lx071 / usb1_ai_generated
Created
Maintained by
lx071
for ai contest
Watch
1
Members
1
lx071
committed a year ago
Report
Introduction
We referred to the USB microarchitecture in the riscduino project. First, we organized the USB microarchitecture to understand the internal components of USB. According to the components and their functions, we designed prompts used ChatGPT to generate Verilog source code for USB sie, USB phy and USB transceiver respectively. In this part, we made multiple modifications of the prompts when we found that there are some limitations of GPT. Then we replaced the corresponding components with GPT generated components. Finally, we performed the functional tests and used OpenLANE to generate GDS from RTL. In addition, we also used the prompts to generate C++ source code.
USB microarchitecture
- Reference: usb1_host
Modules
USB Host Controller
USB Host Controller connects with the wishbone and the pinmux. It has several modules, which are listed as follows.
- u_wb_rst: Wishbone Reset Synchronization
- u_usb_rst: USB Reset Synchronization
- u_async_wb: Async Wishbone Interface. This block does async Wishbone from one clock to other clock domain
Connections between USB Host modules are listed as follows.
USB Core
USB Core handles USB signal transmission, handshake protocol, error detection and correction functions to ensure reliable data transmission and communication between devices. It can be configured, read or written through registers. Its modules are listed as follows.
- usbh_fifo is a queue, which includes RAMs, registers, a read pointer, a write pointer and a counter.
A part of internal connections are listed as follows.
USB Sie
USB Sie is an important part in USB Core. USB Sie receives data from USB Core, passes signals and data after detecting the packet formats. CRC-5 and CRC-16 are used to protect token and data packets.
It has a state machine, including 13 states. Sie follows the sequence to detect packets and send different signals and data. The state machine is listed as follows. In some states, Sie will send data to utmi_data_o and USB Core will receive. Then USB Host Controller receive the data, interacting with USB Phy.
USB Phy
USB Phy also has a state machine, including 15 states. It will check the current state according to the signals. According to different states, it will have different actions, such as sending data, receiving data, resetting and so on. The state machine is listed as follows.
In addition, USB Phy will receive and analyse differential signals from USB Transceiver, which is related to 4 states: SE0 state, J state, K state and invalid state.
USB Transceiver
USB Transceiver is used to implement the data transmission of USB. According to inputs usb_phy_tx_dp_i, usb_phy_tx_dn_i and mode_i, USB Transceiver will assign outputs out_dp and out_dn the value. The table will show the situations.
| mode_i | usb_phy_tx_dp_i | usb_phy_tx_dn_i | out_dp | out_dn |
|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 1 |
| 0 | 0 | 1 | 0 | 0 |
| 0 | 1 | 0 | 1 | 0 |
| 0 | 1 | 1 | 0 | 0 |
| 1 | 0 | 0 | 0 | 0 |
| 1 | 0 | 1 | 0 | 1 |
| 1 | 1 | 0 | 1 | 0 |
| 1 | 1 | 1 | 1 | 1 |
Handshake/Interaction
Prompts
GPT limits
USB components is so complex that ChatGPT couldn't design directly. So we tried to tell GPT how to generate the target code. But just giving simple prompts isn't enough. GPT will not generate the code we want according to the simple prompts. We had to provide details as much and precise as possible, such as the change of one signal. At the same time, we found that GPT may ignore some sentences if the prompt was too long. So we divided long prompts into several parts and saved the important contexts.
Strategy
Our target is to generate source code for USB sie, USB phy and USB transceiver. The original source code is quite long and complex and GPT has limited token for the contexts. We had to divide the original code into several parts based on different functions. For example, when handling USB Sie source code, we first would chat with GPT about variable definitions of USB Sie. Based on these definitions, added the state machine. Because there are quite a few actions in every state, we needed to pass the message of one state at a time , instead of sending all messages once.
Files
The prompts folder and the relationships between prompts and generated code are listed as follows.
prompts
├── C++ prompts
│ ├── usb_fs_phy
│ │ ├── usb_fs_phy.cpp
│ │ ├── prompts_1.md
│ │ ├── ...
│ │ └── prompts_11.md
│ ├── usb_transceiver
│ │ ├── usb_transceiver.cpp
│ │ └── session_1.md
│ ├── usbh_sie
│ │ ├── usbh_sie.cpp
│ │ ├── session_1.md
│ │ └── session_2.md
├── usb_fs_phy
│ ├── prompts_1.txt
│ ├── ...
│ └── prompts_11.txt
├── usb_transceiver
│ └── session.txt
└── usbh_sie
├── session1.txt
├── ...
