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Date:   Fri, 1 May 2020 15:53:09 +0200
From:   Alexandre Belloni <>
To:     Rob Herring <>
Cc:     Thierry Reding <>,
        Lee Jones <>,
        Alessandro Zummo <>,
        Jon Hunter <>,,
        "open list:REAL TIME CLOCK (RTC) SUBSYSTEM" 
        linux-tegra <>,
        "" <>
Subject: Re: [PATCH 1/3] dt-bindings: mfd: Document the RTC present on

On 01/05/2020 08:00:11-0500, Rob Herring wrote:
> > I don't think this is true because in the case of a discrete RTC, its
> > interrupt pin can be connected directly to a PMIC to power up a board
> > instead of being connected to the SoC. In that case we don't have an
> > interrupt property but the RTC is still a wakeup source. This is the
> > usual use case for wakeup-source in the RTC subsystem. Else, if there is
> > an interrupt, then we assume the RTC is a wakeup source and there is no
> > need to have the wakeup-source property.
> Yes, that would be an example of "unless the wakeup mechanism is
> somehow not an interrupt". I guess I should add not an interrupt from
> the perspective of the OS.
> So if the wakeup is self contained within the PMIC, why do we need a
> DT property? The capability is always there and enabling/disabling
> wakeup from it is userspace policy.

Yes, for this particular case, I'm not sure wakeup-source is actually
necessary. If the interrupt line is used to wakeup the SoC, then the
presence of the interrupts property is enough to enable wakeup.

Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering

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