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
10 stage requires compliance with a strict API that may be
11 implemented in several means, including as a static class.
13 Stage Blocks really must be combinatorial blocks. It would be ok
14 to have input come in from sync'd sources (clock-driven) however by
15 doing so they would no longer be deterministic, and chaining such
16 blocks with such side-effects together could result in unexpected,
17 unpredictable, unreproduceable behaviour.
18 So generally to be avoided, then unless you know what you are doing.
20 the methods of a stage instance must be as follows:
22 * ispec() - Input data format specification
23 returns an object or a list or tuple of objects, or
24 a Record, each object having an "eq" function which
25 takes responsibility for copying by assignment all
27 * ospec() - Output data format specification
28 requirements as for ospec
29 * process(m, i) - Processes an ispec-formatted object
30 returns a combinatorial block of a result that
31 may be assigned to the output, by way of the "eq"
33 * setup(m, i) - Optional function for setting up submodules
34 may be used for more complex stages, to link
35 the input (i) to submodules. must take responsibility
36 for adding those submodules to the module (m).
37 the submodules must be combinatorial blocks and
38 must have their inputs and output linked combinatorially.
40 Both StageCls (for use with non-static classes) and Stage (for use
41 by static classes) are abstract classes from which, for convenience
42 and as a courtesy to other developers, anything conforming to the
43 Stage API may *choose* to derive.
48 A useful combinatorial wrapper around stages that chains them together
49 and then presents a Stage-API-conformant interface. By presenting
50 the same API as the stages it wraps, it can clearly be used recursively.
55 The base class for pipelines. Contains previous and next ready/valid/data.
56 Also has an extremely useful "connect" function that can be used to
57 connect a chain of pipelines and present the exact same prev/next
60 Note: pipelines basically do not become pipelines as such until
61 handed to a derivative of ControlBase. ControlBase itself is *not*
62 strictly considered a pipeline class. Wishbone and AXI4 (master or
63 slave) could be derived from ControlBase, for example.
66 from nmigen
import Signal
, Cat
, Const
, Mux
, Module
, Value
, Elaboratable
67 from nmigen
.cli
import verilog
, rtlil
68 from nmigen
.hdl
.rec
import Record
70 from abc
import ABCMeta
, abstractmethod
71 from collections
.abc
import Sequence
, Iterable
72 from collections
import OrderedDict
80 self
.fields
= OrderedDict()
82 def __setattr__(self
, k
, v
):
84 if (k
.startswith('_') or k
in ["fields", "name", "src_loc"] or
85 k
in dir(Object
) or "fields" not in self
.__dict
__):
86 return object.__setattr
__(self
, k
, v
)
89 def __getattr__(self
, k
):
90 if k
in self
.__dict
__:
91 return object.__getattr
__(self
, k
)
95 raise AttributeError(e
)
98 for x
in self
.fields
.values():
99 if isinstance(x
, Iterable
):
106 for (k
, o
) in self
.fields
.items():
110 if isinstance(rres
, Sequence
):
121 class RecordObject(Record
):
122 def __init__(self
, layout
=None, name
=None):
123 Record
.__init
__(self
, layout
=layout
or [], name
=None)
125 def __setattr__(self
, k
, v
):
127 if (k
.startswith('_') or k
in ["fields", "name", "src_loc"] or
128 k
in dir(Record
) or "fields" not in self
.__dict
__):
129 return object.__setattr
__(self
, k
, v
)
131 #print ("RecordObject setattr", k, v)
132 if isinstance(v
, Record
):
133 newlayout
= {k
: (k
, v
.layout
)}
134 elif isinstance(v
, Value
):
135 newlayout
= {k
: (k
, v
.shape())}
137 newlayout
= {k
: (k
, nmoperator
.shape(v
))}
138 self
.layout
.fields
.update(newlayout
)
141 for x
in self
.fields
.values():
142 if isinstance(x
, Iterable
):
151 def _spec(fn
, name
=None):
154 varnames
= dict(inspect
.getmembers(fn
.__code
__))['co_varnames']
155 if 'name' in varnames
:
160 class PrevControl(Elaboratable
):
161 """ contains signals that come *from* the previous stage (both in and out)
162 * valid_i: previous stage indicating all incoming data is valid.
163 may be a multi-bit signal, where all bits are required
164 to be asserted to indicate "valid".
