HANDOFF: U-Boot keyboard bring-up on Lenovo IdeaPad Duet (google,krane, MT8183)

You are taking over a working U-Boot bring-up. The banner and prompt already work on the panel. Your job: make the keyboard work at the U-Boot prompt.

Environment

U-Boot tree: /home/vhaudiquet/u-boot, branch krane (mainline main @ 527115ef + board commits + temporary diagnostics). Build: cd /home/vhaudiquet/u-boot && export CROSS_COMPILE=aarch64-linux-gnu- ARCH=arm && make mt8183_kukui_krane_defconfig && make -j8 After editing the defconfig you MUST re-run make mt8183_kukui_krane_defconfig — gc-sections otherwise silently drops code.
Payload/build/flash script: /home/vhaudiquet/krane-fb-stub/build-uboot-payload.sh (assembles wrapper + u-boot.bin, packs with mkdepthcharge via PYTHONPATH=/root/krane-fb-stub/src/depthcharge-tools, asserts link _start == 0x4C001000 from u-boot.sym, writes krane-uboot-payload.bin).
Flash + verify: dd if=krane-uboot-payload.bin of=/dev/mmcblk0p1 bs=4M conv=fsync, then cmp -n <size> krane-uboot-payload.bin /dev/mmcblk0p1, then futility vbutil_kernel --verify /dev/mmcblk0p1 (must print "Body verification succeeded"). The kernel partition is mmcblk0p1 (pmOS installed, chroot lives on mmcblk0p3; USB stick on sda).
Lab notebook: /home/vhaudiquet/krane-fb-stub/RESEARCH.md — READ IT, especially Rounds 19–32. Every verified step gets a round entry + a commit in BOTH repos (u-boot branch krane, stub repo).
The user tests on the real device: you flash, they reboot, select "Internal storage" in the depthcharge dev menu, and report what appears on screen. Write short observation→meaning decision trees for them. Devkeys only; the SPI firmware is never modified.
Backup of the original kernel partition: /home/vhaudiquet/mmcblk0p1-pmos-backup.img (sha256 20951a54…), also on the USB stick (sda3).

Current working state (payload `34b9660f…` lineage)

depthcharge (device-era, .12573.351.0) loads the payload to 0x40000000 and jumps to +0x40; our wrapper (/home/vhaudiquet/krane-fb-stub/uboot-wrapper.S) revives the display (OVL_EN@0x14008000+0xc, OVL0_2L_EN@+0x100c, backlight GPIOs 43/176 via 0x10005114/0x10005154) and jumps to U-Boot _start at 0x40001000. Do NOT break the placement: CONFIG_TEXT_BASE=0x4C001000 (8-aligned — a 4-byte linker fill shifts _start and corrupts the PIE fixup), U-Boot file at image offset 0x1000 so runtime _start = 0x40001000.
Display: drivers/video/mt8183_scanout.c (UCLASS_VIDEO on the upstream ovl0@14008000 node) revives the depthcharge scanout (fb 0xFD536000, 1200×1920×32bpp, bpl 4800, addr from the coreboot table at 0xffed9000 with OVL_L0_ADDR fallback) and the standard vidconsole renders the banner.
Console: ENV_IS_NOWHERE + board/mediatek/mt8183/krane.env (stdin=serial, stdout=serial,vidconsole, stderr=serial,vidconsole). The video device is probed only through the iomux lazy path — keep that env intact.
get_page_table_size() is overridden in board/mediatek/mt8183/mt8183.c (0x40000): the driver maps the coreboot table and fb dynamically post-relocation; the default budget panics ("Insufficient RAM for page table"). Any new dynamic mmu_map_region calls rely on this headroom.

