[PATCH 0/2] firmware: meson: sm: make power-off work on S4

[christian . koever-draxl]

From: Christian Stefan Kövér-Draxl <ckoever@xxxxxxxxxx>

On S4 the firmware implements PSCI SYSTEM_OFF as DDR self-refresh, and
the power key then resumes into a kernel that is gone, so the board
hangs until it is unplugged. The vendor kernel sets a firmware shutdown
flag first and takes the secondary CPUs down through PSCI; do the same,
keyed on a new amlogic,meson-s4-sm compatible.

Tested: poweroff followed by the remote's power key cold-boots the box.

Tool use (Documentation/process/generated-content.rst):
This work was done with the help of an AI coding assistant, Claude
(Anthropic), used through Claude Code over many sessions. It did a large
part of the hands-on work: it read the vendor kernel and the firmware
interfaces, probed registers on the board, drafted the code and the
changelogs, and ran the builds, checkpatch, dt_binding_check and the
tests on the hardware. I directed the work, reviewed every change and
the final patches, and take responsibility for them. There is no single
prompt to quote; the sessions were of the form "find out why X fails on
this board, fix it, test it on the box".

Tested on an Amediatech X98Q TV box (Amlogic S905W2, S4 family, 2 GiB),
vendor U-Boot and BL31/OP-TEE, Linux 7.3 plus this work.

Christian Stefan Kövér-Draxl (2):
  dt-bindings: firmware: amlogic,meson-gxbb-sm: add amlogic,meson-s4-sm
  firmware: meson: sm: make power-off work on S4

 .../firmware/amlogic,meson-gxbb-sm.yaml       |  4 +-
 drivers/firmware/meson/meson_sm.c             | 46 +++++++++++++++++++
 include/linux/firmware/meson/meson_sm.h       |  1 +
 3 files changed, 50 insertions(+), 1 deletion(-)


base-commit: 7be4bc52fd9e0e55dc9a2e0232b89427d2c4b614
-- 
2.56.0