96fb86f3e91a46f0f8f52d57458d3f2e9cbb3b2c
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
, SyncFIFOBuffered
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
175 from queue
import Queue
178 class RecordObject(Record
):
179 def __init__(self
, layout
=None, name
=None):
180 Record
.__init
__(self
, layout
=layout
or [], name
=None)
182 def __setattr__(self
, k
, v
):
183 if k
in dir(Record
) or "fields" not in self
.__dict
__:
184 return object.__setattr
__(self
, k
, v
)
186 if isinstance(v
, Record
):
187 newlayout
= {k
: (k
, v
.layout
)}
189 newlayout
= {k
: (k
, v
.shape())}
190 self
.layout
.fields
.update(newlayout
)
195 """ contains signals that come *from* the previous stage (both in and out)
196 * i_valid: previous stage indicating all incoming data is valid.
197 may be a multi-bit signal, where all bits are required
198 to be asserted to indicate "valid".
199 * o_ready: output to next stage indicating readiness to accept data
200 * i_data : an input - added by the user of this class
203 def __init__(self
, i_width
=1, stage_ctl
=False):
204 self
.stage_ctl
= stage_ctl
205 self
.i_valid
= Signal(i_width
, name
="p_i_valid") # prev >>in self
206 self
._o
_ready
= Signal(name
="p_o_ready") # prev <<out self
207 self
.i_data
= None # XXX MUST BE ADDED BY USER
209 self
.s_o_ready
= Signal(name
="p_s_o_rdy") # prev <<out self
213 """ public-facing API: indicates (externally) that stage is ready
216 return self
.s_o_ready
# set dynamically by stage
217 return self
._o
_ready
# return this when not under dynamic control
219 def _connect_in(self
, prev
, direct
=False, fn
=None):
220 """ internal helper function to connect stage to an input source.
221 do not use to connect stage-to-stage!
223 i_valid
= prev
.i_valid
if direct
else prev
.i_valid_test
224 i_data
= fn(prev
.i_data
) if fn
is not None else prev
.i_data
225 return [self
.i_valid
.eq(i_valid
),
226 prev
.o_ready
.eq(self
.o_ready
),
227 eq(self
.i_data
, i_data
),
231 def i_valid_test(self
):
232 vlen
= len(self
.i_valid
)
234 # multi-bit case: valid only when i_valid is all 1s
235 all1s
= Const(-1, (len(self
.i_valid
), False))
236 i_valid
= (self
.i_valid
== all1s
)
238 # single-bit i_valid case
239 i_valid
= self
.i_valid
241 # when stage indicates not ready, incoming data
242 # must "appear" to be not ready too
244 i_valid
= i_valid
& self
.s_o_ready
250 """ contains the signals that go *to* the next stage (both in and out)
251 * o_valid: output indicating to next stage that data is valid
252 * i_ready: input from next stage indicating that it can accept data
253 * o_data : an output - added by the user of this class
255 def __init__(self
, stage_ctl
=False):
256 self
.stage_ctl
= stage_ctl
257 self
.o_valid
= Signal(name
="n_o_valid") # self out>> next
258 self
.i_ready
= Signal(name
="n_i_ready") # self <<in next
259 self
.o_data
= None # XXX MUST BE ADDED BY USER
261 self
.d_valid
= Signal(reset
=1) # INTERNAL (data valid)
264 def i_ready_test(self
):
266 return self
.i_ready
& self
.d_valid
269 def connect_to_next(self
, nxt
):
270 """ helper function to connect to the next stage data/valid/ready.
271 data/valid is passed *TO* nxt, and ready comes *IN* from nxt.
272 use this when connecting stage-to-stage
274 return [nxt
.i_valid
.eq(self
.o_valid
),
275 self
.i_ready
.eq(nxt
.o_ready
),
276 eq(nxt
.i_data
, self
.o_data
),
279 def _connect_out(self
, nxt
, direct
=False, fn
=None):
280 """ internal helper function to connect stage to an output source.
281 do not use to connect stage-to-stage!
283 i_ready
= nxt
.i_ready
if direct
else nxt
.i_ready_test
284 o_data
= fn(nxt
.o_data
) if fn
is not None else nxt
.o_data
285 return [nxt
.o_valid
.eq(self
.o_valid
),
286 self
.i_ready
.eq(i_ready
),
287 eq(o_data
, self
.o_data
),
292 """ a helper routine which identifies if it is being passed a list
293 (or tuple) of objects, or signals, or Records, and calls
296 the visiting fn is called when an object is identified.
