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Using OpenLANE to Harden Your Design:

You can utilize the Makefile existing here in this directory to do that.

But, first you need to specify 3 things:

export PDK_ROOT=<The location where the pdk is installed>
export OPENLANE_ROOT=<the absolute path to the openlane directory cloned or to be cloned>

NOTE: rc5 and caravel are still WIP so expect to run into some issues when using it.

If you don't have openlane already, then you can get it from here and checkout out to develop branch. Alternatively, you can clone and build the openlane develop branch through:

    make openlane

NOTE: We are developing caravel using openlane:rc5 which is the current develop branch. openlane:rc5 will be merged to master once the caravel chip is finalized.

NOTE: rc5 (current openlane develop) and rc4 (current openlane master) are using two different concepts of cell padding. rc4 is modifying the LEF, while rc5 is relying on openroad to handle the cell padding. Also, rc4 is using the standalone version of openDP while rc5 is using the one integrated in the openroad app. This affects the concept of PL_TARGET_DENSITY and while in rc4 it was preferred to have PL_TARGET_DENSITY=(FP_CORE_UTIL-(510)/100). Now, in rc5 it is preferred to be PL_TARGET_DENSITY=(FP_CORE_UTIL+(15)/100). FP_CORE_UTIL should be relaxed as well as it became more representative of the actual core utilization, which wasn't so much the case earlier. So, the perception of these two variables as well as CELL_PAD changed between rc4 and rc5 which necessitates a change in the configurations of almost every single design. CELL_PAD should be 4~6 for the skywater libraries in rc5 unlike rc4 which was 8.This will be included in the release notes when rc5 is released as well as the openlane wiki.

Then, you have two options:

  1. Create a macro for your design and harden it, then insert it into user_project_wrapper.

  2. Flatten your design with the user_project_wrapper and harden them as one.

NOTE: The OpenLANE documentation should cover everything you might need to create your design. You can find that here.

Option 1:

This could be done by creating a directory for your design here in this directory, and adding a configuration file for it under the same directory. You can follow the instructions given here to generate an initial configuration file for your design, or you can start with the following:

set script_dir [file dirname [file normalize [info script]]]

set ::env(DESIGN_NAME) <Your Design Name>

set ::env(DESIGN_IS_CORE) 0
set ::env(FP_PDN_CORE_RING) 0
set ::env(GLB_RT_MAXLAYER) 5

set ::env(VERILOG_FILES) "$script_dir/../../verilog/rtl/<Your RTL.v>"

set ::env(CLOCK_PORT) <Clock port name if it exists>
set ::env(CLOCK_PERIOD) <Desired clock period>

Then you can add them as you see fit to get the desired DRC/LVS clean outcome.

After that, run the following command:

make <your design directory name>

Then, follow the instructions given in Option 2.

NOTE: You might have other macros inside your design. In which case, you may need to have some special power configurations. This is covered here.

Option 2:

  1. Add your design to the RTL of the user_project_wrapper.

  2. Modify the configuration file here to include any extra files you may need. Make sure to change these accordingly:

set ::env(CLOCK_NET) "mprj.clk"

set ::env(VERILOG_FILES) "\
	$script_dir/../../verilog/rtl/defines.v \
	$script_dir/../../verilog/rtl/user_project_wrapper.v"

set ::env(VERILOG_FILES_BLACKBOX) "\
	$script_dir/../../verilog/rtl/defines.v \
	$script_dir/../../verilog/rtl/user_proj_example.v"

set ::env(EXTRA_LEFS) "\
	$script_dir/../../lef/user_proj_example.lef"

set ::env(EXTRA_GDS_FILES) "\
	$script_dir/../../gds/user_proj_example.gds"

NOTE: Don't change the size or the pin order!

  1. Remove this line add_macro_placement mprj 1150 1700 N from the interactive script here and replace it with the placement for your macro instances. Or, remove it entirely if you have no macros, along with this line manual_macro_placement f.

  2. Run your design through the flow: make user_project_wrapper

  3. Re-iterate until you have what you want.

  4. Go back to the main README.md and continue the process of boarding the chip.

NOTE: In both cases you might have other macros inside your design. In which case, you may need to have some special power configurations. This is covered here.

Extra Pointers:

  • The OpenLANE documentation should cover everything you might need to create your design. You can find that here.
  • The OpenLANE FAQs can guide through your troubles.
  • Here you can find all the configurations and how to use them.
  • Here you can learn how to write an interactive script.
  • Here you can find a full documentation for all OpenLANE commands.
  • This documentation describes how to use the exploration script to achieve an LVS/DRC clean design.
  • This documentation walks you through hardening a macro and all the decisions you should make.