Re: [PATCH net-next v2 1/2] dt-bindings: net: qcom,bam-dmux: Add memory-region and qcom,vmid properties

[Vishnu Santhosh]

Hi Loic, Krzysztof,

On 21-09-2026 01:46 pm, Loic Poulain wrote:
> Hi Krzysztof,
>
> On Sun, Sep 20, 2026 at 12:36 PM Krzysztof Kozlowski <krzk@xxxxxxxxxx> wrote:
> > On Sun, Sep 20, 2026 at 08:32:29AM +0530, Vishnu Santhosh wrote:
> > > Some Qualcomm SoCs, such as Shikra, run the modem in a separate security
> > > domain with restricted access to system memory. BAM-DMUX DMA mappings
> > Then this is specific to Shikra and should come with its compatible plus
> > constraints per variant.
> >
> > > must therefore be constrained to a designated region that can be shared
> > > with the modem.
> > >
> > > Add an optional memory-region property to reference a restricted DMA
> > > pool used for BAM-DMUX mappings, and a qcom,vmid property to identify the
> > > remote execution environment that is granted access to the pool through
> > > SCM.
> > >
> > > Require memory-region whenever qcom,vmid is specified.
> > >
> > > 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>
> > > ---
> > >   .../devicetree/bindings/net/qcom,bam-dmux.yaml     | 38 ++++++++++++++++++++++
> > >   1 file changed, 38 insertions(+)
> > >
> > > diff --git a/Documentation/devicetree/bindings/net/qcom,bam-dmux.yaml b/Documentation/devicetree/bindings/net/qcom,bam-dmux.yaml
> > > index 33746c238513d72366bc52359fb10f275475b331..5351269b0ab72ede808ae47b55d57580af209038 100644
> > > --- a/Documentation/devicetree/bindings/net/qcom,bam-dmux.yaml
> > > +++ b/Documentation/devicetree/bindings/net/qcom,bam-dmux.yaml
> > > @@ -72,6 +72,24 @@ properties:
> > >         - const: tx
> > >         - const: rx
> > >
> > > +  memory-region:
> > > +    maxItems: 1
> > > +    description:
> > > +      Phandle to a reserved-memory node compatible with restricted-dma-pool.
> > > +      The BAM-DMUX device uses the pool for DMA mappings.
> > > +
> > > +  qcom,vmid:
> I can see several existing drivers, along with a few ongoing series,
> using this same property. Instead of redefining it in every binding,
> should we consider defining the prop/type once in a common soc/qcom
> schema and reusing it across bindings?

The existing users currently differ (rmtfs: qcom,vmid, 1-2 items;
fastrpc: qcom,vmids, unconstrained), so consolidating them needs a
separate discussion with involved module owners.

Krzysztof, do you want this consolidated into a common schema? If yes,
can this series keep the local definition, with the consolidation
handled as a separate change?


Thanks,
Vishnu

> > > +    $ref: /schemas/types.yaml#/definitions/uint32-array
> > > +    minItems: 1
> > Drop
> >
> > > +    maxItems: 1
> > > +    items:
> > > +      minimum: 1
> > > +      maximum: 63
> > > +    description:
> > > +      VMID of the remote execution environment that is granted access to the
> > > +      restricted DMA pool through SCM. The local execution environment is
> > > +      retained automatically and must not be specified.
> > > +
> > >   required:
> > >     - compatible
> > >     - interrupts
> > > @@ -81,12 +99,29 @@ required:
> > >     - dmas
> > >     - dma-names
> > >
> > > +dependencies:
> > > +  qcom,vmid: [ memory-region ]
> > > +
> > >   additionalProperties: false
> > >
> > >   examples:
> > >     - |
> > > +    #include <dt-bindings/firmware/qcom,scm.h>
> > >       #include <dt-bindings/interrupt-controller/irq.h>
> > >
> > > +    reserved-memory {
> > > +        #address-cells = <1>;
> > > +        #size-cells = <1>;
> > > +        ranges;
> > > +
> > > +        bam_dmux_pool: restricted-dma-pool {
> > > +            compatible = "restricted-dma-pool";
> > > +            size = <0x40000>;
> > > +            alignment = <0x40000>;
> > > +            alloc-ranges = <0x80000000 0x80000000>;
> > > +        };
> > > +    };
> > This wasn't here before. Drop.
> >
> > Best regards,
> > Krzysztof