298 Record is a special (unusual, recursive) case, where the input may be
299 specified as a dictionary (which may contain further dictionaries,
300 recursively), where the field names of the dictionary must match
301 the Record's field spec. Alternatively, an object with the same
302 member names as the Record may be assigned: it does not have to
305 ArrayProxy is also special-cased, it's a bit messy: whilst ArrayProxy
306 has an eq function, the object being assigned to it (e.g. a python
307 object) might not. despite the *input* having an eq function,
308 that doesn't help us, because it's the *ArrayProxy* that's being
309 assigned to. so.... we cheat. use the ports() function of the
310 python object, enumerate them, find out the list of Signals that way,
313 def visit(self
, o
, i
, act
):
314 if isinstance(o
, dict):
315 return self
.dict_visit(o
, i
, act
)
318 if not isinstance(o
, Sequence
):
320 for (ao
, ai
) in zip(o
, i
):
321 #print ("visit", fn, ao, ai)
322 if isinstance(ao
, Record
):
323 rres
= self
.record_visit(ao
, ai
, act
)
324 elif isinstance(ao
, ArrayProxy
) and not isinstance(ai
, Value
):
325 rres
= self
.arrayproxy_visit(ao
, ai
, act
)
327 rres
= act
.fn(ao
, ai
)
331 def dict_visit(self
, o
, i
, act
):
333 for (k
, v
) in o
.items():
334 print ("d-eq", v
, i
[k
])
335 res
.append(act
.fn(v
, i
[k
]))
338 def record_visit(self
, ao
, ai
, act
):
340 for idx
, (field_name
, field_shape
, _
) in enumerate(ao
.layout
):
341 if isinstance(field_shape
, Layout
):
345 if hasattr(val
, field_name
): # check for attribute
346 val
= getattr(val
, field_name
)
348 val
= val
[field_name
] # dictionary-style specification
349 val
= self
.visit(ao
.fields
[field_name
], val
, act
)
350 if isinstance(val
, Sequence
):
356 def arrayproxy_visit(self
, ao
, ai
, act
):
359 op
= getattr(ao
, p
.name
)
360 #print (op, p, p.name)
361 res
.append(fn(op
, p
))
372 if not isinstance(rres
, Sequence
):
375 def __call__(self
, o
, i
):
376 return self
.visit(o
, i
, self
)
380 """ makes signals equal: a helper routine which identifies if it is being
381 passed a list (or tuple) of objects, or signals, or Records, and calls
382 the objects' eq function.
388 """ flattens a compound structure recursively using Cat
390 if not isinstance(i
, Sequence
):
394 print ("flatten", ai
)
395 if isinstance(ai
, Record
):
396 print ("record", list(ai
.layout
))
398 for idx
, (field_name
, field_shape
, _
) in enumerate(ai
.layout
):
399 if isinstance(field_shape
, Layout
):
403 if hasattr(val
, field_name
): # check for attribute
404 val
= getattr(val
, field_name
)
406 val
= val
[field_name
] # dictionary-style specification
407 print ("recidx", idx
, field_name
, field_shape
, val
)
409 print ("recidx flat", idx
, val
)
410 if isinstance(val
, Sequence
):
415 elif isinstance(ai
, ArrayProxy
) and not isinstance(ai
, Value
):
418 op
= getattr(ai
, p
.name
)
419 #print (op, p, p.name)
420 rres
.append(flatten(p
))
423 if not isinstance(rres
, Sequence
):
426 print ("flatten res", res
)
431 class StageCls(metaclass
=ABCMeta
):
432 """ Class-based "Stage" API. requires instantiation (after derivation)
434 see "Stage API" above.. Note: python does *not* require derivation
435 from this class. All that is required is that the pipelines *have*
436 the functions listed in this class. Derivation from this class
437 is therefore merely a "courtesy" to maintainers.
440 def ispec(self
): pass # REQUIRED
442 def ospec(self
): pass # REQUIRED
444 #def setup(self, m, i): pass # OPTIONAL
446 def process(self
, i
): pass # REQUIRED
449 class Stage(metaclass
=ABCMeta
):
450 """ Static "Stage" API. does not require instantiation (after derivation)
452 see "Stage API" above. Note: python does *not* require derivation
453 from this class. All that is required is that the pipelines *have*
454 the functions listed in this class. Derivation from this class
455 is therefore merely a "courtesy" to maintainers.
