[otp_ctrl] Remove entropy_src chicken switches #21118
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msfschaffner
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This carries over a change from integrated_dev that removes unnecessary chicken switches for the entropy complex. Note however that this time we do not remove EN_CSRNG_SW_APP_READ since that may still be useful. Signed-off-by: Michael Schaffner <[email protected]>
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jwnrt
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Jan 31, 2024
moidx
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EN_CSRNG_SW_APP_READ will have to be set to true in most cases (including to meet FIPS certification requirements).
It would be nice to document what use cases require EN_CSRNG_SW_APP_READ = False given that the SW CSRNG channel in this configuration would not be usable.
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@vogelpi if this looks good to you, can you merge it? Thanks! |
vogelpi
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Thanks for the PR @msfschaffner , removing these two switches is okay. They enable the following functionality:
- otp_en_entropy_src_fw_over allows enabling the firmware override mode. This is required for evaluation related to certification (in PROD LC state) and to enable the software fallback mode. This gives firmware access to unconditioned entropy only.
- otp_en_entropy_src_fw_read allows routing (un-)conditioned entropy to a separate output path. This is required for KATs especially around the conditioner, which is probably also relevant for certification (in PROD LC state).
I agree to keep the EN_CSRNG_SW_APP_READ switch and I agree to better document this / adapt the use of it. I'll open an issue for that.
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The issue is here #21141 |
This was referenced Feb 6, 2024
This was referenced Mar 29, 2024
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This carries over a change from
integrated_devthat removes unnecessary chicken switches for the entropy complex.Note however that this time we do not remove
EN_CSRNG_SW_APP_READsince that may still be useful.See the following discussion for context https:/lowRISC/opentitan-integrated/pull/319#discussion_r1304821593.
This is in preparation for moving debug-related chicken switches into a new
HW_CFG1partition, similarly as this has been done onintegrated_dev.🐔