[top_earlgrey] Reduce number of PRINCE half rounds for main SRAM scrambling #24378
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Previously, all scrambled memory primitives had to use the same number of PRINCE half rounds which was set to 3. This commit adds a new and optional argument to the mem_bkdr_util constructor, to allow configuring different values. If the argument is not provided, the default of 3 PRINCE half rounds is used. This is a cherry pick of commit 72ea1a1 to branch earlgrey_1.0.0. Signed-off-by: Pirmin Vogel <vogelpi@lowrisc.org>
This is a cherry pick of commit c3732b3 to branch earlgrey_1.0.0. Signed-off-by: Pirmin Vogel <vogelpi@lowrisc.org>
This commit reduces the number of PRINCE half rounds for the scrambling of the main SRAM to 2 half rounds as used in the past. This is done to reduce timing pressure. This is a cherry pick of commit 0ff694a to branch earlgrey_1.0.0. Signed-off-by: Pirmin Vogel <vogelpi@lowrisc.org>
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CHANGE AUTHORIZED: hw/ip/sram_ctrl/data/sram_ctrl.hjson This is an ECO confirmed by the PD team. |
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CHANGE AUTHORIZED: hw/ip/sram_ctrl/data/sram_ctrl.hjson This is an ECO confirmed by the PD team. |
andreaskurth
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Aug 30, 2024
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Cherry picks LGTM. This is aligned with TO partners, thus allowed to go on the release branch.
Thanks @vogelpi!
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This PR contains multiple commits to reduce the number of PRINCE half rounds for the main SRAM scrambling from 3 back to 2 as used for Earlgrey ES. This is done to reduce timing pressure.
The scrambling parameters of the other scrambled memory primitives (retention SRAM, ROM, OTBN IMEM & DMEM) are not touched by this PR.
Note that this PR is currently WIP. It will most likely not pass CI yet as I need to also update the tooling to support backdoor loading of memories using different numbers of scrambling rounds. But this PR is sufficient to allow the PD team kicking off another synthesis run. The RTL changes are okay and I pushed this through lint which hasn't flagged any warnings / errors.
For reference, the PRs where we increased the number of scrambling rounds in the past are:
The counterpart on master is
#24376.#24447 and has now been merged. I've updated this PR to correctly cherry-pick things over.