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Allow input pad locations to be specified using XDC format #20

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jgoeders opened this issue Sep 13, 2020 · 7 comments
Closed

Allow input pad locations to be specified using XDC format #20

jgoeders opened this issue Sep 13, 2020 · 7 comments

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@jgoeders
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It would be nice if you could provide a set of pin constraints from the original bitstream compile, such that when translating fasm to bels, the top-level input names could be mapped back to the original input names.

This would be similar to the "icebox_vlog.py -P" functionality if you are familiar with the icestorm tools.

I'm assuming this option doesn't already exist?

If you're not already working on this, I would be happy to work on it and upstream it. If you have any advice on where to look in the code first, it would be much suggested. Thanks!
@mithro
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mithro commented Sep 14, 2020

@litghost / @acomodi -- Any idea if this already works? I assume that @jgoeders is using an existing vivado design and not something produced from VPR which would have this annotation?

@acomodi
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acomodi commented Sep 14, 2020

I think that what is missing to get the top level IO names are either one of the following options:

  • A PCF constraints file
  • They synthesized eblif file that contains IO_LOC_PAIRS attributes on IO buffer instances. The IO_LOC_PAIRS are added with a yosys plugin at synthesis time.

I think that adding the PCF constraint file should be the way to go and should solve the problem.

@jgoeders
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Ah, ok. I see there is already a --pcf argument. Not sure how I missed that. I assume this only takes PCF and not XDC for pin constraints? @mithro, is there a symbiflow tool that converts between these?

@mithro
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mithro commented Sep 14, 2020

@jgoeders We are generally moving towards supporting XDC / SDC everywhere (rather than PCF). I don't think this has been done for fasm2bels yet?

@jgoeders
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@acomodi If there's no XDC support I can add it and upstream it.

@mithro Is there a standard parser you are using across Symbiflow projects?

@acomodi
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acomodi commented Sep 14, 2020

@jgoeders Currently there is no direct XDC parser to read the pad locations within fasm2bels, so this could be a good addition IMO to the tool.

@jgoeders jgoeders changed the title Allow input constraints file to map inputs to original names Allow input pad locations to be specified using XDC format Sep 14, 2020
@jgoeders
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Fixed in #21

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@mithro @jgoeders @acomodi