8296bf2d4ecd9702cd2d32c20dc345734ed2a641
1 """ Pipeline and BufferedHandshake implementation, conforming to the same API.
2 For multi-input and multi-output variants, see multipipe.
7 a strategically very important function that is identical in function
8 to nmigen's Signal.eq function, except it may take objects, or a list
9 of objects, or a tuple of objects, and where objects may also be
15 stage requires compliance with a strict API that may be
16 implemented in several means, including as a static class.
17 the methods of a stage instance must be as follows:
19 * ispec() - Input data format specification
20 returns an object or a list or tuple of objects, or
21 a Record, each object having an "eq" function which
22 takes responsibility for copying by assignment all
24 * ospec() - Output data format specification
25 requirements as for ospec
26 * process(m, i) - Processes an ispec-formatted object
27 returns a combinatorial block of a result that
28 may be assigned to the output, by way of the "eq"
30 * setup(m, i) - Optional function for setting up submodules
31 may be used for more complex stages, to link
32 the input (i) to submodules. must take responsibility
33 for adding those submodules to the module (m).
34 the submodules must be combinatorial blocks and
35 must have their inputs and output linked combinatorially.
37 Both StageCls (for use with non-static classes) and Stage (for use
38 by static classes) are abstract classes from which, for convenience
39 and as a courtesy to other developers, anything conforming to the
40 Stage API may *choose* to derive.
45 A useful combinatorial wrapper around stages that chains them together
46 and then presents a Stage-API-conformant interface. By presenting
47 the same API as the stages it wraps, it can clearly be used recursively.
52 A convenience class that takes an input shape, output shape, a
53 "processing" function and an optional "setup" function. Honestly
54 though, there's not much more effort to just... create a class
55 that returns a couple of Records (see ExampleAddRecordStage in
61 A convenience class that takes a single function as a parameter,
62 that is chain-called to create the exact same input and output spec.
63 It has a process() function that simply returns its input.
65 Instances of this class are completely redundant if handed to
66 StageChain, however when passed to UnbufferedPipeline they
67 can be used to introduce a single clock delay.
72 The base class for pipelines. Contains previous and next ready/valid/data.
73 Also has an extremely useful "connect" function that can be used to
74 connect a chain of pipelines and present the exact same prev/next
80 A simple stalling clock-synchronised pipeline that has no buffering
81 (unlike BufferedHandshake). Data flows on *every* clock cycle when
82 the conditions are right (this is nominally when the input is valid
83 and the output is ready).
85 A stall anywhere along the line will result in a stall back-propagating
86 down the entire chain. The BufferedHandshake by contrast will buffer
87 incoming data, allowing previous stages one clock cycle's grace before
90 An advantage of the UnbufferedPipeline over the Buffered one is
91 that the amount of logic needed (number of gates) is greatly
92 reduced (no second set of buffers basically)
94 The disadvantage of the UnbufferedPipeline is that the valid/ready
95 logic, if chained together, is *combinatorial*, resulting in
96 progressively larger gate delay.
101 A Control class that introduces a single clock delay, passing its
102 data through unaltered. Unlike RegisterPipeline (which relies
103 on UnbufferedPipeline and PassThroughStage) it handles ready/valid
109 A convenience class that, because UnbufferedPipeline introduces a single
110 clock delay, when its stage is a PassThroughStage, it results in a Pipeline
111 stage that, duh, delays its (unmodified) input by one clock cycle.
116 nmigen implementation of buffered pipeline stage, based on zipcpu:
117 https://zipcpu.com/blog/2017/08/14/strategies-for-pipelining.html
119 this module requires quite a bit of thought to understand how it works
120 (and why it is needed in the first place). reading the above is
121 *strongly* recommended.
123 unlike john dawson's IEEE754 FPU STB/ACK signalling, which requires
124 the STB / ACK signals to raise and lower (on separate clocks) before
125 data may proceeed (thus only allowing one piece of data to proceed
126 on *ALTERNATE* cycles), the signalling here is a true pipeline
127 where data will flow on *every* clock when the conditions are right.
129 input acceptance conditions are when:
130 * incoming previous-stage strobe (p.i_valid) is HIGH
131 * outgoing previous-stage ready (p.o_ready) is LOW
133 output transmission conditions are when:
134 * outgoing next-stage strobe (n.o_valid) is HIGH
135 * outgoing next-stage ready (n.i_ready) is LOW
137 the tricky bit is when the input has valid data and the output is not
138 ready to accept it. if it wasn't for the clock synchronisation, it
139 would be possible to tell the input "hey don't send that data, we're
140 not ready". unfortunately, it's not possible to "change the past":
141 the previous stage *has no choice* but to pass on its data.
