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prjxray_create_place_constraints.py fails for unconstrained PLLE2_ADV on xc7a100T device #1542

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tcal-x opened this issue Jun 23, 2020 · 5 comments
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prjxray_create_place_constraints.py fails for unconstrained PLLE2_ADV on xc7a100T device #1542

tcal-x opened this issue Jun 23, 2020 · 5 comments
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tcal-x commented Jun 23, 2020 •
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Error seen:

Traceback (most recent call last):
  File "/home/tcal/2nd-tcal-x/symbiflow-arch-defs/xc/common/utils/prjxray_create_place_constraints.py", line 693, in <module>
    main()
  File "/home/tcal/2nd-tcal-x/symbiflow-arch-defs/xc/common/utils/prjxray_create_place_constraints.py", line 681, in main
    vpr_grid, loc_in_use, block_locs, blocks, grid_capacities):
  File "/home/tcal/2nd-tcal-x/symbiflow-arch-defs/xc/common/utils/prjxray_create_place_constraints.py", line 514, in place_clocks
    for potential_loc in sorted(available_placements[key]):
KeyError: ('PLLE2_ADV', 5)

To reproduce:

  • Sync to current head of master (a8c60d9 or later).
  • Rerun "make env" to rerun cmake to get the new 100T test targets.
  • Edit the file xc/xc7/tests/soc/litex/mini_ddr/minilitex_ddr_arty100t.v as follows:
    • Delete or comment out the line (* LOC="PLLE2_ADV_X1Y1" *)
  • cd to build/xc/xc7/tests/soc/litex/mini_ddr.
  • Run make minilitex_ddr_arty100t_bin to produce the error.
    • This will take several hours the first time, so run overnight.
    • It takes less than a minute to get to the error in subsequent runs.

Notes:

  • The original 35T design constrained the IDELAYCTRL to X1Y0. With the 100T it is constrained to X1Y1.
  • In the original design, the PLLE2_ADV did not need to be constrained. With 100T, if it is not constrained, we encounter the script error above. If it is constrained to X1Y1, then everything works.

This is not blocking, since there is the workaround of adding the LOC constraint to the PLLE2_ADV.
@tcal-x tcal-x mentioned this issue Jul 1, 2020
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tcal-x commented Jul 17, 2020

Hi @litghost , who is the best person to own this? It involves the constraint solver in the clock placement script. This should be a pretty easy problem to solve, but I can't find anything obvious, such as a hardcoding of clock region X1Y0 (which wouldn't work on 100T)

@litghost
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litghost commented Jul 17, 2020 •
edited

Hi @litghost , who is the best person to own this? It involves the constraint solver in the clock placement script. This should be a pretty easy problem to solve, but I can't find anything obvious, such as a hardcoding of clock region X1Y0 (which wouldn't work on 100T)

I believe this issue is on the list of bugs to fix for useability reasons, so it will get resolved once other issues are closed. Other issues are being actively worked on, and I don't see this as a super high priority because of the ease of the workaround. Do you believe it needs a higher priority?

@tcal-x
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tcal-x commented Jul 17, 2020

Hi @litghost , that exact point of view occurred to me after I posted my note, so we're in complete agreement. It will get done eventually, but it's not blocking anyone now, so there's no urgency, and no reason to bump it to higher priority.

@acomodi acomodi mentioned this issue Sep 7, 2020
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@acomodi I believe this has been fixed?

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acomodi commented Oct 29, 2020

Yes, this has been fixed. Closing

@acomodi acomodi closed this as completed Oct 29, 2020
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