Round 11: mainline U-Boot as payload — target, scanout driver, first flash
Board/defconfig branch built (OF_UPSTREAM bindings-shadowing trap documented), mt8183_scanout video driver porting the validated revival/ LBIO logic, 64-byte Image-header wrapper script. Payload 1fc74a0a… flashed and verified on-device. Reboot result pending.
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vhaudiquet
+81
@@ -466,3 +466,84 @@ of=/dev/mmcblk0p1 bs=4M conv=fsync`.
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"Bad address", not EPERM as first assumed).
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- qemu test updated to the same expectation (colors + held blue); it
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exercises parser + fill logic, not the MMIO revival writes.
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## Round 11 — U-Boot as payload: target, driver, first flash (result pending)
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First mainline-U-Boot flash after the Round-10 pipeline validation.
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### Build (milestone 1)
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- Branch `krane` in `/home/vhaudiquet/u-boot` (mainline main @
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`527115ef`); commits `29aec558` (board/defconfig/MAINTAINERS),
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`923cc754` (dtc include order), `f0470c9b` (video driver).
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- `configs/mt8183_kukui_krane_defconfig` forked from pumpkin: keeps
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`CONFIG_POSITION_INDEPENDENT=y`, DEBUG_UART (0x11002000 @ 26 MHz,
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goes nowhere — absence of colors is not failure), MTK serial/MMC/WDT;
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drops fastboot/TPHY/mtu3/USB. `CONFIG_BOOTDELAY=-1` so the first boot
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stops at the prompt instead of autobooting pmOS from p3.
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- DT: `CONFIG_OF_UPSTREAM=y`, `CONFIG_DEFAULT_DEVICE_TREE="mediatek/
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mt8183-kukui-krane-sku176"` — **with OF_UPSTREAM the name must include
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the vendor dir**; no arch/arm/dts registration needed.
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- **New trap found while building**: U-Boot's legacy
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`include/dt-bindings/clock/mt8183-clk.h` (BSP numbering,
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`CLK_TOP_CLK26M=0`) shadows the upstream
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`dts/upstream/include/dt-bindings/clock/mt8183-clk.h`
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(`CLK_TOP_CLK26M=112`) for OF_UPSTREAM builds — the krane tree failed
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with undefined `CLK_CAM_LARB6`, and even fixing those macros would
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have silently produced wrong clock numbers everywhere. Fix:
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`scripts/Makefile.lib` prefers `dts/upstream/include` when
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`CONFIG_OF_UPSTREAM=y`. Pumpkin's in-tree dts (different binding
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generation) keeps working because its config does not set OF_UPSTREAM.
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### Video driver (milestone 3, flashed before first reboot)
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`drivers/video/mt8183_scanout.c` (`CONFIG_VIDEO_MT8183_SCANOUT`,
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checkpatch-clean), binds the upstream `ovl0@14008000` node
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(`mediatek,mt8183-disp-ovl`; the two 2L overlays match a different
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compatible, so exactly one probe). probe():
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1. revival identical to the stub's stage0: `OVL_EN=1` (+0x000C),
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`OVL0_2L_EN=1` (+0x100C), GPIO dout set for pins 43/176;
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2. LBIO parse at the fixed 0xffed9000 (ported from the stub's
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Round-10-validated `find_framebuffer`; host regression test
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compiled the function standalone against `lbio.bin`: record parsed,
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bad signature rejected);
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3. scanout = LBIO pa if >= 0x40000000, else `OVL_L0_ADDR` (+0x0F40)
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(Round-9 ground truth: 0xFD536000); else probe fails gracefully;
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4. geometry from the record (xRGB 32bpp required; U-Boot's BPP32
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console default composes pixels exactly as r<<16|g<<8|b — checked in
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video-uclass `video_index_to_colour`);
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5. both the coreboot table and the fb sit above the DTB's 2 GiB DRAM
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window (memory@40000000 is 0x80000000 long), so both regions are
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identity-mapped with `mmu_map_region()` first (MMIO < 0x20000000 is
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already mapped Device by `arch/arm/mach-mediatek/armv8-mem-map.c`);
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`video_set_flush_dcache(true)` for the console writes.
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Revival happens BEFORE parsing, so "backlit black" = ran but parse/
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probe failed, "dark" = never reached the driver — same decision tree
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as the stub. No autoboot: U-Boot banner + prompt should stay on panel.
