Re: [PATCH v2 1/8] dt-bindings: arm: Add Live Firmware Activation binding

[Andre Przywara]

Hi,

On 3/18/26 09:04, Krzysztof Kozlowski wrote:
> On Tue, Mar 17, 2026 at 11:33:27AM +0100, Andre Przywara wrote:
> > The Arm Live Firmware Activation spec [1] describes updating firmware
>
> A nit, subject: drop second/last, redundant "binding". The
> "dt-bindings" prefix is already stating that these are bindings.
> See also:
> https://elixir.bootlin.com/linux/v6.17-rc3/source/Documentation/devicetree/bindings/submitting-patches.rst#L18

Sure, will fix.

> > images during runtime, without requiring a reboot. Update images might
> > be deployed out-of-band, for instance via a BMC, in this case the OS
> > needs to be notified about the availability of a new image.
> >
> > This binding describes an interrupt that could be triggered by the
>
> Describe hardware/firmware, not the binding.

Right, sorry, this slipped through.


> > platform, to notify about any changes.
> >
> > [1] https://developer.arm.com/documentation/den0147/latest/
> >
> > Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
> > ---
> >   .../devicetree/bindings/arm/arm,lfa.yaml      | 45 +++++++++++++++++++
> >   1 file changed, 45 insertions(+)
> >   create mode 100644 Documentation/devicetree/bindings/arm/arm,lfa.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/arm/arm,lfa.yaml b/Documentation/devicetree/bindings/arm/arm,lfa.yaml
> > new file mode 100644
> > index 000000000000..92f0564fd672
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/arm/arm,lfa.yaml
> > @@ -0,0 +1,45 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/arm/arm,lfa.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Arm Live Firmware Activation (LFA)
> > +
> > +maintainers:
> > +  - Andre Przywara <andre.przywara@xxxxxxx>
> > +  - Sudeep Holla <sudeep.holla@xxxxxxx>
> > +
> > +description:
> > +  The Arm Live Firmware Activation (LFA) specification [1] describes a
> > +  firmware interface to activate an updated firmware at runtime, without
> > +  requiring a reboot. Updates might be supplied out-of-band, for instance
> > +  via a BMC, in which case the platform needs to notify an OS about pending
> > +  image updates.
> > +  [1] https://developer.arm.com/documentation/den0147/latest/
> > +
> > +properties:
> > +  compatible:
> > +    const: arm,lfa
>
> Does specification has a version? Does it support version discovery?

Yes and yes. there is a mandatory LFA_GET_VERSION call, with major and 
minor version.

And please note that the discovery of the firmware functionality doesn't 
rely on DT (or ACPI) at all - it uses discoverable SMCCC calls instead. 
We just need this DT node to convey the (optional) platform specific 
interrupt number.

> > +
> > +  interrupts:
> > +    maxItems: 1
> > +    description: notification interrupt for changed firmware image status
> > +
> > +required:
> > +  - compatible
> > +  - interrupts
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> > +
> > +    firmware {
> > +        arm-lfa {
>
> Node names should be generic. See also an explanation and list of
> examples (not exhaustive) in DT specification:
> https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html#generic-names-recommendation
> If you cannot find a name matching your device, please check in kernel
> sources for similar cases or you can grow the spec (via pull request to
> DT spec repo).
>
> arm-lfa is specific, so this could be as "fota" or "firmware-update"

OK, will try to come up with a good name.

Thanks for the review!

Cheers,
Andre


> Best regards,
> Krzysztof