143 therefore, the incoming data *must* be accepted - and stored: that
144 is the responsibility / contract that this stage *must* accept.
145 on the same clock, it's possible to tell the input that it must
146 not send any more data. this is the "stall" condition.
148 we now effectively have *two* possible pieces of data to "choose" from:
149 the buffered data, and the incoming data. the decision as to which
150 to process and output is based on whether we are in "stall" or not.
151 i.e. when the next stage is no longer ready, the output comes from
152 the buffer if a stall had previously occurred, otherwise it comes
153 direct from processing the input.
155 this allows us to respect a synchronous "travelling STB" with what
156 dan calls a "buffered handshake".
158 it's quite a complex state machine!
163 Synchronised pipeline, Based on:
164 https://github.com/ZipCPU/dbgbus/blob/master/hexbus/rtl/hbdeword.v
167 from nmigen
import Signal
, Cat
, Const
, Mux
, Module
, Value
168 from nmigen
.cli
import verilog
, rtlil
169 from nmigen
.lib
.fifo
import SyncFIFO
170 from nmigen
.hdl
.ast
import ArrayProxy
171 from nmigen
.hdl
.rec
import Record
, Layout
173 from abc
import ABCMeta
, abstractmethod
174 from collections
.abc
import Sequence
177 class RecordObject(Record
):
178 def __init__(self
, layout
=None, name
=None):
179 Record
.__init
__(self
, layout
=layout
or [], name
=None)
181 def __setattr__(self
, k
, v
):
182 if k
in dir(Record
) or "fields" not in self
.__dict
__:
183 return object.__setattr
__(self
, k
, v
)
185 if isinstance(v
, Record
):
186 newlayout
= {k
: (k
, v
.layout
)}
188 newlayout
= {k
: (k
, v
.shape())}
189 self
.layout
.fields
.update(newlayout
)
194 """ contains signals that come *from* the previous stage (both in and out)
195 * i_valid: previous stage indicating all incoming data is valid.
196 may be a multi-bit signal, where all bits are required
197 to be asserted to indicate "valid".
198 * o_ready: output to next stage indicating readiness to accept data
199 * i_data : an input - added by the user of this class
202 def __init__(self
, i_width
=1, stage_ctl
=False):
203 self
.stage_ctl
= stage_ctl
204 self
.i_valid
= Signal(i_width
, name
="p_i_valid") # prev >>in self
205 self
._o
_ready
= Signal(name
="p_o_ready") # prev <<out self
206 self
.i_data
= None # XXX MUST BE ADDED BY USER
208 self
.s_o_ready
= Signal(name
="p_s_o_rdy") # prev <<out self
212 """ public-facing API: indicates (externally) that stage is ready
215 return self
.s_o_ready
# set dynamically by stage
216 return self
._o
_ready
# return this when not under dynamic control
218 def _connect_in(self
, prev
, direct
=False, fn
=None):
219 """ internal helper function to connect stage to an input source.
220 do not use to connect stage-to-stage!
222 i_valid
= prev
.i_valid
if direct
else prev
.i_valid_test
223 i_data
= fn(prev
.i_data
) if fn
is not None else prev
.i_data
224 return [self
.i_valid
.eq(i_valid
),
225 prev
.o_ready
.eq(self
.o_ready
),
226 eq(self
.i_data
, i_data
),
230 def i_valid_test(self
):
231 vlen
= len(self
.i_valid
)
233 # multi-bit case: valid only when i_valid is all 1s
234 all1s
= Const(-1, (len(self
.i_valid
), False))
235 i_valid
= (self
.i_valid
== all1s
)
237 # single-bit i_valid case
238 i_valid
= self
.i_valid
240 # when stage indicates not ready, incoming data
241 # must "appear" to be not ready too
243 i_valid
= i_valid
& self
.s_o_ready
249 """ contains the signals that go *to* the next stage (both in and out)
250 * o_valid: output indicating to next stage that data is valid
251 * i_ready: input from next stage indicating that it can accept data
252 * o_data : an output - added by the user of this class
254 def __init__(self
, stage_ctl
=False):
255 self
.stage_ctl
= stage_ctl
256 self
.o_valid
= Signal(name
="n_o_valid") # self out>> next
257 self
.i_ready
= Signal(name
="n_i_ready") # self <<in next
258 self
.o_data
= None # XXX MUST BE ADDED BY USER
260 self
.d_valid
= Signal(reset
=1) # INTERNAL (data valid)
263 def i_ready_test(self
):
265 return self
.i_ready
& self
.d_valid
268 def connect_to_next(self
, nxt
):
269 """ helper function to connect to the next stage data/valid/ready.
