watchdog: mediatek: acknowledge pretimeout interrupt

The MediaTek watchdog pretimeout interrupt is level-triggered and does
not have a separate acknowledge register. The interrupt is cleared by
changing WDT_MODE_IRQ_LEVEL_EN and then restoring it to its original
state. Without this transition, the interrupt may remain asserted and
cause an interrupt storm.

After changing WDT_MODE_IRQ_LEVEL_EN, wait 70 us before restoring it.
This is longer than two 32 kHz watchdog clock cycles, allowing the
level change to propagate across the clock domain.

WDT_MODE is also updated by the watchdog start, stop, and pretimeout
operations. Protect its read-modify-write sequences and the complete
IRQ acknowledge sequence with the watchdog spinlock so that concurrent
updates cannot overwrite the temporary IRQ level state.

Signed-off-by: Wanming Gao <wanming.gao@mediatek.com>
Tested-by: Tzung-Bi Shih <tzungbi@kernel.org>
Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
Link: https://patch.msgid.link/20260827092616.2724197-1-wanming.gao@mediatek.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

0 files changed, 0 insertions, 0 deletions