1 """ Pipeline API. For multi-input and multi-output variants, see multipipe.
3 Associated development bugs:
4 * http://bugs.libre-riscv.org/show_bug.cgi?id=64
5 * http://bugs.libre-riscv.org/show_bug.cgi?id=57
7 Important: see Stage API (stageapi.py) in combination with below
12 A convenience class that takes an input shape, output shape, a
13 "processing" function and an optional "setup" function. Honestly
14 though, there's not much more effort to just... create a class
15 that returns a couple of Records (see ExampleAddRecordStage in
21 A convenience class that takes a single function as a parameter,
22 that is chain-called to create the exact same input and output spec.
23 It has a process() function that simply returns its input.
25 Instances of this class are completely redundant if handed to
26 StageChain, however when passed to UnbufferedPipeline they
27 can be used to introduce a single clock delay.
32 The base class for pipelines. Contains previous and next ready/valid/data.
33 Also has an extremely useful "connect" function that can be used to
34 connect a chain of pipelines and present the exact same prev/next
37 Note: pipelines basically do not become pipelines as such until
38 handed to a derivative of ControlBase. ControlBase itself is *not*
39 strictly considered a pipeline class. Wishbone and AXI4 (master or
40 slave) could be derived from ControlBase, for example.
44 A simple stalling clock-synchronised pipeline that has no buffering
45 (unlike BufferedHandshake). Data flows on *every* clock cycle when
46 the conditions are right (this is nominally when the input is valid
47 and the output is ready).
49 A stall anywhere along the line will result in a stall back-propagating
50 down the entire chain. The BufferedHandshake by contrast will buffer
51 incoming data, allowing previous stages one clock cycle's grace before
54 An advantage of the UnbufferedPipeline over the Buffered one is
55 that the amount of logic needed (number of gates) is greatly
56 reduced (no second set of buffers basically)
58 The disadvantage of the UnbufferedPipeline is that the valid/ready
59 logic, if chained together, is *combinatorial*, resulting in
60 progressively larger gate delay.
65 A Control class that introduces a single clock delay, passing its
66 data through unaltered. Unlike RegisterPipeline (which relies
67 on UnbufferedPipeline and PassThroughStage) it handles ready/valid
73 A convenience class that, because UnbufferedPipeline introduces a single
74 clock delay, when its stage is a PassThroughStage, it results in a Pipeline
75 stage that, duh, delays its (unmodified) input by one clock cycle.
80 nmigen implementation of buffered pipeline stage, based on zipcpu:
81 https://zipcpu.com/blog/2017/08/14/strategies-for-pipelining.html
83 this module requires quite a bit of thought to understand how it works
84 (and why it is needed in the first place). reading the above is
85 *strongly* recommended.
87 unlike john dawson's IEEE754 FPU STB/ACK signalling, which requires
88 the STB / ACK signals to raise and lower (on separate clocks) before
89 data may proceeed (thus only allowing one piece of data to proceed
90 on *ALTERNATE* cycles), the signalling here is a true pipeline
91 where data will flow on *every* clock when the conditions are right.
93 input acceptance conditions are when:
94 * incoming previous-stage strobe (p.valid_i) is HIGH
95 * outgoing previous-stage ready (p.ready_o) is LOW
97 output transmission conditions are when:
98 * outgoing next-stage strobe (n.valid_o) is HIGH
99 * outgoing next-stage ready (n.ready_i) is LOW
101 the tricky bit is when the input has valid data and the output is not
102 ready to accept it. if it wasn't for the clock synchronisation, it
103 would be possible to tell the input "hey don't send that data, we're
104 not ready". unfortunately, it's not possible to "change the past":
105 the previous stage *has no choice* but to pass on its data.
107 therefore, the incoming data *must* be accepted - and stored: that
108 is the responsibility / contract that this stage *must* accept.
109 on the same clock, it's possible to tell the input that it must
110 not send any more data. this is the "stall" condition.
112 we now effectively have *two* possible pieces of data to "choose" from:
113 the buffered data, and the incoming data. the decision as to which
114 to process and output is based on whether we are in "stall" or not.
115 i.e. when the next stage is no longer ready, the output comes from
116 the buffer if a stall had previously occurred, otherwise it comes
117 direct from processing the input.
119 this allows us to respect a synchronous "travelling STB" with what
120 dan calls a "buffered handshake".
