linux-kernel - Re: [PATCH] dt-bindings: mfd: x-powers,axp152: make interrupt optional for more chips

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Message-ID: <CAGb2v640tCyf6HU2KGHQnMpOXdDVM6UQKw=DpWi6zhhO+paQEw@mail.gmail.com>
Date:   Tue, 8 Aug 2023 00:34:31 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Andre Przywara <andre.przywara@....com>
Cc:     Rob Herring <robh@...nel.org>, Lee Jones <lee@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Icenowy Zheng <uwu@...nowy.me>,
        Shengyu Qu <wiagn233@...look.com>,
        Martin Botka <martin.botka@...ainline.org>,
        Martin Botka <martin@...u3d.com>,
        Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH] dt-bindings: mfd: x-powers,axp152: make interrupt
 optional for more chips

On Mon, Aug 7, 2023 at 9:42 PM Andre Przywara <andre.przywara@....com> wrote:
>
> On Fri, 4 Aug 2023 09:34:32 -0600
> Rob Herring <robh@...nel.org> wrote:
>
> Hi,
>
> > On Wed, Aug 02, 2023 at 03:18:29PM +0100, Andre Przywara wrote:
> > > All X-Powers PMICs described by this binding have an IRQ pin, and so
> > > far (almost) all boards connected this to some NMI pin or GPIO on the SoC
> > > they are connected to.
> > > However we start to see boards that omit this connection, and technically
> > > the IRQ pin is not essential to the basic PMIC operation.
> > > The existing Linux driver allows skipping an IRQ pin setup for some
> > > chips already, so update the binding to also make the DT property
> > > optional for these chips, so that we can actually have DTs describing
> > > boards with the PMIC interrupt not wired up.
> > >
> > > Signed-off-by: Andre Przywara <andre.przywara@....com>
> > > ---
> > > Hi,
> > >
> > > arguably the IRQ functionality is optional for many more PMICs,
> > > especially if a board doesn't use GPIOs or a power key.
> > > So I wonder if the interrupts property should become optional for all?
> > > After all it's more a board designer's decision to wire up the IRQ pin
> > > or not, and nothing that's really related to a particular PMIC.
> >
> > I would say yes. Particularly if it gets rid of a conditional schema.
>
> I see your point, and we might get there, but after some digging extending
> this to more/all PMICs needs more work, see below.
> Given that I was wondering if we can merge this patch now, as this
> blocks multiple DTs from being merged (and Connor already ACKed it).
> I sent an MFD driver fix to make this actually work for the AXP313a:
> https://lore.kernel.org/lkml/20230807133930.94309-1-andre.przywara@arm.com/

Question is which tree we merge it through. We can't merge the DTs without
this guaranteed to go in the same cycle without causing DT validation
errors.

ChenYu

> For supporting this on more PMICs:
> Currently many Linux (sub-)drivers registered by the MFD driver crash when
> there is no valid interrupt registered, and we so far just special cased
> the very simple PMICs to skip just the power key driver registration,
> which works for those chips. However this affects more drivers (I tested
> ac-power-supply), so it's not clear if that's really something useful for
> the other PMICs providing more functionality. I guess we can postpone this
> until either there is actually a use case for those other PMICs (boards
> without the IRQ line connected), or when this list of exceptions grows too
> large.
>
> Cheers,
> Andre