linux-kernel - Re: [PATCH 1/2] dt-bindings: usb: dwc3: Add system bus request info

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Date: Mon, 29 Jan 2024 10:19:24 -0500
From: Frank Li <Frank.li@....com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc: Conor Dooley <conor@...nel.org>, thinh.nguyen@...opsys.com,
	robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
	conor+dt@...nel.org, balbi@...nel.org, devicetree@...r.kernel.org,
	gregkh@...uxfoundation.org, imx@...ts.linux.dev,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
	mark.rutland@....com, mathias.nyman@...el.com, pku.leo@...il.com,
	sergei.shtylyov@...entembedded.com
Subject: Re: [PATCH 1/2] dt-bindings: usb: dwc3: Add system bus request info

On Tue, Jan 23, 2024 at 05:23:53PM -0500, Frank Li wrote:
> On Tue, Jan 23, 2024 at 10:46:39PM +0100, Krzysztof Kozlowski wrote:
> > On 23/01/2024 20:22, Frank Li wrote:
> > > On Tue, Jan 23, 2024 at 06:42:27PM +0000, Conor Dooley wrote:
> > >> On Tue, Jan 23, 2024 at 01:02:21PM -0500, Frank Li wrote:
> > >>> On Tue, Jan 23, 2024 at 05:51:48PM +0000, Conor Dooley wrote:
> > >>>> On Tue, Jan 23, 2024 at 12:49:27PM -0500, Frank Li wrote:
> > >>>>> On Tue, Jan 23, 2024 at 05:27:13PM +0000, Conor Dooley wrote:
> > >>>>>> On Tue, Jan 23, 2024 at 12:02:05PM -0500, Frank Li wrote:
> > >>>>>>> Add device tree binding allow platform overwrite default value of *REQIN in
> > >>>>>>> GSBUSCFG0.
> > >>>>>>
> > >>>>>> Why might a platform actually want to do this? Why does this need to be
> > >>>>>> set at the board level and being aware of which SoC is in use is not
> > >>>>>> sufficient for the driver to set the correct values?
> > >>>>>
> > >>>>> In snps,dwc3.yaml, there are already similary proptery, such as
> > >>>>> snps,incr-burst-type-adjustment. Use this method can keep whole dwc3 usb
> > >>>>> driver keep consistent. And not all platform try enable hardware
> > >>>>> dma_cohenrence. It is configable for difference platform.
> > >>>>
> > >>>> When you say "platform", what do you mean? I understand that term to
> > >>>> mean a combination of board, soc and firmware.
> > >>>
> > >>> In my company's environment, "platform" is "board". I will use "board" in
> > >>> future. Is it big difference here?
> > >>
> > >> Nah, that's close enough that it makes no difference here.
> > >>
> > >> I'd still like an explanation for why a platform would need to actually
> > >> set these properties though, and why information about coherency cannot
> > >> be determined from whether or not the boss the usb controller is on is
> > >> communicated to be dma coherent via the existing devicetree properties
> > >> for that purpose.
> > > 
> > > Actually, I am not very clear about reason. I guest maybe treat off power
> > > consumption and performance.
> > > 
> > > What's your judgement about proptery, which should be in dts. Such as
> > > reg, clk, reset, dma and irq, which is tighted with SOC. It is the fixed
> > > value for every SOC. The board dts never change these.
> > 
> > Then it can be deduced from the compatible and there is no need for new
> > properties.
> 
> Okay, I think "*reqinfo" match this. When new Soc(using compatible dwc usb
> controller) appear regardless dma-cohorence or not, connect by AXI3 or
> AXI4, needn't add new propterties. 

Anyone have objection? I will prepare v2 to fix rob's bot error.

Frank

> 
> Frank
> 
> > 
> > Best regards,
> > Krzysztof
> >