Add support for QuickLogic devices

[rw1nkler]

This PR adds support for the following QuickLogic devices:

• EOS-S3 (https://www.quicklogic.com/products/eos-s3/)
• PolarPro 3E (https://www.quicklogic.com/products/fpga/fpgas-sram/#polarpro3e)

[litghost]

There are couple open questions here:

• Does this belong in the downstream fork at all?
• If it does belong down here, it oaught to be in wip/ branch, rather than merged directly onto the downstream master branch

@mithro What's the plan here?

[rw1nkler]

This PR has been created to discuss the changes and then add it as a wip/ branch to SymbiFlow Yosys.
The code comes from the QuickLogic Yosys fork (which is actively developed):
https://github.com/QuickLogic-Corp/yosys/tree/quicklogic-rebased

GitHub

QuickLogic-Corp/yosys

Yosys Open SYnthesis Suite. Contribute to QuickLogic-Corp/yosys development by creating an account on GitHub.

[rw1nkler]

Is there any other issue that needs to be addressed before creating wip/quicklogic branch and regenerating Yosys master+wip branch?

[litghost]

Is there any other issue that needs to be addressed before creating wip/quicklogic branch and regenerating Yosys master+wip branch?

I think the broader issue is how to maintain long term maintenance of this wip/ branch. One of the recent pushes has been to eliminate wip/ branches, either by getting the patches merged upstream, or in the case of yosys, making plugins rather than modifying yosys directly. Ideally this would go into upstream yosys, but I understand that might be hard to impossible.

If getting into upstream yosys is not going to happen, then I believe converting this PR into a plugin, likely under its own project, is my preferred path forward.

[rw1nkler]

I believe converting this PR into a plugin, likely under its own project, is my preferred path forward.

Ok, I will create a PR which will add those changes as a separate Yosys plugin.