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[vendor] Keep unstrobed bytes on mailbox threshold writes - #759
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marnovandermaas merged 1 commit intoOct 12, 2026
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Backport pulp-platform/axi@11603194 (in v0.39.10) as a vendor patch. A write to WIRQT or RIRQT with some write strobes low cleared the unstrobed bytes instead of leaving them unchanged, which AXI requires (IHI 0022 H.c A3.4.4). The vendored revision stays at v0.39.9. Signed-off-by: Martin Velay <mvelay@lowrisc.org>
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Thanks for integrating this fix! I've also found the initial issue which I'll link here for future reference: pulp-platform/axi#411
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Backports pulp-platform/axi@11603194 (pulp-platform/axi#412, released in v0.39.10) as a vendor patch, without bumping the vendored revision. A write to the mailbox WIRQT or RIRQT register with some byte strobes low cleared the bytes that were not strobed; they now keep their value, as AXI requires (IHI 0022 H.c A3.4.4). With Mocha's 2-bit thresholds this only shows when byte 0 is not strobed, for example a 32-bit store to the upper half of the register or a write with no strobes, which used to reset the threshold to 0.
The HAL writes both thresholds with 64-bit stores, so software sees no change. Checked with a standalone simulation of
axi_lite_mailbox(partial writes cleared the other bytes before the patch and keep them after it),mailbox_smokeandmailbox_smoke_cherion Xcelium, and the CI lint steps.