class PrevControl:
+ """ contains signals that come *from* the previous stage (both in and out)
+ * i_valid: input from previous stage indicating incoming data is valid
+ * o_ready: output to next stage indicating readiness to accept data
+ * i_data : an input - added by the user of this class
+ """
def __init__(self):
self.i_valid = Signal(name="p_i_valid") # >>in
self.o_ready = Signal(name="p_o_ready") # <<out
+ 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_valid.eq(prev.i_valid),
+ prev.o_ready.eq(self.o_ready),
+ eq(self.i_data, prev.i_data),
+ ]
-class NextControl:
+class NextControl:
+ """ contains the signals that go *to* the next stage (both in and out)
+ * o_valid: output indicating to next stage that data is valid
+ * i_ready: input from next stage indicating that it can accept data
+ * o_data : an output - added by the user of this class
+ """
def __init__(self):
self.o_valid = Signal(name="n_o_valid") # out>>
self.i_ready = Signal(name="n_i_ready") # <<in
+ def connect_to_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_valid.eq(self.o_valid),
+ self.i_ready.eq(nxt.o_ready),
+ eq(nxt.i_data, self.o_data),
+ ]
+
+ def connect_out(self, nxt):
+ """ helper function to connect stage to an output source. do not
+ use to connect stage-to-stage!
+ """
+ return [nxt.o_valid.eq(self.o_valid),
+ self.i_ready.eq(nxt.i_ready),
+ eq(nxt.o_data, self.o_data),
+ ]
+
def eq(o, i):
+ """ makes signals equal: a helper routine which identifies if it is being
+ passsed a list (or tuple) of objects, and calls the objects' eq
+ function.
+ """
if not isinstance(o, Sequence):
o, i = [o], [i]
res = []
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 p.i_valid >>in stage n.o_valid out>> stage+1
- stage-1 p.o_ready <<out stage n.i_ready <<in stage+1
- stage-1 p.data >>in stage n.data out>> stage+1
- | |
- process --->----^
- | |
- +-- r_data ->-+
-
- input data p.data is read (only), is processed and goes into an
- intermediate result store [process()]. this is updated combinatorially.
-
- in a non-stall condition, the intermediate result will go into the
- output (update_output). however if ever there is a stall, it goes
- into r_data instead [update_buffer()].
-
- when the non-stall condition is released, r_data is the first
- to be transferred to the output [flush_buffer()], and the stall
- condition cleared.
-
- on the next cycle (as long as stall is not raised again) the
- input may begin to be processed and transferred directly to output.
+class PipelineBase:
+ """ Common functions for Pipeline API
"""
def __init__(self, stage):
""" pass in a "stage" which may be either a static class or a class
* ispec: returns output signals to the output specification
* process: takes an input instance and returns processed data
- p.data -> process() -> result --> n.data
- | ^
- | |
- +-> r_data -+
+ User must also:
+ * add i_data member to PrevControl and
+ * add o_data member to NextControl
"""
self.stage = stage
self.p = PrevControl()
self.n = NextControl()
- # set up the input and output data
- self.p.data = stage.ispec() # input type
- self.r_data = stage.ospec() # all these are output type
- self.result = stage.ospec()
- self.n.data = stage.ospec()
-
- def connect_next(self, nxt):
+ def connect_to_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.p.i_valid.eq(self.n.o_valid),
- self.n.i_ready.eq(nxt.p.o_ready),
- eq(nxt.p.data, self.n.data),
- ]
+ return self.n.connect_to_next(nxt.p)
def connect_in(self, prev):
""" helper function to connect stage to an input source. do not
use to connect stage-to-stage!
"""
- return [self.p.i_valid.eq(prev.p.i_valid),
- prev.p.o_ready.eq(self.p.o_ready),
- eq(self.p.data, prev.p.data),
- ]
+ return self.p.connect_in(prev.p)
def connect_out(self, nxt):
""" helper function to connect stage to an output source. do not
use to connect stage-to-stage!
"""
- return [nxt.n.o_valid.eq(self.n.o_valid),
- self.n.i_ready.eq(nxt.n.i_ready),
- eq(nxt.n.data, self.n.data),
- ]
+ return self.n.connect_out(nxt.n)
def set_input(self, i):
""" helper function to set the input data
"""
- return eq(self.p.data, i)
+ return eq(self.p.i_data, i)
- def update_buffer(self):
- """ 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 eq(self.r_data, self.result)
+ def ports(self):
+ return [self.p.i_valid, self.n.i_ready,
+ self.n.o_valid, self.p.o_ready,
+ self.p.i_data, self.n.o_data
+ ]
- def update_output(self):
- """ copies the (combinatorial) result into the output
- """
- return eq(self.n.data, self.result)
- def flush_buffer(self):
- """ copies the *intermediate* register r_data into the output
- """
- return eq(self.n.data, self.r_data)
+class BufferedPipeline(PipelineBase):
+ """ 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.
