linux-kernel - Re: [PATCH 1/2] spi: dt-bindings: spi-controller: add wakeup-source and interrupts

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Message-ID: <CAL_JsqKUXPTC-fmUowpaHQpuKTfgfQ6D2n7kOZgkYt+MS7OfaA@mail.gmail.com>
Date:   Fri, 15 Nov 2019 07:52:22 -0600
From:   Rob Herring <robh@...nel.org>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Mark Brown <broonie@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        linux-spi <linux-spi@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        DTML <devicetree@...r.kernel.org>
Subject: Re: [PATCH 1/2] spi: dt-bindings: spi-controller: add wakeup-source
 and interrupts

On Thu, Nov 14, 2019 at 5:09 PM Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
>
> On Thu, Nov 14, 2019 at 2:26 PM Rob Herring <robh@...nel.org> wrote:
> >
> > On Tue, Nov 12, 2019 at 11:36:53AM -0800, Dmitry Torokhov wrote:
> > > On Tue, Nov 12, 2019 at 07:15:47PM +0000, Mark Brown wrote:
> > > > On Tue, Nov 12, 2019 at 11:03:28AM -0800, Dmitry Torokhov wrote:
> > > > > On Tue, Nov 12, 2019 at 12:03:07PM +0000, Mark Brown wrote:
> > > > > > On Mon, Nov 11, 2019 at 09:54:10PM -0800, Dmitry Torokhov wrote:
> > > >
> > > > > > > +      interrupts:
> > > > > > > +        items:
> > > > > > > +          - description: main interrupt (attention) line.
> > > > > > > +          - description: dedicated wakeup interrupt.
> > > > > > > +        minItems: 1 # The wakeup interrupt is optional.
> > > >
> > > > > > > +      interrupt-names:
> > > > > > > +        items:
> > > > > > > +          - const: irq
> > > > > > > +          - const: wakeup
> > > > > > > +        minItems: 1
> > > >
> > > > > > How will this interact with a SPI device that defines interrupts at the
> > > > > > device level, possibly more than one of them?  Especially if the device
> > > > > > has its own idea what the interrupts should be called.
> > > >
> > > > > My understanding that individual drivers should be able to override
> > > > > whatever the default behavior core has configured, and the device can
> > > > > establish their own mapping. We have this in I2C and I believe this
> > > > > works well.
> > > >
> > > > > Is the concern about the device tree scheme or SPI core handling?
> > > >
> > > > Both really.
> > >
> > > So as I mentioned, the driver is not forced to use the interrupt
> > > supplied by the SPI core, and the worst thing is that the core
> > > configures the main IRQ as wakeirq and driver would need to call
> > > dev_pm_clear_wake_irq() before switching to correct one. I expect there
> > > will be just a few drivers needing that and many more would benefit from
> > > the default behavior and not needing to repeat the same boilerplate
> > > code.
> > >
> > > As far as scheme goes - I hope that Rob could confirm that we can
> > > override number of interrupts and names in consumers of the binding, as
> > > needed.
> >
> > This won't work. A device schema doesn't override what's defined here,
> > but just further constrains this schema.
> >
> > You could define a "spi irq" schema which devices can include if they
> > want to, but I don't think this pattern is that common to SPI devices.
> > There's not any spec behind compared to say alert irq for SMBus.
> >
> > The 'wakeup' irq name is standardized (for DT), but that's not SPI
> > specific. About all we could define there is 'wakeup-source' is boolean
> > and if there is more than one interrupt, one should be named 'wakeup'.
>
> OK, so what I am hearing is "interrupt"/"interrupt-names" properties
> should be defined in individual device's bindings, and wakeup-source
> can stay in spi-controller.yaml, right?

It could, but it's not SPI specific. I think we should convert
bindings/power/wakeup-source.txt instead. Something like this:

select: true

properties:
  wakeup-source:
    type: boolean
    description: ...

if:
  properties:
    interrupt-names:
      contains:
        const: wakeup
  required:
    - interrupt-names
then:
  required:
    - wakeup-source

dependencies:
  wakeup-source: [ interrupts ]


Rob

> And as far as SPI core goes, we can still do what I proposed, because
> we already handle "first" interrupt as the default one and the drivers
> can override as needed anyway...
>
> Thanks.
>
> --
> Dmitry