How to efficiently get IO pins positions and reuse them

[lustefan97]

I am currently working on my master thesis where the subject is to enable 3D system implementation using OpenROAD, to achieve 3D stacked designs using face-to-face IO bonding.

I am trying to implement a flow (using the Ibex design as a base), and I already got the bottom die working (detailled routing did not finished, but I think that this is due to the use of the skywater PDK, which is a very old node). I want now to go further and work on the implementation of the top die and to do so I first need to get the IO pins positions of the bottom one.

This is were I am kind of stuck and would like your insight.
My idea is simply to write a .DEF file for the bottom die and read it to store the name and positions of its IO pins into a list, this was all fine and dandy up until I tried to use the "place_pin" command to manually place the pins knowing their name and positions.

Here is my issue : I read and stored the IO's names and positions using a TCL script, I divided the coordinates by 1000 to convert to micron, but when I tried to use the function I got the following error :

" TypeError in method 'microns_to_dbu', argument 1 of type 'double' "

So my questions now are :

1. What does this error mean ?
2. How can I solve this ?
3. Would there be a more efficient/more reliable way to get the pin positions (and eventually modify them to mirror their positions with regard to the x axis, as right now I am just substracting each x position to the die right side position to do so) ?
4. (Since I am here) Is there a possibility to display 2 dies on the gui simultaneously ? Whether it would be on top of one another, or beside one another.

I admit I converted the coordinates to double before dividing them, but I didn't thought that it would be a problem... Let me know if you need more details

[vijayank88]

@lustefan97
Did you refer this document?

[vijayank88]

Please write into .def format and check co-ordinates. This will give exact location for each pins.
@maliberty Is there other way to dump the locations of pins?

[lustefan97]

I know, that is exactly what I did and I've got them in a list with the name of the associated pin.

My issue is with the "reuse" part, I cannot use the coordinates without encountering the TypeError message and I don't want to enter each coordinates manually.
I wrote a script reading the pins names and coordinates and putting them in a list to reuse in another design, but when I want to use the place_pin command with those stored coordinates I have the mentionned error on the "micron_to_db" method, and I don't get why or what it means since I have read nothing about it in the documentation.

[vijayank88]

Are you using the latest commit?
Is that possible to provide reproducible test case?

[vijayank88]

@lustefan97
ord::dbu_to_microns <value> to convert dbu to microns and use that value to place the pins.

[lustefan97]

I think I tried that method before in my tcl script, but I may have used it wrongly as it caused the application to crash...

I am unable to try it again right now, but I will as soon as I am able to and I'll let you know ! Thank you for your help !

[maliberty]

Can you show exactly the TCL you are executing that causes the type error?

[lustefan97]

Yes sure, here is the part of the script were I am extracting the pin positions :

Then here is the command that I want to use, and what I do (it really is the place_pin that gives "TypeError in method 'microns_to_dbu', argument 1 of type 'double' ") :

And this is what I wanted to write at first :

Also I tried to use "ord::dbu_to_microns" as recommended previously, and as used in the save_image.tcl script (same syntax), in the gui TCL command box, but it unfortunately make the gui crash... Just for full disclosure, I base myself off of the flow.tcl script found in OpenROAD-flow-scripts/tools/OpenROAD/test and test my scripts there, if it is a problem or not recommended, please let me know !

[maliberty]

What are the actual values of xPos and yPos when it fails?

[lustefan97]

With the values I get with the 2nd screenshot (IO Placement), I have $xPos = 241.2 and $yPos = 496.2

But I also tried with integers like with $xPos = 241 and $yPos = 496 by changing %.1f to %d in "format", and I have the same error "microns_to_dbu" that is raised

[rovinski]

@lustefan97 there is no reason to be parsing the DEF to get the pin locations. You want to be using the DB interface. You can get a list of the BTerm objects with

set bterms [[[[ord::get_db] getChip] getBlock] getBTerms]

From there you can extract whatever properties you need. For example if you want the bounding box, you could use a script like this

foreach bterm $bterms {
  set bbox [$bterm getBBox]
  puts "Name: [$bterm getName]. BBox: [$bbox ll] [$bbox ur]"
}

The BBox points are reported in DBU so you can use ord::dbu_to_microns to convert to micron if that's what you need.

You should be able to take all this information and create a script which you can then use with place_pin to place the pins in the exact locations you need.

[maliberty]

If you haven't loaded a LEF then the conversion is meaningless. We should not crash though and can give an error instead.

[maliberty]

The crash is addressed in The-OpenROAD-Project/OpenROAD#3652

[lustefan97]

@maliberty @rovinski

Thank you so much for your help, I'll definitely use those methods from now on !
It answers a part of my question, but I still have a TypeError due to ord::microns_to_dbu that comes on when I want to use place_pin and even now with use the DB interface and ord::dbu_to_microns (and by curiosity I checked what happens when I don't convert to microns, and the result is the same).

