The FP6 is 4x Cortex-A520 + 4x Cortex-A720 and this image boots nothing
else, so pass the compiler KCFLAGS="-march=armv8.6-a+fp16fml+aes+sha3+sm4
-mtune=cortex-a720". The stock arm64 build gives the compiler no arch flag
at all (so one image can boot any Armv8 board).
The string is what `gcc -march=native` derives on the phone, re-based on
armv8.6-a so clang can express the same set (clang has no flagm2/rcpc2/
frintts tokens; it reaches them through the architecture level). 8.6 is the
highest level whose mandatory set the phone exposes: 8.7 would assume WFxT
and 9.x SVE2, and neither is in its hwcaps or ID registers. clang emits
identical code for this and for -mcpu=cortex-a720+nosve+nomemtag; the
difference is only which system features (SPE, ETE, TRBE, FPAC) it knows
about, none of which generate code.
Verified on eef717f978f1 with the aport config: builds with zero warnings,
same module set as r100 (417), compat vDSO untouched, boots the dev phone
with a clean dmesg and a GREEN selftest. Record:
fp6 journal/base/captures/2026-09-05-mcpu-a720-verification.md.
Jorijn van der Graaf
a2f5de9de0