122 it's quite a complex state machine!
127 Synchronised pipeline, Based on:
128 https://github.com/ZipCPU/dbgbus/blob/master/hexbus/rtl/hbdeword.v
131 from nmigen
import Signal
, Mux
, Module
, Elaboratable
, Const
132 from nmigen
.cli
import verilog
, rtlil
133 from nmigen
.hdl
.rec
import Record
135 from nmutil
.queue
import Queue
138 from nmutil
.iocontrol
import (PrevControl
, NextControl
, Object
, RecordObject
)
139 from nmutil
.stageapi
import (_spec
, StageCls
, Stage
, StageChain
, StageHelper
)
140 from nmutil
import nmoperator
143 class RecordBasedStage(Stage
):
144 """ convenience class which provides a Records-based layout.
145 honestly it's a lot easier just to create a direct Records-based
146 class (see ExampleAddRecordStage)
148 def __init__(self
, in_shape
, out_shape
, processfn
, setupfn
=None):
149 self
.in_shape
= in_shape
150 self
.out_shape
= out_shape
151 self
.__process
= processfn
152 self
.__setup
= setupfn
153 def ispec(self
): return Record(self
.in_shape
)
154 def ospec(self
): return Record(self
.out_shape
)
155 def process(seif
, i
): return self
.__process
(i
)
156 def setup(seif
, m
, i
): return self
.__setup
(m
, i
)
159 class PassThroughStage(StageCls
):
160 """ a pass-through stage with its input data spec identical to its output,
161 and "passes through" its data from input to output (does nothing).
163 use this basically to explicitly make any data spec Stage-compliant.
164 (many APIs would potentially use a static "wrap" method in e.g.
165 StageCls to achieve a similar effect)
167 def __init__(self
, iospecfn
): self
.iospecfn
= iospecfn
168 def ispec(self
): return self
.iospecfn()
169 def ospec(self
): return self
.iospecfn()
172 class ControlBase(StageHelper
, Elaboratable
):
173 """ Common functions for Pipeline API. Note: a "pipeline stage" only
174 exists (conceptually) when a ControlBase derivative is handed
175 a Stage (combinatorial block)
177 NOTE: ControlBase derives from StageHelper, making it accidentally
178 compliant with the Stage API. Using those functions directly
179 *BYPASSES* a ControlBase instance ready/valid signalling, which
180 clearly should not be done without a really, really good reason.
182 def __init__(self
, stage
=None, in_multi
=None, stage_ctl
=False, maskwid
=0):
183 """ Base class containing ready/valid/data to previous and next stages
185 * p: contains ready/valid to the previous stage
186 * n: contains ready/valid to the next stage
188 Except when calling Controlbase.connect(), user must also:
189 * add data_i member to PrevControl (p) and
190 * add data_o member to NextControl (n)
191 Calling ControlBase._new_data is a good way to do that.
193 print ("ControlBase", self
, stage
, in_multi
, stage_ctl
)
194 StageHelper
.__init
__(self
, stage
)
196 # set up input and output IO ACK (prev/next ready/valid)
197 self
.p
= PrevControl(in_multi
, stage_ctl
, maskwid
=maskwid
)
198 self
.n
= NextControl(stage_ctl
, maskwid
=maskwid
)
200 # set up the input and output data
201 if stage
is not None:
202 self
._new
_data
("data")
204 def _new_data(self
, name
):
205 """ allocates new data_i and data_o
207 self
.p
.data_i
, self
.n
.data_o
= self
.new_specs(name
)
211 return self
.process(self
.p
.data_i
)
213 def connect_to_next(self
, nxt
):
214 """ helper function to connect to the next stage data/valid/ready.
216 return self
.n
.connect_to_next(nxt
.p
)
218 def _connect_in(self
, prev
):
219 """ internal helper function to connect stage to an input source.
220 do not use to connect stage-to-stage!
222 return self
.p
._connect
_in
(prev
.p
)
224 def _connect_out(self
, nxt
):
225 """ internal helper function to connect stage to an output source.
226 do not use to connect stage-to-stage!