I don't know exactly what this error means, and how I can solve it since from my understanding TCL is not a typed language and basically everything can be considered as a string (and if true, to me, that excludes a theory I had that place_pin expects a string instead of the double that is passed to it since the number is stored as a double in memory).

I have here a small script that I used to quickly test placing pins, get their positions and use place_pin to place them back a the exact same place (the expected behaviour being that nothing changes, or I get a warning/error saying that something has already been placed there). I use it in the TCL commands box of the gui while in OpenROAD-flow-scripts/tools/OpenROAD/test, if you want to try for yourself. The exact error I get is [ERROR GUI-0070] TypeError in method 'microns_to_dbu', argument 1 of type 'double'

source "helpers.tcl"
source "flow_helpers.tcl"

source "sky130hd/sky130hd.vars"
set place_density 0.7   

set design "ibex"
set top_module "ibex_core"
set synth_verilog "ibex_sky130hd.v"
set sdc_file "ibex_sky130hd.sdc"
set core_utilization 45

set slew_margin 30
set cap_margin 25

read_libraries
read_verilog $synth_verilog
link_design $top_module
read_sdc $sdc_file

# Step 1 : Initialize the floorplan of the die
#-----------------------------------------------
set aspect_ratio 1.0
set core_margin 1.0

initialize_floorplan -utilization $core_utilization \
                     -aspect_ratio $aspect_ratio    \
                     -core_space $core_margin       \
                     -site $site                                 

# Source the tracks (for : ) definition  
source $tracks_file

# Remove the buffers introduced by the synthesis tool (during synthesis).
remove_buffers   


define_pin_shape_pattern -layer met5 -x_step 3.4 -y_step 3.4 -region {10 10 525 525} -size {1.6 1.6}
set_io_pin_constraint -pin_names * -region "up:*"
place_pins -random -hor_layers $io_placer_hor_layer -ver_layers $io_placer_ver_layer

eval tapcell $tapcell_args

source $pdn_cfg
pdngen

global_placement -skip_io -density $place_density -pad_left $global_place_pad \
                                                  -pad_right $global_place_pad

define_pin_shape_pattern -layer met5 -x_step 3.4 -y_step 3.4 -region {10 10 525 525} -size {1.6 1.6}
place_pins -hor_layer $io_placer_hor_layer -ver_layer $io_placer_ver_layer


#------------------------------------------------------------------------------
# This is where I am trying to get the pins coordinates and use place_pin 
#------------------------------------------------------------------------------

# Get the pins locations info + set half pin width value to add to the low left coordinates

set bterms [[[[ord::get_db] getChip] getBlock] getBTerms]
set hpinw 0.8

foreach bterm $bterms {
  set bbox [$bterm getBBox]
  puts "Name: [$bterm getName]. BBox: [$bbox ll] [$bbox ur]"
  puts "Name of the pin : [$bterm getName]"
  #set one [lindex [$bbox ll] 0]
  set one [ord::dbu_to_microns [lindex [$bbox ll] 0]]  
  set one [expr {$one + $hpinw}]
  puts "X position : $one"
  #set two [lindex [$bbox ll] 1]
  set two [ord::dbu_to_microns [lindex [$bbox ll] 1]]
  set two [expr {$two + $hpinw}]
  puts "Y position : $two"
  place_pin -pin_name [$bterm getName] -layer met5 -location {$one $two} -pin_size {1.6 1.6}
}

# This last line with place_pin is what is giving "TypeError" 

[rovinski]

@lustefan97 You're getting caught by Tcl syntax. Braces ({}) create literal expressions and don't allow dereferencing variables with $.
When you use -location {$one $two} it resolves to a list of the two strings $one $two which are indeed not convertible to doubles.

Change the line to this and it should work:

place_pin -pin_name [$bterm getName] -layer met5 -location [list $one $two] -pin_size {1.6 1.6}

[rovinski]

Another thing is that you can look up methods of objects between db.h and geom.h. There are better accessor methods for Rect objects.

[lindex [$bbox ll] 0]] is equivalent to [$bbox xMin]
Instead of getting the lower left plus some offset you could just use $bbox xCenter and $bbox yCenter
etc.

You can also mistype a method for an object in the shell to print out a list of methods. It's sometimes faster.

openroad> $bbox asdf
Invalid method. Must be one of: configure cget -acquire -disown -delete = init reset moveTo moveDelta mergeInit isInverted minDXDY maxDXDY getDir set_xlo set_xhi set_ylo set_yhi xMin yMin xMax yMax dx dy xCenter yCenter getPoints ll ul ur lr intersects overlaps contains inside closestPtInside merge bloat intersection intersect area margin printf print

[lustefan97]

I see, I tried a similar line but always with braces and switching to brackets solved the problem, some TCL trickiness I guess. I'll keep that in mind from now on, thanks for your help !