linux-kernel - Re: [PATCH v1 3/6] of: irq: add wake capable bit to of_irq

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Date: Fri, 15 Dec 2023 13:56:47 -0700
From: Mark Hasemeyer <markhas@...omium.org>
To: Rob Herring <robh@...nel.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Raul Rangel <rrangel@...omium.org>, 
	Frank Rowand <frowand.list@...il.com>, devicetree@...r.kernel.org, 
	Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH v1 3/6] of: irq: add wake capable bit to of_irq_resource()

On Fri, Dec 15, 2023 at 8:30 AM Rob Herring <robh@...nel.org> wrote:
>
> On Thu, Dec 14, 2023 at 02:05:16PM -0700, Mark Hasemeyer wrote:
> > > If a device has multiple interrupts, but none named "wakeup" you are
> > > saying all the interrupts are wakeup capable. That's not right though.
> > > Only the device knows which interrupts are wakeup capable. You need:
> > >
> > > return wakeindex >= 0 && wakeindex == index;
> >
> > I was assuming logic described in the DT bindings:
> > https://www.kernel.org/doc/Documentation/devicetree/bindings/power/wakeup-source.txt
> > "Also, if device is marked as a wakeup source, then all the primary
> > interrupt(s) can be used as wakeup interrupt(s)."
>
> Also not the best wording I think.
>
> Which interrupts are primary interrupts?
>
> If we can't determine which interrupt, then we should just leave it up
> to the device.
>
> Rob

+Sudeep who authored the documentation and Rob Ack'd: a68eee4c748c
("Documentation: devicetree: standardize/consolidate on "wakeup-source"
property")

I think what Rob is suggesting more closely matches what ACPI supports: where
interrupt resources are individually marked as wake capable.  The binding
documentation should be updated though.

Something like:
```
If the device is marked as a wakeup-source, interrupt wake capability depends
on the device specific "interrupt-names" property. If no interrupts are labeled
as wake capable, then it is up to the device to determine which interrupts can
wake the system.

However if a device has a dedicated interrupt as the wakeup source, then it
needs to specify/identify it using a device specific interrupt name. In such
cases only that interrupt can be used as a wakeup interrupt.

While various legacy interrupt names exist, new devices should use "wakeup" as
the canonical interrupt name.
```

Parts of the kernel (I2C, bluetooth, MMC) assume "wakeup" as the
interrupt-name. I added some wording to clarify the assumption.

Thoughts?