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

[Vishnu Santhosh <vishnu.santhosh@oss.qualcomm.com>]

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@kernel.org> 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@oss.qualcomm.com>
>>> Signed-off-by: Deepak Kumar Singh <deepak.singh@oss.qualcomm.com>
>>> Signed-off-by: Vishnu Santhosh <vishnu.santhosh@oss.qualcomm.com>
>>> ---
>>>   .../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
>>