467 #def setup(m, i): pass
474 class RecordBasedStage(Stage
):
475 """ convenience class which provides a Records-based layout.
476 honestly it's a lot easier just to create a direct Records-based
477 class (see ExampleAddRecordStage)
479 def __init__(self
, in_shape
, out_shape
, processfn
, setupfn
=None):
480 self
.in_shape
= in_shape
481 self
.out_shape
= out_shape
482 self
.__process
= processfn
483 self
.__setup
= setupfn
484 def ispec(self
): return Record(self
.in_shape
)
485 def ospec(self
): return Record(self
.out_shape
)
486 def process(seif
, i
): return self
.__process
(i
)
487 def setup(seif
, m
, i
): return self
.__setup
(m
, i
)
490 class StageChain(StageCls
):
491 """ pass in a list of stages, and they will automatically be
492 chained together via their input and output specs into a
495 the end result basically conforms to the exact same Stage API.
497 * input to this class will be the input of the first stage
498 * output of first stage goes into input of second
499 * output of second goes into input into third (etc. etc.)
500 * the output of this class will be the output of the last stage
502 def __init__(self
, chain
, specallocate
=False):
504 self
.specallocate
= specallocate
507 return self
.chain
[0].ispec()
510 return self
.chain
[-1].ospec()
512 def _specallocate_setup(self
, m
, i
):
513 for (idx
, c
) in enumerate(self
.chain
):
514 if hasattr(c
, "setup"):
515 c
.setup(m
, i
) # stage may have some module stuff
516 o
= self
.chain
[idx
].ospec() # last assignment survives
517 m
.d
.comb
+= eq(o
, c
.process(i
)) # process input into "o"
518 if idx
== len(self
.chain
)-1:
520 i
= self
.chain
[idx
+1].ispec() # new input on next loop
521 m
.d
.comb
+= eq(i
, o
) # assign to next input
522 return o
# last loop is the output
524 def _noallocate_setup(self
, m
, i
):
525 for (idx
, c
) in enumerate(self
.chain
):
526 if hasattr(c
, "setup"):
527 c
.setup(m
, i
) # stage may have some module stuff
528 i
= o
= c
.process(i
) # store input into "o"
529 return o
# last loop is the output
531 def setup(self
, m
, i
):
532 if self
.specallocate
:
533 self
.o
= self
._specallocate
_setup
(m
, i
)
535 self
.o
= self
._noallocate
_setup
(m
, i
)
537 def process(self
, i
):
538 return self
.o
# conform to Stage API: return last-loop output
542 """ Common functions for Pipeline API
544 def __init__(self
, stage
=None, in_multi
=None, stage_ctl
=False):
545 """ Base class containing ready/valid/data to previous and next stages
547 * p: contains ready/valid to the previous stage
548 * n: contains ready/valid to the next stage
550 Except when calling Controlbase.connect(), user must also:
551 * add i_data member to PrevControl (p) and
552 * add o_data member to NextControl (n)
556 # set up input and output IO ACK (prev/next ready/valid)
557 self
.p
= PrevControl(in_multi
, stage_ctl
)
558 self
.n
= NextControl(stage_ctl
)
560 # set up the input and output data
561 if stage
is not None:
562 self
.p
.i_data
= stage
.ispec() # input type
563 self
.n
.o_data
= stage
.ospec()
565 def connect_to_next(self
, nxt
):
566 """ helper function to connect to the next stage data/valid/ready.
568 return self
.n
.connect_to_next(nxt
.p
)
570 def _connect_in(self
, prev
):
571 """ internal helper function to connect stage to an input source.
572 do not use to connect stage-to-stage!
574 return self
.p
._connect
_in
(prev
.p
)
576 def _connect_out(self
, nxt
):
577 """ internal helper function to connect stage to an output source.
578 do not use to connect stage-to-stage!
580 return self
.n
._connect
_out
(nxt
.n
)
582 def connect(self
, pipechain
):
583 """ connects a chain (list) of Pipeline instances together and
584 links them to this ControlBase instance:
586 in <----> self <---> out
589 [pipe1, pipe2, pipe3, pipe4]
592 out---in out--in out---in
594 Also takes care of allocating i_data/o_data, by looking up
595 the data spec for each end of the pipechain. i.e It is NOT
596 necessary to allocate self.p.i_data or self.n.o_data manually:
597 this is handled AUTOMATICALLY, here.