└── session16.txt
| folder | generated code | prompt nums |
|---|---|---|
| usb_fs_phy(Verilog) | usb_fs_phy.v | 11 |
| usb_transceiver(Verilog) | usb_transceiver.v | 1 |
| usbh_sie(Verilog) | usbh_sie.sv | 16 |
| usb_fs_phy(C++) | usb_fs_phy.v | 11 |
| usb_transceiver(C++) | usb_transceiver.v | 1 |
| usbh_sie(C++) | usbh_sie.sv | 2 |
Validation
The way to verifying the generated code is to replace the originalwith the generated. Then write a configuration file, add this design and check the operation by simulation. Finally configure OpenLANE and run the code. The result will be compared with another result before replacement.
Generate C++ code
We modified the original prompts to generate C++ code. It will be the control validation in subsequent studies. Besides, it will be used on other C++ test framework in the future.
Strategy
Based on the steps of original prompts, The way to giving prompts is similar. We follow the original prompts. First deal with variable definitions. Then append other functions. Like USB Phy, we gave the detailed actions in every state to GPT once instead of giving all messages. But when dealing with USB Sie, we merged the prompts(sessions) about states because there were repetitive conversations(variable definitions) could be ignored in Sie prompts.
Problems
Because of the time limit, we had no restrictions on the format of the generated C++ code. The original prompts is to generate Verilog code. We found that the generated code was in a mess because there are some Implementation such as variable definitions. For example, when GPT got an 8 bit register(reg[7:0]) in Verilog, it generated the C++ code that appeared these types: int, bool[8] and bitset<8>. And the usage of variables became precarious. We had to make more modifications on generated code. However, there maybe exists potential problems because we have no time to test the code.
Apache License
Version 2.0, January 2004
http://www.apache.org/licenses/
TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
1. Definitions.
"License" shall mean the terms and conditions for use, reproduction,
and distribution as defined by Sections 1 through 9 of this document.
"Licensor" shall mean the copyright owner or entity authorized by
the copyright owner that is granting the License.
"Legal Entity" shall mean the union of the acting entity and all
other entities that control, are controlled by, or are under common
control with that entity. For the purposes of this definition,
"control" means (i) the power, direct or indirect, to cause the
direction or management of such entity, whether by contract or
otherwise, or (ii) ownership of fifty percent (50%) or more of the
outstanding shares, or (iii) beneficial ownership of such entity.
"You" (or "Your") shall mean an individual or Legal Entity
exercising permissions granted by this License.
"Source" form shall mean the preferred form for making modifications,
including but not limited to software source code, documentation
source, and configuration files.
"Object" form shall mean any form resulting from mechanical
transformation or translation of a Source form, including but
not limited to compiled object code, generated documentation,
and conversions to other media types.
"Work" shall mean the work of authorship, whether in Source or
Object form, made available under the License, as indicated by a
copyright notice that is included in or attached to the work
(an example is provided in the Appendix below).
"Derivative Works" shall mean any work, whether in Source or Object
form, that is based on (or derived from) the Work and for which the
editorial revisions, annotations, elaborations, or other modifications
represent, as a whole, an original work of authorship. For the purposes
of this License, Derivative Works shall not include works that remain
separable from, or merely link (or bind by name) to the interfaces of,
the Work and Derivative Works thereof.
"Contribution" shall mean any work of authorship, including
the original version of the Work and any modifications or additions
to that Work or Derivative Works thereof, that is intentionally
submitted to Licensor for inclusion in the Work by the copyright owner
or by an individual or Legal Entity authorized to submit on behalf of
the copyright owner. For the purposes of this definition, "submitted"
means any form of electronic, verbal, or written communication sent
to the Licensor or its representatives, including but not limited to
communication on electronic mailing lists, source code control systems,
and issue tracking systems that are managed by, or on behalf of, the
Licensor for the purpose of discussing and improving the Work, but
excluding communication that is conspicuously marked or otherwise
designated in writing by the copyright owner as "Not a Contribution."
"Contributor" shall mean Licensor and any individual or Legal Entity
on behalf of whom a Contribution has been received by Licensor and
subsequently incorporated within the Work.
2. Grant of Copyright License. Subject to the terms and conditions of
this License, each Contributor hereby grants to You a perpetual,
worldwide, non-exclusive, no-charge, royalty-free, irrevocable
copyright license to reproduce, prepare Derivative Works of,
publicly display, publicly perform, sublicense, and distribute the
Work and such Derivative Works in Source or Object form.