165 * ready_o: output to next stage indicating readiness to accept data
166 * data_i : an input - MUST be added by the USER of this class
169 def __init__(self
, i_width
=1, stage_ctl
=False):
170 self
.stage_ctl
= stage_ctl
171 self
.valid_i
= Signal(i_width
, name
="p_valid_i") # prev >>in self
172 self
._ready
_o
= Signal(name
="p_ready_o") # prev <<out self
173 self
.data_i
= None # XXX MUST BE ADDED BY USER
175 self
.s_ready_o
= Signal(name
="p_s_o_rdy") # prev <<out self
176 self
.trigger
= Signal(reset_less
=True)
180 """ public-facing API: indicates (externally) that stage is ready
183 return self
.s_ready_o
# set dynamically by stage
184 return self
._ready
_o
# return this when not under dynamic control
186 def _connect_in(self
, prev
, direct
=False, fn
=None):
187 """ internal helper function to connect stage to an input source.
188 do not use to connect stage-to-stage!
190 valid_i
= prev
.valid_i
if direct
else prev
.valid_i_test
191 data_i
= fn(prev
.data_i
) if fn
is not None else prev
.data_i
192 return [self
.valid_i
.eq(valid_i
),
193 prev
.ready_o
.eq(self
.ready_o
),
194 nmoperator
.eq(self
.data_i
, data_i
),
198 def valid_i_test(self
):
199 vlen
= len(self
.valid_i
)
201 # multi-bit case: valid only when valid_i is all 1s
202 all1s
= Const(-1, (len(self
.valid_i
), False))
203 valid_i
= (self
.valid_i
== all1s
)
205 # single-bit valid_i case
206 valid_i
= self
.valid_i
208 # when stage indicates not ready, incoming data
209 # must "appear" to be not ready too
211 valid_i
= valid_i
& self
.s_ready_o
215 def elaborate(self
, platform
):
217 m
.d
.comb
+= self
.trigger
.eq(self
.valid_i_test
& self
.ready_o
)
221 return [self
.data_i
.eq(i
.data_i
),
222 self
.ready_o
.eq(i
.ready_o
),
223 self
.valid_i
.eq(i
.valid_i
)]
228 if hasattr(self
.data_i
, "ports"):
229 yield from self
.data_i
.ports()
230 elif isinstance(self
.data_i
, Sequence
):
231 yield from self
.data_i
239 class NextControl(Elaboratable
):
240 """ contains the signals that go *to* the next stage (both in and out)
241 * valid_o: output indicating to next stage that data is valid
242 * ready_i: input from next stage indicating that it can accept data
243 * data_o : an output - MUST be added by the USER of this class
245 def __init__(self
, stage_ctl
=False):
246 self
.stage_ctl
= stage_ctl
247 self
.valid_o
= Signal(name
="n_valid_o") # self out>> next
248 self
.ready_i
= Signal(name
="n_ready_i") # self <<in next
249 self
.data_o
= None # XXX MUST BE ADDED BY USER
251 self
.d_valid
= Signal(reset
=1) # INTERNAL (data valid)
252 self
.trigger
= Signal(reset_less
=True)
255 def ready_i_test(self
):
257 return self
.ready_i
& self
.d_valid
260 def connect_to_next(self
, nxt
):
261 """ helper function to connect to the next stage data/valid/ready.
262 data/valid is passed *TO* nxt, and ready comes *IN* from nxt.
263 use this when connecting stage-to-stage
265 return [nxt
.valid_i
.eq(self
.valid_o
),
266 self
.ready_i
.eq(nxt
.ready_o
),
267 nmoperator
.eq(nxt
.data_i
, self
.data_o
),
270 def _connect_out(self
, nxt
, direct
=False, fn
=None):
271 """ internal helper function to connect stage to an output source.
272 do not use to connect stage-to-stage!
274 ready_i
= nxt
.ready_i
if direct
else nxt
.ready_i_test
275 data_o
= fn(nxt
.data_o
) if fn
is not None else nxt
.data_o
276 return [nxt
.valid_o
.eq(self
.valid_o
),
277 self
.ready_i
.eq(ready_i
),
278 nmoperator
.eq(data_o
, self
.data_o
),
281 def elaborate(self
, platform
):
283 m
.d
.comb
+= self
.trigger
.eq(self
.ready_i_test
& self
.valid_o
)
289 if hasattr(self
.data_o
, "ports"):
290 yield from self
.data_o
.ports()
291 elif isinstance(self
.data_o
, Sequence
):
292 yield from self
.data_o
300 class StageCls(metaclass
=ABCMeta
):
301 """ Class-based "Stage" API. requires instantiation (after derivation)
303 see "Stage API" above.. Note: python does *not* require derivation
304 from this class. All that is required is that the pipelines *have*
305 the functions listed in this class. Derivation from this class
306 is therefore merely a "courtesy" to maintainers.
