linux-kernel - Re: [PATCH v3 1/2] dt-bindings: usb: dwc3: Clean up hs_phy

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Date:   Thu, 14 Dec 2023 16:24:01 +0530
From:   Krishna Kurapati PSSNV <quic_kriskura@...cinc.com>
To:     Johan Hovold <johan@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
CC:     Rob Herring <robh+dt@...nel.org>,
        Wesley Cheng <quic_wcheng@...cinc.com>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Andy Gross <agross@...nel.org>,
        "Conor Dooley" <conor+dt@...nel.org>, <devicetree@...r.kernel.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        <quic_ppratap@...cinc.com>, <quic_jackp@...cinc.com>,
        Bjorn Andersson <andersson@...nel.org>
Subject: Re: [PATCH v3 1/2] dt-bindings: usb: dwc3: Clean up hs_phy_irq in
 bindings



On 12/14/2023 3:26 PM, Johan Hovold wrote:
> On Wed, Dec 13, 2023 at 09:48:57PM +0530, Krishna Kurapati PSSNV wrote:
>> On 12/13/2023 12:45 PM, Krzysztof Kozlowski wrote:
>>> On 11/12/2023 13:11, Krishna Kurapati wrote:
>>>> The high speed related interrupts present on QC targets are as follows:
> 
>>>> Classiffy SoC's into four groups based on whether qusb2_phy interrupt
> 
> typo: Classify
> 
>>>> or {dp/dm}_hs_phy_irq is used for wakeup in high speed and whether the
>>>> SoCs have hs_phy_irq present in them or not.
>>>>
>>>> The ss_phy_irq is optional interrupt because there are mutliple SoC's
>>>> which either support only High Speed or there are multiple controllers
>>>> within same Soc and the secondary controller is High Speed only capable.
>>>>
>>>> This breaks ABI on targets running older kernels, but since the interrupt
>>>> definitions are given wrong on many targets and to establish proper rules
>>>> for usage of DWC3 interrupts on Qualcomm platforms, DT binding update is
>>>> necessary.
>>>
>>> This still does not explain why missing property has to be added as
>>> first one, causing huge reordering of everything here and in DTS.
>>>
>>> If pwr_event is required and we already break the ABI, reduce the impact
>>> of the change by putting it after all required interrupts. Otherwise
>>> please explain here and in commit msg why different approach is taken.
>>>
>>
>> Hi Krzysztof. I don't know much about the effect of the ordering on ABI.
>> I will try to learn up on it. Would the series be good if we just move
>> the pwr_event to the end and keep everything in v3 as it is, and push v4
>> for now ?
> 
> Since all SoCs have the pwr_event (HS) interrupt, but not all
> controllers have the SS PHY interrupt, this would prevent expressing
> that the SS PHY is optional by keeping it last in the binding schema and
> making sure that minItem = maxItems - 1.
> 
> And as we discussed, the aim here is to group the three classes of SoCs
> (qusb2, qusb2+, femto) and fix the order of these interrupts once and
> for all so that random reorderings, renames and omissions do not make it
> into the bindings next time someone grabs a downstream DT and sends it
> upstream.
> 

Hi Krzysztof,

  One more reason is that all targets do have a pwr_event interrupts for 
sure and ss_phy is optional as Johan mentioned. So with this reasoning, 
can we put pwr_event first followed by others and push ss_phy to the end 
of list ?

Regards,
Krishna,