Has anyone gotten decap mismatches Why would this be ```Subc

Question

Has anyone gotten decap mismatches Why would this be ```Subcircuit summary Circuit 1 user project wrapper |Circuit 2 user project wrapper | sky130 fd sc hd tapvpwrvgnd 1 1 |sky130 fd sc hd tapvpwrvgnd 1 1 sky130 fd sc hd and2 1 333 |sky130 fd sc hd and2 1 333 sky130 fd sc hd and2 2 38 |sky130 fd sc hd and2 2 38 sky130 fd sc hd decap 3 2917 |sky130 fd sc hd decap 3 1 Mismatch sky130 fd sc hd clkbuf 2 227 |sky130 fd sc hd clkbuf 2 227 ```

Matthew Guthaus · Answer

< U016EM8L91B> This seems like a netgen issue There are definitely more than 1 of these decap cells in the Verilog right netlist The setup tcl from sky130A seems to have some options for these to be parallelized Do you know what this might be

Matthew Guthaus · Answer

It looks like the setup tcl used to have them ignored but that is commented out ``` if regexp sky130 fd sc ^ + decap digit + $cell match ignore class circuit2 $cell ```

Matthew Guthaus · Answer

< U017X0NM2E7> It looks like a commit from you commented them out ```44b715a8 sky130 netgen sky130 setup tcl Mitch Bailey 2020 12 19 21 48 18 +0900 307 if regexp sky130 fd sc ^ + decap digit + $cell match 44b715a8 sky130 netgen sky130 setup tcl Mitch Bailey 2020 12 19 21 48 18 +0900 308 ignore class circuit1 $cell 44b715a8 sky130 netgen sky130 setup tcl Mitch Bailey 2020 12 19 21 48 18 +0900 309 ``` but the commit was supposed to IGNORE fill and tap cells ```commit 44b715a8cb733069b55d892ebe4786a79b9d5893 tag 1 0 91 Author Mitch Bailey lt d m bailey users noreply github com gt Date Sat Dec 19 21 48 18 2020 +0900 Ignore fill and tap cells in device level LVS```

Mitch Bailey · Answer

< U0175T39732> Right fill and tap cells contain no extracted devices LVS was extracting them as undefined subcircuits and ignoring them solved the problem On the other hand decap cells contain devices and ignoring them could result in mismatches netgen s setup file has parallel reduction for decap devices but recently I ve noticed that it hasn t been working in all cases I can see from your list that there are `sky130 fd sc hd tapvpwrvgnd 1` cells also being considered during LVS The sky130A netgen setup file should ignore these too Can you post your netgen command

Matthew Guthaus · Answer

Differences in decap shouldn t really be a mismatch as that could be safe to ignore Correctness isn t dependent on exact decap This is using the setup tcl from open pdks in the openlane flow ```Reading netlist file project openlane user project wrapper runs user project wrapper results magic user project wrapper spice Reading netlist file project openlane user project wrapper runs user project wrapper results lvs user project wrapper lvs powered v Reading setup file software PDKs sky130A libs tech netgen sky130A setup tcl Comparison output logged to file project openlane user project wrapper runs user project wrapper results lvs user project wrapper lvs lef log Logging to file project openlane user project wrapper runs user project wrapper results lvs user project wrapper lvs lef log enabled```

Matthew Guthaus · Answer

The version of open pdks is the one installed from openlane with make pdk

Matthew Guthaus · Answer

```commit 14db32aa8ba330e88632ff3ad2ff52f4f4dae1ad HEAD tag 1 0 234 Author Tim Edwards lt tim opencircuitdesign com gt Date Mon Oct 25 13 18 42 2021 0400 Updated version to go along with the merge of pull request 169 from Manar Abdelatty ```

Matthew Guthaus · Answer

In my MPW2 submission that passed LVS it had 1 instance of each decap type in both netlists when it matched

Mitch Bailey · Answer

Ok so this is a result of `flow tcl design user project wrapper`

Matthew Guthaus · Answer

Yeah

Matthew Guthaus · Answer

Using the mpw 3 tagged stuff

Mitch Bailey · Answer

`mpw 3` or `mpw 3a`

Mitch Bailey · Answer

Can you check the LVS results for the `decap` cells in the `user project wrapper` LVS log I m thinking that it s trying to do a black box compare because I doubt that the spice library is being added to the verilog

Tim Edwards · Answer

< U0175T39732> Ignoring cells is always dangerous because you could have for example a cell inserted upside down or something like that and ignoring it would mean you never see the issue The main thing is that the decap cells in the layout have not been combined in parallel you should end up basically with one decap cell of each type on each side Since decaps connect only to power and ground you need to figure out what s going on with the power and ground in your layout netlist

Mitch Bailey · Answer

< U016EM8L91B> I ve recently within the last 3 months noticed non parallelization of `decap` cells I think Has there been a change to netgen not to parallelize non empty cells

Tim Edwards · Answer

No They should all be parallel

Mitch Bailey · Answer

Correct me if I m wrong but parallel reduction only occurs if there s a mismatch right

Tim Edwards · Answer

No parallel reduction happens automatically although if there are parameters like with parallel reduction of devices then the parameters are chained together in a record But the devices are still considered parallel

Tobias Strauch · Answer

< U0175T39732> I had the same issue within the last days Also filler mismatches I was working hard to rebuild the testcase but wasn t able to sorry All I can do is to confirm it I use the resizer fixed docker to match the latest Openlane pdks release and I don t have decap filler LVS issues these days

Matthew Guthaus · Answer

< U016EM8L91B> I see thanks for the parallel explanation I got through this and there was a PDN DRC error that is probably related If the supplies are messed up it won t do the reduction right

Matthew Guthaus · Answer

< U02HH4W2ZG8> ^^ Did you check your supplies

Tobias Strauch · Answer

< U0175T39732> Good to know but didn t check it back then Layout hiccups don t have highest priority right now I still have time as I m targeting MPW4 where the flow will just work like a charm magic wand

Mitch Bailey · Answer

< U0175T39732> What version of netgen May be related to a recent change

Matthew Guthaus · Answer

I used the version with tag mpw 3a Not sure what that is The error was due to a bad power stripe that shorted some power rails

Mitch Bailey · Answer

Ok FWIW `netgen batch` will give you the version

Matthew Guthaus · Answer

I m trying to not use custom versions in this tape out Approved versions only