- def ports(self):
- return [self.p.data, self.n.data]
+ stage-1 p.i_valid >>in stage n.o_valid out>> stage+1
+ stage-1 p.o_ready <<out stage n.i_ready <<in stage+1
+ stage-1 p.i_data >>in stage n.o_data out>> stage+1
+ | |
+ process --->----^
+ | |
+ +-- r_data ->-+
+
+ input data p.i_data is read (only), is processed and goes into an
+ intermediate result store [process()]. this is updated combinatorially.
+
+ in a non-stall condition, the intermediate result will go into the
+ output (update_output). however if ever there is a stall, it goes
+ into r_data instead [update_buffer()].
+
+ when the non-stall condition is released, r_data is the first
+ to be transferred to the output [flush_buffer()], and the stall
+ condition cleared.
+
+ 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):
+ PipelineBase.__init__(self, stage)
+
+ # set up the input and output data
+ self.p.i_data = stage.ispec() # input type
+ self.n.o_data = stage.ospec()
def elaborate(self, platform):
m = Module()
+
+ result = self.stage.ospec()
+ r_data = self.stage.ospec()
if hasattr(self.stage, "setup"):
- self.stage.setup(m, self.p.data)
+ self.stage.setup(m, self.p.i_data)
# establish some combinatorial temporaries
o_n_validn = Signal(reset_less=True)
# store result of processing in combinatorial temporary
with m.If(self.p.i_valid): # input is valid: process it
- m.d.comb += eq(self.result, self.stage.process(self.p.data))
+ m.d.comb += eq(result, self.stage.process(self.p.i_data))
# if not in stall condition, update the temporary register
with m.If(self.p.o_ready): # not stalled
- m.d.sync += self.update_buffer()
+ m.d.sync += eq(r_data, result) # update buffer
#with m.If(self.p.i_rst): # reset
# m.d.sync += self.n.o_valid.eq(0)
with m.If(self.p.o_ready): # not stalled
# nothing in buffer: send (processed) input direct to output
m.d.sync += [self.n.o_valid.eq(self.p.i_valid),
- self.update_output(),
+ eq(self.n.o_data, result), # update output
]
with m.Else(): # p.o_ready is false, and something is in buffer.
# Flush the [already processed] buffer to the output port.
m.d.sync += [self.n.o_valid.eq(1),
- self.flush_buffer(),
+ eq(self.n.o_data, r_data), # flush buffer
# clear stall condition, declare register empty.
self.p.o_ready.eq(1),
]
m.d.sync += [self.n.o_valid.eq(self.p.i_valid),
self.p.o_ready.eq(1), # Keep the buffer empty
# set the output data (from comb result)
- self.update_output(),
+ eq(self.n.o_data, result),
]
# (n.i_ready) false and (n.o_valid) true:
with m.Elif(i_p_valid_o_p_ready):
return m
- def ports(self):
- return [self.p.i_valid, self.n.i_ready,
- self.n.o_valid, self.p.o_ready,
- ]
-
class ExampleAddStage:
""" an example of how to use the buffered pipeline, as a class instance
BufferedPipeline.__init__(self, ExampleStage)
-class CombPipe:
+class CombPipe(PipelineBase):
"""A simple pipeline stage containing combinational logic that can execute
completely in one clock cycle.
"""
def __init__(self, stage):
- self.stage = stage
+ PipelineBase.__init__(self, stage)
self._data_valid = Signal()
- # set up input and output IO ACK (prev/next ready/valid)
- self.p = PrevControl()
- self.n = NextControl()
# set up the input and output data
- self.p.data = stage.ispec() # input type
- self.r_data = stage.ispec() # input type
- self.result = stage.ospec() # output data
- self.n.data = stage.ospec() # output type
- self.n.data.name = "outdata"
-
- def set_input(self, i):
- """ helper function to set the input data
- """
- return eq(self.p.data, i)
+ self.p.i_data = stage.ispec() # input type
+ self.n.o_data = stage.ospec() # output type
def elaborate(self, platform):
m = Module()
+
+ r_data = self.stage.ispec() # input type
+ result = self.stage.ospec() # output data
if hasattr(self.stage, "setup"):
- self.stage.setup(m, self.r_data)
- m.d.comb += eq(self.result, self.stage.process(self.r_data))
+ self.stage.setup(m, r_data)
+
+ m.d.comb += eq(result, self.stage.process(r_data))
m.d.comb += self.n.o_valid.eq(self._data_valid)
m.d.comb += self.p.o_ready.eq(~self._data_valid | self.n.i_ready)
m.d.sync += self._data_valid.eq(self.p.i_valid | \
(~self.n.i_ready & self._data_valid))
with m.If(self.p.i_valid & self.p.o_ready):
- m.d.sync += eq(self.r_data, self.p.data)
- m.d.comb += eq(self.n.data, self.result)
+ m.d.sync += eq(r_data, self.p.i_data)
+ m.d.comb += eq(self.n.o_data, result)
return m
- def ports(self):
- return [self.p.data, self.n.data]
-
class ExampleCombPipe(CombPipe):
""" an example of how to use the combinatorial pipeline.
projects / ieee754fpu.git / blobdiff