228 return self
.n
._connect
_out
(nxt
.n
)
230 def connect(self
, pipechain
):
231 """ connects a chain (list) of Pipeline instances together and
232 links them to this ControlBase instance:
234 in <----> self <---> out
237 [pipe1, pipe2, pipe3, pipe4]
240 out---in out--in out---in
242 Also takes care of allocating data_i/data_o, by looking up
243 the data spec for each end of the pipechain. i.e It is NOT
244 necessary to allocate self.p.data_i or self.n.data_o manually:
245 this is handled AUTOMATICALLY, here.
247 Basically this function is the direct equivalent of StageChain,
248 except that unlike StageChain, the Pipeline logic is followed.
250 Just as StageChain presents an object that conforms to the
251 Stage API from a list of objects that also conform to the
252 Stage API, an object that calls this Pipeline connect function
253 has the exact same pipeline API as the list of pipline objects
256 Thus it becomes possible to build up larger chains recursively.
257 More complex chains (multi-input, multi-output) will have to be
262 * :pipechain: - a sequence of ControlBase-derived classes
263 (must be one or more in length)
267 * a list of eq assignments that will need to be added in
268 an elaborate() to m.d.comb
270 assert len(pipechain
) > 0, "pipechain must be non-zero length"
271 assert self
.stage
is None, "do not use connect with a stage"
272 eqs
= [] # collated list of assignment statements
274 # connect inter-chain
275 for i
in range(len(pipechain
)-1):
276 pipe1
= pipechain
[i
] # earlier
277 pipe2
= pipechain
[i
+1] # later (by 1)
278 eqs
+= pipe1
.connect_to_next(pipe2
) # earlier n to later p
280 # connect front and back of chain to ourselves
281 front
= pipechain
[0] # first in chain
282 end
= pipechain
[-1] # last in chain
283 self
.set_specs(front
, end
) # sets up ispec/ospec functions
284 self
._new
_data
("chain") # NOTE: REPLACES existing data
285 eqs
+= front
._connect
_in
(self
) # front p to our p
286 eqs
+= end
._connect
_out
(self
) # end n to our n
290 def set_input(self
, i
):
291 """ helper function to set the input data (used in unit tests)
293 return nmoperator
.eq(self
.p
.data_i
, i
)
296 yield from self
.p
# yields ready/valid/data (data also gets yielded)
297 yield from self
.n
# ditto
302 def elaborate(self
, platform
):
303 """ handles case where stage has dynamic ready/valid functions
306 m
.submodules
.p
= self
.p
307 m
.submodules
.n
= self
.n
309 self
.setup(m
, self
.p
.data_i
)
311 if not self
.p
.stage_ctl
:
314 # intercept the previous (outgoing) "ready", combine with stage ready
315 m
.d
.comb
+= self
.p
.s_ready_o
.eq(self
.p
._ready
_o
& self
.stage
.d_ready
)
317 # intercept the next (incoming) "ready" and combine it with data valid
318 sdv
= self
.stage
.d_valid(self
.n
.ready_i
)
319 m
.d
.comb
+= self
.n
.d_valid
.eq(self
.n
.ready_i
& sdv
)
324 class BufferedHandshake(ControlBase
):
325 """ buffered pipeline stage. data and strobe signals travel in sync.
326 if ever the input is ready and the output is not, processed data
327 is shunted in a temporary register.
329 Argument: stage. see Stage API above
331 stage-1 p.valid_i >>in stage n.valid_o out>> stage+1
332 stage-1 p.ready_o <<out stage n.ready_i <<in stage+1
333 stage-1 p.data_i >>in stage n.data_o out>> stage+1
339 input data p.data_i is read (only), is processed and goes into an
340 intermediate result store [process()]. this is updated combinatorially.
342 in a non-stall condition, the intermediate result will go into the
343 output (update_output). however if ever there is a stall, it goes
344 into r_data instead [update_buffer()].
346 when the non-stall condition is released, r_data is the first
347 to be transferred to the output [flush_buffer()], and the stall
350 on the next cycle (as long as stall is not raised again) the
351 input may begin to be processed and transferred directly to output.
