| commit | 0c6bac8e5df34691ffc7ecb06dd23b98be30db64 | [log] [tgz] |
|---|---|---|
| author | Michael Schaffner <msf@opentitan.org> | Tue Jul 13 18:13:33 2021 -0700 |
| committer | Michael Schaffner <msf@google.com> | Wed Jul 14 10:32:27 2021 -0700 |
| tree | 2907571dc409c22a22b84a86de35facadfc2b85e | |
| parent | f85555ddd39ca77567f8d5d54bf304c31841d703 [diff] |
[lc_ctrl] Add scrap state for main FSM This adds a scrap state to the main FSM in order to break an unintended, circular logical dependency. I.e., the life cycle FSM decodes the SCRAP life cycle state as any other state and keeps on sampling the life cycle vector coming from OTP. However, since the SCRAP state asserts `lc_escalate_en`, OTP escalates and resets all partition outputs back to the default, causing the LC controller to latch an invalid LC vector encoding. This has a few unintended side effects. For instance, it causes the `lc_escalate_en` signals to toggle from ON -> OFF -> ON. Also, it leads to an incorrect life cycle TAP readout, as the life cycle state reads back as "INVALID" instead of "SCRAP". This commit introduces the following fixes: 1) the ON -> OFF -> ON toggle is fixed in the `lc_ctrl_signal_decode` logic, which now asserts `lc_escalate_en` when the data valid indication from OTP unexpectedly goes to 0. 2) the FSM is moved into a terminal `ScrapSt` right away when a SCRAP life cycle state is detected. In that state, the life cycle vector coming from OTP is not sampled anymore, thereby breaking the logical loop mentioned above. Note that 2) has the additional benefit that life cycle transition operations are now explicitly disallowed when the device is in SCRAP. Before, this was checked only after initiating a life cycle transition as part of the transition checking logic. This fixes #7286 Signed-off-by: Michael Schaffner <msf@opentitan.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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