Re: [PATCH 3/3] arm64: dts: qcom: msm8953: Add device tree for Billion Capture+

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 6/21/25 11:27 AM, Luca Weiss wrote:
> On 21-06-2025 9:07 a.m., cristian_ci wrote:
>> On Saturday, June 21st, 2025 at 00:20, Luca Weiss <luca@lucaweiss.eu> wrote:
>>
>>>> +
>>>> + reserved-memory {
>>>> + qseecom@0 {
>>>
>>>
>>> qseecom@84a00000 ?
>>>
>>>> + reg = <0x00 0x84a00000 0x00 0x1900000>;
>>>> + no-map;
>>>> + };
>>
>> Looking at downstream devicetree, every reserved-memory nodes with "removed-dma-pool" compatible has unit address 0. OTOH, kernel documentation [1] says:
>> "  Following the generic-names recommended practice, node names should
>>    reflect the purpose of the node (ie. "framebuffer" or "dma-pool").
>>    Unit address (@<address>) should be appended to the name if the node
>>    is a static allocation."
>>
>> In my case, downstream devicetree shows:
>>
>>         other_ext_region@0 {
>>             compatible = "removed-dma-pool";
>>             no-map;
>>             reg = <0x00 0x84a00000 0x00 0x1e00000>;
>>         };
>>
>> which will be 'qseecom' reserved-memory node in mainline devicetree.
>>
>> OTOH, 'qseecom' node in downstream devicetree also shows:
>>
>>         qseecom@84a00000 {
>>             compatible = "qcom,qseecom";
>>             reg = <0x84a00000 0x1900000>;
>>                          ...
>>
>> If you confirm what you suggest, 'qseecom' reserved-memory node will look like the following:
>>
>>         qseecom_mem: qseecom@84a00000 {
>>             reg = <0x0 0x84a00000 0x0 0x1900000>;
>>             no-map;
>>         };
>>
>> [1] https://www.kernel.org/doc/Documentation/devicetree/bindings/reserved-memory/reserved-memory.yaml
> 
> The name (qseecom@84a00000) mostly does not matter at runtime, it's just a nice label we give it. The reg is the important bit that gets used in reserved-memory.
> 
> But actually re-checking, I don't think your reserved-memory works right now, msm8953.dtsi has
> 
>     soc: soc@0 {
>         #address-cells = <1>;
>         #size-cells = <1>;
> 
> which means that you should only have one value for address, and one for size, so "reg = <0x84a00000 0x1900000>;". This is different to most other Qualcomm arm64 SoCs.

reserved-memory {
                #address-cells = <2>;
                #size-cells = <2>;
                ranges;


Konrad