kernel

Mainline kernel for the Skylight Calendar 15

Linux 6.18.56 from kernel.org with the board files here, built by build.sh into boot-skylight.img: an Android boot image (header v2, the stock load addresses) whose second stage is a Rockchip resource image holding the device tree (as rk-kernel.dtb, d156-mipi.dtb and d156-edp.dtb, so the stock U-Boot cannot pick one of its own) and the boot logo. uname -r says 6.18.56-skylight.

INSTALLER=1 build.sh is a release build. It makes, in $WORK/out:

• boot-skylight.img: TECHO5's kernel, which goes into recovery. Its ramdisk is empty: the root is techo5-store.
• boot-skylight-installer.img: the same kernel with the installer's initramfs, for one boot.
• linux-6.18.56-techo5-skylight-source.tar.xz: the source of both, for the GPL. It is the kernel.org tree with the board files, the panel driver's Kconfig and Makefile lines and the boot logo in it, and the build's configuration as techo5-skylight.config. Entries are sorted, owned by 0:0 and at the build's time, so the same tree makes the same tarball.
• SHA256SUMS, the kernel's parts and kernel.config.

check-boot.py checks a boot image (--installer the installer image: exactly its files, a matching data image, no key or firmware; --kernel-of that it carries the boot image's kernel) and check-source.py a source tarball against the image it built: the board files the same as here, the configuration the one the kernel carries (CONFIG_IKCONFIG). build.sh runs both, and also refuses a source tarball that names anything of the computer it was built on.

The bench and installer images carry busybox (Alpine's armv7 busybox-static, unmodified, from inputs/ as tools/fetch-inputs.py fetches it; the kernel runs 32-bit programs) with a SOURCES file saying where its source is, and reboot-normal, which is built without a C library.

• rk3566-skylight-cal150.dts: the board. Its values are the unit's stock device tree's.
• panel-skylight-cal150.c: the display, a DSI-to-LVDS bridge set up with the stock panel's 38 generic writes; the chip is not identified.
• skylight.config: merged over arm64 defconfig; build.sh checks that every line stuck. CONFIG_MODULES stays on, as defconfig has it, but no module is built or shipped, so what the board and TECHO5 need is built in (netfilter for the Wi-Fi firewall, IPv6, Bluetooth, the sound card, /dev/i2c-N for the light sensor).
• pack-sky.py: the boot image. Its header ID is checked against the stock image's algorithm.
• check-boot.py, check-source.py: the checks above.
• mklogo.py: the kernel's boot logo and U-Boot's logo.bmp, from logo/TECHO5_logo.png.
• reboot-normal.c: restarts with the boot mode register saying normal (the bench and installer images use it, so it ships in the release's installer image).
• bench/: the bench initramfs (a root shell on USB serial, BENCH=1).
• installer/: the installer image's /init (INSTALLER=1): it runs ../install/install.sh on the set tools/install-skylight.py stages on /cache, then restarts into TECHO5, or into Android when it stopped before writing anything.

Things learned on the unit:

• The panel's GPIOs must be requested as outputs; left as inputs, setting them drives nothing.
• dclk_vop1 cannot set VPLL's rate itself, so VPLL is given 912 MHz (152 MHz times 6).
• The speaker amplifier hangs off the codec's headphone outputs.
• mmc-pwrseq-simple needs CONFIG_RESET_GPIO; built-in cfg80211 needs CONFIG_RFKILL=y; built-in hci_uart needs CONFIG_POWER_SEQUENCING=y.
• brcmfmac asks for its firmware at about 1.8 s, after the root is mounted: the firmware lives in the store's /lib/firmware, where a ramdisk copy would already be hidden.
• fbcon refuses a logo as tall as the screen, so the logo is 1064 rows, centered.
• The stock U-Boot draws its own logo.bmp only through vendor display nodes this tree does not carry, so the first seconds stay dark.