linux-kernel - Re: [PATCH 1/3] dt-bindings: mfd: Document the RTC present on MAX77620

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Message-ID: <20200511142849.GT34497@piout.net>
Date:   Mon, 11 May 2020 16:28:49 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Rob Herring <robh@...nel.org>, Lee Jones <lee.jones@...aro.org>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Jon Hunter <jonathanh@...dia.com>, devicetree@...r.kernel.org,
        "open list:REAL TIME CLOCK (RTC) SUBSYSTEM" 
        <linux-rtc@...r.kernel.org>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] dt-bindings: mfd: Document the RTC present on
 MAX77620

Hi,

On 08/05/2020 13:02:26+0200, Thierry Reding wrote:
> On Fri, May 01, 2020 at 03:53:09PM +0200, Alexandre Belloni wrote:
> > 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.
> 
> So yes, the wakeup-source property isn't necessary. The goal of patches
> 1 and 2 was to allow the RTC to be actually disabled as a wakeup-source
> in case it didn't work as intended. But since the RTC is enabled as a
> wakeup source on these PMICs by default, the idea was to add a new sub-
> node for the RTC and required the wakeup-source in that subnode if that
> subnode was present.
> 
> That said, patch 3 actually does make the RTC work as a wakeup source
> on the particular board that I tested this, so patches 1 and 2 are no
> longer really required from my point of view.
> 
> Do you want me to send patch 3/3 again separately or can you pick it up
> from this series?
> 

I applied it.

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com