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

[Andre Przywara <andre.przywara@arm.com>]

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@arm.com>
>> ---
>>   .../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@arm.com>
>> +  - Sudeep Holla <sudeep.holla@arm.com>
>> +
>> +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
>