[PATCH v2 0/3] watchdog: ma35d1: Add support for MA35D1 Watchdog

This patch series introduces watchdog timer support for the Nuvoton MA35D1
SoC platform.

The MA35D1 watchdog timer hardware provides a programmable countdown timer
capable of triggering a system reset upon timeout expiration or generating
an interrupt to wake up the system from low-power states.

Key features supported in this driver:
 - Standard watchdog operations (start, stop, ping, set_timeout).
 - Boot status detection to identify watchdog reset events (WDIOF_CARDRESET).
 - Power management support including suspend/resume and wakeup functionality.

Series breakdown:
 - Patch 1: Add DT binding documentation for Nuvoton MA35D1 watchdog.
 - Patch 2: Add the watchdog driver implementation for MA35D1.
 - Patch 3: Add the watchdog node in the MA35D1 SoC DeviceTree file.

Testing:
 - Tested on the Nuvoton MA35D1 development board using standard watchdog
   test utilities (e.g., watchdog-test from tools/testing/selftests/watchdog).

Signed-off-by: Zi-Yu Chen <[email protected]>
---
Changes in v2:
 - Added `watchdog_stop_on_reboot()` and `watchdog_stop_on_unregister()`.
Addressed automated review feedback (Sashiko AI) and reviewer comments:
 - Remove redundant 'struct device *dev' from driver private structure.
 - Add ma35d1_wdt_wait_sync() after writing WDTEN to REG_WDT_CTL in
   ma35d1_wdt_start().
 - Preserve wdt_dev->timeout when requested timeout exceeds hardware maximum.
 - Replace dev_pm_set_wake_irq with devm_pm_set_wake_irq.
 - Set WDOG_HW_RUNNING if watchdog was already enabled by bootloader.
 - Fix IRQ variable type from u32 to int.
 - Removed unnecessary `select MFD_SYSCON` from Kconfig.

 Note: RMW operations on REG_WDT_CTL have no runtime side-effects on W1C
       flags as IF/WKF are only utilized during PM suspend/resume window.

Zi-Yu Chen (3):
  dt-bindings: watchdog: Add MA35D1 Watchdog binding
  watchdog: Add Nuvoton MA35D1 watchdog driver support
  arm64: dts: nuvoton: Add WDT node for MA35D1 SoC

 .../bindings/watchdog/nuvoton,ma35d1-wdt.yaml |  55 +++
 arch/arm64/boot/dts/nuvoton/ma35d1.dtsi       |   7 +
 drivers/watchdog/Kconfig                      |  10 +
 drivers/watchdog/Makefile                     |   1 +
 drivers/watchdog/ma35d1_wdt.c                 | 358 ++++++++++++++++++
 5 files changed, 431 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/watchdog/nuvoton,ma35d1-wdt.yaml
 create mode 100644 drivers/watchdog/ma35d1_wdt.c

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2.34.1