[top_earlgrey] Reduce number of PRINCE half rounds for main SRAM scrambling #24376
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Signed-off-by: Pirmin Vogel <[email protected]>
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. Signed-off-by: Pirmin Vogel <[email protected]>
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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: