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

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Message-ID:
 <SA1PR19MB490961745C428F56D7E114F7C234A@SA1PR19MB4909.namprd19.prod.outlook.com>
Date: Fri, 15 Aug 2025 07:07:59 +0000
From: Yi xin Zhu <yzhu@...linear.com>
To: Krzysztof Kozlowski <krzk@...nel.org>, "vkoul@...nel.org"
	<vkoul@...nel.org>, "robh@...nel.org" <robh@...nel.org>, "krzk+dt@...nel.org"
	<krzk+dt@...nel.org>, "conor+dt@...nel.org" <conor+dt@...nel.org>,
	"p.zabel@...gutronix.de" <p.zabel@...gutronix.de>, "kees@...nel.org"
	<kees@...nel.org>, "dave.jiang@...el.com" <dave.jiang@...el.com>,
	"av2082000@...il.com" <av2082000@...il.com>, "dmaengine@...r.kernel.org"
	<dmaengine@...r.kernel.org>, "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 1/3] dt-bindings: lgm-dma: Added intel,dma-sw-desc
 property.

Hi Krzysztof,

On 08/08/2025 14:10, Krzysztof wrote:
> 
> 
> Where is the changelog?
> 
Sorry for missing the changelog.  I will include it in V3 patch.

> > +  intel,dma-sw-desc:
> > +    type: boolean
> > +    description:
> > +      Indicates that the DMA driver should operate in 
> > + software-managed
> mode.
> > +      If this property is not present, it implies that DMA 
> > + descriptors are
> managed and generated by another hardware component that controls the 
> DMA engine.
> 
> Nothing improved:
> 1. Still wrongly wrapped.
> 2. Still SW property.
> 
> I don't think you read the feedback. You need to describe hardware, not SW.
> 
> Best regards,
> Krzysztof

Could you please give me some advice with regarding to the device tree attribute?
My understanding is if I can create a phandle link to describe the DMA descriptors are provided by some HW component.  
That follows the comments. Something like this:

intel,dma-desc-provider = <&xxx_hw>;

Then it describes some HW component manages the DMA descriptors.
Without it, it means SW manage the DMA descriptors.
Please correct me if my understanding is wrong.

However, in the existing driver,  HW manages descriptor mode is the default mode.
I can't create such link in the device tree without breaking the devicetree ABI.
So, is it okay I create an attribute like below ?

Intel,dma-desc-provider = "CPU";   // it means CPU manage DMA descriptors.

Intel,dma-desc-provider = "XXX_HW";  // it means XX_HW manage DMA descriptors.

Please advise.

Best regards,
Yixin