599 Basically this function is the direct equivalent of StageChain,
600 except that unlike StageChain, the Pipeline logic is followed.
602 Just as StageChain presents an object that conforms to the
603 Stage API from a list of objects that also conform to the
604 Stage API, an object that calls this Pipeline connect function
605 has the exact same pipeline API as the list of pipline objects
608 Thus it becomes possible to build up larger chains recursively.
609 More complex chains (multi-input, multi-output) will have to be
612 eqs
= [] # collated list of assignment statements
614 # connect inter-chain
615 for i
in range(len(pipechain
)-1):
617 pipe2
= pipechain
[i
+1]
618 eqs
+= pipe1
.connect_to_next(pipe2
)
620 # connect front of chain to ourselves
622 self
.p
.i_data
= front
.stage
.ispec()
623 eqs
+= front
._connect
_in
(self
)
625 # connect end of chain to ourselves
627 self
.n
.o_data
= end
.stage
.ospec()
628 eqs
+= end
._connect
_out
(self
)
632 def _postprocess(self
, i
):
633 if hasattr(self
.stage
, "postprocess"):
634 return self
.stage
.postprocess(i
)
637 def set_input(self
, i
):
638 """ helper function to set the input data
640 return eq(self
.p
.i_data
, i
)
643 res
= [self
.p
.i_valid
, self
.n
.i_ready
,
644 self
.n
.o_valid
, self
.p
.o_ready
,
646 if hasattr(self
.p
.i_data
, "ports"):
647 res
+= self
.p
.i_data
.ports()
650 if hasattr(self
.n
.o_data
, "ports"):
651 res
+= self
.n
.o_data
.ports()
656 def _elaborate(self
, platform
):
657 """ handles case where stage has dynamic ready/valid functions
661 if self
.stage
is not None and hasattr(self
.stage
, "setup"):
662 self
.stage
.setup(m
, self
.p
.i_data
)
664 if not self
.p
.stage_ctl
:
667 # intercept the previous (outgoing) "ready", combine with stage ready
668 m
.d
.comb
+= self
.p
.s_o_ready
.eq(self
.p
._o
_ready
& self
.stage
.d_ready
)
670 # intercept the next (incoming) "ready" and combine it with data valid
671 sdv
= self
.stage
.d_valid(self
.n
.i_ready
)
672 m
.d
.comb
+= self
.n
.d_valid
.eq(self
.n
.i_ready
& sdv
)
677 class BufferedHandshake(ControlBase
):
678 """ buffered pipeline stage. data and strobe signals travel in sync.
679 if ever the input is ready and the output is not, processed data
680 is shunted in a temporary register.
682 Argument: stage. see Stage API above
684 stage-1 p.i_valid >>in stage n.o_valid out>> stage+1
685 stage-1 p.o_ready <<out stage n.i_ready <<in stage+1
686 stage-1 p.i_data >>in stage n.o_data out>> stage+1
692 input data p.i_data is read (only), is processed and goes into an
693 intermediate result store [process()]. this is updated combinatorially.
695 in a non-stall condition, the intermediate result will go into the
696 output (update_output). however if ever there is a stall, it goes
697 into r_data instead [update_buffer()].
699 when the non-stall condition is released, r_data is the first
700 to be transferred to the output [flush_buffer()], and the stall
703 on the next cycle (as long as stall is not raised again) the
704 input may begin to be processed and transferred directly to output.