309 def ispec(self
): pass # REQUIRED
311 def ospec(self
): pass # REQUIRED
313 #def setup(self, m, i): pass # OPTIONAL
315 def process(self
, i
): pass # REQUIRED
318 class Stage(metaclass
=ABCMeta
):
319 """ Static "Stage" API. does not require instantiation (after derivation)
321 see "Stage API" above. Note: python does *not* require derivation
322 from this class. All that is required is that the pipelines *have*
323 the functions listed in this class. Derivation from this class
324 is therefore merely a "courtesy" to maintainers.
336 #def setup(m, i): pass
343 class StageChain(StageCls
):
344 """ pass in a list of stages, and they will automatically be
345 chained together via their input and output specs into a
346 combinatorial chain, to create one giant combinatorial block.
348 the end result basically conforms to the exact same Stage API.
350 * input to this class will be the input of the first stage
351 * output of first stage goes into input of second
352 * output of second goes into input into third
354 * the output of this class will be the output of the last stage
356 NOTE: whilst this is very similar to ControlBase.connect(), it is
357 *really* important to appreciate that StageChain is pure
358 combinatorial and bypasses (does not involve, at all, ready/valid
359 signalling of any kind).
361 ControlBase.connect on the other hand respects, connects, and uses
362 ready/valid signalling.
366 * :chain: a chain of combinatorial blocks conforming to the Stage API
367 NOTE: StageChain.ispec and ospect have to have something
368 to return (beginning and end specs of the chain),
369 therefore the chain argument must be non-zero length
371 * :specallocate: if set, new input and output data will be allocated
372 and connected (eq'd) to each chained Stage.
373 in some cases if this is not done, the nmigen warning
374 "driving from two sources, module is being flattened"
377 NOTE: do NOT use StageChain with combinatorial blocks that have
378 side-effects (state-based / clock-based input) or conditional
379 (inter-chain) dependencies, unless you really know what you are doing.
381 def __init__(self
, chain
, specallocate
=False):
382 assert len(chain
) > 0, "stage chain must be non-zero length"
384 self
.specallocate
= specallocate
387 """ returns the ispec of the first of the chain
389 return _spec(self
.chain
[0].ispec
, "chainin")
392 """ returns the ospec of the last of the chain
394 return _spec(self
.chain
[-1].ospec
, "chainout")
396 def _specallocate_setup(self
, m
, i
):
397 o
= i
# in case chain is empty
398 for (idx
, c
) in enumerate(self
.chain
):
399 if hasattr(c
, "setup"):
400 c
.setup(m
, i
) # stage may have some module stuff
401 ofn
= self
.chain
[idx
].ospec
# last assignment survives
402 o
= _spec(ofn
, 'chainin%d' % idx
)
403 m
.d
.comb
+= nmoperator
.eq(o
, c
.process(i
)) # process input into "o"
404 if idx
== len(self
.chain
)-1:
406 ifn
= self
.chain
[idx
+1].ispec
# new input on next loop
407 i
= _spec(ifn
, 'chainin%d' % (idx
+1))
408 m
.d
.comb
+= nmoperator
.eq(i
, o
) # assign to next input
409 return o
# last loop is the output
411 def _noallocate_setup(self
, m
, i
):
412 o
= i
# in case chain is empty
413 for (idx
, c
) in enumerate(self
.chain
):
414 if hasattr(c
, "setup"):
415 c
.setup(m
, i
) # stage may have some module stuff
416 i
= o
= c
.process(i
) # store input into "o"
417 return o
# last loop is the output
419 def setup(self
, m
, i
):
420 if self
.specallocate
:
421 self
.o
= self
._specallocate
_setup
(m
, i
)
423 self
.o
= self
._noallocate
_setup
(m
, i
)
425 def process(self
, i
):
426 return self
.o
# conform to Stage API: return last-loop output
429 class ControlBase(Elaboratable
):
430 """ Common functions for Pipeline API. Note: a "pipeline stage" only
431 exists (conceptually) when a ControlBase derivative is handed
432 a Stage (combinatorial block)
434 def __init__(self
, stage
=None, in_multi
=None, stage_ctl
=False):
435 """ Base class containing ready/valid/data to previous and next stages
437 * p: contains ready/valid to the previous stage
438 * n: contains ready/valid to the next stage
440 Except when calling Controlbase.connect(), user must also:
441 * add data_i member to PrevControl (p) and
442 * add data_o member to NextControl (n)
446 # set up input and output IO ACK (prev/next ready/valid)
447 self
.p
= PrevControl(in_multi
, stage_ctl
)
448 self
.n
= NextControl(stage_ctl
)
450 # set up the input and output data
451 if stage
is not None:
452 self
.p
.data_i
= _spec(stage
.ispec
, "data_i") # input type
453 self
.n
.data_o
= _spec(stage
.ospec
, "data_o") # output type
455 def connect_to_next(self
, nxt
):
456 """ helper function to connect to the next stage data/valid/ready.