354 def elaborate(self
, platform
):
355 self
.m
= ControlBase
.elaborate(self
, platform
)
357 result
= _spec(self
.stage
.ospec
, "r_tmp")
358 r_data
= _spec(self
.stage
.ospec
, "r_data")
360 # establish some combinatorial temporaries
361 o_n_validn
= Signal(reset_less
=True)
362 n_ready_i
= Signal(reset_less
=True, name
="n_i_rdy_data")
363 nir_por
= Signal(reset_less
=True)
364 nir_por_n
= Signal(reset_less
=True)
365 p_valid_i
= Signal(reset_less
=True)
366 nir_novn
= Signal(reset_less
=True)
367 nirn_novn
= Signal(reset_less
=True)
368 por_pivn
= Signal(reset_less
=True)
369 npnn
= Signal(reset_less
=True)
370 self
.m
.d
.comb
+= [p_valid_i
.eq(self
.p
.valid_i_test
),
371 o_n_validn
.eq(~self
.n
.valid_o
),
372 n_ready_i
.eq(self
.n
.ready_i_test
),
373 nir_por
.eq(n_ready_i
& self
.p
._ready
_o
),
374 nir_por_n
.eq(n_ready_i
& ~self
.p
._ready
_o
),
375 nir_novn
.eq(n_ready_i | o_n_validn
),
376 nirn_novn
.eq(~n_ready_i
& o_n_validn
),
377 npnn
.eq(nir_por | nirn_novn
),
378 por_pivn
.eq(self
.p
._ready
_o
& ~p_valid_i
)
381 # store result of processing in combinatorial temporary
382 self
.m
.d
.comb
+= nmoperator
.eq(result
, self
.data_r
)
384 # if not in stall condition, update the temporary register
385 with self
.m
.If(self
.p
.ready_o
): # not stalled
386 self
.m
.d
.sync
+= nmoperator
.eq(r_data
, result
) # update buffer
388 # data pass-through conditions
389 with self
.m
.If(npnn
):
390 data_o
= self
._postprocess
(result
) # XXX TBD, does nothing right now
391 self
.m
.d
.sync
+= [self
.n
.valid_o
.eq(p_valid_i
), # valid if p_valid
392 nmoperator
.eq(self
.n
.data_o
, data_o
), # update out
394 # buffer flush conditions (NOTE: can override data passthru conditions)
395 with self
.m
.If(nir_por_n
): # not stalled
396 # Flush the [already processed] buffer to the output port.
397 data_o
= self
._postprocess
(r_data
) # XXX TBD, does nothing right now
398 self
.m
.d
.sync
+= [self
.n
.valid_o
.eq(1), # reg empty
399 nmoperator
.eq(self
.n
.data_o
, data_o
), # flush
401 # output ready conditions
402 self
.m
.d
.sync
+= self
.p
._ready
_o
.eq(nir_novn | por_pivn
)
407 class MaskCancellable(ControlBase
):
408 """ Mask-activated Cancellable pipeline
410 Argument: stage. see Stage API above
412 stage-1 p.valid_i >>in stage n.valid_o out>> stage+1
413 stage-1 p.ready_o <<out stage n.ready_i <<in stage+1
414 stage-1 p.data_i >>in stage n.data_o out>> stage+1
418 def __init__(self
, stage
, maskwid
, in_multi
=None, stage_ctl
=False):
419 ControlBase
.__init
__(self
, stage
, in_multi
, stage_ctl
, maskwid
)
422 def elaborate(self
, platform
):
423 self
.m
= m
= ControlBase
.elaborate(self
, platform
)
425 # store result of processing in combinatorial temporary
426 result
= _spec(self
.stage
.ospec
, "r_tmp")
427 m
.d
.comb
+= nmoperator
.eq(result
, self
.data_r
)
429 # establish if the data should be passed on. cancellation is
431 # XXX EXCEPTIONAL CIRCUMSTANCES: inspection of the data payload
432 # is NOT "normal" for the Stage API.
433 p_valid_i
= Signal(reset_less
=True)
434 #print ("self.p.data_i", self.p.data_i)
435 maskedout
= Signal(len(self
.p
.mask_i
), reset_less
=True)
436 m
.d
.comb
+= maskedout
.eq(self
.p
.mask_i
& ~self
.p
.stop_i
)
437 m
.d
.comb
+= p_valid_i
.eq(maskedout
.bool())
439 # if idmask nonzero, mask gets passed on (and register set).
