apic.c (aarch64): fix GIC base address for real Pi 5 hardware

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FABRIC-3.md §IV.3 item 7's code audit found GICD_BASE_PA/GICC_BASE_PA
hardcoded to QEMU virt-machine constants (0x08000000/0x08010000),
self-documented as a deliberate exception because QEMU's aarch64 UEFI
firmware never forwards a DTB. That premise doesn't hold on the native
Pi 5 boot path (rpi5_native_boot.c), which does have a real DTB and calls
this same, unmodified apic_init() -- which ignored boot_info entirely and
always programmed the QEMU addresses. Real BCM2712 GIC-400 is at
0x10_7fff9000 (confirmed against bcm2712.dtsi's axi/gicv2 nodes), a
completely different region of the address space. Fixed per direct
instruction, naming this finding specifically.

apic_init() now calls gic_bases_from_dtb() first: fdt_valid(dtb) ->
fdt_find_node_by_compatible(dtb, "arm,gic-400") ->
fdt_find_prop_in_node(..., "reg", ...), reading the first two
2-address-cell/2-size-cell entries (GICD, then GICC -- the standard
arm,gic-400 binding order). Falls back to the QEMU constants on any
failure (no DTB, no matching node), so the existing QEMU/UEFI path is
unchanged. GICD_BASE_PA/GICC_BASE_PA became s_gicd_base/s_gicc_base
(module-static uintptr_t, no longer compile-time constants on this path)
-- every MMIO call site (apic_init, apic_spi_enable, apic_read_iar,
apic_eoi_intid) now reads through them.

Three-arch QEMU acceptance run exercised the guard itself, not just
compiled it: the aarch64 boot log shows "GICv2: no DTB GIC node -- using
QEMU virt-machine defaults" followed by the unchanged "distributor+CPU
interface enabled, PPI 30" line, then boots clean to zuse)ok>. The
success branch (a real DTB with a matching node) stays unverified until
real Pi 5 hardware -- this build never has a devicetree to exercise it
against.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019YcT3H2PQeyujrzjqS3Var

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This commit is contained in:

Robert Allan James

2026-09-04 23:54:39 -04:00

co-authored by Claude Sonnet 5

parent 0f798256a0

commit dc9445abec

10 changed files with 27754 additions and 60 deletions

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experiments/bare_metal/runs/doe-aarch64-20260904-235007.csv

experiments/bare_metal/runs/doe-amd64-20260904-234706.csv

experiments/bare_metal/runs/doe-riscv64-20260904-235246.csv