72 lines
5.1 KiB
Markdown
72 lines
5.1 KiB
Markdown
# hp-chell project notes
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## Agent-accessible host
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- **hp-chell** (`hp-chell.lan.1qaz.ca`) — KDE neon (Debian-based) x86_64 laptop (Intel Core m7-6Y75, 4 cores, 15GiB RAM, 117GB disk, Intel HD Graphics 515), full sudo (nopasswd) account `agent-user` (uid 60123). Provisioned 2026-09-03.
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- Auth: SSH key preferred (this machine's `~/.ssh/id_ed25519.pub` is already in the host's `authorized_keys`) — `ssh agent-user@hp-chell.lan.1qaz.ca`.
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- Fallback password: stored in local Bitwarden vault, item id `1db3b9f6-a82e-4692-846a-b4bb002a5be6` (name "agent-user@hp-chell.lan.1qaz.ca (SSH)") — fetch with `bw get password 1db3b9f6-a82e-4692-846a-b4bb002a5be6` (vault must be unlocked; `bw unlock`).
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- Host inventory/specs: see `~/AGENT_INFO.md` on the host itself. Original provisioning prompt saved at `~/AGENT_PROMPT.txt` on the host.
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- Groups: adm,cdrom,sudo,dip,plugdev,lpadmin,sambashare,docker. Has docker, tailscale0 interface (not connected as of provisioning), python3.12, git, jq, rsync, tmux.
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## Hardware identity (confirmed via `sudo dmidecode -t system -t baseboard -t bios`)
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This is a real **HP Chromebook 13 G1** ("chell" board), converted from ChromeOS to a normal Linux boot via custom coreboot firmware (MrChromebox project) and now running KDE neon as its OS.
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- BIOS/firmware: `coreboot`, version `MrChromebox-2512.2` (release date 01/25/2026) — confirms MrChromebox custom firmware, not stock ChromeOS firmware.
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- System: Manufacturer `Google`, Product Name `Chell`, Family `Google_Glados`, Serial `5CD732BLC9` — `Chell`/`Glados` is the Google Chrome OS board/reference codename for the HP Chromebook 13 G1.
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- Baseboard: Manufacturer `Google`, Product Name `Chell`, Serial `PFYTU018J90043`.
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- Implication: fanless Core m CPU, no way to add a fan — keep sustained-load expectations modest; eMMC (`mmcblk0`, ~29GB) is the original ChromeOS storage, while `/` lives on `sda` (117GB), suggesting an internal drive swap/upgrade was done as part of the conversion.
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## Kernel 7.x black-screen bug (diagnosed and fixed 2026-09-03)
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Multiple kernels are installed: `6.17.0-42-generic` (and `-35`) work fine at
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boot. `7.0.0-30-generic` (and `-14`) hit a cold-boot display bug: the panel's
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backlight comes on but no image ever appears — looks like a dead screen.
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**Root cause**: on a 7.x kernel, i915's very first modeset at boot (Xorg/
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Weston auto-configuring the panel's native `3200x1800@60`) leaves pipe A
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stuck — `dmesg` shows a `CPU pipe A FIFO underrun` right after `Reducing
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the compressed framebuffer size...`. Everything above that layer (DRM
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connector/plane/CRTC state, backlight sysfs, Xorg/Weston logs) reports
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fully healthy — `eDP-1` connected/enabled/dpms=On, pipe active, plane
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visible with real framebuffer content — yet the panel shows nothing. A
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*second* modeset (any resolution change via `xrandr`) reliably un-sticks
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the pipe and it works perfectly afterward, including back at full native
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resolution and 12bpc color. This is a kernel/i915 bug, not specific to a
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display server — confirmed identical failure under both Xorg (`sddm`
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default) and Wayland (`sddm` + `weston`, via `DisplayServer=wayland` in
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`sddm.conf.d`, which needs the `weston` package or it silently falls back
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to X11).
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**Ruled out** (each verified, none of these were the actual cause):
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- Dim/stale backlight (`/var/lib/systemd/backlight/...` restoring a low
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saved value) — this was a *real but separate* red herring encountered
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early in diagnosis; fixed by just adjusting brightness once logged in
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normally. Not the cause of the later, reproducible black-screen bug.
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- `cros-ec-gpio: Failed to attach ACPI GPIO chip` / `EC:ENABLE_BACKLIGHT`
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GPIO name collisions — present identically on working 6.17 boots too.
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- `i915.nuclear_pageflip=0` boot param — was already present during the
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original failures; adding/removing it makes no difference (legacy
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atomic-modeset override, irrelevant on modern i915; also needlessly
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taints the kernel — removed from `/etc/default/grub`).
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- `i915.enable_fbc=0`, `i915.enable_psr=0`, `i915.enable_sagv=0` — each
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tried individually via kernel cmdline, none fixed it.
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**Fix in place**: `/usr/share/sddm/scripts/Xsetup` (SDDM's root-run hook,
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fires right after the X/Wayland server starts, before the greeter draws)
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detects a `7.*` kernel via `uname -r` and runs
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`xrandr --output eDP-1 --mode 1600x900` — a second modeset that un-sticks
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the pipe. `1600x900` was chosen (rather than cycling back to native) since
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it's an exact half of the panel's native `3200x1800` (clean 2x integer
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scaling) and it's only the greeter — the actual logged-in Plasma/Wayland
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session correctly renews the modeset itself and comes up at full native
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`3200x1800` with 125% scaling, confirmed working. No kernel cmdline
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workarounds are needed — `/etc/default/grub`'s `GRUB_CMDLINE_LINUX_DEFAULT`
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is back to a clean `'splash'`.
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Confirmed reliable across multiple clean `sudo systemctl poweroff` /
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power-on cycles. The GRUB default entry (index 0, `GRUB_DEFAULT=0`) auto-
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selects the newest installed kernel, so `7.0.0-30-generic` is what boots
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by default now; `6.17.0-42-generic` remains available via the GRUB
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"Advanced options" submenu as a known-good fallback if ever needed.
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