X-Git-Url: https://git.libre-soc.org/?a=blobdiff_plain;f=src%2Fadd%2Fexample_buf_pipe.py;h=0f4fb20cf952cb23fd53d71022e0e0e136c6ee9b;hb=d5bbd15168c3295b8979a6dbb0df126211713e0a;hp=aab10a917e4c53b59439c122d5dde9950fbc1488;hpb=0ebc09c0a7b74e4807ccdb60ca0a10cbb605666a;p=ieee754fpu.git

diff --git a/src/add/example_buf_pipe.py b/src/add/example_buf_pipe.py
index aab10a91..0f4fb20c 100644
--- a/src/add/example_buf_pipe.py
+++ b/src/add/example_buf_pipe.py
@@ -13,11 +13,11 @@
 
     input acceptance conditions are when:
         * incoming previous-stage strobe (i.p_valid) is HIGH
-        * outgoing previous-stage busy   (o.p_busy) is LOW
+        * outgoing previous-stage ready   (o.p_ready) is LOW
 
     output transmission conditions are when:
         * outgoing next-stage strobe (o.n_valid) is HIGH
-        * outgoing next-stage busy   (i.n_busy) is LOW
+        * outgoing next-stage ready   (i.n_ready) is LOW
 
     the tricky bit is when the input has valid data and the output is not
     ready to accept it.  if it wasn't for the clock synchronisation, it
@@ -33,7 +33,7 @@
     we now effectively have *two* possible pieces of data to "choose" from:
     the buffered data, and the incoming data.  the decision as to which
     to process and output is based on whether we are in "stall" or not.
-    i.e. when the next stage is no longer busy, the output comes from
+    i.e. when the next stage is no longer ready, the output comes from
     the buffer if a stall had previously occurred, otherwise it comes
     direct from processing the input.
 
@@ -45,12 +45,44 @@
 
 from nmigen import Signal, Cat, Const, Mux, Module
 from nmigen.cli import verilog, rtlil
+from collections.abc import Sequence
 
 
-class ExampleStage:
-    """ an example of how to use the buffered pipeline.  actual names of
-        variables (i_data, r_data, o_data, result) below do not matter:
-        the functions however do.
+class IOAckIn:
+
+    def __init__(self):
+        self.p_valid = Signal() # >>in - comes in from PREVIOUS stage
+        self.n_ready = Signal() # in<< - comes in from the NEXT stage
+
+
+class IOAckOut:
+
+    def __init__(self):
+        self.n_valid = Signal() # out>> - goes out to the NEXT stage
+        self.p_ready = Signal() # <<out - goes out to the PREVIOUS stage
+
+
+def eq(o, i):
+    if not isinstance(o, Sequence):
+        o, i = [o], [i]
+    res = []
+    for (ao, ai) in zip(o, i):
+        res.append(ao.eq(ai))
+    return res
+
+
+class BufferedPipeline:
+    """ buffered pipeline stage.  data and strobe signals travel in sync.
+        if ever the input is ready and the output is not, processed data
+        is stored in a temporary register.
+
+        stage-1   i.p_valid >>in   stage   o.n_valid out>>   stage+1
+        stage-1   o.p_ready <<out  stage   i.n_ready <<in    stage+1
+        stage-1   i.data    >>in   stage   o.data    out>>   stage+1
+                              |             |
+                            process --->----^
+                              |             |
+                              +-- r_data ->-+
 
         input data i_data is read (only), is processed and goes into an
         intermediate result store [process()].  this is updated combinatorially.
@@ -66,147 +98,194 @@ class ExampleStage:
         on the next cycle (as long as stall is not raised again) the
         input may begin to be processed and transferred directly to output.
     """
+    def __init__(self, stage):
+        """ pass in a "stage" which may be either a static class or a class
+            instance, which has three functions:
+            * ispec: returns input signals according to the input specification
+            * ispec: returns output signals to the output specification
+            * process: takes an input instance and returns processed data
+
+            i_data -> process() -> result --> o.data
+                                     |           ^
+                                     |           |
+                                     +-> r_data -+
+        """
+        self.stage = stage
 
