linux-kernel - RE: [EXT] Re: [PATCH v3 1/3] dt-bindings: usb: cdns-imx8qm: add imx8qm cdns3 glue bindings

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Message-ID: <AM6PR04MB4838ECE2917EF132943830EA88869@AM6PR04MB4838.eurprd04.prod.outlook.com>
Date:   Wed, 22 Mar 2023 21:57:14 +0000
From:   Frank Li <frank.li@....com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
CC:     "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "festevam@...il.com" <festevam@...il.com>,
        "imx@...ts.linux.dev" <imx@...ts.linux.dev>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        dl-linux-imx <linux-imx@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>
Subject: RE: [EXT] Re: [PATCH v3 1/3] dt-bindings: usb: cdns-imx8qm: add
 imx8qm cdns3 glue bindings



> -----Original Message-----
> From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> Sent: Wednesday, March 22, 2023 4:43 PM
> To: Frank Li <frank.li@....com>
> Cc: devicetree@...r.kernel.org; festevam@...il.com; imx@...ts.linux.dev;
> kernel@...gutronix.de; krzysztof.kozlowski+dt@...aro.org; linux-arm-
> kernel@...ts.infradead.org; dl-linux-imx <linux-imx@....com>; linux-
> kernel@...r.kernel.org; robh+dt@...nel.org; s.hauer@...gutronix.de;
> shawnguo@...nel.org
> Subject: Re: [EXT] Re: [PATCH v3 1/3] dt-bindings: usb: cdns-imx8qm: add
> imx8qm cdns3 glue bindings
> 
> Caution: EXT Email
> 
> On 22/03/2023 22:40, Frank Li wrote:
> >
> >
> >> -----Original Message-----
> >> From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> >> Sent: Wednesday, March 22, 2023 4:38 PM
> >> To: Frank Li <frank.li@....com>
> >> Cc: devicetree@...r.kernel.org; festevam@...il.com;
> imx@...ts.linux.dev;
> >> kernel@...gutronix.de; krzysztof.kozlowski+dt@...aro.org; linux-arm-
> >> kernel@...ts.infradead.org; dl-linux-imx <linux-imx@....com>; linux-
> >> kernel@...r.kernel.org; robh+dt@...nel.org; s.hauer@...gutronix.de;
> >> shawnguo@...nel.org
> >> Subject: Re: [EXT] Re: [PATCH v3 1/3] dt-bindings: usb: cdns-imx8qm: add
> >> imx8qm cdns3 glue bindings
> >>
> >> Caution: EXT Email
> >>
> >> On 22/03/2023 22:36, Frank Li wrote:
> >>>
> >>>
> >>>> -----Original Message-----
> >>>> From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> >>>> Sent: Wednesday, March 22, 2023 4:32 PM
> >>>> To: Frank Li <frank.li@....com>
> >>>> Cc: devicetree@...r.kernel.org; festevam@...il.com;
> >> imx@...ts.linux.dev;
> >>>> kernel@...gutronix.de; krzysztof.kozlowski+dt@...aro.org; linux-arm-
> >>>> kernel@...ts.infradead.org; dl-linux-imx <linux-imx@....com>; linux-
> >>>> kernel@...r.kernel.org; robh+dt@...nel.org;
> s.hauer@...gutronix.de;
> >>>> shawnguo@...nel.org
> >>>> Subject: Re: [EXT] Re: [PATCH v3 1/3] dt-bindings: usb: cdns-imx8qm:
> add
> >>>> imx8qm cdns3 glue bindings
> >>>>
> >>>> Caution: EXT Email
> >>>>
> >>>> On 22/03/2023 15:34, Frank Li wrote:
> >>>>>
> >>>>>
> >>>>>> -----Original Message-----
> >>>>>> From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> >>>>>> Sent: Wednesday, March 22, 2023 2:32 AM
> >>>>>> To: Frank Li <frank.li@....
> >>>>>>> +      - const: usb3_aclk
> >>>>>>> +      - const: usb3_ipg_clk
> >>>>>>> +      - const: usb3_core_pclk
> >>>>>>> +
> >>>>>>> +  assigned-clocks:
> >>>>>>> +    items:
> >>>>>>> +      - description: Phandle and clock specifoer of
> >>>>>> IMX_SC_PM_CLK_MST_BUS.
> >>>>>>
> >>>>>> Drop useless pieces so "Phandle and clock specifoer of " and name
> the
> >>>>>> hardware, not the syntax.
> >>>>>>
> >>>>>>> +
> >>>>>>> +  assigned-clock-rates:
> >>>>>>> +    items:
> >>>>>>> +      - description: Should be in Range 100 - 600 Mhz.
> >>>>>>
> >>>>>> That's better but I still do not understand why do you need it in the
> >>>>>> bindings. You never actually answered this question.
> >>>>>
> >>>>> I am not sure 100% sure the reason.
> >>>>> I think difference system target's  axi bus frequency is difference,
> >>>>> And just one time work, needn't software to manage it.
> >>>>> Following other driver's code style may be another reason.
> >>>>
> >>>> That's the reason of heaving it in DTS. But I am asking about bindings.
> >>>> You do understand you define here interface?
> >>>
> >>> I defined here is descript AXI frequency for usb controller. Supposed
> >> difference
> >>> Platform will have difference working frequency.
> >>
> >> I don't understand how does this answer my concerns of having it in DT
> >> bindings. If you do not add it, you "will have difference working
> >> frequency", so what's the point?
> >
> > For example: imx8qxp, it need set to 250Mhz,  i.MX8QM need set to
> 200Mhz.
> > Maybe future chip can set to 400Mhz.
> 
> And? So as you can see you will still have different frequencies, so
> what's the point? What is the benefit? Dunno, maybe we do not understand
> each other, because I don't think you are answering my questions at all.

Benefit: New chip just need change dts file for the same IP, like change base
Reg address and irq number.  

Your question is:  "why need this assigned-clock-rates IMX_SC_PM_CLK_MST_BUS property?"  

My answer: it is one of hardware property, like reg base address and irq number.

If can't match your expectation, can you change another words or provide me an example?  

> 
> Best regards,
> Krzysztof