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SDD
6cbb362bb9
The OS's DUART1 driver services the 0x6400000 window from the INT2 stub
(0x0F30 -> 0x3FA93070); with the default INT1 wiring the DUART1 TxRDY IRQ is
handed to the INT1 stub's 0x5800000 board-DMA handler (0x3F7151F0 ->
0x3F9D5B40), which never reads the DUART ISR, so INTPEND's INT1 bit stays
latched and the CPU re-enters the handler ~387x per frame.
Empirical A/B (level-1-skipped boot via VT1200_DUART_IP3):
default (INT1): INT1 stub entered 387x in one frame; screen frozen.
VT1200_DUART1_INT2=1: zero interrupt entries in a one-frame trace;
the OS reads DUART1 ISR (reg5) at pc=3FB43900 right after the IRQ.
INTENB reads 0x0606 (INT1|INT2|HI|DI), so the routing (not the enable mask)
is what identifies the line. Opt-in; default unchanged.
osprobe.lua: also print INTENB and DUART1 MR1A/CSRA in the globals dump.