Add support for watchdog on Armada38x

[bsz_semihalf.com]

Summary

A38X watchdog support was implemented in sys/arm/mv/timer.c driver. It
required following modifications:

• add "marvell,armada-380-wdt" compatibility, which supports only watchdog
  • in this case driver returns before attaching timers
• correct and enhance definitions related to timer control register
• unmask reset capability in RSTOUTn_MASK register
• use dedicated watchdog timer on A38X instead of second timer

Obtained from: Semihalf
Sponsored by: Stormshield
Submitted by: Bartosz Szczepanek <[e-mail]>

[andrew]

I don't fully understand why you are not attaching to the interrupt.

[bsz_semihalf.com]

Interrupt is required by timers (we already use mpcore timers), watchdog doesn't need it. It simply resets system on timeout.

[andrew]

Can you change the data in mv_timer_compat to encode if the device is supported & if the interrupt is optional similar to how we do it in the mpcore timer driver. It would then simplify supporting new devices with this driver.

[bsz_semihalf.com]

In D4423#94478, @andrew wrote:

Can you change the data in mv_timer_compat to encode if the device is supported & if the interrupt is optional similar to how we do it in the mpcore timer driver. It would then simplify supporting new devices with this driver.

Done.