270 data/valid is passed *TO* nxt, and ready comes *IN* from nxt.
271 use this when connecting stage-to-stage
273 return [nxt
.i_valid
.eq(self
.o_valid
),
274 self
.i_ready
.eq(nxt
.o_ready
),
275 eq(nxt
.i_data
, self
.o_data
),
278 def _connect_out(self
, nxt
, direct
=False, fn
=None):
279 """ internal helper function to connect stage to an output source.
280 do not use to connect stage-to-stage!
282 i_ready
= nxt
.i_ready
if direct
else nxt
.i_ready_test
283 o_data
= fn(self
.o_data
) if fn
is not None else self
.o_data
284 return [nxt
.o_valid
.eq(self
.o_valid
),
285 self
.i_ready
.eq(i_ready
),
286 eq(nxt
.o_data
, o_data
),
291 """ a helper routine which identifies if it is being passed a list
292 (or tuple) of objects, or signals, or Records, and calls
295 the visiting fn is called when an object is identified.
297 Record is a special (unusual, recursive) case, where the input may be
298 specified as a dictionary (which may contain further dictionaries,
299 recursively), where the field names of the dictionary must match
300 the Record's field spec. Alternatively, an object with the same
301 member names as the Record may be assigned: it does not have to
304 ArrayProxy is also special-cased, it's a bit messy: whilst ArrayProxy
305 has an eq function, the object being assigned to it (e.g. a python
306 object) might not. despite the *input* having an eq function,
307 that doesn't help us, because it's the *ArrayProxy* that's being
308 assigned to. so.... we cheat. use the ports() function of the
309 python object, enumerate them, find out the list of Signals that way,
312 def visit(self
, o
, i
, act
):
313 if isinstance(o
, dict):
314 return self
.dict_visit(o
, i
, act
)
317 if not isinstance(o
, Sequence
):
319 for (ao
, ai
) in zip(o
, i
):
320 #print ("visit", fn, ao, ai)
321 if isinstance(ao
, Record
):
322 rres
= self
.record_visit(ao
, ai
, act
)
323 elif isinstance(ao
, ArrayProxy
) and not isinstance(ai
, Value
):
324 rres
= self
.arrayproxy_visit(ao
, ai
, act
)
326 rres
= act
.fn(ao
, ai
)
330 def dict_visit(self
, o
, i
, act
):
332 for (k
, v
) in o
.items():
333 print ("d-eq", v
, i
[k
])
334 res
.append(act
.fn(v
, i
[k
]))
337 def record_visit(self
, ao
, ai
, act
):
339 for idx
, (field_name
, field_shape
, _
) in enumerate(ao
.layout
):
340 if isinstance(field_shape
, Layout
):
344 if hasattr(val
, field_name
): # check for attribute
345 val
= getattr(val
, field_name
)
347 val
= val
[field_name
] # dictionary-style specification
348 val
= self
.visit(ao
.fields
[field_name
], val
, act
)
349 if isinstance(val
, Sequence
):
355 def arrayproxy_visit(self
, ao
, ai
, act
):
358 op
= getattr(ao
, p
.name
)
359 #print (op, p, p.name)
360 res
.append(fn(op
, p
))
371 if not isinstance(rres
, Sequence
):
374 def __call__(self
, o
, i
):
375 return self
.visit(o
, i
, self
)
379 """ makes signals equal: a helper routine which identifies if it is being
380 passed a list (or tuple) of objects, or signals, or Records, and calls
381 the objects' eq function.