440 # register is left as-is if idmask is zero, but out-mask is set to zero
441 # note however: only the *uncancelled* mask bits get passed on
442 m
.d
.sync
+= self
.n
.valid_o
.eq(p_valid_i
)
443 m
.d
.sync
+= self
.n
.mask_o
.eq(Mux(p_valid_i
, maskedout
, 0))
444 with m
.If(p_valid_i
):
445 data_o
= self
._postprocess
(result
) # XXX TBD, does nothing right now
446 m
.d
.sync
+= nmoperator
.eq(self
.n
.data_o
, data_o
) # update output
449 # input always "ready"
450 #m.d.comb += self.p._ready_o.eq(self.n.ready_i_test)
451 m
.d
.comb
+= self
.p
._ready
_o
.eq(Const(1))
453 # always pass on stop (as combinatorial: single signal)
454 m
.d
.comb
+= self
.n
.stop_o
.eq(self
.p
.stop_i
)
459 class SimpleHandshake(ControlBase
):
460 """ simple handshake control. data and strobe signals travel in sync.
461 implements the protocol used by Wishbone and AXI4.
463 Argument: stage. see Stage API above
465 stage-1 p.valid_i >>in stage n.valid_o out>> stage+1
466 stage-1 p.ready_o <<out stage n.ready_i <<in stage+1
467 stage-1 p.data_i >>in stage n.data_o out>> stage+1
472 Inputs Temporary Output Data
473 ------- ---------- ----- ----
474 P P N N PiV& ~NiR& N P
481 0 0 1 0 0 0 0 1 process(data_i)
482 0 0 1 1 0 0 0 1 process(data_i)
486 0 1 1 0 0 0 0 1 process(data_i)
487 0 1 1 1 0 0 0 1 process(data_i)
491 1 0 1 0 0 0 0 1 process(data_i)
492 1 0 1 1 0 0 0 1 process(data_i)
494 1 1 0 0 1 0 1 0 process(data_i)
495 1 1 0 1 1 1 1 0 process(data_i)
496 1 1 1 0 1 0 1 1 process(data_i)
497 1 1 1 1 1 0 1 1 process(data_i)
501 def elaborate(self
, platform
):
502 self
.m
= m
= ControlBase
.elaborate(self
, platform
)
505 result
= _spec(self
.stage
.ospec
, "r_tmp")
507 # establish some combinatorial temporaries
508 n_ready_i
= Signal(reset_less
=True, name
="n_i_rdy_data")
509 p_valid_i_p_ready_o
= Signal(reset_less
=True)
510 p_valid_i
= Signal(reset_less
=True)
511 m
.d
.comb
+= [p_valid_i
.eq(self
.p
.valid_i_test
),
512 n_ready_i
.eq(self
.n
.ready_i_test
),
513 p_valid_i_p_ready_o
.eq(p_valid_i
& self
.p
.ready_o
),
516 # store result of processing in combinatorial temporary
517 m
.d
.comb
+= nmoperator
.eq(result
, self
.data_r
)
519 # previous valid and ready
520 with m
.If(p_valid_i_p_ready_o
):
521 data_o
= self
._postprocess
(result
) # XXX TBD, does nothing right now
522 m
.d
.sync
+= [r_busy
.eq(1), # output valid
523 nmoperator
.eq(self
.n
.data_o
, data_o
), # update output
525 # previous invalid or not ready, however next is accepting
526 with m
.Elif(n_ready_i
):
527 data_o
= self
._postprocess
(result
) # XXX TBD, does nothing right now
528 m
.d
.sync
+= [nmoperator
.eq(self
.n
.data_o
, data_o
)]
529 # TODO: could still send data here (if there was any)
530 #m.d.sync += self.n.valid_o.eq(0) # ...so set output invalid
531 m
.d
.sync
+= r_busy
.eq(0) # ...so set output invalid
533 m
.d
.comb
+= self
.n
.valid_o
.eq(r_busy
)
534 # if next is ready, so is previous
535 m
.d
.comb
+= self
.p
._ready
_o
.eq(n_ready_i
)
540 class UnbufferedPipeline(ControlBase
):
541 """ A simple pipeline stage with single-clock synchronisation
542 and two-way valid/ready synchronised signalling.
544 Note that a stall in one stage will result in the entire pipeline
547 Also that unlike BufferedHandshake, the valid/ready signalling does NOT
548 travel synchronously with the data: the valid/ready signalling
549 combines in a *combinatorial* fashion. Therefore, a long pipeline
550 chain will lengthen propagation delays.