707 def elaborate(self
, platform
):
708 self
.m
= ControlBase
._elaborate
(self
, platform
)
710 result
= self
.stage
.ospec()
711 r_data
= self
.stage
.ospec()
713 # establish some combinatorial temporaries
714 o_n_validn
= Signal(reset_less
=True)
715 n_i_ready
= Signal(reset_less
=True, name
="n_i_rdy_data")
716 nir_por
= Signal(reset_less
=True)
717 nir_por_n
= Signal(reset_less
=True)
718 p_i_valid
= Signal(reset_less
=True)
719 nir_novn
= Signal(reset_less
=True)
720 nirn_novn
= Signal(reset_less
=True)
721 por_pivn
= Signal(reset_less
=True)
722 npnn
= Signal(reset_less
=True)
723 self
.m
.d
.comb
+= [p_i_valid
.eq(self
.p
.i_valid_test
),
724 o_n_validn
.eq(~self
.n
.o_valid
),
725 n_i_ready
.eq(self
.n
.i_ready_test
),
726 nir_por
.eq(n_i_ready
& self
.p
._o
_ready
),
727 nir_por_n
.eq(n_i_ready
& ~self
.p
._o
_ready
),
728 nir_novn
.eq(n_i_ready | o_n_validn
),
729 nirn_novn
.eq(~n_i_ready
& o_n_validn
),
730 npnn
.eq(nir_por | nirn_novn
),
731 por_pivn
.eq(self
.p
._o
_ready
& ~p_i_valid
)
734 # store result of processing in combinatorial temporary
735 self
.m
.d
.comb
+= eq(result
, self
.stage
.process(self
.p
.i_data
))
737 # if not in stall condition, update the temporary register
738 with self
.m
.If(self
.p
.o_ready
): # not stalled
739 self
.m
.d
.sync
+= eq(r_data
, result
) # update buffer
741 # data pass-through conditions
742 with self
.m
.If(npnn
):
743 o_data
= self
._postprocess
(result
)
744 self
.m
.d
.sync
+= [self
.n
.o_valid
.eq(p_i_valid
), # valid if p_valid
745 eq(self
.n
.o_data
, o_data
), # update output
747 # buffer flush conditions (NOTE: can override data passthru conditions)
748 with self
.m
.If(nir_por_n
): # not stalled
749 # Flush the [already processed] buffer to the output port.
750 o_data
= self
._postprocess
(r_data
)
751 self
.m
.d
.sync
+= [self
.n
.o_valid
.eq(1), # reg empty
752 eq(self
.n
.o_data
, o_data
), # flush buffer
754 # output ready conditions
755 self
.m
.d
.sync
+= self
.p
._o
_ready
.eq(nir_novn | por_pivn
)
760 class SimpleHandshake(ControlBase
):
761 """ simple handshake control. data and strobe signals travel in sync.
762 implements the protocol used by Wishbone and AXI4.
764 Argument: stage. see Stage API above
766 stage-1 p.i_valid >>in stage n.o_valid out>> stage+1
767 stage-1 p.o_ready <<out stage n.i_ready <<in stage+1
768 stage-1 p.i_data >>in stage n.o_data out>> stage+1
773 Inputs Temporary Output Data
774 ------- ---------- ----- ----
775 P P N N PiV& ~NiR& N P
782 0 0 1 0 0 0 0 1 process(i_data)
783 0 0 1 1 0 0 0 1 process(i_data)
787 0 1 1 0 0 0 0 1 process(i_data)
788 0 1 1 1 0 0 0 1 process(i_data)
792 1 0 1 0 0 0 0 1 process(i_data)
793 1 0 1 1 0 0 0 1 process(i_data)
795 1 1 0 0 1 0 1 0 process(i_data)
796 1 1 0 1 1 1 1 0 process(i_data)
797 1 1 1 0 1 0 1 1 process(i_data)
798 1 1 1 1 1 0 1 1 process(i_data)
802 def elaborate(self
, platform
):
803 self
.m
= m
= ControlBase
._elaborate
(self
, platform
)
806 result
= self
.stage
.ospec()
808 # establish some combinatorial temporaries
809 n_i_ready
= Signal(reset_less
=True, name
="n_i_rdy_data")
810 p_i_valid_p_o_ready
= Signal(reset_less
=True)
811 p_i_valid
= Signal(reset_less
=True)
812 m
.d
.comb
+= [p_i_valid
.eq(self
.p
.i_valid_test
),
813 n_i_ready
.eq(self
.n
.i_ready_test
),
814 p_i_valid_p_o_ready
.eq(p_i_valid
& self
.p
.o_ready
),
817 # store result of processing in combinatorial temporary
818 m
.d
.comb
+= eq(result
, self
.stage
.process(self
.p
.i_data
))
820 # previous valid and ready
821 with m
.If(p_i_valid_p_o_ready
):
822 o_data
= self
._postprocess
(result
)
823 m
.d
.sync
+= [r_busy
.eq(1), # output valid
824 eq(self
.n
.o_data
, o_data
), # update output
826 # previous invalid or not ready, however next is accepting
827 with m
.Elif(n_i_ready
):
828 o_data
= self
._postprocess
(result
)
829 m
.d
.sync
+= [eq(self
.n
.o_data
, o_data
)]
830 # TODO: could still send data here (if there was any)
831 #m.d.sync += self.n.o_valid.eq(0) # ...so set output invalid
832 m
.d
.sync
+= r_busy
.eq(0) # ...so set output invalid
834 m
.d
.comb
+= self
.n
.o_valid
.eq(r_busy
)
835 # if next is ready, so is previous
836 m
.d
.comb
+= self
.p
._o
_ready
.eq(n_i_ready
)
841 class UnbufferedPipeline(ControlBase
):
842 """ A simple pipeline stage with single-clock synchronisation
843 and two-way valid/ready synchronised signalling.
