ot_keymgr: Only go idle on reset and op_status write
#204
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The keymgr should only change its `OP_STATUS` to idle upon reset, or if it is explicitly cleared by SW. The `DONE_ERROR` and `DONE_SUCCESS` operation status values need to be latched to be queried by software, but subsequent FSM ticks (e.g. scheduled by the BH) can then change the operation status back to idle. In HW, this value is latched and only updated when `op_start`, i.e. when the operation is ongoing. When the operation is not ongoing, the value is thus not reset back to idle outside of SW writes/resets. Signed-off-by: Alex Jones <alex.jones@lowrisc.org>
jwnrt
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Oct 1, 2025
rivos-eblot
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Oct 1, 2025
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This should fix failures in Earlgrey ROM_EXT regressions after lowRISC/opentitan@abac206 was (correctly) merged in upstream
earlgrey_1.0.0. Also see discussion on the relevant RTL and SW drivers in lowRISC/opentitan#27683. This is a case of the SW being made more stringent and catching an issue in the QEMU implementation.The keymgr should only change its
OP_STATUSto idle upon reset, or if it is explicitly cleared by SW. TheDONE_ERRORandDONE_SUCCESSoperation status values need to be latched to be queried by software, but subsequent FSM ticks (e.g. scheduled with a timer) can then change the operation status back to idle.In HW, this value is latched and only updated when
op_start, i.e. when the operation is ongoing. When the operation is not ongoing, the value is thus not reset back to idle outside of SW writes/resets. See the relevant RTL.This wasn't being caught before because SW was either reading fast enough / only in cases before any subsequent FSM ticks, and/or was just discarding the incorrect
IDLEstate.