This is currently supported in firmware deployed on oak, hana and elm mt8173 chromebook devices. The kernel driver is written to be a generic SMC watchdog driver.
Arm Trusted Firmware upstreaming review: https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/3405 Patch to add oak, hana, elm device tree: https://lore.kernel.org/linux-arm-kernel/20200110073730.213789-1-hsi...@chromium.org/ I would like to add the device tree support after the above patch is accepted. Changes in v6: - Don't use dt default - Use default arm,smc-id value if non provided by dt Changes in v5: - Change compatible to arm,smc-wdt - Make timeleft return 0 on error - Use type punning on smc_func_id to save an alloc - Change compatible to arm,smc-wdt Changes in v4: - Add arm,smc-id property - Get smc-id from of property - Return a1 instead of a0 in timeleft Changes in v3: - Change name back to arm - Add optional get_timeleft op - change name to arm_smc_wdt Changes in v2: - Change name arm > mt8173 - use watchdog_stop_on_reboot - use watchdog_stop_on_unregister - use devm_watchdog_register_device - remove smcwd_shutdown, smcwd_remove - change error codes Evan Benn (1): dt-bindings: watchdog: Add ARM smc wdt for mt8173 watchdog Julius Werner (1): watchdog: Add new arm_smc_wdt watchdog driver .../bindings/watchdog/arm-smc-wdt.yaml | 37 ++++ MAINTAINERS | 7 + arch/arm64/configs/defconfig | 1 + drivers/watchdog/Kconfig | 13 ++ drivers/watchdog/Makefile | 1 + drivers/watchdog/arm_smc_wdt.c | 188 ++++++++++++++++++ 6 files changed, 247 insertions(+) create mode 100644 Documentation/devicetree/bindings/watchdog/arm-smc-wdt.yaml create mode 100644 drivers/watchdog/arm_smc_wdt.c -- 2.26.2.526.g744177e7f7-goog