387 """ flattens a compound structure recursively using Cat
389 if not isinstance(i
, Sequence
):
393 print ("flatten", ai
)
394 if isinstance(ai
, Record
):
395 print ("record", list(ai
.layout
))
397 for idx
, (field_name
, field_shape
, _
) in enumerate(ai
.layout
):
398 if isinstance(field_shape
, Layout
):
402 if hasattr(val
, field_name
): # check for attribute
403 val
= getattr(val
, field_name
)
405 val
= val
[field_name
] # dictionary-style specification
406 print ("recidx", idx
, field_name
, field_shape
, val
)
408 print ("recidx flat", idx
, val
)
409 if isinstance(val
, Sequence
):
414 elif isinstance(ai
, ArrayProxy
) and not isinstance(ai
, Value
):
417 op
= getattr(ai
, p
.name
)
418 #print (op, p, p.name)
419 rres
.append(flatten(p
))
422 if not isinstance(rres
, Sequence
):
425 print ("flatten res", res
)
430 class StageCls(metaclass
=ABCMeta
):
431 """ Class-based "Stage" API. requires instantiation (after derivation)
433 see "Stage API" above.. Note: python does *not* require derivation
434 from this class. All that is required is that the pipelines *have*
435 the functions listed in this class. Derivation from this class
436 is therefore merely a "courtesy" to maintainers.
439 def ispec(self
): pass # REQUIRED
441 def ospec(self
): pass # REQUIRED
443 #def setup(self, m, i): pass # OPTIONAL
445 def process(self
, i
): pass # REQUIRED
448 class Stage(metaclass
=ABCMeta
):
449 """ Static "Stage" API. does not require instantiation (after derivation)
451 see "Stage API" above. Note: python does *not* require derivation
452 from this class. All that is required is that the pipelines *have*
453 the functions listed in this class. Derivation from this class
454 is therefore merely a "courtesy" to maintainers.
466 #def setup(m, i): pass
473 class RecordBasedStage(Stage
):
474 """ convenience class which provides a Records-based layout.
475 honestly it's a lot easier just to create a direct Records-based
476 class (see ExampleAddRecordStage)
478 def __init__(self
, in_shape
, out_shape
, processfn
, setupfn
=None):
479 self
.in_shape
= in_shape
480 self
.out_shape
= out_shape
481 self
.__process
= processfn
482 self
.__setup
= setupfn
483 def ispec(self
): return Record(self
.in_shape
)
484 def ospec(self
): return Record(self
.out_shape
)
485 def process(seif
, i
): return self
.__process
(i
)
486 def setup(seif
, m
, i
): return self
.__setup
(m
, i
)
489 class StageChain(StageCls
):
490 """ pass in a list of stages, and they will automatically be
491 chained together via their input and output specs into a
494 the end result basically conforms to the exact same Stage API.
496 * input to this class will be the input of the first stage
497 * output of first stage goes into input of second
498 * output of second goes into input into third (etc. etc.)
499 * the output of this class will be the output of the last stage
501 def __init__(self
, chain
, specallocate
=False):
503 self
.specallocate
= specallocate
506 return self
.chain
[0].ispec()
509 return self
.chain
[-1].ospec()
511 def _specallocate_setup(self
, m
, i
):
512 for (idx
, c
) in enumerate(self
.chain
):
513 if hasattr(c
, "setup"):
514 c
.setup(m
, i
) # stage may have some module stuff
515 o
= self
.chain
[idx
].ospec() # last assignment survives
516 m
.d
.comb
+= eq(o
, c
.process(i
)) # process input into "o"
517 if idx
== len(self
.chain
)-1:
519 i
= self
.chain
[idx
+1].ispec() # new input on next loop
520 m
.d
.comb
+= eq(i
, o
) # assign to next input
521 return o
# last loop is the output
523 def _noallocate_setup(self
, m
, i
):
524 for (idx
, c
) in enumerate(self
.chain
):
525 if hasattr(c
, "setup"):
526 c
.setup(m
, i
) # stage may have some module stuff
527 i
= o
= c
.process(i
) # store input into "o"
528 return o
# last loop is the output
530 def setup(self
, m
, i
):
531 if self
.specallocate
:
532 self
.o
= self
._specallocate
_setup
(m
, i
)
534 self
.o
= self
._noallocate
_setup
(m
, i
)
536 def process(self
, i
):
537 return self
.o
# conform to Stage API: return last-loop output
541 """ Common functions for Pipeline API
543 def __init__(self
, stage
=None, in_multi
=None, stage_ctl
=False):
544 """ Base class containing ready/valid/data to previous and next stages
546 * p: contains ready/valid to the previous stage
547 * n: contains ready/valid to the next stage
549 Except when calling Controlbase.connect(), user must also:
550 * add i_data member to PrevControl (p) and
551 * add o_data member to NextControl (n)
555 # set up input and output IO ACK (prev/next ready/valid)
556 self
.p
= PrevControl(in_multi
, stage_ctl
)
557 self
.n
= NextControl(stage_ctl
)
559 # set up the input and output data
560 if stage
is not None:
561 self
.p
.i_data
= stage
.ispec() # input type
562 self
.n
.o_data
= stage
.ospec()
564 def connect_to_next(self
, nxt
):
565 """ helper function to connect to the next stage data/valid/ready.
