) disconnected, they are not equivalent, because some
pins may not be able to support input buffers at all, either because
there are no input buffers, or because the input buffers are consumed
by some other resource.

E.g. this can happen on iCE40 when the input buffer is consumed by
a PLL.

nmigen/build/dsl.py

@@ -9,7 +9,7 @@ class Pins:
         self.names = names.split()
 
         if dir not in ("i", "o", "io"):
-            raise TypeError("Direction must be one of \"i\", \"o\" or \"io\", not {!r}"
+            raise TypeError("Direction must be one of \"i\", \"o\", \"oe\", or \"io\", not {!r}"
                             .format(dir))
         self.dir = dir
 

nmigen/build/plat.py

@@ -127,16 +127,20 @@ class Platform(ConstraintManager, metaclass=ABCMeta):
                 add_pin_fragment(pin, self.get_input(pin, port, extras))
             if pin.dir == "o":
                 add_pin_fragment(pin, self.get_output(pin, port, extras))
+            if pin.dir == "oe":
+                add_pin_fragment(pin, self.get_tristate(pin, port, extras))
             if pin.dir == "io":
-                add_pin_fragment(pin, self.get_input(pin, port, extras))
+                add_pin_fragment(pin, self.get_input_output(pin, port, extras))
 
         for pin, p_port, n_port, extras in self.iter_differential_pins():
             if pin.dir == "i":
                 add_pin_fragment(pin, self.get_diff_input(pin, p_port, n_port))
             if pin.dir == "o":
                 add_pin_fragment(pin, self.get_diff_output(pin, p_port, n_port))
-            if pin.dir == "io":
+            if pin.dir == "oe":
                 add_pin_fragment(pin, self.get_diff_tristate(pin, p_port, n_port))
+            if pin.dir == "io":
+                add_pin_fragment(pin, self.get_diff_input_output(pin, p_port, n_port))
 
         return self.toolchain_prepare(fragment, name, **kwargs)
 
@@ -187,6 +191,19 @@ class Platform(ConstraintManager, metaclass=ABCMeta):
         self._check_feature("single-ended tristate", pin, extras,
                             valid_xdrs=(0,), valid_extras=None)
 
+        m = Module()
+        m.submodules += Instance("$tribuf",
+            p_WIDTH=pin.width,
+            i_EN=pin.oe,
+            i_A=pin.o,
+            o_Y=port,
+        )
+        return m
+
+    def get_input_output(self, pin, port, extras):
+        self._check_feature("single-ended input/output", pin, extras,
+                            valid_xdrs=(0,), valid_extras=None)
+
         m = Module()
         m.submodules += Instance("$tribuf",
             p_WIDTH=pin.width,
@@ -209,6 +226,10 @@ class Platform(ConstraintManager, metaclass=ABCMeta):
         self._check_feature("differential tristate", pin, extras,
                             valid_xdrs=(), valid_extras=None)
 
+    def get_diff_input_output(self, pin, p_port, n_port, extras):
+        self._check_feature("differential input/output", pin, extras,
+                            valid_xdrs=(), valid_extras=None)
+
 
 class TemplatedPlatform(Platform):
     file_templates    = abstractproperty()

nmigen/build/res.py

@@ -84,14 +84,14 @@ class ConstraintManager:
                     dir = subsignal.io[0].dir
                 if xdr is None:
                     xdr = 0
-                if dir not in ("i", "o", "io", "-"):
+                if dir not in ("i", "o", "oe", "io", "-"):
-                    raise TypeError("Direction must be one of \"i\", \"o\", \"io\", or \"-\", "
+                    raise TypeError("Direction must be one of \"i\", \"o\", \"oe\", \"io\", "
-                                    "not {!r}"
+                                    "or \"-\", not {!r}"
                                     .format(dir))
                 if dir != subsignal.io[0].dir and not (subsignal.io[0].dir == "io" or dir == "-"):
                     raise ValueError("Direction of {!r} cannot be changed from \"{}\" to \"{}\"; "
-                                     "direction can be changed from \"io\" to \"i\", from \"io\""
+                                     "direction can be changed from \"io\" to \"i\", \"o\", or "
-                                     "to \"o\", or from anything to \"-\""
+                                     "\"oe\", or from anything to \"-\""
                                      .format(subsignal.io[0], subsignal.io[0].dir, dir))
                 if not isinstance(xdr, int) or xdr < 0:
                     raise ValueError("Data rate of {!r} must be a non-negative integer, not {!r}"

nmigen/test/test_build_dsl.py

@@ -17,7 +17,7 @@ class PinsTestCase(FHDLTestCase):
 
     def test_wrong_dir(self):
         with self.assertRaises(TypeError,
-                msg="Direction must be one of \"i\", \"o\" or \"io\", not 'wrong'"):
+                msg="Direction must be one of \"i\", \"o\", \"oe\", or \"io\", not 'wrong'"):
             p = Pins("A0 A1", dir="wrong")
 
 

nmigen/test/test_build_res.py

@@ -197,13 +197,14 @@ class ConstraintManagerTestCase(FHDLTestCase):
 
     def test_wrong_request_with_dir(self):
         with self.assertRaises(TypeError,
-                msg="Direction must be one of \"i\", \"o\", \"io\", or \"-\", not 'wrong'"):
+                msg="Direction must be one of \"i\", \"o\", \"oe\", \"io\", or \"-\", "
+                    "not 'wrong'"):
             user_led = self.cm.request("user_led", 0, dir="wrong")
 
     def test_wrong_request_with_dir_io(self):
         with self.assertRaises(ValueError,
                 msg="Direction of (pins o A0) cannot be changed from \"o\" to \"i\"; direction "
-                    "can be changed from \"io\" to \"i\", from \"io\"to \"o\", or from anything "
+                    "can be changed from \"io\" to \"i\", \"o\", or \"oe\", or from anything "
                     "to \"-\""):
             user_led = self.cm.request("user_led", 0, dir="i")
 

nmigen/vendor/fpga/lattice_ice40.py

@@ -9,7 +9,8 @@ from ...hdl.ir import *
 from ...build import *
 
 
-__all__ = ["LatticeICE40Platform", "IceStormProgrammerMixin", "IceBurnProgrammerMixin", "TinyProgrammerMixin"]
+__all__ = ["LatticeICE40Platform",
+           "IceStormProgrammerMixin", "IceBurnProgrammerMixin", "TinyProgrammerMixin"]
 
 
 class LatticeICE40Platform(TemplatedPlatform):
@@ -140,6 +141,16 @@ class LatticeICE40Platform(TemplatedPlatform):
         return self._get_io_buffer(port, extras, lambda bit: [
             # PIN_OUTPUT_TRISTATE|PIN_INPUT_REGISTERED
             ("p", "PIN_TYPE",       0b1010_00),
+            ("i", "D_OUT_0",        pin.o[bit]),
+            ("i", "OUTPUT_ENABLE",  pin.oe),
+        ])
+
+    def get_input_output(self, pin, port, extras):
+        self._check_feature("single-ended input/output", pin, extras,
+                            valid_xdrs=(0,), valid_extras=True)
+        return self._get_io_buffer(port, extras, lambda bit: [
+            # PIN_OUTPUT_TRISTATE|PIN_INPUT
+            ("p", "PIN_TYPE",       0b1010_01),
             ("o", "D_IN_0",         pin.i[bit]),
             ("i", "D_OUT_0",        pin.o[bit]),
             ("i", "OUTPUT_ENABLE",  pin.oe),