845 Note that a stall in one stage will result in the entire pipeline
848 Also that unlike BufferedHandshake, the valid/ready signalling does NOT
849 travel synchronously with the data: the valid/ready signalling
850 combines in a *combinatorial* fashion. Therefore, a long pipeline
851 chain will lengthen propagation delays.
853 Argument: stage. see Stage API, above
855 stage-1 p.i_valid >>in stage n.o_valid out>> stage+1
856 stage-1 p.o_ready <<out stage n.i_ready <<in stage+1
857 stage-1 p.i_data >>in stage n.o_data out>> stage+1
865 p.i_data : StageInput, shaped according to ispec
867 p.o_data : StageOutput, shaped according to ospec
869 r_data : input_shape according to ispec
870 A temporary (buffered) copy of a prior (valid) input.
871 This is HELD if the output is not ready. It is updated
873 result: output_shape according to ospec
874 The output of the combinatorial logic. it is updated
875 COMBINATORIALLY (no clock dependence).
879 Inputs Temp Output Data
901 1 1 0 0 0 1 1 process(i_data)
902 1 1 0 1 1 1 0 process(i_data)
903 1 1 1 0 0 1 1 process(i_data)
904 1 1 1 1 0 1 1 process(i_data)
907 Note: PoR is *NOT* involved in the above decision-making.
910 def elaborate(self
, platform
):
911 self
.m
= m
= ControlBase
._elaborate
(self
, platform
)
913 data_valid
= Signal() # is data valid or not
914 r_data
= self
.stage
.ospec() # output type
917 p_i_valid
= Signal(reset_less
=True)
918 pv
= Signal(reset_less
=True)
919 buf_full
= Signal(reset_less
=True)
920 m
.d
.comb
+= p_i_valid
.eq(self
.p
.i_valid_test
)
921 m
.d
.comb
+= pv
.eq(self
.p
.i_valid
& self
.p
.o_ready
)
922 m
.d
.comb
+= buf_full
.eq(~self
.n
.i_ready_test
& data_valid
)
924 m
.d
.comb
+= self
.n
.o_valid
.eq(data_valid
)
925 m
.d
.comb
+= self
.p
._o
_ready
.eq(~data_valid | self
.n
.i_ready_test
)
926 m
.d
.sync
+= data_valid
.eq(p_i_valid | buf_full
)
929 m
.d
.sync
+= eq(r_data
, self
.stage
.process(self
.p
.i_data
))
930 o_data
= self
._postprocess
(r_data
)
931 m
.d
.comb
+= eq(self
.n
.o_data
, o_data
)
936 class UnbufferedPipeline2(ControlBase
):
937 """ A simple pipeline stage with single-clock synchronisation
938 and two-way valid/ready synchronised signalling.
940 Note that a stall in one stage will result in the entire pipeline
943 Also that unlike BufferedHandshake, the valid/ready signalling does NOT
944 travel synchronously with the data: the valid/ready signalling
945 combines in a *combinatorial* fashion. Therefore, a long pipeline
946 chain will lengthen propagation delays.
948 Argument: stage. see Stage API, above
950 stage-1 p.i_valid >>in stage n.o_valid out>> stage+1
951 stage-1 p.o_ready <<out stage n.i_ready <<in stage+1
952 stage-1 p.i_data >>in stage n.o_data out>> stage+1
957 p.i_data : StageInput, shaped according to ispec
959 p.o_data : StageOutput, shaped according to ospec
961 buf : output_shape according to ospec
962 A temporary (buffered) copy of a valid output
963 This is HELD if the output is not ready. It is updated
966 Inputs Temp Output Data
968 P P N N ~NiR& N P (buf_full)
973 0 0 0 0 0 0 1 process(i_data)
974 0 0 0 1 1 1 0 reg (odata, unchanged)
975 0 0 1 0 0 0 1 process(i_data)
976 0 0 1 1 0 0 1 process(i_data)
978 0 1 0 0 0 0 1 process(i_data)
979 0 1 0 1 1 1 0 reg (odata, unchanged)
980 0 1 1 0 0 0 1 process(i_data)
981 0 1 1 1 0 0 1 process(i_data)
983 1 0 0 0 0 1 1 process(i_data)
984 1 0 0 1 1 1 0 reg (odata, unchanged)
985 1 0 1 0 0 1 1 process(i_data)
986 1 0 1 1 0 1 1 process(i_data)
988 1 1 0 0 0 1 1 process(i_data)
989 1 1 0 1 1 1 0 reg (odata, unchanged)
990 1 1 1 0 0 1 1 process(i_data)
991 1 1 1 1 0 1 1 process(i_data)
