Add hp-chell host notes and kernel 7.x i915 black-screen fix script

2026-09-03 23:38:47 -04:00
commit ab376891d6
2 changed files with 145 additions and 0 deletions
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+#!/bin/sh
+# setup-i915-kernel7-fix.sh
+#
+# Run on a fresh hp-chell (HP Chromebook 13 "chell", coreboot/MrChromebox
+# firmware, KDE neon) install to apply two things:
+#
+#   1. The kernel 7.x cold-boot black-screen workaround: a
+#      /usr/share/sddm/scripts/Xsetup hook that forces a second modeset
+#      on eDP-1 to un-stick i915's pipe A on 7.x kernels. See project
+#      CLAUDE.md for the full diagnosis writeup.
+#   2. GRUB_TIMEOUT=5 / GRUB_TIMEOUT_STYLE=menu, so the boot menu is
+#      visible for 5 seconds (useful for picking a fallback kernel like
+#      6.17.0-42-generic if a future 7.x point release regresses again).
+#
+# Safe to re-run; idempotent.
+
+set -eu
+
+if [ "$(id -u)" -ne 0 ]; then
+    echo "must run as root (sudo $0)" >&2
+    exit 1
+fi
+
+echo "==> installing SDDM Xsetup i915 kernel-7.x workaround"
+cat > /usr/share/sddm/scripts/Xsetup << 'EOF'
+#!/bin/sh
+# Xsetup - run as root before the login dialog appears
+
+if [ -e /sbin/prime-offload ]; then
+    echo running NVIDIA Prime setup /sbin/prime-offload
+    /sbin/prime-offload
+fi
+
+# Workaround: on kernel 7.x, the first i915 modeset at cold boot (Xorg's
+# auto-modeset to the panel's native 3200x1800) leaves pipe A in a bad
+# state (persistent CPU pipe A FIFO underrun -> blank panel, backlight
+# still on, even though DRM/plane state reports healthy). Forcing a
+# second modeset unsticks it. Rather than cycle back to native, just
+# land on 1600x900 (exact half of 3200x1800, clean 2x integer scaling)
+# and stay there -- it's only the login screen; the logged-in session
+# renews the modeset itself and comes up at full native resolution.
+# Not needed on 6.17.x kernels. See project CLAUDE.md for the full
+# writeup.
+case "$(uname -r)" in
+    7.*)
+        xrandr --output eDP-1 --mode 1600x900 >/tmp/xsetup-modeset.log 2>&1
+        echo "set eDP-1 to 1600x900 (i915 kernel 7.x cold-boot workaround)"
+        ;;
+esac
+EOF
+chmod 755 /usr/share/sddm/scripts/Xsetup
+
+echo "==> setting GRUB_TIMEOUT=5 / GRUB_TIMEOUT_STYLE=menu"
+grub_conf=/etc/default/grub
+
+set_grub_key() {
+    key=$1
+    value=$2
+    if grep -q "^${key}=" "$grub_conf"; then
+        sed -i "s|^${key}=.*|${key}=${value}|" "$grub_conf"
+    elif grep -q "^#${key}=" "$grub_conf"; then
+        sed -i "s|^#${key}=.*|${key}=${value}|" "$grub_conf"
+    else
+        echo "${key}=${value}" >> "$grub_conf"
+    fi
+}
+
+set_grub_key GRUB_TIMEOUT 5
+set_grub_key GRUB_TIMEOUT_STYLE menu
+
+echo "==> running update-grub"
+update-grub
+
+echo "==> done"