552 Argument: stage. see Stage API, above
554 stage-1 p.valid_i >>in stage n.valid_o out>> stage+1
555 stage-1 p.ready_o <<out stage n.ready_i <<in stage+1
556 stage-1 p.data_i >>in stage n.data_o out>> stage+1
564 p.data_i : StageInput, shaped according to ispec
566 p.data_o : StageOutput, shaped according to ospec
568 r_data : input_shape according to ispec
569 A temporary (buffered) copy of a prior (valid) input.
570 This is HELD if the output is not ready. It is updated
572 result: output_shape according to ospec
573 The output of the combinatorial logic. it is updated
574 COMBINATORIALLY (no clock dependence).
578 Inputs Temp Output Data
600 1 1 0 0 0 1 1 process(data_i)
601 1 1 0 1 1 1 0 process(data_i)
602 1 1 1 0 0 1 1 process(data_i)
603 1 1 1 1 0 1 1 process(data_i)
606 Note: PoR is *NOT* involved in the above decision-making.
609 def elaborate(self
, platform
):
610 self
.m
= m
= ControlBase
.elaborate(self
, platform
)
612 data_valid
= Signal() # is data valid or not
613 r_data
= _spec(self
.stage
.ospec
, "r_tmp") # output type
616 p_valid_i
= Signal(reset_less
=True)
617 pv
= Signal(reset_less
=True)
618 buf_full
= Signal(reset_less
=True)
619 m
.d
.comb
+= p_valid_i
.eq(self
.p
.valid_i_test
)
620 m
.d
.comb
+= pv
.eq(self
.p
.valid_i
& self
.p
.ready_o
)
621 m
.d
.comb
+= buf_full
.eq(~self
.n
.ready_i_test
& data_valid
)
623 m
.d
.comb
+= self
.n
.valid_o
.eq(data_valid
)
624 m
.d
.comb
+= self
.p
._ready
_o
.eq(~data_valid | self
.n
.ready_i_test
)
625 m
.d
.sync
+= data_valid
.eq(p_valid_i | buf_full
)
628 m
.d
.sync
+= nmoperator
.eq(r_data
, self
.data_r
)
629 data_o
= self
._postprocess
(r_data
) # XXX TBD, does nothing right now
630 m
.d
.comb
+= nmoperator
.eq(self
.n
.data_o
, data_o
)
635 class UnbufferedPipeline2(ControlBase
):
636 """ A simple pipeline stage with single-clock synchronisation
637 and two-way valid/ready synchronised signalling.
639 Note that a stall in one stage will result in the entire pipeline
642 Also that unlike BufferedHandshake, the valid/ready signalling does NOT
643 travel synchronously with the data: the valid/ready signalling
644 combines in a *combinatorial* fashion. Therefore, a long pipeline
645 chain will lengthen propagation delays.
647 Argument: stage. see Stage API, above
649 stage-1 p.valid_i >>in stage n.valid_o out>> stage+1
650 stage-1 p.ready_o <<out stage n.ready_i <<in stage+1
651 stage-1 p.data_i >>in stage n.data_o out>> stage+1
656 p.data_i : StageInput, shaped according to ispec
658 p.data_o : StageOutput, shaped according to ospec
660 buf : output_shape according to ospec
661 A temporary (buffered) copy of a valid output
662 This is HELD if the output is not ready. It is updated
665 Inputs Temp Output Data
667 P P N N ~NiR& N P (buf_full)
672 0 0 0 0 0 0 1 process(data_i)
673 0 0 0 1 1 1 0 reg (odata, unchanged)
674 0 0 1 0 0 0 1 process(data_i)
675 0 0 1 1 0 0 1 process(data_i)
677 0 1 0 0 0 0 1 process(data_i)
678 0 1 0 1 1 1 0 reg (odata, unchanged)
679 0 1 1 0 0 0 1 process(data_i)
680 0 1 1 1 0 0 1 process(data_i)
682 1 0 0 0 0 1 1 process(data_i)
683 1 0 0 1 1 1 0 reg (odata, unchanged)
684 1 0 1 0 0 1 1 process(data_i)
685 1 0 1 1 0 1 1 process(data_i)
687 1 1 0 0 0 1 1 process(data_i)
688 1 1 0 1 1 1 0 reg (odata, unchanged)
689 1 1 1 0 0 1 1 process(data_i)
690 1 1 1 1 0 1 1 process(data_i)