994 Note: PoR is *NOT* involved in the above decision-making.
997 def elaborate(self
, platform
):
998 self
.m
= m
= ControlBase
._elaborate
(self
, platform
)
1000 buf_full
= Signal() # is data valid or not
1001 buf
= self
.stage
.ospec() # output type
1004 p_i_valid
= Signal(reset_less
=True)
1005 m
.d
.comb
+= p_i_valid
.eq(self
.p
.i_valid_test
)
1007 m
.d
.comb
+= self
.n
.o_valid
.eq(buf_full | p_i_valid
)
1008 m
.d
.comb
+= self
.p
._o
_ready
.eq(~buf_full
)
1009 m
.d
.sync
+= buf_full
.eq(~self
.n
.i_ready_test
& self
.n
.o_valid
)
1011 o_data
= Mux(buf_full
, buf
, self
.stage
.process(self
.p
.i_data
))
1012 if hasattr(self
.stage
, "postprocess"):
1013 o_data
= self
.stage
.postprocess(o_data
)
1014 m
.d
.comb
+= eq(self
.n
.o_data
, o_data
)
1015 m
.d
.sync
+= eq(buf
, self
.n
.o_data
)
1020 class PassThroughStage(StageCls
):
1021 """ a pass-through stage which has its input data spec equal to its output,
1022 and "passes through" its data from input to output.
1024 def __init__(self
, iospecfn
):
1025 self
.iospecfn
= iospecfn
1026 def ispec(self
): return self
.iospecfn()
1027 def ospec(self
): return self
.iospecfn()
1028 def process(self
, i
): return i
1031 class PassThroughHandshake(ControlBase
):
1032 """ A control block that delays by one clock cycle.
1034 Inputs Temporary Output Data
1035 ------- ------------------ ----- ----
1036 P P N N PiV& PiV| NiR| pvr N P (pvr)
1037 i o i o PoR ~PoR ~NoV o o
1041 0 0 0 0 0 1 1 0 1 1 odata (unchanged)
1042 0 0 0 1 0 1 0 0 1 0 odata (unchanged)
1043 0 0 1 0 0 1 1 0 1 1 odata (unchanged)
1044 0 0 1 1 0 1 1 0 1 1 odata (unchanged)
1046 0 1 0 0 0 0 1 0 0 1 odata (unchanged)
1047 0 1 0 1 0 0 0 0 0 0 odata (unchanged)
1048 0 1 1 0 0 0 1 0 0 1 odata (unchanged)
1049 0 1 1 1 0 0 1 0 0 1 odata (unchanged)
1051 1 0 0 0 0 1 1 1 1 1 process(in)
1052 1 0 0 1 0 1 0 0 1 0 odata (unchanged)
1053 1 0 1 0 0 1 1 1 1 1 process(in)
1054 1 0 1 1 0 1 1 1 1 1 process(in)
1056 1 1 0 0 1 1 1 1 1 1 process(in)
1057 1 1 0 1 1 1 0 0 1 0 odata (unchanged)
1058 1 1 1 0 1 1 1 1 1 1 process(in)
1059 1 1 1 1 1 1 1 1 1 1 process(in)
1064 def elaborate(self
, platform
):
1065 self
.m
= m
= ControlBase
._elaborate
(self
, platform
)
1067 r_data
= self
.stage
.ospec() # output type
1070 p_i_valid
= Signal(reset_less
=True)
1071 pvr
= Signal(reset_less
=True)
1072 m
.d
.comb
+= p_i_valid
.eq(self
.p
.i_valid_test
)
1073 m
.d
.comb
+= pvr
.eq(p_i_valid
& self
.p
.o_ready
)
1075 m
.d
.comb
+= self
.p
.o_ready
.eq(~self
.n
.o_valid | self
.n
.i_ready_test
)
1076 m
.d
.sync
+= self
.n
.o_valid
.eq(p_i_valid | ~self
.p
.o_ready
)
1078 odata
= Mux(pvr
, self
.stage
.process(self
.p
.i_data
), r_data
)
1079 m
.d
.sync
+= eq(r_data
, odata
)
1080 if hasattr(self
.stage
, "postprocess"):
1081 r_data
= self
.stage
.postprocess(r_data
)
1082 m
.d
.comb
+= eq(self
.n
.o_data
, r_data
)
1087 class RegisterPipeline(UnbufferedPipeline
):
1088 """ A pipeline stage that delays by one clock cycle, creating a
1089 sync'd latch out of o_data and o_valid as an indirect byproduct
1090 of using PassThroughStage
1092 def __init__(self
, iospecfn
):
1093 UnbufferedPipeline
.__init
__(self
, PassThroughStage(iospecfn
))
1096 class FIFOControl(ControlBase
):
1097 """ FIFO Control. Uses SyncFIFO to store data, coincidentally
1098 happens to have same valid/ready signalling as Stage API.
