Re: [PATCH v3] arm64: dts: qcom: shikra: Add BAM-DMUX support

[Konrad Dybcio]

On 10/21/26 7:16 AM, Vishnu Santhosh wrote:
> 
> On 15-10-2026 02:52 pm, Konrad Dybcio wrote:
>> On 9/20/26 5:28 AM, Vishnu Santhosh wrote:
>>> Add the SMSM state entries, BAM-DMUX node, and BAM DMA controller needed
>>> to provide modem data channels on Shikra.
>>>
>>> Reserve a 256 KiB restricted DMA pool and reference it from both the
>>> BAM-DMUX and BAM DMA nodes. Set qcom,vmid to NAV so the BAM-DMUX driver
>>> can grant the modem access to the complete pool before requesting the DMA
>>> channels.
>> [...]
>>
>>> +    smsm {
>>> +        compatible = "qcom,smsm";
>>> +        #address-cells = <1>;
>>> +        #size-cells = <0>;
>>> +        mboxes = <0>, <&apcs_glb 13>;
>> Why is there a "null" reference?
> 
> Each mboxes entry is the outgoing doorbell for the SMSM host with the
> same index. Index 0 is the apps processor itself (apps@0), which has no
> doorbell, so <0> keeps the modem doorbell at index 1. msm8916.dtsi uses
> the same layout.

Got it, thanks

Konrad