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Using ClockSignal in platform.add_clock_constraint #542

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rroohhh opened this issue Nov 11, 2020 · 3 comments · Fixed by #1288
Closed

Using ClockSignal in platform.add_clock_constraint #542

rroohhh opened this issue Nov 11, 2020 · 3 comments · Fixed by #1288
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improvement meta:help-wanted
Milestone
0.5

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@rroohhh
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rroohhh commented Nov 11, 2020

Currently one cannot use a ClockSignal in platform.add_clock_constraint:

from nmigen import *
from nmigen_boards.microzed_z010 import *

plat = MicroZedZ010Platform()
plat.add_clock_constraint(ClockSignal(), 25e6)

fails with

Traceback (most recent call last):
  File "a.py", line 5, in <module>
    plat.add_clock_constraint(ClockSignal(), 25e6)
  File "/home/robin/.guix-profile/lib/python3.8/site-packages/nmigen/vendor/xilinx_7series.py", line 184, in add_clock_constraint
    super().add_clock_constraint(clock, frequency)
  File "/home/robin/.guix-profile/lib/python3.8/site-packages/nmigen/build/res.py", line 223, in add_clock_constraint
    raise TypeError("Object {!r} is not a Signal".format(clock))
TypeError: Object (clk sync) is not a Signal

It be nice to be able to use a ClockSignal directly in platform.add_clock_constraint.
@whitequark
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That's not possible--the Platform does not know the context of any particular ClockSignal, and without the context, it is ambiguous.

@awygle
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awygle commented Nov 12, 2020

I'd like to recommend enhancing the error message for this case, or else explaining in more detail here for future reference. Even with your comment above, it's not immediately obvious to me why plat.add_clock_constraint(ClockSignal(), 25e6) doesn't work but

cs = ClockSignal()
s = Signal()
m.d.comb += s.eq(cs)
plat.add_clock_constraint(s, 25e6)

does.

@awygle awygle reopened this Nov 12, 2020
@awygle
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awygle commented Feb 10, 2021 •
edited

Throwing some spaghetti at the wall for the error message:

TypeError: Object (clk sync) is not a Signal, it is a ClockSignal. You may be able to assign the value of (clk sync) to a Signal, which can then be used to add a clock constraint.

Thoughts?

@whitequark whitequark added this to the 0.5 milestone Feb 9, 2024
@whitequark whitequark mentioned this issue Mar 22, 2024
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wanda-phi added a commit to wanda-phi/amaranth that referenced this issue Apr 6, 2024
@wanda-phi
build.res: give a more specific error for `add_clock_constraint(Clock…
72a76c3 
…Signal)`.

Fixes amaranth-lang#542.
@wanda-phi wanda-phi mentioned this issue Apr 6, 2024
Merged
wanda-phi added a commit to wanda-phi/amaranth that referenced this issue Apr 6, 2024
@wanda-phi
build.res: give a more specific error for `add_clock_constraint(Clock…
183496e 
…Signal)`.

Fixes amaranth-lang#542.
wanda-phi added a commit to wanda-phi/amaranth that referenced this issue Apr 7, 2024
@wanda-phi
build.res: give a more specific error for `add_clock_constraint(Clock…
1164ae0 
…Signal)`.

Fixes amaranth-lang#542.
wanda-phi added a commit to wanda-phi/amaranth that referenced this issue Apr 7, 2024
@wanda-phi
build.res: give a more specific error for `add_clock_constraint(Clock…
bdd0ebf 
…Signal)`.

Fixes amaranth-lang#542.
github-merge-queue bot pushed a commit that referenced this issue Apr 7, 2024
@wanda-phi @whitequark
build.res: give a more specific error for `add_clock_constraint(Clock…
38ad357 
…Signal)`.

Fixes #542.
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build.res: give a more specific error for add_clock_constraint(ClockSignal) wanda-phi/amaranth
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@whitequark @rroohhh @awygle