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Requiring a NULL tile at (0, 0) is Xilinx-specific #34

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gatecat opened this issue Mar 17, 2021 · 5 comments
Open

Requiring a NULL tile at (0, 0) is Xilinx-specific #34

gatecat opened this issue Mar 17, 2021 · 5 comments

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@gatecat
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gatecat commented Mar 17, 2021

https://github.com/SymbiFlow/python-fpga-interchange/blob/master/fpga_interchange/populate_chip_info.py#L1139 assumes that the tile at (0, 0) is NULL.

This works for Xilinx, and can be made to work for Nexus by renaming that tile (because it's equivalent to a NULL tile) but this should be made generic in the future.
@litghost
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litghost commented Mar 17, 2021 •
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I agree this should be fixed! We can probably detect the "NULL" tile by checking if it has sites or connected routing.

@gatecat
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gatecat commented Mar 17, 2021

I don't think there is a guarantee that there will be a "NULL" tile - I think some iCE40 devices have something in every tile, for example.

@litghost
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I don't think there is a guarantee that there will be a "NULL" tile - I think some iCE40 devices have something in every tile, for example.

Weird! What is in the "corner" of ice40 FPGA's?

@litghost
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The other option here is to glom the constant source site onto a unique tile in the fabric. Does the ice40 fabric has at least 1 unique tile in the fabric?

@gatecat
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gatecat commented Mar 17, 2021

Weird! What is in the "corner" of ice40 FPGA's?

the UltraPlus notionally has hard IP and SPRAM located there

The other option here is to glom the constant source site onto a unique tile in the fabric. Does the ice40 fabric has at least 1 unique tile in the fabric?

yeah, the (0, 0) corner tile is good enough for this just might not necessarily be empty

@gatecat gatecat mentioned this issue May 25, 2021
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@litghost @gatecat