3. Grant of Patent License. Subject to the terms and conditions of
this License, each Contributor hereby grants to You a perpetual,
worldwide, non-exclusive, no-charge, royalty-free, irrevocable
(except as stated in this section) patent license to make, have made,
use, offer to sell, sell, import, and otherwise transfer the Work,
where such license applies only to those patent claims licensable
by such Contributor that are necessarily infringed by their
Contribution(s) alone or by combination of their Contribution(s)
with the Work to which such Contribution(s) was submitted. If You
institute patent litigation against any entity (including a
cross-claim or counterclaim in a lawsuit) alleging that the Work
or a Contribution incorporated within the Work constitutes direct
or contributory patent infringement, then any patent licenses
granted to You under this License for that Work shall terminate
as of the date such litigation is filed.
4. Redistribution. You may reproduce and distribute copies of the
Work or Derivative Works thereof in any medium, with or without
modifications, and in Source or Object form, provided that You
meet the following conditions:
(a) You must give any other recipients of the Work or
Derivative Works a copy of this License; and
(b) You must cause any modified files to carry prominent notices
stating that You changed the files; and
(c) You must retain, in the Source form of any Derivative Works
that You distribute, all copyright, patent, trademark, and
attribution notices from the Source form of the Work,
excluding those notices that do not pertain to any part of
the Derivative Works; and
(d) If the Work includes a "NOTICE" text file as part of its
distribution, then any Derivative Works that You distribute must
include a readable copy of the attribution notices contained
within such NOTICE file, excluding those notices that do not
pertain to any part of the Derivative Works, in at least one
of the following places: within a NOTICE text file distributed
as part of the Derivative Works; within the Source form or
documentation, if provided along with the Derivative Works; or,
within a display generated by the Derivative Works, if and
wherever such third-party notices normally appear. The contents
of the NOTICE file are for informational purposes only and
do not modify the License. You may add Your own attribution
notices within Derivative Works that You distribute, alongside
or as an addendum to the NOTICE text from the Work, provided
that such additional attribution notices cannot be construed
as modifying the License.
You may add Your own copyright statement to Your modifications and
may provide additional or different license terms and conditions
for use, reproduction, or distribution of Your modifications, or
for any such Derivative Works as a whole, provided Your use,
reproduction, and distribution of the Work otherwise complies with
the conditions stated in this License.
5. Submission of Contributions. Unless You explicitly state otherwise,
any Contribution intentionally submitted for inclusion in the Work
by You to the Licensor shall be under the terms and conditions of
this License, without any additional terms or conditions.
Notwithstanding the above, nothing herein shall supersede or modify
the terms of any separate license agreement you may have executed
with Licensor regarding such Contributions.
6. Trademarks. This License does not grant permission to use the trade
names, trademarks, service marks, or product names of the Licensor,
except as required for reasonable and customary use in describing the
origin of the Work and reproducing the content of the NOTICE file.
7. Disclaimer of Warranty. Unless required by applicable law or
agreed to in writing, Licensor provides the Work (and each
Contributor provides its Contributions) on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
implied, including, without limitation, any warranties or conditions
of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
PARTICULAR PURPOSE. You are solely responsible for determining the
appropriateness of using or redistributing the Work and assume any
risks associated with Your exercise of permissions under this License.
8. Limitation of Liability. In no event and under no legal theory,
whether in tort (including negligence), contract, or otherwise,
unless required by applicable law (such as deliberate and grossly
negligent acts) or agreed to in writing, shall any Contributor be
liable to You for damages, including any direct, indirect, special,
incidental, or consequential damages of any character arising as a
result of this License or out of the use or inability to use the
Work (including but not limited to damages for loss of goodwill,
work stoppage, computer failure or malfunction, or any and all
other commercial damages or losses), even if such Contributor
has been advised of the possibility of such damages.
9. Accepting Warranty or Additional Liability. While redistributing
the Work or Derivative Works thereof, You may choose to offer,
and charge a fee for, acceptance of support, warranty, indemnity,
or other liability obligations and/or rights consistent with this
License. However, in accepting such obligations, You may act only
on Your own behalf and on Your sole responsibility, not on behalf
of any other Contributor, and only if You agree to indemnify,
defend, and hold each Contributor harmless for any liability
incurred by, or claims asserted against, such Contributor by reason
of your accepting any such warranty or additional liability.
END OF TERMS AND CONDITIONS
APPENDIX: How to apply the Apache License to your work.
To apply the Apache License to your work, attach the following
boilerplate notice, with the fields enclosed by brackets "[]"
replaced with your own identifying information. (Don't include
the brackets!) The text should be enclosed in the appropriate
comment syntax for the file format. We also recommend that a
file or class name and description of purpose be included on the
same "printed page" as the copyright notice for easier
identification within third-party archives.
Copyright [yyyy] [name of copyright owner]
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.