Switch to the new PDN from OpenROAD.

[cbalint13]

This PR fixes issue #1037 related to openroad new PDN behaviour.

(1) By two decimal rounding it fixes the error:

[ERROR PDN-0175] Pitch 28.8270 is too small for, must be atleast 28.8300

(2) Final conversion to new PDN part fixes the error:

Consider using "convert_pdn_config /home/cbalint/{...}/pdn_cfg.tcl" to convert the legacy configuration.
[INFO PDN-9008] Design name is spm.
[INFO PDN-9009] Reading technology data.
[ERROR PDN-9017] No stdcell grid specification found - no rails can be inserted.

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This now pass latest openlane builds & regression .
Q: do we need discriminate within pdn.tcl the old vs new PDN or just lets go with it forward (drop old) ?

Cc @arlpetergadfort , @maliberty

Thanks,
~cristian.

[cbalint13]

@maliberty , @arlpetergadfort

Let's leave out from here the very failure on SPM, will need a separate fix (another PR) for the grid / rounding issue.

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Q: For my understanding (for future fix), for the case of spm design sample, having FP_PDN_AUTO_ADJUST :

The grid i.e. 0.005 must be perfect divisor of that Pitch width/height numbers ?

• If so, actual div() by 3.0 (for spm sample) in floorplan.tcl leads to infinite decimal , inevitably will round somewhere.
• The final roundings of the div() (e.g 28.826666...) will never divide/align a fixed grid of 0.00X decimal number.

(Will debate this part on separate PR).

Thanks,
~cristian.

[donn]

@maliberty I need your review on this.

[maliberty]

@donn I do not recommend merging this. @arlpetergadfort is working on making off-grid into an error. I do not think pdn should snap the user input.

I don't know why you are dividing by 3 but you should snap the result to the grid.

[cbalint13]

@donn I do not recommend merging this. @arlpetergadfort is working on making off-grid into an error. I do not think pdn should snap the user input.

I don't know why you are dividing by 3 but you should snap the result to the grid.

@donn

Wait, @maliberty:

1. I dropped out from here the part with roundings (will see another PR for that) !
2. Let'ts just merge remaining part "source $::env(PDN_CFG) + pdngen" as new behavior, proposed by @arlpetergadfort .

Please have another quick look on this PR final diff summary.