Re: [PATCH RFC 1/4] dt-bindings: soc: google: Add modemsmem

[Bjorn Andersson <andersson@kernel.org>]

On Sun, Sep 06, 2026 at 02:41:12AM +0200, David Heidelberg via B4 Relay wrote:
> From: David Heidelberg <david@ixit.cz>
> 
> The modem firmware on Google Pixel 3 - 5a devices expects the application
> processor to publish SoC platform information in a vendor-defined SMEM
> item before the modem boots.
> 
> Assisted-by: LLM
> Signed-off-by: David Heidelberg <david@ixit.cz>
> ---
>  .../bindings/soc/google/google,modemsmem.yaml      | 39 ++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/soc/google/google,modemsmem.yaml b/Documentation/devicetree/bindings/soc/google/google,modemsmem.yaml
> new file mode 100644
> index 0000000000000..a5214a8093ba0
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/soc/google/google,modemsmem.yaml
> @@ -0,0 +1,39 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/soc/google/google,modemsmem.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Google Modem Shared Memory
> +
> +maintainers:
> +  - Richard Acayan <mailingradian@gmail.com>
> +
> +description:
> +  The modem firmware on Google Pixel devices (Pixel 3 through Pixel 5a)
> +  expects the application processor to publish SoC information (platform
> +  type and revision) in a vendor-defined Qualcomm Shared Memory (SMEM)
> +  item before the modem boots.
> +
> +properties:
> +  compatible:
> +    const: google,modemsmem

To me it is seems node represents the attribute of the modem remoteproc
requiring this information to be populated before its started, rather
than a thing of its own.

How about representing this as a property of the modem remoteproc node
instead (perhaps "google,require-socinfo"?) and then put the conditional
snippet in the remoteproc driver?


I'm not particularly fond of the additional codepath in the remoteproc
drivers, but I think the DeviceTree representation would be more
appropriate - and the driver changes are reasonably isolated.

> +
> +  qcom,smem-id:

Let's just hard code this in the implementation until there's a need for
this to change.

Regards,
Bjorn

> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      Identifier of the SMEM item the SoC information is written to. Google
> +      firmware uses the first vendor-reserved item.
> +
> +required:
> +  - compatible
> +  - qcom,smem-id
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    modemsmem {
> +        compatible = "google,modemsmem";
> +        qcom,smem-id = <134>;
> +    };
> 
> -- 
> 2.55.0
> 
>