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### Wrap + flash (milestone 2)
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`krane-fb-stub/build-uboot-payload.sh`: 64-byte arm64 Image header
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(code0 `b +0x40` = 0x14000010, image_size = 64 + len(u-boot.bin),
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flags bit3, magic at 0x38) prepended to `u-boot.bin`, mkdepthcharge
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with the krane DTB, `vbutil_kernel --verify`. (Header-bytes were
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checked with `od` after an edit mishap dropped the flags word — always
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re-verify the raw header bytes.) depthcharge decompresses the FIT and
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jumps to the first byte — U-Boot's `_start` lands at +0x40, PC-relative
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(PIC) so the arbitrary 2 MiB slot is fine.
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- Payload `krane-uboot-payload.bin` sha256 `1fc74a0a…`, flashed to
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`mmcblk0p1` (dd 4M conv=fsync), `cmp` OK (589824 bytes), on-device
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`vbutil_kernel --verify` → body verification succeeded.
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- Backup `mmcblk0p1-pmos-backup.img` (sha256 `20951a54…`) copied onto
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the USB stick (sda3) — recovery no longer depends on eMMC.
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### Expected observation
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Panel shows the U-Boot banner (white/light-gray text on black, portrait
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1200×1920) and the prompt, frozen (BOOTDELAY=-1). Nothing on panel = boot
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path or early crash; backlit black = reached handoff but driver probe
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failed. The x0-FDT-zeros trap is bypassed: U-Boot uses its embedded DTB
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and never reads the handoff FDT.
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Executable
+55
@@ -0,0 +1,55 @@
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#!/bin/sh
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# build-uboot-payload.sh — wrap /home/vhaudiquet/u-boot/u-boot.bin with the
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# 64-byte arm64 Image header (same contract as stub.S: depthcharge jumps to
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# the first byte of the image, so code0 must branch past the header) and
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# pack it into a dev-signed depthcharge FIT for mmcblk0p1.
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#
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# Image header layout (linux/Documentation/arch/arm64/booting.rst, verified
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# against depthcharge src/arch/arm/boot64.c):
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# 0x00 code0 b +0x40 (branch past header; entry point)
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# 0x04 code1 0
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# 0x08 text_offset 0 (image sits AT the 2 MiB-aligned base)
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# 0x10 image_size header + u-boot.bin size (LE, patched below)
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# 0x18 flags bit3 = place anywhere (KASLR slot math)
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# 0x20..0x37 reserved 0
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# 0x38 magic 0x644d5241 "ARM\x64"
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# 0x3c res5 0
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set -e
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cd "$(dirname "$0")"
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UBOOT_BIN="${UBOOT_BIN:-/home/vhaudiquet/u-boot/u-boot.bin}"
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DTB="${DTB:-krane-sku176.dtb}"
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OUT_IMG=krane-uboot.bin
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OUT_PAYLOAD=krane-uboot-payload.bin
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python3 - "$UBOOT_BIN" "$OUT_IMG" <<'EOF'
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import struct, sys
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src, out = sys.argv[1], sys.argv[2]
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uboot = open(src, 'rb').read()
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hdr = bytearray(64)
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# code0: b .+0x40 => 0x14000000 | (0x40 >> 2)
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hdr[0:4] = struct.pack('<I', 0x14000010)
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# text_offset = 0 (left as zero)
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struct.pack_into('<Q', hdr, 0x10, 64 + len(uboot)) # image_size
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struct.pack_into('<Q', hdr, 0x18, 1 << 3) # flags: bit3
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hdr[0x38:0x3c] = b'ARM\x64' # magic
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with open(out, 'wb') as f:
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f.write(hdr)
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f.write(uboot)
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print("wrapped: %d = 64 + %d bytes" % (64 + len(uboot), len(uboot)))
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EOF
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PYTHONPATH=/root/krane-fb-stub/src/depthcharge-tools python3 -m depthcharge_tools.mkdepthcharge \
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-A arm64 \
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-o "$OUT_PAYLOAD" \
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-n "krane u-boot framebuffer console" \
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-d "$OUT_IMG" \
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-b "$DTB"
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echo "---- verify ----"
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futility vbutil_kernel --verify "$OUT_PAYLOAD"
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sha256sum "$OUT_PAYLOAD"
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