693 Note: PoR is *NOT* involved in the above decision-making.
696 def elaborate(self
, platform
):
697 self
.m
= m
= ControlBase
.elaborate(self
, platform
)
699 buf_full
= Signal() # is data valid or not
700 buf
= _spec(self
.stage
.ospec
, "r_tmp") # output type
703 p_valid_i
= Signal(reset_less
=True)
704 m
.d
.comb
+= p_valid_i
.eq(self
.p
.valid_i_test
)
706 m
.d
.comb
+= self
.n
.valid_o
.eq(buf_full | p_valid_i
)
707 m
.d
.comb
+= self
.p
._ready
_o
.eq(~buf_full
)
708 m
.d
.sync
+= buf_full
.eq(~self
.n
.ready_i_test
& self
.n
.valid_o
)
710 data_o
= Mux(buf_full
, buf
, self
.data_r
)
711 data_o
= self
._postprocess
(data_o
) # XXX TBD, does nothing right now
712 m
.d
.comb
+= nmoperator
.eq(self
.n
.data_o
, data_o
)
713 m
.d
.sync
+= nmoperator
.eq(buf
, self
.n
.data_o
)
718 class PassThroughHandshake(ControlBase
):
719 """ A control block that delays by one clock cycle.
721 Inputs Temporary Output Data
722 ------- ------------------ ----- ----
723 P P N N PiV& PiV| NiR| pvr N P (pvr)
724 i o i o PoR ~PoR ~NoV o o
728 0 0 0 0 0 1 1 0 1 1 odata (unchanged)
729 0 0 0 1 0 1 0 0 1 0 odata (unchanged)
730 0 0 1 0 0 1 1 0 1 1 odata (unchanged)
731 0 0 1 1 0 1 1 0 1 1 odata (unchanged)
733 0 1 0 0 0 0 1 0 0 1 odata (unchanged)
734 0 1 0 1 0 0 0 0 0 0 odata (unchanged)
735 0 1 1 0 0 0 1 0 0 1 odata (unchanged)
736 0 1 1 1 0 0 1 0 0 1 odata (unchanged)
738 1 0 0 0 0 1 1 1 1 1 process(in)
739 1 0 0 1 0 1 0 0 1 0 odata (unchanged)
740 1 0 1 0 0 1 1 1 1 1 process(in)
741 1 0 1 1 0 1 1 1 1 1 process(in)
743 1 1 0 0 1 1 1 1 1 1 process(in)
744 1 1 0 1 1 1 0 0 1 0 odata (unchanged)
745 1 1 1 0 1 1 1 1 1 1 process(in)
746 1 1 1 1 1 1 1 1 1 1 process(in)
751 def elaborate(self
, platform
):
752 self
.m
= m
= ControlBase
.elaborate(self
, platform
)
754 r_data
= _spec(self
.stage
.ospec
, "r_tmp") # output type
757 p_valid_i
= Signal(reset_less
=True)
758 pvr
= Signal(reset_less
=True)
759 m
.d
.comb
+= p_valid_i
.eq(self
.p
.valid_i_test
)
760 m
.d
.comb
+= pvr
.eq(p_valid_i
& self
.p
.ready_o
)
762 m
.d
.comb
+= self
.p
.ready_o
.eq(~self
.n
.valid_o | self
.n
.ready_i_test
)
763 m
.d
.sync
+= self
.n
.valid_o
.eq(p_valid_i | ~self
.p
.ready_o
)
765 odata
= Mux(pvr
, self
.data_r
, r_data
)
766 m
.d
.sync
+= nmoperator
.eq(r_data
, odata
)
767 r_data
= self
._postprocess
(r_data
) # XXX TBD, does nothing right now
768 m
.d
.comb
+= nmoperator
.eq(self
.n
.data_o
, r_data
)
773 class RegisterPipeline(UnbufferedPipeline
):
774 """ A pipeline stage that delays by one clock cycle, creating a
775 sync'd latch out of data_o and valid_o as an indirect byproduct
776 of using PassThroughStage
778 def __init__(self
, iospecfn
):
779 UnbufferedPipeline
.__init
__(self
, PassThroughStage(iospecfn
))
782 class FIFOControl(ControlBase
):
783 """ FIFO Control. Uses Queue to store data, coincidentally
784 happens to have same valid/ready signalling as Stage API.