567 return self
.n
.connect_to_next(nxt
.p
)
569 def _connect_in(self
, prev
):
570 """ internal helper function to connect stage to an input source.
571 do not use to connect stage-to-stage!
573 return self
.p
._connect
_in
(prev
.p
)
575 def _connect_out(self
, nxt
):
576 """ internal helper function to connect stage to an output source.
577 do not use to connect stage-to-stage!
579 return self
.n
._connect
_out
(nxt
.n
)
581 def connect(self
, pipechain
):
582 """ connects a chain (list) of Pipeline instances together and
583 links them to this ControlBase instance:
585 in <----> self <---> out
588 [pipe1, pipe2, pipe3, pipe4]
591 out---in out--in out---in
593 Also takes care of allocating i_data/o_data, by looking up
594 the data spec for each end of the pipechain. i.e It is NOT
595 necessary to allocate self.p.i_data or self.n.o_data manually:
596 this is handled AUTOMATICALLY, here.
598 Basically this function is the direct equivalent of StageChain,
599 except that unlike StageChain, the Pipeline logic is followed.
601 Just as StageChain presents an object that conforms to the
602 Stage API from a list of objects that also conform to the
603 Stage API, an object that calls this Pipeline connect function
604 has the exact same pipeline API as the list of pipline objects
607 Thus it becomes possible to build up larger chains recursively.
608 More complex chains (multi-input, multi-output) will have to be
611 eqs
= [] # collated list of assignment statements
613 # connect inter-chain
614 for i
in range(len(pipechain
)-1):
616 pipe2
= pipechain
[i
+1]
617 eqs
+= pipe1
.connect_to_next(pipe2
)
619 # connect front of chain to ourselves
621 self
.p
.i_data
= front
.stage
.ispec()
622 eqs
+= front
._connect
_in
(self
)
624 # connect end of chain to ourselves
626 self
.n
.o_data
= end
.stage
.ospec()
627 eqs
+= end
._connect
_out
(self
)
631 def set_input(self
, i
):
632 """ helper function to set the input data
634 return eq(self
.p
.i_data
, i
)
637 res
= [self
.p
.i_valid
, self
.n
.i_ready
,
638 self
.n
.o_valid
, self
.p
.o_ready
,
640 if hasattr(self
.p
.i_data
, "ports"):
641 res
+= self
.p
.i_data
.ports()
644 if hasattr(self
.n
.o_data
, "ports"):
645 res
+= self
.n
.o_data
.ports()
650 def _elaborate(self
, platform
):
651 """ handles case where stage has dynamic ready/valid functions
655 if self
.stage
is not None and hasattr(self
.stage
, "setup"):
656 self
.stage
.setup(m
, self
.p
.i_data
)
658 if not self
.p
.stage_ctl
:
661 # intercept the previous (outgoing) "ready", combine with stage ready
662 m
.d
.comb
+= self
.p
.s_o_ready
.eq(self
.p
._o
_ready
& self
.stage
.d_ready
)
664 # intercept the next (incoming) "ready" and combine it with data valid
665 sdv
= self
.stage
.d_valid(self
.n
.i_ready
)
666 m
.d
.comb
+= self
.n
.d_valid
.eq(self
.n
.i_ready
& sdv
)
671 class BufferedHandshake(ControlBase
):
672 """ buffered pipeline stage. data and strobe signals travel in sync.
673 if ever the input is ready and the output is not, processed data
674 is shunted in a temporary register.
676 Argument: stage. see Stage API above
678 stage-1 p.i_valid >>in stage n.o_valid out>> stage+1
679 stage-1 p.o_ready <<out stage n.i_ready <<in stage+1
680 stage-1 p.i_data >>in stage n.o_data out>> stage+1
686 input data p.i_data is read (only), is processed and goes into an
687 intermediate result store [process()]. this is updated combinatorially.
689 in a non-stall condition, the intermediate result will go into the
690 output (update_output). however if ever there is a stall, it goes
691 into r_data instead [update_buffer()].