The problem

The prompt is dead to keyboard input. Krane is the IdeaPad Duet — a tablet; its keyboard is the detachable pogo-pin keyboard, which is a USB HID device (it enumerates as USB). So the work is USB bring-up + USB keyboard, not i2c:

The krane defconfig (configs/mt8183_kukui_krane_defconfig) was forked from mt8183_pumpkin minus USB/fastboot/PHY — CONFIG_USB*, CONFIG_PHY_MTK_* are all absent. Re-add the USB stack: CONFIG_DM_USB, CONFIG_USB=y, CONFIG_USB_XHCI_HCD=y (MT8183 has a MediaTek xHCI, node ssusb@11201000 in the upstream DT), the MTK T-PHY (CONFIG_PHY_MTK_TPHY, node usb-phy@11e10000/u3phy), CONFIG_USB_KEYBOARD=y and whatever DM_REGULATOR/power nodes the DT needs for VBUS.
Upstream device tree: dts/upstream/src/arm64/mediatek/mt8183-kukui*.dtsi (do NOT fork the DTs; CONFIG_OF_UPSTREAM=y and the include-order fix in scripts/Makefile.lib from earlier rounds is already in place). Check which USB nodes/phy/regulators the kukui DT provides and whether the U-Boot drivers bind them (bootph-all flags may be needed for pre-reloc, but the keyboard is post-reloc so plain nodes usually suffice).
The MTK xHCI glue in mainline U-Boot: check drivers/usb/host/xhci-mtk.c (mt7622-era) vs plain xhci with phys. The Duet's keyboard port may be the dedicated pogo USB port — check the kukui DT for which controller/port the keyboard uses, and whether VBUS is switched by a PMIC regulator (mt6358, CONFIG_DM_REGULATOR).
After USB works: add usbkbd to stdin in board/mediatek/mt8183/krane.env (stdin=serial,usbkbd) — USB devices are only probed when the USB stack runs; check how usb_kbd gets probed pre-prompt (CONFIG_USB_KEYBOARD + usb_kbd_register, initr_usb, or usb start in BOOTCOMMAND — with CONFIG_BOOTDELAY=-1 there is no autoboot window, so USB init must happen in an initcall (initr_usb) or you must set a small bootdelay/usb start).
Do NOT disturb the display path; CONFIG_USB_KEYBOARD pulls in font/console bits that are already fine.

Debugging aids already in the tree (TEMPORARY, to revert before upstreaming)

CONFIG_PANIC_HANG=y: any synchronous abort freezes the screen with a dump — and do_sync in arch/arm/lib/interrupts_64.c draws ABORT! ESR=0x… ELR=0x… FAR=0x… on the panel (via the fb text logger in drivers/video/mt8183_scanout.c). If the device instead RESETS to the depthcharge menu in <1 s, that's a panic without the hang — check CONFIG_PANIC_HANG is still set.
krane_fb_log() in drivers/video/mt8183_scanout.c — minimal 8×16-font framebuffer text logger (white text, bottom rows y≥1700, static cursor). Reuse it freely for USB bring-up logs (e.g. "XHCI-PROBE", "PORT-OK", "KB-ENUM") — it works before the console exists.
Colored band checkpoints: krane_diag_band() (same file), video-uclass.c/board_f.c/main.c/mt8183.c have band calls. All marked TEMPORARY.
There is no working serial on the device (baud 921600 debug UART exists in config but the user cannot see it) — the panel logger is your only output channel. Keep log lines short (the logger wraps at 1200 px / 150 chars).

Constraints

Everything upstreamable: checkpatch-clean, DM/uclass APIs, Kconfig/Makefile style of neighbours, small single-purpose commits, MAINTAINERS entries. Board-specific workarounds in board code, magic registers documented with sources. Do not fork upstream DTs.
Never break the working display/prompt path; the payload layout constants are load-bearing (see above).
Record every verified step as a RESEARCH.md round + commits in both repos; before flashing, always dd + cmp + vbutil verify.

Suggested first steps

Read RESEARCH.md (esp. Rounds 30–32) and git log both repos.
Dump the upstream kukui DT USB nodes (ssusb, u3phy, regulators) and mainline's mt8183-compatible xhci/tphy drivers; decide glue vs plain xhci.
Add the USB/PHY/keyboard Kconfigs + any bootph flags; re-run defconfig; build; log probe stages with krane_fb_log (XHCI probe, PHY init, port status, device enumeration, HID attach).
If enumeration works but no keys: check stdin env, usb_kbd stdio registration, and that the console's stdio_devices[stdin] includes it (coninfo would tell you — you can print it to the panel via the logger).
Deliver: a fix commit + a RESEARCH.md round; leave the diagnostics in place unless they break something.

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