[usb / top] Hook-up usb rx enable

- Currently the rx enable is assumed to be dynamic, but this may
  change based on Nuvoton feedback.

There was a discussion regarding whether we should make most of the usbdev inter-signals instead of pinmux signals.
See below for rationale.

In addition to dp/dn, sense and dp/dn_pullup_en all have to remain pinmux-able signals.
Sense may need to come through pinmux since it is used to detect vbus power.  As long as the vbus voltage is not too high (or is clamped to a safe range), it can be muxed on nay pin.
dp/dn_pullup_en make use of pinmux's sleep capture as part of usbdev's suspend / resume feature.

This ends up leaving a few scattered signals that may or may not fall into the pinmux category.
Ultimateily, it is difficult from the perspective of the usbdev to know whether a signal should be pinmuxed or directly signaled out.

The ideal solution are two-fold

1. Make all signals inter-signal, and use a top specific wrapper that connects the necessary signals to pinmux.
2. Make all signals pinmuxable, and manually handle the pad connections where required.

In our design, we currently have most of the support needed for 2, (see #6042) for possible enhancements

Signed-off-by: Timothy Chen <timothytim@google.com>
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  1. .github/
  2. ci/
  3. doc/
  4. hw/
  5. site/
  6. sw/
  7. test/
  8. util/
  9. .clang-format
  10. .dockerignore
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  16. _index.md
  17. apt-requirements.txt
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  19. check_tool_requirements.core
  20. CLA
  21. COMMITTERS
  22. CONTRIBUTING.md
  23. LICENSE
  24. meson.build
  25. meson_init.sh
  26. meson_options.txt
  27. python-requirements.txt
  28. README.md
  29. tool_requirements.py
  30. toolchain.txt
  31. topgen-generator.core
  32. topgen-reg-only.core
  33. topgen.core
  34. yum-requirements.txt
README.md

OpenTitan

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About the project

OpenTitan is an open source silicon Root of Trust (RoT) project. OpenTitan will make the silicon RoT design and implementation more transparent, trustworthy, and secure for enterprises, platform providers, and chip manufacturers. OpenTitan is administered by lowRISC CIC as a collaborative project to produce high quality, open IP for instantiation as a full-featured product. See the OpenTitan site and OpenTitan docs for more information about the project.

About this repository

This repository contains hardware, software and utilities written as part of the OpenTitan project. It is structured as monolithic repository, or “monorepo”, where all components live in one repository. It exists to enable collaboration across partners participating in the OpenTitan project.

Documentation

The project contains comprehensive documentation of all IPs and tools. You can access it online at docs.opentitan.org.

How to contribute

Have a look at CONTRIBUTING for guidelines on how to contribute code to this repository.

Licensing

Unless otherwise noted, everything in this repository is covered by the Apache License, Version 2.0 (see LICENSE for full text).