-    def __init__(self):
-        """ i_data can be a DIFFERENT type from everything else
-            o_data, r_data and result must be of the same type
+        # set up input and output IO ACK (prev/next ready/valid)
+        self.i = IOAckIn()
+        self.o = IOAckOut()
+
+        # set up the input and output data
+        self.i.data = stage.ispec() # input type
+        self.r_data = stage.ospec() # all these are output type
+        self.result = stage.ospec()
+        self.o.data = stage.ospec()
+
+    def connect_next(self, nxt):
+        """ helper function to connect to the next stage data/valid/ready.
+            data/valid is passed *TO* nxt, and ready comes *IN* from nxt.
+        """
+        return [nxt.i.p_valid.eq(self.o.n_valid),
+                self.i.n_ready.eq(nxt.o.p_ready),
+                eq(nxt.i.data, self.o.data),
+               ]
+
+    def connect_in(self, prev):
+        """ helper function to connect stage to an input source.  do not
+            use to connect stage-to-stage!
+        """
+        return [self.i.p_valid.eq(prev.i.p_valid),
+                prev.o.p_ready.eq(self.o.p_ready),
+                eq(self.i.data, prev.i.data),
+               ]
+
+    def connect_out(self, nxt):
+        """ helper function to connect stage to an output source.  do not
+            use to connect stage-to-stage!
         """
-        self.i_data = Signal(16)
-        self.r_data = Signal(16)
-        self.o_data = Signal(16)
-        self.result = Signal(16)
-
-    def process(self):
-        """ process the input data and store it in result.
-            (not needed to be known: result is combinatorial)
+        return [nxt.o.n_valid.eq(self.o.n_valid),
+                self.i.n_ready.eq(nxt.i.n_ready),
+                eq(nxt.o.data, self.o.data),
+               ]
+
+    def set_input(self, i):
+        """ helper function to set the input data
         """
-        return self.result.eq(self.i_data + 1)
+        return eq(self.i.data, i)
 
     def update_buffer(self):
-        """ copies the result into the intermediate register r_data
+        """ copies the result into the intermediate register r_data,
+            which will need to be outputted on a subsequent cycle
+            prior to allowing "normal" operation.
         """
-        return self.r_data.eq(self.result)
+        return eq(self.r_data, self.result)
 
     def update_output(self):
         """ copies the (combinatorial) result into the output
         """
-        return self.o_data.eq(self.result)
+        return eq(self.o.data, self.result)
 
     def flush_buffer(self):
         """ copies the *intermediate* register r_data into the output
         """
-        return self.o_data.eq(self.r_data)
+        return eq(self.o.data, self.r_data)
 
     def ports(self):
-        return [self.i_data, self.o_data]
-
-class IOAckIn:
-
-    def __init__(self):
-        self.p_valid = Signal()  # >>in - comes in from PREVIOUS stage
-        self.n_busy = Signal() # in<< - comes in from the NEXT stage
-
-
-class IOAckOut:
-
-    def __init__(self):
-        self.n_valid = Signal()  # out>> - goes out to the NEXT stage
-        self.p_busy = Signal() # <<out - goes out to the PREVIOUS stage
-
-
-class BufferedPipeline:
-    """ buffered pipeline stage
-
-        stage-1   i.p_valid  >>in   stage   o.n_valid  out>>   stage+1
-        stage-1   o.p_busy <<out  stage   i.n_busy <<in    stage+1
-        stage-1   i_data   >>in   stage   o_data   out>>   stage+1
-                              |             |
-                              +------->  process
-                              |             |
-                              +-- r_data ---+
-    """
-    def __init__(self):
-        # input: strobe comes in from previous stage, busy comes in from next
-        self.i = IOAckIn()
-        #self.i.p_valid = Signal()    # >>in - comes in from PREVIOUS stage
-        #self.i.n_busy = Signal()   # in<< - comes in from the NEXT stage
-
-        # output: strobe goes out to next stage, busy comes in from previous
-        self.o = IOAckOut()
-        #self.o.n_valid = Signal()    # out>> - goes out to the NEXT stage
-        #self.o.p_busy = Signal()   # <<out - goes out to the PREVIOUS stage
+        return [self.i.data, self.o.data]
 
     def elaborate(self, platform):
         m = Module()
 
         # establish some combinatorial temporaries
-        o_p_busyn = Signal(reset_less=True)
         o_n_validn = Signal(reset_less=True)
-        i_n_busyn = Signal(reset_less=True)
-        i_p_valid_o_p_busyn = Signal(reset_less=True)
-        m.d.comb += [i_n_busyn.eq(~self.i.n_busy),
-                     o_n_validn.eq(~self.o.n_valid),
-                     o_p_busyn.eq(~self.o.p_busy),
-                     i_p_valid_o_p_busyn.eq(self.i.p_valid & o_p_busyn),
+        i_p_valid_o_p_ready = Signal(reset_less=True)
+        m.d.comb += [o_n_validn.eq(~self.o.n_valid),
+                     i_p_valid_o_p_ready.eq(self.i.p_valid & self.o.p_ready),
         ]
 
         # store result of processing in combinatorial temporary
         with m.If(self.i.p_valid): # input is valid: process it
-            m.d.comb += self.stage.process()
+            m.d.comb += eq(self.result, self.stage.process(self.i.data))
         # if not in stall condition, update the temporary register
-        with m.If(o_p_busyn): # not stalled
-            m.d.sync += self.stage.update_buffer()
+        with m.If(self.o.p_ready): # not stalled
+            m.d.sync += self.update_buffer()
 
