Full coherent shell on the mainline kernel, display and touch

2026-10-06. Physical UART, camera and real-finger evidence for the mainline DRM kernel, following clock ownership. All candidate boots used the guarded staging pattern, volatile U-Boot selection and the reviewed recovery checker; every run below returned to the protected normal system (distinct boot, exact identities, eight boot hashes, three services, registration absent). runs.json binds each private capture by SHA256.

Display: the purple screen

With spi2axi fixed the console system logged in, but the panel showed a uniform purple (still). Nothing draws purple: the VO background register is written 0xffffff, which the hardware treats as YUV, so with no layer visible only the background colour reached the panel. The DRM state and the OSD4 shadow registers all pointed at fbcon’s buffer, and writing a pattern into /dev/fb0 changed nothing; blanking still worked.

The earlier unused-gate list had been read through head -150 and was incomplete. A full clk_summary from a live clk_ignore_unused boot listed ten more on-but-unclaimed gates. Camera-judged bisection (no operator resets, each passing boot rebooted itself): holding those ten restored the console (M10), as did vpu_ddrcp2 + vpu_axi (N1) and vpu_ddrcp2 alone (N2/N2b; the operator also saw the NixOS login prompt). Fix 7fd13b68 marks K230_VPU_DDRCP2_GATE (sysctl 0x60 bit 5, a DDR controller port) critical, and moves dphy_dft_gate from 0x100 bit 0 (aliased onto the USB 480M/100M bit) to 0x104 bit 0 per the vendor dphy_test_clk. The rebuilt console bundle shows the console on black (still). Power domains were not the cause: pm_genpd_summary shows disp_domain on with display-subsystem active.

Full shell

k230-mainline-drm-shell (bb4f49b6) is k230-coherent-shell with only the mainline DRM kernel swapped in and the vendor-tree Wi-Fi module removed; only 30 store paths (~175 MB) were missing on the board. Its first boot was qualified by the controller, but shell.service restart-looped: sway reported Failed to open device: '/dev/dri/card0': Invalid argument and the kernel warned at drm_file.c:329. Since v6.12 drm_open_helper() rejects fops without FOP_UNSIGNED_OFFSET; the hand-ported canaan fops lacked it. Fix dfe2cd2c adds the flag. The rebuilt full shell (bundle 1lc4jd6v…) was qualified candidate-ready-qualified-ordinary-init; shell, shell-ui and seatd were active, sway mapped the card shell, and the panel matched the normal system’s Home photographed from the same position seconds later (comparison, mainline top). firewall.service failed (kernel netfilter options, not investigated). The PMU power key and Wi-Fi drivers are vendor-only and absent; audio was not tested. The camera angle is oblique; this is a visual match, not a pixel comparison. Sway logs Failed to import buffer for scan-out at debug level (direct scan-out falls back to composition).

Deliberate touch

On the fixed console candidate (0b327025), the controller’s touch --real-touch phase ran evtest on the Goodix Berlin touchscreen for 30 s while the operator touched the glass: 533 multitouch position events, 4 BTN_TOUCH down/up pairs and matching tracking-ID releases; the camera shows the finger on the glass during the window (still). The controller itself returned touch retrieval completion unverified: reading ~240 KB of evtest text back at 115200 baud outlasted its wait, so the event counts above come from the raw serial capture, not the controller’s parser. Touch inside the full shell (sway input) was not separately exercised.