1100 i_data -> fifo.din -> FIFO -> fifo.dout -> o_data
1103 def __init__(self
, depth
, stage
, in_multi
=None, stage_ctl
=False,
1104 fwft
=True, buffered
=False):
1107 * depth: number of entries in the FIFO
1108 * stage: data processing block
1109 * fwft : first word fall-thru mode (non-fwft introduces delay)
1110 * buffered: use buffered FIFO (introduces extra cycle delay)
1112 NOTE 1: FPGAs may have trouble with the defaults for SyncFIFO
1113 (fwft=True, buffered=False)
1115 NOTE 2: i_data *must* have a shape function. it can therefore
1116 be a Signal, or a Record, or a RecordObject.
1118 data is processed (and located) as follows:
1120 self.p self.stage temp fn temp fn temp fp self.n
1121 i_data->process()->result->flatten->din.FIFO.dout->flatten(o_data)
1123 yes, really: flatten produces a Cat() which can be assigned to.
1124 this is how the FIFO gets de-flattened without needing a de-flatten
1128 assert not (fwft
and buffered
), "buffered cannot do fwft"
1132 self
.buffered
= buffered
1134 ControlBase
.__init
__(self
, stage
, in_multi
, stage_ctl
)
1136 def elaborate(self
, platform
):
1137 self
.m
= m
= ControlBase
._elaborate
(self
, platform
)
1139 # make a FIFO with a signal of equal width to the o_data.
1140 (fwidth
, _
) = self
.n
.o_data
.shape()
1142 fifo
= SyncFIFOBuffered(fwidth
, self
.fdepth
)
1144 fifo
= Queue(fwidth
, self
.fdepth
, fwft
=self
.fwft
)
1145 m
.submodules
.fifo
= fifo
1147 # store result of processing in combinatorial temporary
1148 result
= self
.stage
.ospec()
1149 m
.d
.comb
+= eq(result
, self
.stage
.process(self
.p
.i_data
))
1151 # connect previous rdy/valid/data - do flatten on i_data
1152 # NOTE: cannot do the PrevControl-looking trick because
1153 # of need to process the data. shaaaame....
1154 m
.d
.comb
+= [fifo
.we
.eq(self
.p
.i_valid_test
),
1155 self
.p
.o_ready
.eq(fifo
.writable
),
1156 eq(fifo
.din
, flatten(result
)),
1159 # connect next rdy/valid/data - do flatten on o_data
1160 connections
= [self
.n
.o_valid
.eq(fifo
.readable
),
1161 fifo
.re
.eq(self
.n
.i_ready_test
),
1163 if self
.fwft
or self
.buffered
:
1164 m
.d
.comb
+= connections
1166 m
.d
.sync
+= connections
# unbuffered fwft mode needs sync
1167 o_data
= flatten(self
.n
.o_data
).eq(fifo
.dout
)
1168 if hasattr(self
.stage
, "postprocess"):
1169 o_data
= self
.stage
.postprocess(o_data
)
1175 class BufferedHandshake(FIFOControl):
1176 def __init__(self, stage, in_multi=None, stage_ctl=False):
1177 FIFOControl.__init__(self, 2, stage, in_multi, stage_ctl,
1178 fwft=True, buffered=False)