458 return self
.n
.connect_to_next(nxt
.p
)
460 def _connect_in(self
, prev
):
461 """ internal helper function to connect stage to an input source.
462 do not use to connect stage-to-stage!
464 return self
.p
._connect
_in
(prev
.p
)
466 def _connect_out(self
, nxt
):
467 """ internal helper function to connect stage to an output source.
468 do not use to connect stage-to-stage!
470 return self
.n
._connect
_out
(nxt
.n
)
472 def connect(self
, pipechain
):
473 """ connects a chain (list) of Pipeline instances together and
474 links them to this ControlBase instance:
476 in <----> self <---> out
479 [pipe1, pipe2, pipe3, pipe4]
482 out---in out--in out---in
484 Also takes care of allocating data_i/data_o, by looking up
485 the data spec for each end of the pipechain. i.e It is NOT
486 necessary to allocate self.p.data_i or self.n.data_o manually:
487 this is handled AUTOMATICALLY, here.
489 Basically this function is the direct equivalent of StageChain,
490 except that unlike StageChain, the Pipeline logic is followed.
492 Just as StageChain presents an object that conforms to the
493 Stage API from a list of objects that also conform to the
494 Stage API, an object that calls this Pipeline connect function
495 has the exact same pipeline API as the list of pipline objects
498 Thus it becomes possible to build up larger chains recursively.
499 More complex chains (multi-input, multi-output) will have to be
504 * :pipechain: - a sequence of ControlBase-derived classes
505 (must be one or more in length)
509 * a list of eq assignments that will need to be added in
510 an elaborate() to m.d.comb
512 assert len(pipechain
) > 0, "pipechain must be non-zero length"
513 eqs
= [] # collated list of assignment statements
515 # connect inter-chain
516 for i
in range(len(pipechain
)-1):
518 pipe2
= pipechain
[i
+1]
519 eqs
+= pipe1
.connect_to_next(pipe2
)
521 # connect front of chain to ourselves
523 self
.p
.data_i
= _spec(front
.stage
.ispec
, "chainin")
524 eqs
+= front
._connect
_in
(self
)
526 # connect end of chain to ourselves
528 self
.n
.data_o
= _spec(end
.stage
.ospec
, "chainout")
529 eqs
+= end
._connect
_out
(self
)
533 def _postprocess(self
, i
): # XXX DISABLED
534 return i
# RETURNS INPUT
535 if hasattr(self
.stage
, "postprocess"):
536 return self
.stage
.postprocess(i
)
539 def set_input(self
, i
):
540 """ helper function to set the input data
542 return nmoperator
.eq(self
.p
.data_i
, i
)
551 def elaborate(self
, platform
):
552 """ handles case where stage has dynamic ready/valid functions
555 m
.submodules
.p
= self
.p
556 m
.submodules
.n
= self
.n
558 if self
.stage
is not None and hasattr(self
.stage
, "setup"):
559 self
.stage
.setup(m
, self
.p
.data_i
)
561 if not self
.p
.stage_ctl
:
564 # intercept the previous (outgoing) "ready", combine with stage ready
565 m
.d
.comb
+= self
.p
.s_ready_o
.eq(self
.p
._ready
_o
& self
.stage
.d_ready
)
567 # intercept the next (incoming) "ready" and combine it with data valid
568 sdv
= self
.stage
.d_valid(self
.n
.ready_i
)
569 m
.d
.comb
+= self
.n
.d_valid
.eq(self
.n
.ready_i
& sdv
)