Robert Allan JamesandClaude Sonnet 5
ecdb32e0d6
Researched against the official raspberrypi.com config.txt reference and one real, working Pi 5 bare-metal project's own checked-in config.txt (leopoldch/BatMetal), not assumed from general Pi knowledge: - kernel=kernel_2712.img, os_check=0, device_tree=bcm2712-rpi-5-b.dtb - enable_uart=1 added (correction to the item's original text): costs nothing when unused, and is the only diagnostic channel that would survive a framebuffer failure on the untested mailbox path (rpi5_native_boot.c). - arm_64bit=1 dropped (correction to the item's original text): confirmed inert on Pi 5 by official docs. - dtparam=pciex1 researched, deliberately omitted with rationale recorded -- community-reported only, not needed until item 5's re-scoped RP1/PCIe work. - os_check=0 vs. BatMetal's own config (which omits it) recorded as an open, unresolved discrepancy rather than silently picked. boot_media/rpi5/README.md notes the one remaining gap this exposes: kernel_2712.img names a file nothing currently builds (item 1's separate-image build target is still outstanding future work). Doc-and-config only, no compiled code changed. Three-arch QEMU acceptance (amd64/aarch64/riscv64, in order) run to confirm non-regression only. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_019YcT3H2PQeyujrzjqS3Var
63 lines
3.6 KiB
Plaintext
63 lines
3.6 KiB
Plaintext
# LithosAnanke native (non-UEFI) boot config for Raspberry Pi 5 (BCM2712).
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# FABRIC-3.md §IV.3 item 6 -- see that section's own doc comment for the
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# research trail behind each line (confirmed against raspberrypi.com's
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# current config.txt reference and a real, working Pi 5 bare-metal
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# project's own checked-in config.txt, not assumed from general Pi
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# knowledge).
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# Load our own kernel image directly -- no UEFI, no Linux. kernel_2712.img
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# is the real filename Pi 5/500/CM5 firmware looks for first (its own
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# 16K-page-size build); naming our own image this exactly, rather than
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# falling back to kernel8.img, removes any ambiguity about which file the
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# firmware picks up.
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kernel=kernel_2712.img
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# Disable the firmware's Linux-compatible-image sanity check. Without
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# this, official docs describe it as checking for "a compatible Device
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# Tree file before attempting to boot" and warn that "older non-compatible
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# kernels would be loaded and then hang" -- documented specifically as the
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# bare-metal-development escape hatch. One real working Pi 5 bare-metal
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# project's own config.txt does NOT set this and still boots, so it may
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# not be strictly required for every non-Linux image; kept here anyway
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# since the official doc names this exact use case and there is no
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# hardware in hand yet to verify which behavior is actually gated.
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os_check=0
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# Pin the exact devicetree explicitly rather than relying on the
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# firmware's own board-revision auto-selection (which would also resolve
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# to this file on real Pi 5 hardware, per general config.txt convention --
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# explicit is certain, not just probably-correct).
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device_tree=bcm2712-rpi-5-b.dtb
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# Enable the dedicated debug UART (Pi 5's own JST connector, not the GPIO
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# 14/15 header pins). Not because serial capture hardware is set up for
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# this bring-up (that decision is HDMI-only, FABRIC-3.md §IV) -- this is
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# a firmware-side switch that costs nothing when nothing is listening, and
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# it is the only diagnostic channel that survives a framebuffer failure.
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# rpi5_uart_base() (rpi5_dtb.c) already exists and is currently uncalled;
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# this is the hook a UART-based fallback console would use if the mailbox
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# framebuffer driver's two documented unverified details turn out wrong on
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# real hardware.
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enable_uart=1
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# Deliberately NOT set, researched but not included this pass:
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# dtoverlay=uart0 -- GPIO 14/15 header UART; needs a USB-serial
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# adapter this bring-up doesn't have (HDMI-only
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# decision). enable_uart=1 above covers the JST
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# debug UART instead, which needs no extra cable.
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# dtparam=pciex1 -- one real Pi 5 bare-metal project's own config.txt
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# comments this as "Required for RP1 access", which
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# would be surprising (RP1 is always-on in stock Pi
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# 5 boots) and is community-reported, not confirmed
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# against official docs. Not needed for this boot
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# (no RP1 access yet -- FABRIC-3.md §IV.3 item 5 is
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# still re-scoped, not implemented). Revisit if that
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# item's own real Broadcom-indirect PCIe work needs
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# it.
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# arm_64bit=1 -- researched and dropped: official docs state
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# "Models that only support a 64-bit kernel ignore
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# this flag" -- inert on Pi 5, not wrong to include,
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# just meaningless. The original item 6 wording
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# named this; corrected here rather than carried
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# forward.
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