# Custom Placement of Two-Row Tall Cells

Tool: Detailed Placement

Subcategory: Placement violation

## Conversation

### harshkhandeparkar
In the OpenFASoC [LDO generator](https://github.com/idea-fasoc/OpenFASOC/tree/main/openfasoc/generators/ldo-gen), a two-row tall comparator latch is custom placed using the `place_cell` command in a [tcl script](https://github.com/idea-fasoc/OpenFASOC/blob/f7b3440c485ff2accbf549aa11a12a75c01186c1/openfasoc/generators/ldo-gen/flow/scripts/openfasoc/custom_place.tcl#L7).

This used to work in earlier versions of OpenROAD, but recently the CI is [failing](https://github.com/idea-fasoc/OpenFASOC/actions/runs/7301239627/job/19897490889#step:4:1990) with the following error:
```
[ERROR DPL-0017] cannot place instance cmp1.
```
 The custom placement is done before running the `detailed_placement` command in the [detail_place.tcl](https://github.com/idea-fasoc/OpenFASOC/blob/main/openfasoc/generators/ldo-gen/flow/scripts/detail_place.tcl) script. If the `detailed_placement` command is removed, the following error is returned:
```
[ERROR DPL-0044] Cell cmp1 with height 8140 is taller than any row.
Error: detail_place.tcl, 26 DPL-0044
```

Relevant Information:
- OpenROAD Version hash: `e89829335596b351ce665dcc3b73619c0b191c14`
- Comparator Latch Cell: [LEF](https://github.com/idea-fasoc/OpenFASOC/blob/main/openfasoc/generators/ldo-gen/blocks/sky130hvl/lef/LDO_COMPARATOR_LATCH.lef) / [GDS](https://github.com/idea-fasoc/OpenFASOC/blob/main/openfasoc/generators/ldo-gen/blocks/sky130hvl/gds/LDO_COMPARATOR_LATCH.gds)
- Custom placement script: [custom_place.tcl](https://github.com/idea-fasoc/OpenFASOC/blob/main/openfasoc/generators/ldo-gen/flow/scripts/openfasoc/custom_place.tcl)

Is there a way to place this cell (not as a macro) without placement violations?

cc: @msaligane 

### rovinski
Have you tried marking the cells as `FIXED` instead of `PLACED`?

### maliberty
We have recently being doing work related to multi-height cells.  The error indicates that the detailed placer is trying to legalize this instance which is sounds like you don't want.  FIRM should work for that purpose.  Can you provide a test case?

### maliberty
Your other option is to provide double height site rows.