693 when the non-stall condition is released, r_data is the first
694 to be transferred to the output [flush_buffer()], and the stall
697 on the next cycle (as long as stall is not raised again) the
698 input may begin to be processed and transferred directly to output.
701 def elaborate(self
, platform
):
702 self
.m
= ControlBase
._elaborate
(self
, platform
)
704 result
= self
.stage
.ospec()
705 r_data
= self
.stage
.ospec()
707 # establish some combinatorial temporaries
708 o_n_validn
= Signal(reset_less
=True)
709 n_i_ready
= Signal(reset_less
=True, name
="n_i_rdy_data")
710 nir_por
= Signal(reset_less
=True)
711 nir_por_n
= Signal(reset_less
=True)
712 p_i_valid
= Signal(reset_less
=True)
713 nir_novn
= Signal(reset_less
=True)
714 nirn_novn
= Signal(reset_less
=True)
715 por_pivn
= Signal(reset_less
=True)
716 npnn
= Signal(reset_less
=True)
717 self
.m
.d
.comb
+= [p_i_valid
.eq(self
.p
.i_valid_test
),
718 o_n_validn
.eq(~self
.n
.o_valid
),
719 n_i_ready
.eq(self
.n
.i_ready_test
),
720 nir_por
.eq(n_i_ready
& self
.p
._o
_ready
),
721 nir_por_n
.eq(n_i_ready
& ~self
.p
._o
_ready
),
722 nir_novn
.eq(n_i_ready | o_n_validn
),
723 nirn_novn
.eq(~n_i_ready
& o_n_validn
),
724 npnn
.eq(nir_por | nirn_novn
),
725 por_pivn
.eq(self
.p
._o
_ready
& ~p_i_valid
)
728 # store result of processing in combinatorial temporary
729 self
.m
.d
.comb
+= eq(result
, self
.stage
.process(self
.p
.i_data
))
731 # if not in stall condition, update the temporary register
732 with self
.m
.If(self
.p
.o_ready
): # not stalled
733 self
.m
.d
.sync
+= eq(r_data
, result
) # update buffer
735 # data pass-through conditions
736 with self
.m
.If(npnn
):
737 self
.m
.d
.sync
+= [self
.n
.o_valid
.eq(p_i_valid
), # valid if p_valid
738 eq(self
.n
.o_data
, result
), # update output
740 # buffer flush conditions (NOTE: can override data passthru conditions)
741 with self
.m
.If(nir_por_n
): # not stalled
742 # Flush the [already processed] buffer to the output port.
743 self
.m
.d
.sync
+= [self
.n
.o_valid
.eq(1), # reg empty
744 eq(self
.n
.o_data
, r_data
), # flush buffer
746 # output ready conditions
747 self
.m
.d
.sync
+= self
.p
._o
_ready
.eq(nir_novn | por_pivn
)
752 class SimpleHandshake(ControlBase
):
753 """ simple handshake control. data and strobe signals travel in sync.
754 implements the protocol used by Wishbone and AXI4.
756 Argument: stage. see Stage API above
758 stage-1 p.i_valid >>in stage n.o_valid out>> stage+1
759 stage-1 p.o_ready <<out stage n.i_ready <<in stage+1
760 stage-1 p.i_data >>in stage n.o_data out>> stage+1
765 Inputs Temporary Output
766 ------- ---------- -----
767 P P N N PiV& ~NiV& N P
794 def elaborate(self
, platform
):
795 self
.m
= m
= ControlBase
._elaborate
(self
, platform
)
798 result
= self
.stage
.ospec()
800 # establish some combinatorial temporaries
801 n_i_ready
= Signal(reset_less
=True, name
="n_i_rdy_data")
802 p_i_valid_p_o_ready
= Signal(reset_less
=True)
803 p_i_valid
= Signal(reset_less
=True)
804 m
.d
.comb
+= [p_i_valid
.eq(self
.p
.i_valid_test
),
805 n_i_ready
.eq(self
.n
.i_ready_test
),
806 p_i_valid_p_o_ready
.eq(p_i_valid
& self
.p
.o_ready
),
809 # store result of processing in combinatorial temporary
810 m
.d
.comb
+= eq(result
, self
.stage
.process(self
.p
.i_data
))
812 # previous valid and ready
813 with m
.If(p_i_valid_p_o_ready
):
814 m
.d
.sync
+= [r_busy
.eq(1), # output valid
815 eq(self
.n
.o_data
, result
), # update output
817 # previous invalid or not ready, however next is accepting
818 with m
.Elif(n_i_ready
):
819 m
.d
.sync
+= [eq(self
.n
.o_data
, result
)]
820 # TODO: could still send data here (if there was any)
821 #m.d.sync += self.n.o_valid.eq(0) # ...so set output invalid
822 m
.d
.sync
+= r_busy
.eq(0) # ...so set output invalid
824 m
.d
.comb
+= self
.n
.o_valid
.eq(r_busy
)
825 # if next is ready, so is previous
826 m
.d
.comb
+= self
.p
._o
_ready
.eq(n_i_ready
)
831 class UnbufferedPipeline(ControlBase
):
832 """ A simple pipeline stage with single-clock synchronisation
833 and two-way valid/ready synchronised signalling.
