linux-kernel - Re: [PATCH 1/5] arm64: dts: qcom: sc8280xp: Add missing dwc3 quirks

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Date:   Tue, 28 Mar 2023 15:08:53 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Johan Hovold <johan@...nel.org>
Cc:     andersson@...nel.org, Thinh.Nguyen@...opsys.com,
        gregkh@...uxfoundation.org, mathias.nyman@...el.com,
        konrad.dybcio@...aro.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, linux-arm-msm@...r.kernel.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 1/5] arm64: dts: qcom: sc8280xp: Add missing dwc3 quirks

On Tue, Mar 28, 2023 at 10:54:53AM +0200, Johan Hovold wrote:
> On Sat, Mar 25, 2023 at 10:22:13PM +0530, Manivannan Sadhasivam wrote:
> > Add missing quirks for the USB DWC3 IP.
> 
> This is not an acceptable commit message generally and certainly not for
> something that you have tagged for stable.
> 
> At a minimum, you need to describe why these are needed and what the
> impact is.
> 

I can certainly improve the commit message. But usually the quirks are copied
from the downstream devicetree where qualcomm engineers would've added them
based on the platform requirements.

> Also, why are you sending as part of a series purporting to enable
> runtime PM when it appears to be all about optimising specific gadget
> applications?
> 

It's not related to this series I agree but just wanted to group it with a
series touching usb so that it won't get lost.

I could respin it separately though in v2.

> Did you confirm that the below makes any sense or has this just been
> copied verbatim from the vendor devicetree (it looks like that)?
> 

As you've mentioned, most of the quirks are for gadget mode which is not
supported by the upstream supported boards. So I haven't really tested them but
for I assumed that Qcom engineers did.

> The fact that almost none of the qcom SoCs sets these also indicates
> that something is not right here.
> 
> > Cc: stable@...r.kernel.org # 5.20
> > Fixes: 152d1faf1e2f ("arm64: dts: qcom: add SC8280XP platform")
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > ---
> >  arch/arm64/boot/dts/qcom/sc8280xp.dtsi | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> > 
> > diff --git a/arch/arm64/boot/dts/qcom/sc8280xp.dtsi b/arch/arm64/boot/dts/qcom/sc8280xp.dtsi
> > index 0d02599d8867..266a94c712aa 100644
> > --- a/arch/arm64/boot/dts/qcom/sc8280xp.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/sc8280xp.dtsi
> > @@ -3040,6 +3040,13 @@ usb_0_dwc3: usb@...0000 {
> >  				iommus = <&apps_smmu 0x820 0x0>;
> >  				phys = <&usb_0_hsphy>, <&usb_0_qmpphy QMP_USB43DP_USB3_PHY>;
> >  				phy-names = "usb2-phy", "usb3-phy";
> > +				snps,hird-threshold = /bits/ 8 <0x0>;
> > +				snps,usb2-gadget-lpm-disable;
> 
> Here you are disabling LPM for gadget mode, which makes most of the
> other properties entirely pointless.
> 
> > +				snps,is-utmi-l1-suspend;
> > +				snps,dis-u1-entry-quirk;
> > +				snps,dis-u2-entry-quirk;
> 
> These appear to be used to optimise certain gadget application and
> likely not something that should be set in a dtsi.
> 

I will cross check these with Qcom and respin accordingly.

- Mani

> > +				snps,has-lpm-erratum;
> > +				tx-fifo-resize;
> 
> Same here.
> 
> >  				port {
> >  					usb_0_role_switch: endpoint {
> 
> Johan

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