| commit | ab5c2ecf9c4e9cf55392d5a9e5c9a17f87a1b097 | [log] [tgz] |
|---|---|---|
| author | Jes B. Klinke <jbk@chromium.org> | Wed Nov 24 13:56:01 2021 -0800 |
| committer | cfrantz <frantzcj+github@gmail.com> | Thu Dec 02 08:14:13 2021 -0800 |
| tree | 3f999bfd96ed860f894b9c24256b7142f5adfe42 | |
| parent | c1bd139dc158a06af943b4f93130a9ffeccc381e [diff] |
[opentitantool] Fixes to bootstrap of legacy Titan This newly added code has a few bugs. 1. A bug was introduced during review, when the code to set the "final" flag on the last frame was move out of the loop. The hash of the block needs to be computed after the flag is set. (This bug would have been caught had I run the one and only unit test in this file.) 2. The above lead to the discovery that the existing logic (also in primitive.rs) does not attempt to verify the ack of the very last block, leading to the false claim of successful bootstrapping. 3. Further real-life testing revealed more shortcomings of the existing logic. Ordinarily, the bidirectional transaction is used such that the boot rom will ack the previously transmitted frame, at the same time as receiving the next one. I.e. the Rust code will look for ack of frame 3 while transmitting frame 4. If an unrecognized checksum is received, the code will go back and retransmit frame 3 repeatedly, until ack of frame 3 is received. However, if the cause of the original bad ack was not in the boot rom, but due to noise on the CIDO line, then the bootrom may have successfully received frame 3, and possibly also frame 4. If the latter is the case, the boot rom (on H1Dx at least) will repeat the ack of block 4 while frame 3 is being retransmitted. This CL introduces code to recognize this case, and others, rather than only looking for ack of the frame most recently transmitted. TEST=Repeatedly flashed H1Dx while manipulating CIDO capacitance Signed-off-by: Jes B. Klinke <jbk@chromium.org>
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.
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