835 Note that a stall in one stage will result in the entire pipeline
838 Also that unlike BufferedHandshake, the valid/ready signalling does NOT
839 travel synchronously with the data: the valid/ready signalling
840 combines in a *combinatorial* fashion. Therefore, a long pipeline
841 chain will lengthen propagation delays.
843 Argument: stage. see Stage API, above
845 stage-1 p.i_valid >>in stage n.o_valid out>> stage+1
846 stage-1 p.o_ready <<out stage n.i_ready <<in stage+1
847 stage-1 p.i_data >>in stage n.o_data out>> stage+1
855 p.i_data : StageInput, shaped according to ispec
857 p.o_data : StageOutput, shaped according to ospec
859 r_data : input_shape according to ispec
860 A temporary (buffered) copy of a prior (valid) input.
861 This is HELD if the output is not ready. It is updated
863 result: output_shape according to ospec
864 The output of the combinatorial logic. it is updated
865 COMBINATORIALLY (no clock dependence).
897 Note: PoR is *NOT* involved in the above decision-making.
900 def elaborate(self
, platform
):
901 self
.m
= m
= ControlBase
._elaborate
(self
, platform
)
903 data_valid
= Signal() # is data valid or not
904 r_data
= self
.stage
.ospec() # output type
907 p_i_valid
= Signal(reset_less
=True)
908 pv
= Signal(reset_less
=True)
909 m
.d
.comb
+= p_i_valid
.eq(self
.p
.i_valid_test
)
910 m
.d
.comb
+= pv
.eq(self
.p
.i_valid
& self
.p
.o_ready
)
912 m
.d
.comb
+= self
.n
.o_valid
.eq(data_valid
)
913 m
.d
.comb
+= self
.p
._o
_ready
.eq(~data_valid | self
.n
.i_ready_test
)
914 m
.d
.sync
+= data_valid
.eq(p_i_valid | \
915 (~self
.n
.i_ready_test
& data_valid
))
917 m
.d
.sync
+= eq(r_data
, self
.stage
.process(self
.p
.i_data
))
918 m
.d
.comb
+= eq(self
.n
.o_data
, r_data
)
923 class UnbufferedPipeline2(ControlBase
):
924 """ A simple pipeline stage with single-clock synchronisation
925 and two-way valid/ready synchronised signalling.
927 Note that a stall in one stage will result in the entire pipeline
930 Also that unlike BufferedHandshake, the valid/ready signalling does NOT
931 travel synchronously with the data: the valid/ready signalling
932 combines in a *combinatorial* fashion. Therefore, a long pipeline
933 chain will lengthen propagation delays.
935 Argument: stage. see Stage API, above
937 stage-1 p.i_valid >>in stage n.o_valid out>> stage+1
938 stage-1 p.o_ready <<out stage n.i_ready <<in stage+1
939 stage-1 p.i_data >>in stage n.o_data out>> stage+1
944 p.i_data : StageInput, shaped according to ispec
946 p.o_data : StageOutput, shaped according to ospec
948 buf : output_shape according to ospec
949 A temporary (buffered) copy of a valid output
950 This is HELD if the output is not ready. It is updated
954 def elaborate(self
, platform
):
955 self
.m
= m
= ControlBase
._elaborate
(self
, platform
)
957 buf_full
= Signal() # is data valid or not
958 buf
= self
.stage
.ospec() # output type
961 p_i_valid
= Signal(reset_less
=True)
962 m
.d
.comb
+= p_i_valid
.eq(self
.p
.i_valid_test
)
964 m
.d
.comb
+= self
.n
.o_valid
.eq(buf_full | p_i_valid
)
965 m
.d
.comb
+= self
.p
._o
_ready
.eq(~buf_full
)
966 m
.d
.sync
+= buf_full
.eq(~self
.n
.i_ready_test
& self
.n
.o_valid
)
968 odata
= Mux(buf_full
, buf
, self
.stage
.process(self
.p
.i_data
))
969 m
.d
.comb
+= eq(self
.n
.o_data
, odata
)
970 m
.d
.sync
+= eq(buf
, self
.n
.o_data
)
975 class PassThroughStage(StageCls
):
976 """ a pass-through stage which has its input data spec equal to its output,
977 and "passes through" its data from input to output.
