Re: [PATCH 2/2] dt-bindings: watchdog: fsl-imx: document continue in low power mode

[Nandor Han]

On 1/7/26 12:48, Krzysztof Kozlowski wrote:
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> On 07/01/2026 10:12, Nandor Han wrote:
> > On 12/30/25 14:34, Krzysztof Kozlowski wrote:
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> > >
> > > On Mon, Dec 29, 2025 at 04:50:00PM +0200, Nandor Han wrote:
> > > > Property "fsl,wdt-continue-in-low-power" allows the watchdog to continue
> > > > running in low power modes (STOP and DOZE). By default, the watchdog is
> > > > suspended in these modes. This property provides the option to keep the
> > > > watchdog active during low power states when needed.
> > > And why exactly would that be a DT property? If system is sleeping
> > > (assuming this is what you meant by low power), no one will pet the dog,
> > > thus watchdog makes no sense.
> > Thanks for the feedback Krzysztof and Guenter.
> >
> > In our case, low-power mode is disabled. However, we have identified that under certain conditions,
> If your system has low power mode disabled, then you do not need this
> property - you already know that watchdog must continue (or whatever you
> want to achieve here).
>
> > specifically during simulated high-load scenarios, the device becomes unresponsive because it enters
> > one of these power states.
> Device as watchdog? I really do not understand your explanations, but
> for sure system load is not relevant to DT property.
>
> > > Otherwise I fail to see how this is a hardware property and we do not
> > > accept SW properties (see writing bindings, numerous presentations).
> > Our system is based on the i.MX7D CPU and the watchdog peripheral supports the configuration:
> >
> > (From i.MX 7Dual Applications Processor Reference Manual, Rev. 1, 01/2018, page: 1174)
> > ---
> > WDZST
> > Watchdog Low Power. Determines the operation of the WDOG during low-power modes. This bit is write
> > once-only.
> > ---
> > Given that our system does not support low-power modes, we intend to enable the watchdog across all power
> > states to ensure the device can recover properly under these conditions.
> That's not what your property said. Your property said watchdog should
> continue in low power modes. So when system enters low power mode, how
> the watchdog petting would work?
>
> Now you claim you want to enable it in low power mode but you do not
> have low power mode? Does not make sense to me at all.
>
> Best regards,
> Krzysztof
Sorry if anything is unclear. I would try to explain the change from the driver's point of view.

According to i.MX7D Reference Manual, the watchdog controller allows, via the WDOGx_WCR register, control over whether the watchdog continues or suspends in:

a)WAIT power state (bit 7: WDW)
b)STOP and DOSE power state(bit 0: WDZST).

The current driver implementation provides a Device Tree binding `fsl,suspend-in-wait` for configuring case (a) and forces the watchdog to be suspended in case (b).

My patch adds the ability to configure case (b) as well.

Regards,
Nandor