786 data_i -> fifo.din -> FIFO -> fifo.dout -> data_o
788 def __init__(self
, depth
, stage
, in_multi
=None, stage_ctl
=False,
789 fwft
=True, pipe
=False):
792 * :depth: number of entries in the FIFO
793 * :stage: data processing block
794 * :fwft: first word fall-thru mode (non-fwft introduces delay)
795 * :pipe: specifies pipe mode.
797 when fwft = True it indicates that transfers may occur
798 combinatorially through stage processing in the same clock cycle.
799 This requires that the Stage be a Moore FSM:
800 https://en.wikipedia.org/wiki/Moore_machine
802 when fwft = False it indicates that all output signals are
803 produced only from internal registers or memory, i.e. that the
804 Stage is a Mealy FSM:
805 https://en.wikipedia.org/wiki/Mealy_machine
807 data is processed (and located) as follows:
809 self.p self.stage temp fn temp fn temp fp self.n
810 data_i->process()->result->cat->din.FIFO.dout->cat(data_o)
812 yes, really: cat produces a Cat() which can be assigned to.
813 this is how the FIFO gets de-catted without needing a de-cat
819 ControlBase
.__init
__(self
, stage
, in_multi
, stage_ctl
)
821 def elaborate(self
, platform
):
822 self
.m
= m
= ControlBase
.elaborate(self
, platform
)
824 # make a FIFO with a signal of equal width to the data_o.
825 (fwidth
, _
) = nmoperator
.shape(self
.n
.data_o
)
826 fifo
= Queue(fwidth
, self
.fdepth
, fwft
=self
.fwft
, pipe
=self
.pipe
)
827 m
.submodules
.fifo
= fifo
829 def processfn(data_i
):
830 # store result of processing in combinatorial temporary
831 result
= _spec(self
.stage
.ospec
, "r_temp")
832 m
.d
.comb
+= nmoperator
.eq(result
, self
.process(data_i
))
833 return nmoperator
.cat(result
)
835 ## prev: make the FIFO (Queue object) "look" like a PrevControl...
836 m
.submodules
.fp
= fp
= PrevControl()
837 fp
.valid_i
, fp
._ready
_o
, fp
.data_i
= fifo
.we
, fifo
.writable
, fifo
.din
838 m
.d
.comb
+= fp
._connect
_in
(self
.p
, fn
=processfn
)
840 # next: make the FIFO (Queue object) "look" like a NextControl...
841 m
.submodules
.fn
= fn
= NextControl()
842 fn
.valid_o
, fn
.ready_i
, fn
.data_o
= fifo
.readable
, fifo
.re
, fifo
.dout
843 connections
= fn
._connect
_out
(self
.n
, fn
=nmoperator
.cat
)
845 # ok ok so we can't just do the ready/valid eqs straight:
846 # first 2 from connections are the ready/valid, 3rd is data.
848 m
.d
.comb
+= connections
[:2] # combinatorial on next ready/valid
850 m
.d
.sync
+= connections
[:2] # non-fwft mode needs sync
851 data_o
= connections
[2] # get the data
852 data_o
= self
._postprocess
(data_o
) # XXX TBD, does nothing right now
859 class UnbufferedPipeline(FIFOControl
):
860 def __init__(self
, stage
, in_multi
=None, stage_ctl
=False):
861 FIFOControl
.__init
__(self
, 1, stage
, in_multi
, stage_ctl
,
862 fwft
=True, pipe
=False)
864 # aka "BreakReadyStage" XXX had to set fwft=True to get it to work
865 class PassThroughHandshake(FIFOControl
):
866 def __init__(self
, stage
, in_multi
=None, stage_ctl
=False):
867 FIFOControl
.__init
__(self
, 1, stage
, in_multi
, stage_ctl
,
868 fwft
=True, pipe
=True)
870 # this is *probably* BufferedHandshake, although test #997 now succeeds.
871 class BufferedHandshake(FIFOControl
):
872 def __init__(self
, stage
, in_multi
=None, stage_ctl
=False):
873 FIFOControl
.__init
__(self
, 2, stage
, in_multi
, stage_ctl
,
874 fwft
=True, pipe
=False)
878 # this is *probably* SimpleHandshake (note: memory cell size=0)
879 class SimpleHandshake(FIFOControl):
880 def __init__(self, stage, in_multi=None, stage_ctl=False):
881 FIFOControl.__init__(self, 0, stage, in_multi, stage_ctl,
882 fwft=True, pipe=False)