         #with m.If(self.i.p_rst): # reset
         #    m.d.sync += self.o.n_valid.eq(0)
-        #    m.d.sync += self.o.p_busy.eq(0)
-        with m.If(i_n_busyn): # next stage is not busy
-            with m.If(o_p_busyn): # not stalled
+        #    m.d.sync += self.o.p_ready.eq(0)
+        with m.If(self.i.n_ready): # next stage is ready
+            with m.If(self.o.p_ready): # not stalled
                 # nothing in buffer: send (processed) input direct to output
                 m.d.sync += [self.o.n_valid.eq(self.i.p_valid),
-                             self.stage.update_output(),
+                             self.update_output(),
                             ]
-            with m.Else(): # o.p_busy is true, and something is in our buffer.
+            with m.Else(): # o.p_ready is false, and something is in buffer.
                 # Flush the [already processed] buffer to the output port.
                 m.d.sync += [self.o.n_valid.eq(1),
-                             self.stage.flush_buffer(),
+                             self.flush_buffer(),
                              # clear stall condition, declare register empty.
-                             self.o.p_busy.eq(0),
+                             self.o.p_ready.eq(1),
                             ]
-                # ignore input, since o.p_busy is also true.
+                # ignore input, since o.p_ready is also false.
 
-        # (i.n_busy) is true here: next stage is busy
-        with m.Elif(o_n_validn): # next stage being told "not busy"
+        # (i.n_ready) is false here: next stage is ready
+        with m.Elif(o_n_validn): # next stage being told "ready"
             m.d.sync += [self.o.n_valid.eq(self.i.p_valid),
-                         self.o.p_busy.eq(0), # Keep the buffer empty
+                         self.o.p_ready.eq(1), # Keep the buffer empty
                          # set the output data (from comb result)
-                         self.stage.update_output(),
+                         self.update_output(),
                         ]
-        # (i.n_busy) and (o.n_valid) both true:
-        with m.Elif(i_p_valid_o_p_busyn):
-            # If next stage *is* busy, and not stalled yet, accept input
-            m.d.sync += self.o.p_busy.eq(self.i.p_valid & self.o.n_valid)
+        # (i.n_ready) false and (o.n_valid) true:
+        with m.Elif(i_p_valid_o_p_ready):
+            # If next stage *is* ready, and not stalled yet, accept input
+            m.d.sync += self.o.p_ready.eq(~(self.i.p_valid & self.o.n_valid))
 
         return m
 
     def ports(self):
-        return [self.i.p_valid, self.i.n_busy,
-                self.o.n_valid, self.o.p_busy,
+        return [self.i.p_valid, self.i.n_ready,
+                self.o.n_valid, self.o.p_ready,
                ]
 
 
-class BufPipe(BufferedPipeline):
+class ExampleAddStage:
+    """ an example of how to use the buffered pipeline, as a class instance
+    """
+
+    def ispec(self):
+        """ returns a tuple of input signals which will be the incoming data
+        """
+        return (Signal(16), Signal(16))
+
+    def ospec(self):
+        """ returns an output signal which will happen to contain the sum
+            of the two inputs
+        """
+        return Signal(16)
+
+    def process(self, i):
+        """ process the input data (sums the values in the tuple) and returns it
+        """
+        return i[0] + i[1]
+
+
+class ExampleBufPipeAdd(BufferedPipeline):
+    """ an example of how to use the buffered pipeline, using a class instance
+    """
 
     def __init__(self):
-        BufferedPipeline.__init__(self)
-        self.stage = ExampleStage()
+        addstage = ExampleAddStage()
+        BufferedPipeline.__init__(self, addstage)
 
-    def ports(self):
-        return self.stage.ports() + BufferedPipeline.ports(self)
+
+class ExampleStage:
+    """ an example of how to use the buffered pipeline, in a static class
+        fashion
+    """
+
+    def ispec():
+        return Signal(16)
+
+    def ospec():
+        return Signal(16)
+
+    def process(i):
+        """ process the input data and returns it (adds 1)
+        """
+        return i + 1
+
+
+class ExampleBufPipe(BufferedPipeline):
+    """ an example of how to use the buffered pipeline.
+    """
+
+    def __init__(self):
+        BufferedPipeline.__init__(self, ExampleStage)
 
 
 if __name__ == '__main__':
-    dut = BufPipe()
+    dut = ExampleBufPipe()
     vl = rtlil.convert(dut, ports=dut.ports())
     with open("test_bufpipe.il", "w") as f:
         f.write(vl)