Re: [PATCH v2 1/3] dt-bindings: lgm-dma: Added intel,dma-sw-desc property.

[Krzysztof Kozlowski <krzk@kernel.org>]

On 18/08/2025 10:41, Yi xin Zhu wrote:
> Hi Krzysztof,
> 
> On 15/08/2025 18:40, Krzysztof wrote:
>>
>>
>> What is a "SoC level configuration"?
>>
>> From your explanation 1+2 it feels like consumer chooses it. Where is a full DTS
>> showing all this?
>>
>>
>>> of the DMA instances work in hardware descriptor mode while other DMA
>>> instances work in software descriptor mode or all in HW/SW mode.
>>>
>>
>> Best regards,
>> Krzysztof
> 
> In the LGM SoC,  The DMA instances are default connected to CBM(central buffer manager) to automate the DMA descriptors.  
> It can also be detached from CBM to use it in different use cases individually.
> 
> In the HW descriptor case,  the device tree would be like:
> 
> dma1tx: dma-controller@e7300000 {
>       compatible = "intel,lgm-dma1tx";
>       reg = <0xe7300000 0x1000>;
>       ...
>       #dma-cells = <3>;
>       intel,dma-poll-cnt = <16>;
> };
> 
> cbm: cbm@e1000000 {
>    dmas = <&dma1tx 0 0 64>, <&dma1tx 1 0 64> ... <&dma1tx 15 0 64>;
>    
> };
> 
> DMA HW feature, desc_fod(descriptor fetch on demand) and desc_in_sram are turned on in the DMA controller in this case.
> These HW features are defined in platform data in the existing DMA driver as default enabled.
> static const struct ldma_inst_data dma1tx = {
> 	...
> 	.desc_fod = true;
> 	.desc_in_sram = true;
> };
> 
> In the SW descriptor management case,  the device tree would be like:
> 
> dma1tx: dma-controller@e7300000 {
>       compatible = "intel,lgm-dma1tx";
>       reg = <0xe7300000 0x1000>;
>       ...
>       #dma-cells = <3>;
>       intel,dma-poll-cnt = <16>;
>       intel,dma-sw-desc;

That's then implied by compatible, no? If you disagree, please post
complete upstream DTS.

Best regards,
Krzysztof