Add big endian support #3057

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nazar-codethink wants to merge 9 commits into openhwgroup:master from CodethinkLabs:nazar/lsu_be

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nazar-codethink commented Jul 15, 2025 •

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Add ability to work in big endian mode.

This adds big endian support for Load/Store unit, MMU, and atomic operations. For atomic operations we had to change axi_riscv_atomics submodule, the changes are in this branch https://github.com/CodethinkLabs/axi_riscv_atomics/commits/be_amo/

With these changes we can boot big endian Linux.

What do you think?

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nazar-codethink force-pushed the nazar/lsu_be branch 2 times, most recently from fe7fe86 to 73b43f2 Compare

July 15, 2025 15:33

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nazar-codethink force-pushed the nazar/lsu_be branch from f7fc2ba to 0832b33 Compare

July 22, 2025 12:48

nazar-codethink changed the title ~~Add big endian support for Load/Store unit~~ Add big endian support

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nazar-codethink force-pushed the nazar/lsu_be branch from 7a2a4c5 to e6d1e98 Compare

July 22, 2025 12:56

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nazar-codethink marked this pull request as ready for review

July 22, 2025 12:58

nazar-codethink requested a review from JeanRochCoulon as a code owner

July 22, 2025 12:58

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July 22, 2025 15:47

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July 22, 2025 15:55

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July 24, 2025 13:39

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July 29, 2025 12:58

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July 29, 2025 13:10

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JeanRochCoulon commented Aug 16, 2025

Hello @nazar-codethink
Sorry for the delay. Your proposal is interesting. But I think the compilers currently do not support big endian. This will limit the use of your contribution.

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LawrenceHunter commented Aug 17, 2025

Hello @nazar-codethink Sorry for the delay. Your proposal is interesting. But I think the compilers currently do not support big endian. This will limit the use of your contribution.

Hello, the riscv-gnu-toolchain supports big endian compilation with -mbig-endian. As part of our work to test this we booted a big endian Linux and played Tetris! We also have some other tests we have written here

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LawrenceHunter commented Aug 27, 2025

@JeanRochCoulon any additional feedback? We'd like to work to get this support

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JeanRochCoulon commented Sep 21, 2025

Could you rebase ?

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JeanRochCoulon commented Oct 17, 2025

@nazar-codethink I cannot merge without rebase, and I do not have the rights to do it because your branch is protected

LawrenceHunter and others added 9 commits

October 17, 2025 20:04


          Add UBE and SBE as MBE clones

5937ddc

Co-authored-by: Nazar Kazakov <[email protected]>


          Fix MSTATUSH BE fields

9347c45


          Forward MBE value from CSR to Load/Store unit

8d76d93

Forward the MBE flag from the CSR_REGFILE to the load and store units.


          Add big endian support for Load/Store unit

bbf06fa

Co-authored-by: Joseph Baker <[email protected]>


          Add big endian support for MMU

57fbd1a


          Add big endian support for cache

8107f87


          Add big endian support for atomic ops

86623fe


          Fix typos

2da0f67


          Make CI linter happy

d3a5e84

nazar-codethink force-pushed the nazar/lsu_be branch from b18e925 to d3a5e84 Compare

October 17, 2025 19:05

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nazar-codethink commented Oct 17, 2025

Sorry, forgot about it :/

Rebased now

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