979 def __init__(self
, iospecfn
):
980 self
.iospecfn
= iospecfn
981 def ispec(self
): return self
.iospecfn()
982 def ospec(self
): return self
.iospecfn()
983 def process(self
, i
): return i
986 class PassThroughHandshake(ControlBase
):
987 """ A control block that delays by one clock cycle.
990 def elaborate(self
, platform
):
991 self
.m
= m
= ControlBase
._elaborate
(self
, platform
)
994 p_i_valid
= Signal(reset_less
=True)
995 pvr
= Signal(reset_less
=True)
996 m
.d
.comb
+= p_i_valid
.eq(self
.p
.i_valid_test
)
997 m
.d
.comb
+= pvr
.eq(p_i_valid
& self
.p
.o_ready
)
999 m
.d
.comb
+= self
.p
.o_ready
.eq(~self
.n
.o_valid | self
.n
.i_ready_test
)
1000 m
.d
.sync
+= self
.n
.o_valid
.eq(p_i_valid | ~self
.p
.o_ready
)
1002 odata
= Mux(pvr
, self
.stage
.process(self
.p
.i_data
), self
.n
.o_data
)
1003 m
.d
.sync
+= eq(self
.n
.o_data
, odata
)
1008 class RegisterPipeline(UnbufferedPipeline
):
1009 """ A pipeline stage that delays by one clock cycle, creating a
1010 sync'd latch out of o_data and o_valid as an indirect byproduct
1011 of using PassThroughStage
1013 def __init__(self
, iospecfn
):
1014 UnbufferedPipeline
.__init
__(self
, PassThroughStage(iospecfn
))
1017 class FIFOtest(ControlBase
):
1018 """ A test of using a SyncFIFO to see if it will work.
1019 Note: the only things it will accept is a Signal of width "width".
1022 def __init__(self
, iospecfn
, width
, depth
):
1024 self
.iospecfn
= iospecfn
1025 self
.fwidth
= width
# XXX temporary
1027 #stage = PassThroughStage(iospecfn)
1028 ControlBase
.__init
__(self
, stage
=self
)
1030 def ispec(self
): return self
.iospecfn()
1031 def ospec(self
): return Signal(self
.fwidth
, name
="dout")
1032 def process(self
, i
): return i
1034 def elaborate(self
, platform
):
1035 self
.m
= m
= ControlBase
._elaborate
(self
, platform
)
1037 (fwidth
, _
) = self
.p
.i_data
.shape()
1038 fifo
= SyncFIFO(fwidth
, self
.fdepth
)
1039 m
.submodules
.fifo
= fifo
1041 # XXX TODO: would be nice to do these...
1042 ## prev: make the FIFO "look" like a PrevControl...
1044 fp
.i_valid
= fifo
.we
1045 fp
._o
_ready
= fifo
.writable
1046 fp
.i_data
= fifo
.din
1047 m
.d
.comb
+= fp
._connect
_in
(self
.p
, True, fn
=flatten
)
1049 # next: make the FIFO "look" like a NextControl...
1051 fn
.o_valid
= fifo
.readable
1052 fn
.i_ready
= fifo
.re
1053 fn
.o_data
= fifo
.dout
1054 # ... so we can do this!
1055 m
.d
.comb
+= fn
._connect
_out
(self
.n
, fn
=flatten
)
1057 # connect previous rdy/valid/data - do flatten on i_data
1058 #m.d.comb += [fifo.we.eq(self.p.i_valid_test),
1059 # self.p.o_ready.eq(fifo.writable),
1060 # eq(fifo.din, flatten(self.p.i_data)),
1063 # connect next rdy/valid/data - do flatten on o_data
1064 #m.d.comb += [self.n.o_valid.eq(fifo.readable),
1065 # fifo.re.eq(self.n.i_ready_test),
1066 # flatten(self.n.o_data).eq(fifo.dout),
1069 # err... that should be all!