Re: [PATCH v2] dt-bindings: dma: qcom,bam-dma: Allow memory-region property

[Krzysztof Kozlowski]

On Sun, Sep 20, 2026 at 08:03:05AM +0530, Vishnu Santhosh wrote:
> Some Qualcomm SoCs, such as Shikra, run the modem in a separate security
> domain, preventing it from accessing BAM descriptor FIFOs allocated from
> arbitrary host memory.
> 
> Add an optional memory-region property to constrain DMA allocations made
> by the BAM DMA controller to a restricted DMA pool. Access permissions
> for the remote execution environment are managed separately.
> 
> Co-developed-by: Deepak Kumar Singh <deepak.singh@xxxxxxxxxxxxxxxx>
> Signed-off-by: Deepak Kumar Singh <deepak.singh@xxxxxxxxxxxxxxxx>
> Signed-off-by: Vishnu Santhosh <vishnu.santhosh@xxxxxxxxxxxxxxxx>
> ---
> Changes in v2:
> - Replace the qcom,vmid property and BAM DMA driver SCM assignment with
>   the standard memory-region restricted DMA pool mechanism.
> - Rely on generic DMA handling to constrain descriptor FIFO allocations
>   to the restricted pool.
> - Drop the Shikra-specific BAM compatible and all BAM DMA driver changes.
> - Link to v1: https://lore.kernel.org/r/20260714-qcom-bam-dma-vmid-ext-v1-0-cef87c57b7dc@xxxxxxxxxxxxxxxx

And a reason to drop review?

> ---
>  .../devicetree/bindings/dma/qcom,bam-dma.yaml       | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/dma/qcom,bam-dma.yaml b/Documentation/devicetree/bindings/dma/qcom,bam-dma.yaml
> index e72adc172af102d8f400044ea0dc32db6b2365be..1e4324799f2b3b8a9ebf9f084e457e66aad20d28 100644
> --- a/Documentation/devicetree/bindings/dma/qcom,bam-dma.yaml
> +++ b/Documentation/devicetree/bindings/dma/qcom,bam-dma.yaml
> @@ -50,6 +50,13 @@ properties:
>      minItems: 1
>      maxItems: 7
>  
> +  memory-region:
> +    maxItems: 1
> +    description:
> +      Phandle to a reserved-memory node compatible with restricted-dma-pool.
> +      The BAM DMA controller uses the pool for DMA allocations, including
> +      channel descriptor FIFOs.
> +
>    num-channels:
>      $ref: /schemas/types.yaml#/definitions/uint32
>      description:
> @@ -137,6 +144,20 @@ examples:
>              qcom,num-ees = <4>;
>              num-channels = <20>;
>              qcom,controlled-remotely;
> +            memory-region = <&bam_dmux_pool>;
> +        };
> +    };
> +
> +    reserved-memory {

No need for this.

Best regards,
Krzysztof